Experimental demonstration of MIMO-OFDM underwater wireless optical communication

NASA Astrophysics Data System (ADS)

Song, Yuhang; Lu, Weichao; Sun, Bin; Hong, Yang; Qu, Fengzhong; Han, Jun; Zhang, Wei; Xu, Jing

2017-11-01

In this paper, we propose and experimentally demonstrate a multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) underwater wireless optical communication (UWOC) system, with a gross bit rate of 33.691 Mb/s over a 2-m water channel using low-cost blue light-emitting-diodes (LEDs) and 10-MHz PIN photodiodes. The system is capable of realizing robust data transmission within a relatively large reception area, leading to relaxed alignment requirement for UWOC. In addition, we have compared the system performance of repetition coding OFDM (RC-OFDM), Alamouti-OFDM and multiple-input single-output OFDM (MISO-OFDM) in turbid water. Results show that the Alamouti-OFDM UWOC is more resistant to delay than the RC-OFDM-based system.

Forward and correctional OFDM-based visible light positioning

NASA Astrophysics Data System (ADS)

Li, Wei; Huang, Zhitong; Zhao, Runmei; He, Peixuan; Ji, Yuefeng

2017-09-01

Visible light positioning (VLP) has attracted much attention in both academic and industrial areas due to the extensive deployment of light-emitting diodes (LEDs) as next-generation green lighting. Generally, the coverage of a single LED lamp is limited, so LED arrays are always utilized to achieve uniform illumination within the large-scale indoor environment. However, in such dense LED deployment scenario, the superposition of the light signals becomes an important challenge for accurate VLP. To solve this problem, we propose a forward and correctional orthogonal frequency division multiplexing (OFDM)-based VLP (FCO-VLP) scheme with low complexity in generating and processing of signals. In the first forward procedure of FCO-VLP, an initial position is obtained by the trilateration method based on OFDM-subcarriers. The positioning accuracy will be further improved in the second correctional procedure based on the database of reference points. As demonstrated in our experiments, our approach yields an improved average positioning error of 4.65 cm and an enhanced positioning accuracy by 24.2% compared with trilateration method.

Optimized OFDM Transmission of Encrypted Image Over Fading Channel

NASA Astrophysics Data System (ADS)

Eldin, Salwa M. Serag

2014-11-01

This paper compares the quality of diffusion-based and permutation-based encrypted image transmission using orthogonal frequency division multiplexing (OFDM) over wireless fading channel. Sensitivity to carrier frequency offsets (CFOs) is one of the limitations in OFDM transmission that was compensated here. Different OFDM diffusions are investigated to study encrypted image transmission optimization. Peak signal-to-noise ratio between the original image and the decrypted image is used to evaluate the received image quality. Chaotic encrypted image modulated with CFOs compensated FFT-OFDM was found to give outstanding performance against other encryption and modulation techniques.

Potential of OFDM for next generation optical access

NASA Astrophysics Data System (ADS)

Fritzsche, Daniel; Weis, Erik; Breuer, Dirk

2011-01-01

This paper shows the requirements for next generation optical access (NGOA) networks and analyzes the potential of OFDM (orthogonal frequency division multiplexing) for the use in such network scenarios. First, we show the motivation for NGOA systems based on the future requirements on FTTH access systems and list the advantages of OFDM in such scenarios. In the next part, the basics of OFDM and different methods to generate and detect optical OFDM signals are explained and analyzed. At the transmitter side the options include intensity modulation and the more advanced field modulation of the optical OFDM signal. At the receiver there is the choice between direct detection and coherent detection. As the result of this discussion we show our vision of the future use of OFDM in optical access networks.

PAPR reduction based on tone reservation scheme for DCO-OFDM indoor visible light communications.

PubMed

Bai, Jurong; Li, Yong; Yi, Yang; Cheng, Wei; Du, Huimin

2017-10-02

High peak-to-average power ratio (PAPR) leads to out-of-band power and in-band distortion in the direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) systems. In order to effectively reduce the PAPR with faster convergence and lower complexity, this paper proposes a tone reservation based scheme, which is the combination of the signal-to-clipping noise ratio (SCR) procedure and the least squares approximation (LSA) procedure. In the proposed scheme, the transmitter of the DCO-OFDM indoor visible light communication (VLC) system is designed to transform the PAPR reduced signal into real-valued positive OFDM signal without doubling the transmission bandwidth. Moreover, the communication distance and the light emitting diode (LED) irradiance angle are taking into consideration in the evaluation of the system bit error rate (BER). The PAPR reduction efficiency of the proposed scheme is remarkable for DCO-OFDM indoor VLC systems.

On-the-field performance of quintuple-play long-reach OFDM-based WDM-PON optical access networks.

PubMed

Llorente, Roberto; Morant, Maria; Pellicer, Eloy; Herman, Milan; Nagy, Zsolt; Alves, Tiago; Cartaxo, Adolfo; Herrera, Javier; Correcher, Jose; Quinlan, Terence; Walker, Stuart; Rodrigues, Cláudio; Cluzeaud, Pierre; Schmidt, Axel; Piesiewicz, Radoslaw; Sambaraju, Rakesh

2014-03-24

In this paper the on-the-field performance of a WDM-PON optical access providing quintuple-play services using orthogonal frequency division multiplexing (OFDM) modulation is evaluated in a real fiber-to-the-home (FTTH) network deployed by Towercom operator in Bratislava (Slovakia). A bundle of quintuple-play services comprising full-standard OFDM-based signals (LTE, WiMAX, UWB and DVB-T) and an ad-hoc OFDM-GbE signal is transmitted in coexistence per single user. Both downstream and upstream transmission performances are evaluated in different on-the-field long-reach optical link distance configurations. Four wavelength multi-user transmission of quintuple-play OFDM services is demonstrated exceeding 60.8 km reach in standard single mode fiber.

A new precoding scheme for spectral efficient optical OFDM systems

NASA Astrophysics Data System (ADS)

Hardan, Saad Mshhain; Bayat, Oguz; Abdulkafi, Ayad Atiyah

2018-07-01

Achieving high spectral efficiency is the key requirement of 5G and optical wireless communication systems and has recently attracted much attention, aiming to satisfy the ever increasing demand for high data rates in communications systems. In this paper, we propose a new precoding/decoding algorithm for spectral efficient optical orthogonal frequency division multiplexing (OFDM) scheme based visible light communication (VLC) systems. The proposed coded modulated optical (CMO) based OFDM system can be applied for both single input single output (SISO) and multiple input multiple-output (MIMO) architectures. Firstly, the real OFDM time domain signal is obtained through invoking the precoding/decoding algorithm without the Hermitian symmetry. After that, the positive signal is achieved either by adding a DC-bias or by using the spatial multiplexing technique. The proposed CMO-OFDM scheme efficiently improves the spectral efficiency of the VLC system as it does not require the Hermitian symmetry constraint to yield real signals. A comparison of the performance improvement of the proposed scheme with other OFDM approaches is also presented in this work. Simulation results show that the proposed CMO-OFDM scheme can not only enhance the spectral efficiency of OFDM-based VLC systems but also improve bit error rate (BER) performance compared with other optical OFDM schemes.

71-Mbit/s ultraviolet-B LED communication link based on 8-QAM-OFDM modulation.

PubMed

Sun, Xiaobin; Zhang, Zhenyu; Chaaban, Anas; Ng, Tien Khee; Shen, Chao; Chen, Rui; Yan, Jianchang; Sun, Haiding; Li, Xiaohang; Wang, Junxi; Li, Jinmin; Alouini, Mohamed-Slim; Ooi, Boon S

2017-09-18

A demonstration of ultraviolet-B (UVB) communication link is implemented utilizing quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM). The demonstration is based on a 294-nm UVB-light-emitting-diode (UVB-LED) with a full-width at half-maximum (FWHM) of 9 nm and light output power of 190 μW, at 7 V, with a special silica gel lens on top of it. A -3-dB bandwidth of 29 MHz was measured and a high-speed near-solar-blind communication link with a data rate of 71 Mbit/s was achieved using 8-QAM-OFDM at perfect alignment. 23.6 Mbit/s using 2-QAM-OFDM when the angle subtended by the pointing directions of the UVB-LED and photodetector (PD) is 12 degrees, thus establishing a diffuse-line-of-sight (LOS) link. The measured bit-error rate (BER) of 2.8 ×10 -4 and 2.4 ×10 -4 , respectively, are well below the forward error correction (FEC) criterion of 3.8 ×10 -3 . The demonstrated high data-rate OFDM-based UVB communication link paves the way for realizing high-speed non-line-of-sight free-space optical communications.

Analysis and iterative equalization of transient and adiabatic chirp effects in DML-based OFDM transmission systems.

PubMed

Wei, Chia-Chien

2012-11-05

This work theoretically studies the transmission performance of a DML-based OFDM system by small-signal approximation, and the model considers both the transient and adiabatic chirps. The dispersion-induced distortion is modeled as subcarrier-to-subcarrier intermixing interference (SSII), and the theoretical SSII agrees with the distortion obtained from large-signal simulation statistically and deterministically. The analysis shows that the presence of the adiabatic chirp will ease power fading or even provide gain, but will increase the SSII to deteriorate OFDM signals after dispersive transmission. Furthermore, this work also proposes a novel iterative equalization to eliminate the SSII. From the simulation, the distortion could be effectively mitigated by the proposed equalization such that the maximum transmission distance of the DML-based OFDM signal is significantly improved. For instance, the transmission distance of a 30-Gbps DML-based OFDM signal can be extended from 10 km to more than 100 km. Besides, since the dispersion-induced distortion could be effectively mitigated by the equalization, negative power penalties are observed at some distances due to chirp-induced power gain.

Experimental demonstration of OFDM/OQAM transmission with DFT-based channel estimation for visible laser light communications

NASA Astrophysics Data System (ADS)

He, Jing; Shi, Jin; Deng, Rui; Chen, Lin

2017-08-01

Recently, visible light communication (VLC) based on light-emitting diodes (LEDs) is considered as a candidate technology for fifth-generation (5G) communications, VLC is free of electromagnetic interference and it can simplify the integration of VLC into heterogeneous wireless networks. Due to the data rates of VLC system limited by the low pumping efficiency, small output power and narrow modulation bandwidth, visible laser light communication (VLLC) system with laser diode (LD) has paid more attention. In addition, orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) is currently attracting attention in optical communications. Due to the non-requirement of cyclic prefix (CP) and time-frequency domain well-localized pulse shapes, it can achieve high spectral efficiency. Moreover, OFDM/OQAM has lower out-of-band power leakage so that it increases the system robustness against inter-carrier interference (ICI) and frequency offset. In this paper, a Discrete Fourier Transform (DFT)-based channel estimation scheme combined with the interference approximation method (IAM) is proposed and experimentally demonstrated for VLLC OFDM/OQAM system. The performance of VLLC OFDM/OQAM system with and without DFT-based channel estimation is investigated. Moreover, the proposed DFT-based channel estimation scheme and the intra-symbol frequency-domain averaging (ISFA)-based method are also compared for the VLLC OFDM/OQAM system. The experimental results show that, the performance of EVM using the DFT-based channel estimation scheme is improved about 3dB compared with the conventional IAM method. In addition, the DFT-based channel estimation scheme can resist the channel noise effectively than that of the ISFA-based method.

Link Correlation Based Transmit Sector Antenna Selection for Alamouti Coded OFDM

NASA Astrophysics Data System (ADS)

Ahn, Chang-Jun

In MIMO systems, the deployment of a multiple antenna technique can enhance the system performance. However, since the cost of RF transmitters is much higher than that of antennas, there is growing interest in techniques that use a larger number of antennas than the number of RF transmitters. These methods rely on selecting the optimal transmitter antennas and connecting them to the respective. In this case, feedback information (FBI) is required to select the optimal transmitter antenna elements. Since FBI is control overhead, the rate of the feedback is limited. This motivates the study of limited feedback techniques where only partial or quantized information from the receiver is conveyed back to the transmitter. However, in MIMO/OFDM systems, it is difficult to develop an effective FBI quantization method for choosing the space-time, space-frequency, or space-time-frequency processing due to the numerous subchannels. Moreover, MIMO/OFDM systems require antenna separation of 5 ∼ 10 wavelengths to keep the correlation coefficient below 0.7 to achieve a diversity gain. In this case, the base station requires a large space to set up multiple antennas. To reduce these problems, in this paper, we propose the link correlation based transmit sector antenna selection for Alamouti coded OFDM without FBI.

Adaptively loaded IM/DD optical OFDM based on set-partitioned QAM formats.

PubMed

Zhao, Jian; Chen, Lian-Kuan

2017-04-17

We investigate the constellation design and symbol error rate (SER) of set-partitioned (SP) quadrature amplitude modulation (QAM) formats. Based on the SER analysis, we derive the adaptive bit and power loading algorithm for SP QAM based intensity-modulation direct-detection (IM/DD) orthogonal frequency division multiplexing (OFDM). We experimentally show that the proposed system significantly outperforms the conventional adaptively-loaded IM/DD OFDM and can increase the data rate from 36 Gbit/s to 42 Gbit/s in the presence of severe dispersion-induced spectral nulls after 40-km single-mode fiber. It is also shown that the adaptive algorithm greatly enhances the tolerance to fiber nonlinearity and allows for more power budget.

Hybrid Resource Allocation Scheme with Proportional Fairness in OFDMA-Based Cognitive Radio Systems

NASA Astrophysics Data System (ADS)

Li, Li; Xu, Changqing; Fan, Pingzhi; He, Jian

In this paper, the resource allocation problem for proportional fairness in hybrid Cognitive Radio (CR) systems is studied. In OFDMA-based CR systems, traditional resource allocation algorithms can not guarantee proportional rates among CR users (CRU) in each OFDM symbol because the number of available subchannels might be smaller than that of CRUs in some OFDM symbols. To deal with this time-varying nature of available spectrum resource, a hybrid CR scheme in which CRUs are allowed to use subchannels in both spectrum holes and primary users (PU) bands is adopted and a resource allocation algorithm is proposed to guarantee proportional rates among CRUs with no undue interference to PUs.

MIMO-OFDM signal optimization for SAR imaging radar

NASA Astrophysics Data System (ADS)

Baudais, J.-Y.; Méric, S.; Riché, V.; Pottier, É.

2016-12-01

This paper investigates the optimization of the coded orthogonal frequency division multiplexing (OFDM) transmitted signal in a synthetic aperture radar (SAR) context. We propose to design OFDM signals to achieve range ambiguity mitigation. Indeed, range ambiguities are well known to be a limitation for SAR systems which operates with pulsed transmitted signal. The ambiguous reflected signal corresponding to one pulse is then detected when the radar has already transmitted the next pulse. In this paper, we demonstrate that the range ambiguity mitigation is possible by using orthogonal transmitted wave as OFDM pulses. The coded OFDM signal is optimized through genetic optimization procedures based on radar image quality parameters. Moreover, we propose to design a multiple-input multiple-output (MIMO) configuration to enhance the noise robustness of a radar system and this configuration is mainly efficient in the case of using orthogonal waves as OFDM pulses. The results we obtain show that OFDM signals outperform conventional radar chirps for range ambiguity suppression and for robustness enhancement in 2 ×2 MIMO configuration.

Multifrequency OFDM SAR in Presence of Deception Jamming

NASA Astrophysics Data System (ADS)

Schuerger, Jonathan; Garmatyuk, Dmitriy

2010-12-01

Orthogonal frequency division multiplexing (OFDM) is considered in this paper from the perspective of usage in imaging radar scenarios with deception jamming. OFDM radar signals are inherently multifrequency waveforms, composed of a number of subbands which are orthogonal to each other. While being employed extensively in communications, OFDM has not found comparatively wide use in radar, and, particularly, in synthetic aperture radar (SAR) applications. In this paper, we aim to show the advantages of OFDM-coded radar signals with random subband composition when used in deception jamming scenarios. Two approaches to create a radar signal by the jammer are considered: instantaneous frequency (IF) estimator and digital-RF-memory- (DRFM-) based reproducer. In both cases, the jammer aims to create a copy of a valid target image via resending the radar signal at prescribed time intervals. Jammer signals are derived and used in SAR simulations with three types of signal models: OFDM, linear frequency modulated (LFM), and frequency-hopped (FH). Presented results include simulated peak side lobe (PSL) and peak cross-correlation values for random OFDM signals, as well as simulated SAR imagery with IF and DRFM jammers'-induced false targets.

Evaluation of multiple-channel OFDM based airborne ultrasonic communications.

PubMed

Jiang, Wentao; Wright, William M D

2016-09-01

Orthogonal frequency division multiplexing (OFDM) modulation has been extensively used in both wired and wireless communication systems. The use of OFDM technology allows very high spectral efficiency data transmission without using complex equalizers to correct the effect of a frequency-selective channel. This work investigated OFDM methods in an airborne ultrasonic communication system, using commercially available capacitive ultrasonic transducers operating at 50kHz to transmit information through the air. Conventional modulation schemes such as binary phase shift keying (BPSK) and quadrature amplitude modulation (QAM) were used to modulate sub-carrier signals, and the performances were evaluated in an indoor laboratory environment. Line-of-sight (LOS) transmission range up to 11m with no measurable errors was achieved using BPSK at a data rate of 45kb/s and a spectral efficiency of 1b/s/Hz. By implementing a higher order modulation scheme (16-QAM), the system data transfer rate was increased to 180kb/s with a spectral efficiency of 4b/s/Hz at attainable transmission distances up to 6m. Diffraction effects were incorporated into a model of the ultrasonic channel that also accounted for beam spread and attenuation in air. The simulations were a good match to the measured signals and non-LOS signals could be demodulated successfully. The effects of multipath interference were also studied in this work. By adding cyclic prefix (CP) to the OFDM symbols, the bit error rate (BER) performance was significantly improved in a multipath environment. Copyright © 2016 Elsevier B.V. All rights reserved.

Constant envelope OFDM scheme for 6PolSK-QPSK

NASA Astrophysics Data System (ADS)

Li, Yupeng; Ding, Ding

2018-03-01

A constant envelope OFDM scheme with phase modulator (PM-CE-OFDM) for 6PolSK-QPSK modulation was demonstrated. Performance under large fiber launch power is measured to check its advantages in counteracting fiber nonlinear impairments. In our simulation, PM-CE-OFDM, RF-assisted constant envelope OFDM (RF-CE-OFDM) and conventional OFDM (Con-OFDM) are transmitted through 80 km standard single mode fiber (SSMF) single channel and WDM system. Simulation results confirm that PM-CE-OFDM has best performance in resisting fiber nonlinearity. In addition, benefiting from the simple system structure, the complexity and cost of PM-CE-OFDM system could be reduced effectively.

OFDM inspired waveforms for 5G

DOE PAGES

Farhang-Boroujeny, Behrouz; Moradi, Hussein

2016-05-12

As the standardization activities are being formed to lay the foundation of 5G wireless networks, there is a common consensus on the need to replace the celebrated OFDM by a more effective air interface that better serves the challenging needs of 5G. The main reason that has made OFDM popular in the past is related to the fact that information symbols are carried over a number of pure tones/sinusoidal signals. Moreover, with the use of cyclic prefix (CP), it is assured that the information carrying tones are only affected by the channel (complex) gains at the respective frequencies. Accordingly, themore » channel effect can be trivially compensated for (equalized) in the frequency domain through a single complex tap per subcarrier. However, as network air interfaces become more complex and the demand for multiuser services grows, OFDM is found to be incapable of handling the inevitable loss of synchronization among users. In the recent past, two novel waveforms (namely, GFDM and C-FBMC) have been discussed in the literature to overcome this and other drawbacks of OFDM. Interestingly, and at the same time not surprising, these methods share a common fundamental property with OFDM: each data packet is made up of a number of tones that are modulated by information symbols. In this tutorial article, we build a common framework based on the said OFDM principle and derive GFDM and C-FBMC waveforms from this point of view. This derivation provides a new prospective that facilitates straightforward understanding of channel equalization and the application of these new waveforms to MIMO channels. As a result, it also facilitates derivation of new structures for more efficient synthesis/analysis of these waveforms than those that have been reported in the literature.« less

Hybrid time-frequency domain equalization for LED nonlinearity mitigation in OFDM-based VLC systems.

PubMed

Li, Jianfeng; Huang, Zhitong; Liu, Xiaoshuang; Ji, Yuefeng

2015-01-12

A novel hybrid time-frequency domain equalization scheme is proposed and experimentally demonstrated to mitigate the white light emitting diode (LED) nonlinearity in visible light communication (VLC) systems based on orthogonal frequency division multiplexing (OFDM). We handle the linear and nonlinear distortion separately in a nonlinear OFDM system. The linear part is equalized in frequency domain and the nonlinear part is compensated by an adaptive nonlinear time domain equalizer (N-TDE). The experimental results show that with only a small number of parameters the nonlinear equalizer can efficiently mitigate the LED nonlinearity. With the N-TDE the modulation index (MI) and BER performance can be significantly enhanced.

Pilot-based parametric channel estimation algorithm for DCO-OFDM-based visual light communications

NASA Astrophysics Data System (ADS)

Qian, Xuewen; Deng, Honggui; He, Hailang

2017-10-01

Due to wide modulation bandwidth in optical communication, multipath channels may be non-sparse and deteriorate communication performance heavily. Traditional compressive sensing-based channel estimation algorithm cannot be employed in this kind of situation. In this paper, we propose a practical parametric channel estimation algorithm for orthogonal frequency division multiplexing (OFDM)-based visual light communication (VLC) systems based on modified zero correlation code (ZCC) pair that has the impulse-like correlation property. Simulation results show that the proposed algorithm achieves better performances than existing least squares (LS)-based algorithm in both bit error ratio (BER) and frequency response estimation.

Adaptive reconfigurable V-BLAST type equalizer for cognitive MIMO-OFDM radios

NASA Astrophysics Data System (ADS)

Ozden, Mehmet Tahir

2015-12-01

An adaptive channel shortening equalizer design for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) radio receivers is considered in this presentation. The proposed receiver has desirable features for cognitive and software defined radio implementations. It consists of two sections: MIMO decision feedback equalizer (MIMO-DFE) and adaptive multiple Viterbi detection. In MIMO-DFE section, a complete modified Gram-Schmidt orthogonalization of multichannel input data is accomplished using sequential processing multichannel Givens lattice stages, so that a Vertical Bell Laboratories Layered Space Time (V-BLAST) type MIMO-DFE is realized at the front-end section of the channel shortening equalizer. Matrix operations, a major bottleneck for receiver operations, are accordingly avoided, and only scalar operations are used. A highly modular and regular radio receiver architecture that has a suitable structure for digital signal processing (DSP) chip and field programable gate array (FPGA) implementations, which are important for software defined radio realizations, is achieved. The MIMO-DFE section of the proposed receiver can also be reconfigured for spectrum sensing and positioning functions, which are important tasks for cognitive radio applications. In connection with adaptive multiple Viterbi detection section, a systolic array implementation for each channel is performed so that a receiver architecture with high computational concurrency is attained. The total computational complexity is given in terms of equalizer and desired response filter lengths, alphabet size, and number of antennas. The performance of the proposed receiver is presented for two-channel case by means of mean squared error (MSE) and probability of error evaluations, which are conducted for time-invariant and time-variant channel conditions, orthogonal and nonorthogonal transmissions, and two different modulation schemes.

Adaptively loaded SP-offset-QAM OFDM for IM/DD communication systems.

PubMed

Zhao, Jian; Chan, Chun-Kit

2017-09-04

In this paper, we propose adaptively loaded set-partitioned offset quadrature amplitude modulation (SP-offset-QAM) orthogonal frequency division multiplexing (OFDM) for low-cost intensity-modulation direct-detection (IM/DD) communication systems. We compare this scheme with multi-band carrier-less amplitude phase modulation (CAP) and conventional OFDM, and demonstrate >40 Gbit/s transmission over 50-km single-mode fiber. It is shown that the use of SP-QAM formats, together with the adaptive loading algorithm specifically designed to this group of formats, results in significant performance improvement for all these three schemes. SP-offset-QAM OFDM exhibits greatly reduced complexity compared to SP-QAM based multi-band CAP, via parallelized implementation and minimized memory length for spectral shaping. On the other hand, this scheme shows better performance than SP-QAM based conventional OFDM at both back-to-back and after transmission. We also characterize the proposed scheme in terms of enhanced tolerance to fiber intra-channel nonlinearity and the potential to increase the communication security. The studies show that adaptive SP-offset-QAM OFDM is a promising IM/DD solution for medium- and long-reach optical access networks and data center connections.

IRCI-Free MIMO-OFDM SAR Using Circularly Shifted Zadoff-Chu Sequences

NASA Astrophysics Data System (ADS)

Cao, Yun-He; Xia, Xiang-Gen

2015-05-01

Cyclic prefix (CP) based MIMO-OFDM radar has been recently proposed for distributed transmit antennas, where there is no inter-range-cell interference (IRCI). It can collect full spatial diversity and each transmitter transmits signals with the same frequency band, i.e., the range resolution is not reduced. However, it needs to transmit multiple OFDM pulses consecutively to obtain range profiles for a single swath, which may be too long in time for a reasonable swath width. In this letter, we propose a CP based MIMO-OFDM synthetic aperture radar (SAR) system, where each transmitter transmits only a single OFDM pulse to obtain range profiles for a swath and has the same frequency band, thus the range resolution is not reduced. It is IRCI free and can collect the full spatial diversity if the transmit antennas are distributed. Our main idea is to use circularly shifted Zadoff-Chu sequences as the weighting coefficients in the OFDM pulses for different transmit antennas and apply spatial filters with multiple receive antennas to divide the whole swath into multiple subswaths, and then each subswath is reconstructed/imaged using our proposed IRCI free range reconstruction method.

A channel estimation scheme for MIMO-OFDM systems

NASA Astrophysics Data System (ADS)

He, Chunlong; Tian, Chu; Li, Xingquan; Zhang, Ce; Zhang, Shiqi; Liu, Chaowen

2017-08-01

In view of the contradiction of the time-domain least squares (LS) channel estimation performance and the practical realization complexity, a reduced complexity channel estimation method for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) based on pilot is obtained. This approach can transform the complexity of MIMO-OFDM channel estimation problem into a simple single input single output-orthogonal frequency division multiplexing (SISO-OFDM) channel estimation problem and therefore there is no need for large matrix pseudo-inverse, which greatly reduces the complexity of algorithms. Simulation results show that the bit error rate (BER) performance of the obtained method with time orthogonal training sequences and linear minimum mean square error (LMMSE) criteria is better than that of time-domain LS estimator and nearly optimal performance.

Adaptive OFDM Waveform Design for Spatio-Temporal-Sparsity Exploited STAP Radar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Satyabrata

In this chapter, we describe a sparsity-based space-time adaptive processing (STAP) algorithm to detect a slowly moving target using an orthogonal frequency division multiplexing (OFDM) radar. The motivation of employing an OFDM signal is that it improves the target-detectability from the interfering signals by increasing the frequency diversity of the system. However, due to the addition of one extra dimension in terms of frequency, the adaptive degrees-of-freedom in an OFDM-STAP also increases. Therefore, to avoid the construction a fully adaptive OFDM-STAP, we develop a sparsity-based STAP algorithm. We observe that the interference spectrum is inherently sparse in the spatio-temporal domain,more » as the clutter responses occupy only a diagonal ridge on the spatio-temporal plane and the jammer signals interfere only from a few spatial directions. Hence, we exploit that sparsity to develop an efficient STAP technique that utilizes considerably lesser number of secondary data compared to the other existing STAP techniques, and produces nearly optimum STAP performance. In addition to designing the STAP filter, we optimally design the transmit OFDM signals by maximizing the output signal-to-interference-plus-noise ratio (SINR) in order to improve the STAP performance. The computation of output SINR depends on the estimated value of the interference covariance matrix, which we obtain by applying the sparse recovery algorithm. Therefore, we analytically assess the effects of the synthesized OFDM coefficients on the sparse recovery of the interference covariance matrix by computing the coherence measure of the sparse measurement matrix. Our numerical examples demonstrate the achieved STAP-performance due to sparsity-based technique and adaptive waveform design.« less

Performance of MIMO-OFDM using convolution codes with QAM modulation

NASA Astrophysics Data System (ADS)

Astawa, I. Gede Puja; Moegiharto, Yoedy; Zainudin, Ahmad; Salim, Imam Dui Agus; Anggraeni, Nur Annisa

2014-04-01

Performance of Orthogonal Frequency Division Multiplexing (OFDM) system can be improved by adding channel coding (error correction code) to detect and correct errors that occur during data transmission. One can use the convolution code. This paper present performance of OFDM using Space Time Block Codes (STBC) diversity technique use QAM modulation with code rate ½. The evaluation is done by analyzing the value of Bit Error Rate (BER) vs Energy per Bit to Noise Power Spectral Density Ratio (Eb/No). This scheme is conducted 256 subcarrier which transmits Rayleigh multipath fading channel in OFDM system. To achieve a BER of 10-3 is required 10dB SNR in SISO-OFDM scheme. For 2×2 MIMO-OFDM scheme requires 10 dB to achieve a BER of 10-3. For 4×4 MIMO-OFDM scheme requires 5 dB while adding convolution in a 4x4 MIMO-OFDM can improve performance up to 0 dB to achieve the same BER. This proves the existence of saving power by 3 dB of 4×4 MIMO-OFDM system without coding, power saving 7 dB of 2×2 MIMO-OFDM and significant power savings from SISO-OFDM system.

MB-OFDM-UWB Based Wireless Multimedia Sensor Networks for Underground Coalmine: A Survey.

PubMed

Han, Ruisong; Yang, Wei; You, Kaiming

2016-12-16

Safety production of coalmines is a task of top priority which plays an important role in guaranteeing, supporting and promoting the continuous development of the coal industry. Since traditional wireless sensor networks (WSNs) cannot fully meet the requirements of comprehensive environment monitoring of underground coalmines, wireless multimedia sensor networks (WMSNs), enabling the retrieval of multimedia information, are introduced to realize fine-grained and precise environment surveillance. In this paper, a framework for designing underground coalmine WMSNs based on Multi-Band Orthogonal Frequency-Division Multiplexing Ultra-wide Band (MB-OFDM-UWB) is presented. The selection of MB-OFDM-UWB wireless transmission solution is based on the characteristics of underground coalmines. Network structure and design challenges are analyzed first, which is the foundation for further discussion. Then, key supporting technologies and open research areas in different layers are surveyed, and we provide a detailed literature review of the state of the art strategies, algorithms and general solutions in these issues. Finally, other research issues like localization, information processing, and network management are discussed.

MB-OFDM-UWB Based Wireless Multimedia Sensor Networks for Underground Coalmine: A Survey

PubMed Central

Han, Ruisong; Yang, Wei; You, Kaiming

2016-01-01

Safety production of coalmines is a task of top priority which plays an important role in guaranteeing, supporting and promoting the continuous development of the coal industry. Since traditional wireless sensor networks (WSNs) cannot fully meet the requirements of comprehensive environment monitoring of underground coalmines, wireless multimedia sensor networks (WMSNs), enabling the retrieval of multimedia information, are introduced to realize fine-grained and precise environment surveillance. In this paper, a framework for designing underground coalmine WMSNs based on Multi-Band Orthogonal Frequency-Division Multiplexing Ultra-wide Band (MB-OFDM-UWB) is presented. The selection of MB-OFDM-UWB wireless transmission solution is based on the characteristics of underground coalmines. Network structure and design challenges are analyzed first, which is the foundation for further discussion. Then, key supporting technologies and open research areas in different layers are surveyed, and we provide a detailed literature review of the state of the art strategies, algorithms and general solutions in these issues. Finally, other research issues like localization, information processing, and network management are discussed. PMID:27999258

A Self-organized MIMO-OFDM-based Cellular Network

NASA Astrophysics Data System (ADS)

Grünheid, Rainer; Fellenberg, Christian

2012-05-01

This paper presents a system proposal for a self-organized cellular network, which is based on the MIMO-OFDM transmission technique. Multicarrier transmission, combined with appropriate beamforming concepts, yields high bandwidth-efficiency and shows a robust behavior in multipath radio channels. Moreover, it provides a fine and tuneable granularity of space-time-frequency resources. Using a TDD approach and interference measurements in each cell, the Base Stations (BSs) decide autonomously which of the space-time-frequency resource blocks are allocated to the Mobile Terminals (MTs) in the cell, in order to fulfil certain Quality of Service (QoS) parameters. Since a synchronized Single Frequency Network (SFN), i.e., a re-use factor of one is applied, the resource blocks can be shared adaptively and flexibly among the cells, which is very advantageous in the case of a non-uniform MT distribution.

A Golay complementary TS-based symbol synchronization scheme in variable rate LDPC-coded MB-OFDM UWBoF system

NASA Astrophysics Data System (ADS)

He, Jing; Wen, Xuejie; Chen, Ming; Chen, Lin

2015-09-01

In this paper, a Golay complementary training sequence (TS)-based symbol synchronization scheme is proposed and experimentally demonstrated in multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband over fiber (UWBoF) system with a variable rate low-density parity-check (LDPC) code. Meanwhile, the coding gain and spectral efficiency in the variable rate LDPC-coded MB-OFDM UWBoF system are investigated. By utilizing the non-periodic auto-correlation property of the Golay complementary pair, the start point of LDPC-coded MB-OFDM UWB signal can be estimated accurately. After 100 km standard single-mode fiber (SSMF) transmission, at the bit error rate of 1×10-3, the experimental results show that the short block length 64QAM-LDPC coding provides a coding gain of 4.5 dB, 3.8 dB and 2.9 dB for a code rate of 62.5%, 75% and 87.5%, respectively.

A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions

PubMed Central

Yen, Chih-Ta; Chen, Wen-Bin

2016-01-01

Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA) system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI) and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM) is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC) equalizer element of OFDM integrated with the dispersion compensation fiber (DCF) is used in the proposed radio-over-fiber (RoF) system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF) and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved. PMID:27618042

Power-efficient method for IM-DD optical transmission of multiple OFDM signals.

PubMed

Effenberger, Frank; Liu, Xiang

2015-05-18

We propose a power-efficient method for transmitting multiple frequency-division multiplexed (FDM) orthogonal frequency-division multiplexing (OFDM) signals in intensity-modulation direct-detection (IM-DD) optical systems. This method is based on quadratic soft clipping in combination with odd-only channel mapping. We show, both analytically and experimentally, that the proposed approach is capable of improving the power efficiency by about 3 dB as compared to conventional FDM OFDM signals under practical bias conditions, making it a viable solution in applications such as optical fiber-wireless integrated systems where both IM-DD optical transmission and OFDM signaling are important.

Adaptive OFDM Radar Waveform Design for Improved Micro-Doppler Estimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Satyabrata

Here we analyze the performance of a wideband orthogonal frequency division multiplexing (OFDM) signal in estimating the micro-Doppler frequency of a rotating target having multiple scattering centers. The use of a frequency-diverse OFDM signal enables us to independently analyze the micro-Doppler characteristics with respect to a set of orthogonal subcarrier frequencies. We characterize the accuracy of micro-Doppler frequency estimation by computing the Cramer-Rao bound (CRB) on the angular-velocity estimate of the target. Additionally, to improve the accuracy of the estimation procedure, we formulate and solve an optimization problem by minimizing the CRB on the angular-velocity estimate with respect to themore » OFDM spectral coefficients. We present several numerical examples to demonstrate the CRB variations with respect to the signal-to-noise ratios, number of temporal samples, and number of OFDM subcarriers. We also analysed numerically the improvement in estimation accuracy due to the adaptive waveform design. A grid-based maximum likelihood estimation technique is applied to evaluate the corresponding mean-squared error performance.« less

A ROF transport system using phase & polarization modulation based on OFDM technique

NASA Astrophysics Data System (ADS)

Mallick, Khaleda; Patra, Ardhendu Sekhar

2018-05-01

A radio-over-fiber (ROF) transport system using phase and polarization modulator based on orthogonal frequency division multiplexing (OFDM) technique has been proposed and demonstrated, to transmit 2.5 Gbps at 7.5 GHz over 40 km single mode fiber (SMF). The transmission performance is observed by proper bit error rate and clear eye diagram. Our proposed system become a prominent alternative, as it has advantages of communication link for greater bandwidth and data rates.

All-optical virtual private network and ONUs communication in optical OFDM-based PON system.

PubMed

Zhang, Chongfu; Huang, Jian; Chen, Chen; Qiu, Kun

2011-11-21

We propose and demonstrate a novel scheme, which enables all-optical virtual private network (VPN) and all-optical optical network units (ONUs) inter-communications in optical orthogonal frequency-division multiplexing-based passive optical network (OFDM-PON) system using the subcarrier bands allocation for the first time (to our knowledge). We consider the intra-VPN and inter-VPN communications which correspond to two different cases: VPN communication among ONUs in one group and in different groups. The proposed scheme can provide the enhanced security and a more flexible configuration for VPN users compared to the VPN in WDM-PON or TDM-PON systems. The all-optical VPN and inter-ONU communications at 10-Gbit/s with 16 quadrature amplitude modulation (16 QAM) for the proposed optical OFDM-PON system are demonstrated. These results verify that the proposed scheme is feasible. © 2011 Optical Society of America

Physical-layer network coding in coherent optical OFDM systems.

PubMed

Guan, Xun; Chan, Chun-Kit

2015-04-20

We present the first experimental demonstration and characterization of the application of optical physical-layer network coding in coherent optical OFDM systems. It combines two optical OFDM frames to share the same link so as to enhance system throughput, while individual OFDM frames can be recovered with digital signal processing at the destined node.

2x2 MIMO-OFDM Gigabit fiber-wireless access system based on polarization division multiplexed WDM-PON.

PubMed

Deng, Lei; Pang, Xiaodan; Zhao, Ying; Othman, M B; Jensen, Jesper Bevensee; Zibar, Darko; Yu, Xianbin; Liu, Deming; Monroy, Idelfonso Tafur

2012-02-13

We propose a spectral efficient radio over wavelength division multiplexed passive optical network (WDM-PON) system by combining optical polarization division multiplexing (PDM) and wireless multiple input multiple output (MIMO) spatial multiplexing techniques. In our experiment, a training-based zero forcing (ZF) channel estimation algorithm is designed to compensate the polarization rotation and wireless multipath fading. A 797 Mb/s net data rate QPSK-OFDM signal with error free (<1 × 10(5)) performance and a 1.59 Gb/s net data rate 16QAM-OFDM signal with BER performance of 1.2 × 10(2) are achieved after transmission of 22.8 km single mode fiber followed by 3 m and 1 m air distances, respectively.

Experimental demonstration of non-iterative interpolation-based partial ICI compensation in100G RGI-DP-CO-OFDM transport systems.

PubMed

Mousa-Pasandi, Mohammad E; Zhuge, Qunbi; Xu, Xian; Osman, Mohamed M; El-Sahn, Ziad A; Chagnon, Mathieu; Plant, David V

2012-07-02

We experimentally investigate the performance of a low-complexity non-iterative phase noise induced inter-carrier interference (ICI) compensation algorithm in reduced-guard-interval dual-polarization coherent-optical orthogonal-frequency-division-multiplexing (RGI-DP-CO-OFDM) transport systems. This interpolation-based ICI compensator estimates the time-domain phase noise samples by a linear interpolation between the CPE estimates of the consecutive OFDM symbols. We experimentally study the performance of this scheme for a 28 Gbaud QPSK RGI-DP-CO-OFDM employing a low cost distributed feedback (DFB) laser. Experimental results using a DFB laser with the linewidth of 2.6 MHz demonstrate 24% and 13% improvement in transmission reach with respect to the conventional equalizer (CE) in presence of weak and strong dispersion-enhanced-phase-noise (DEPN), respectively. A brief analysis of the computational complexity of this scheme in terms of the number of required complex multiplications is provided. This practical approach does not suffer from error propagation while enjoying low computational complexity.

Proposal of DCS-OFDM-PON upstream transmission with intensity modulator and collective self-coherent detection

NASA Astrophysics Data System (ADS)

Zhang, Jing; Yang, Heming; Zhao, Difu; Qiu, Kun

2016-07-01

We introduce digital coherent superposition (DCS) into optical access network and propose a DCS-OFDM-PON upstream transmission scheme using intensity modulator and collective self-coherent detection. The generated OFDM signal is real based on Hermitian symmetry, which can be used to estimate the common phase error (CPE) by complex conjugate subcarrier pairs without any pilots. In simulation, we transmit an aggregated 40 Gb/s optical OFDM signal from two ONUs. The transmission performance with DCS is slightly better after 25 km transmission without relative transmission time delay. The fiber distance for different ONUs to RN are not same in general and there is relative transmission time delay between ONUs, which causes inter-carrier-interference (ICI) power increasing and degrades the transmission performance. The DCS can mitigate the ICI power and the DCS-OFDM-PON upstream transmission outperforms the conventional OFDM-PON. The CPE estimation is by using two pairs of complex conjugate subcarriers without redundancy. The power variation can be 9 dB in DCS-OFDM-PON, which is enough to tolerate several kilometers fiber length difference between the ONUs.

Golay sequences coded coherent optical OFDM for long-haul transmission

NASA Astrophysics Data System (ADS)

Qin, Cui; Ma, Xiangrong; Hua, Tao; Zhao, Jing; Yu, Huilong; Zhang, Jian

2017-09-01

We propose to use binary Golay sequences in coherent optical orthogonal frequency division multiplexing (CO-OFDM) to improve the long-haul transmission performance. The Golay sequences are generated by binary Reed-Muller codes, which have low peak-to-average power ratio and certain error correction capability. A low-complexity decoding algorithm for the Golay sequences is then proposed to recover the signal. Under same spectral efficiency, the QPSK modulated OFDM with binary Golay sequences coding with and without discrete Fourier transform (DFT) spreading (DFTS-QPSK-GOFDM and QPSK-GOFDM) are compared with the normal BPSK modulated OFDM with and without DFT spreading (DFTS-BPSK-OFDM and BPSK-OFDM) after long-haul transmission. At a 7% forward error correction code threshold (Q2 factor of 8.5 dB), it is shown that DFTS-QPSK-GOFDM outperforms DFTS-BPSK-OFDM by extending the transmission distance by 29% and 18%, in non-dispersion managed and dispersion managed links, respectively.

Performance comparison of a fiber optic communication system based on optical OFDM and an optical OFDM-MIMO with Alamouti code by using numerical simulations

NASA Astrophysics Data System (ADS)

Serpa-Imbett, C. M.; Marín-Alfonso, J.; Gómez-Santamaría, C.; Betancur-Agudelo, L.; Amaya-Fernández, F.

2013-12-01

Space division multiplexing in multicore fibers is one of the most promise technologies in order to support transmissions of next-generation peta-to-exaflop-scale supercomputers and mega data centers, owing to advantages in terms of costs and space saving of the new optical fibers with multiple cores. Additionally, multicore fibers allow photonic signal processing in optical communication systems, taking advantage of the mode coupling phenomena. In this work, we numerically have simulated an optical MIMO-OFDM (multiple-input multiple-output orthogonal frequency division multiplexing) by using the coded Alamouti to be transmitted through a twin-core fiber with low coupling. Furthermore, an optical OFDM is transmitted through a core of a singlemode fiber, using pilot-aided channel estimation. We compare the transmission performance in the twin-core fiber and in the singlemode fiber taking into account numerical results of the bit-error rate, considering linear propagation, and Gaussian noise through an optical fiber link. We carry out an optical fiber transmission of OFDM frames using 8 PSK and 16 QAM, with bit rates values of 130 Gb/s and 170 Gb/s, respectively. We obtain a penalty around 4 dB for the 8 PSK transmissions, after 100 km of linear fiber optic propagation for both singlemode and twin core fiber. We obtain a penalty around 6 dB for the 16 QAM transmissions, with linear propagation after 100 km of optical fiber. The transmission in a two-core fiber by using Alamouti coded OFDM-MIMO exhibits a better performance, offering a good alternative in the mitigation of fiber impairments, allowing to expand Alamouti coded in multichannel systems spatially multiplexed in multicore fibers.

An improved scheme for Flip-OFDM based on Hartley transform in short-range IM/DD systems.

PubMed

Zhou, Ji; Qiao, Yaojun; Cai, Zhuo; Ji, Yuefeng

2014-08-25

In this paper, an improved Flip-OFDM scheme is proposed for IM/DD optical systems, where the modulation/demodulation processing takes advantage of the fast Hartley transform (FHT) algorithm. We realize the improved scheme in one symbol period while conventional Flip-OFDM scheme based on fast Fourier transform (FFT) in two consecutive symbol periods. So the complexity of many operations in improved scheme is half of that in conventional scheme, such as CP operation, polarity inversion and symbol delay. Compared to FFT with complex input constellation, the complexity of FHT with real input constellation is halved. The transmission experiment over 50-km SSMF has been realized to verify the feasibility of improved scheme. In conclusion, the improved scheme has the same BER performance with conventional scheme, but great superiority on complexity.

OFDM and PAM comparison using a high baudrate low resolution IM/DD interface for 400G Ethernet access.

PubMed

André, Nuno Sequeira; Louchet, Hadrien; Filsinger, Volker; Hansen, Erik; Richter, André

2016-05-30

We compare OFDM and PAM for 400G Ethernet based on a 3-bit high baudrate IM/DD interface at 1550nm. We demonstrate 27Gb/s and 32Gb/s transmission over 10km SSMF using OFDM and PAM respectively. We show that capacity can be improved through adaptation/equalization to achieve 42Gb/s and 64Gb/s for OFDM and PAM respectively. Experimental results are used to create realistic simulations to extrapolate the performance of both modulation formats under varied conditions. For the considered interface we found that PAM has the best performance, OFDM is impaired by quantization noise. When the resolution limitation is relaxed, OFDM shows better performance.

A two layer chaotic encryption scheme of secure image transmission for DCT precoded OFDM-VLC transmission

NASA Astrophysics Data System (ADS)

Wang, Zhongpeng; Chen, Fangni; Qiu, Weiwei; Chen, Shoufa; Ren, Dongxiao

2018-03-01

In this paper, a two-layer image encryption scheme for a discrete cosine transform (DCT) precoded orthogonal frequency division multiplexing (OFDM) visible light communication (VLC) system is proposed. Firstly, in the proposed scheme the transmitted image is first encrypted by a chaos scrambling sequence,which is generated from the hybrid 4-D hyper- and Arnold map in the upper-layer. After that, the encrypted image is converted into digital QAM modulation signal, which is re-encrypted by chaos scrambling sequence based on Arnold map in physical layer to further enhance the security of the transmitted image. Moreover, DCT precoding is employed to improve BER performance of the proposed system and reduce the PAPR of OFDM signal. The BER and PAPR performances of the proposed system are evaluated by simulation experiments. The experiment results show that the proposed two-layer chaos scrambling schemes achieve image secure transmission for image-based OFDM VLC. Furthermore, DCT precoding can reduce the PAPR and improve the BER performance of OFDM-based VLC.

Theoretical and experimental study on PMD-supported transmission using polarization diversity in coherent optical OFDM systems.

PubMed

Shieh, W; Yi, X; Ma, Y; Tang, Y

2007-08-06

In this paper, we conduct theoretical and experimental study on the PMD-supported transmission with coherent optical orthogonal frequency-division multiplexing (CO-OFDM). We first present the model for the optical fiber communication channel in the presence of the polarization effects. It shows that the optical fiber channel model can be treated as a special kind of multiple-input multiple-output (MIMO) model, namely, a two-input two-output (TITO) model which is intrinsically represented by a two-element Jones vector familiar to the optical communications community. The detailed discussions on various coherent optical MIMO-OFDM (CO-MIMO-OFDM) models are presented. Furthermore, we show the first experiment of polarization-diversity detection in CO-OFDM systems. In particular, a CO-OFDM signal at 10.7 Gb/s is successfully recovered after 900 ps differential-group-delay (DGD) and 1000-km transmission through SSMF fiber without optical dispersion compensation. The transmission experiment with higher-order PMD further confirms the immunity of the CO-OFDM signal to PMD in the transmission fiber. The nonlinearity performance of PMD-supported transmission is also reported. For the first time, nonlinear phase noise mitigation based on receiver digital signal processing is experimentally demonstrated for CO-OFDM transmission.

Blind Equalization and Fading Channel Signal Recovery of OFDM Modulation

DTIC Science & Technology

2011-03-01

Square LTI Linear Time Invariant MIMO Multiple-Input Multiple-Output OFDM Orthogonal Frequency-Division Multiplexing QPSK Quadrature Phase-Shift...AND FADING CHANNEL SIGNAL RECOVERY OF OFDM MODULATION by Anthony G. Stranges March 2011 Thesis Co-Advisors: Roberto Cristi Frank Kragh...Master’s Thesis 4. TITLE AND SUBTITLE Blind Equalization and Fading Channel Signal Recovery of OFDM Modulation 6. AUTHOR(S) Anthony G. Stranges

Remote heterodyne millimeter-wave over fiber based OFDM-PON with master-to-slave injected dual-mode colorless FPLD pair.

PubMed

Chen, Hsiang-Yu; Chi, Yu-Chieh; Lin, Gong-Ru

2015-08-24

A remote heterodyne millimeter-wave (MMW) carrier at 47.7 GHz over fiber synthesized with the master-to-slave injected dual-mode colorless FPLD pair is proposed, which enables the future connection between the wired fiber-optic 64-QAM OFDM-PON at 24 Gb/s with the MMW 4-QAM OFDM wireless network at 2 Gb/s. Both the single- and dual-mode master-to-slave injection-locked colorless FPLD pairs are compared to optimize the proposed 64-QAM OFDM-PON. For the unamplified single-mode master, the slave colorless FPLD successfully performs the 64-QAM OFDM data at 24 Gb/s with EVM, SNR and BER of 8.5%, 21.5 dB and 2.9 × 10(-3), respectively. In contrast, the dual-mode master-to-slave injection-locked colorless FPLD pair with amplified and unfiltered master can transmit 64-QAM OFDM data at 18 Gb/s over 25-km SMF to provide EVM, SNR and BER of 8.2%, 21.8 dB and 2.2 × 10(-3), respectively. For the dual-mode master-to-slave injection-locked colorless FPLD pair, even though the modal dispersion occurred during 25-km SMF transmission makes it sacrifice the usable OFDM bandwidth by only 1 GHz, which guarantees the sufficient encoding bitrate for the optically generated MMW carrier to implement the fusion of MMW wireless LAN and DWDM-PON with cost-effective and compact architecture. As a result, the 47.7-GHz MMW carrier remotely beat from the dual-mode master-to-slave injection-locked colorless FPLD pair exhibits an extremely narrow bandwidth of only 0.48 MHz. After frequency down-conversion operation, the 47.7-GHz MMW carrier successfully delivers 4-QAM OFDM data up to 2 Gb/s with EVM, SNR and BER of 33.5%, 9.51 dB and 1.4 × 10(-3), respectively.

Performance analysis of a finite radon transform in OFDM system under different channel models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawood, Sameer A.; Anuar, M. S.; Fayadh, Rashid A.

In this paper, a class of discrete Radon transforms namely Finite Radon Transform (FRAT) was proposed as a modulation technique in the realization of Orthogonal Frequency Division Multiplexing (OFDM). The proposed FRAT operates as a data mapper in the OFDM transceiver instead of the conventional phase shift mapping and quadrature amplitude mapping that are usually used with the standard OFDM based on Fast Fourier Transform (FFT), by the way that ensure increasing the orthogonality of the system. The Fourier domain approach was found here to be the more suitable way for obtaining the forward and inverse FRAT. This structure resultedmore » in a more suitable realization of conventional FFT- OFDM. It was shown that this application increases the orthogonality significantly in this case due to the use of Inverse Fast Fourier Transform (IFFT) twice, namely, in the data mapping and in the sub-carrier modulation also due to the use of an efficient algorithm in determining the FRAT coefficients called the optimal ordering method. The proposed approach was tested and compared with conventional OFDM, for additive white Gaussian noise (AWGN) channel, flat fading channel, and multi-path frequency selective fading channel. The obtained results showed that the proposed system has improved the bit error rate (BER) performance by reducing inter-symbol interference (ISI) and inter-carrier interference (ICI), comparing with conventional OFDM system.« less

Performance analysis of a finite radon transform in OFDM system under different channel models

NASA Astrophysics Data System (ADS)

Dawood, Sameer A.; Malek, F.; Anuar, M. S.; Fayadh, Rashid A.; Abdullah, Farrah Salwani

2015-05-01

In this paper, a class of discrete Radon transforms namely Finite Radon Transform (FRAT) was proposed as a modulation technique in the realization of Orthogonal Frequency Division Multiplexing (OFDM). The proposed FRAT operates as a data mapper in the OFDM transceiver instead of the conventional phase shift mapping and quadrature amplitude mapping that are usually used with the standard OFDM based on Fast Fourier Transform (FFT), by the way that ensure increasing the orthogonality of the system. The Fourier domain approach was found here to be the more suitable way for obtaining the forward and inverse FRAT. This structure resulted in a more suitable realization of conventional FFT- OFDM. It was shown that this application increases the orthogonality significantly in this case due to the use of Inverse Fast Fourier Transform (IFFT) twice, namely, in the data mapping and in the sub-carrier modulation also due to the use of an efficient algorithm in determining the FRAT coefficients called the optimal ordering method. The proposed approach was tested and compared with conventional OFDM, for additive white Gaussian noise (AWGN) channel, flat fading channel, and multi-path frequency selective fading channel. The obtained results showed that the proposed system has improved the bit error rate (BER) performance by reducing inter-symbol interference (ISI) and inter-carrier interference (ICI), comparing with conventional OFDM system.

High performance and cost effective CO-OFDM system aided by polar code.

PubMed

Liu, Ling; Xiao, Shilin; Fang, Jiafei; Zhang, Lu; Zhang, Yunhao; Bi, Meihua; Hu, Weisheng

2017-02-06

A novel polar coded coherent optical orthogonal frequency division multiplexing (CO-OFDM) system is proposed and demonstrated through experiment for the first time. The principle of a polar coded CO-OFDM signal is illustrated theoretically and the suitable polar decoding method is discussed. Results show that the polar coded CO-OFDM signal achieves a net coding gain (NCG) of more than 10 dB at bit error rate (BER) of 10^-3 over 25-Gb/s 480-km transmission in comparison with conventional CO-OFDM. Also, compared to the 25-Gb/s low-density parity-check (LDPC) coded CO-OFDM 160-km system, the polar code provides a NCG of 0.88 dB @BER = 10^-3. Moreover, the polar code can relieve the laser linewidth requirement massively to get a more cost-effective CO-OFDM system.

Experimental demonstration of the transmission performance for LDPC-coded multiband OFDM ultra-wideband over fiber system

NASA Astrophysics Data System (ADS)

He, Jing; Wen, Xuejie; Chen, Ming; Chen, Lin; Su, Jinshu

2015-01-01

To improve the transmission performance of multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) over optical fiber, a pre-coding scheme based on low-density parity-check (LDPC) is adopted and experimentally demonstrated in the intensity-modulation and direct-detection MB-OFDM UWB over fiber system. Meanwhile, a symbol synchronization and pilot-aided channel estimation scheme is implemented on the receiver of the MB-OFDM UWB over fiber system. The experimental results show that the LDPC pre-coding scheme can work effectively in the MB-OFDM UWB over fiber system. After 70 km standard single-mode fiber (SSMF) transmission, at the bit error rate of 1 × 10-3, the receiver sensitivities are improved about 4 dB when the LDPC code rate is 75%.

Joint Channel and Phase Noise Estimation in MIMO-OFDM Systems

NASA Astrophysics Data System (ADS)

Ngebani, I. M.; Chuma, J. M.; Zibani, I.; Matlotse, E.; Tsamaase, K.

2017-05-01

The combination of multiple-input multiple-output (MIMO) techniques with orthogonal frequency division multiplexing (OFDM), MIMO-OFDM, is a promising way of achieving high spectral efficiency in wireless communication systems. However, the performance of MIMO-ODFM systems is highly degraded by radio frequency (RF) impairments such as phase noise. Similar to the single-input single-output (SISO) case, phase noise in MIMO-OFDM systems results in a common phase error (CPE) and inter carrier interference (ICI). In this paper the problem of joint channel and phase noise estimation in a system with multiple transmit and receive antennas where each antenna is equipped with its own independent oscillator is tackled. The technique employed makes use of a novel placement of pilot carriers in the preamble and data portion of the MIMO-OFDM frame. Numerical results using a 16 and 64 quadrature amplitude modulation QAM schemes are provided to illustrate the effectiveness of the proposed scheme for MIMO-OFDM systems.

Suppression of laser phase noise in direct-detection optical OFDM transmission using phase-conjugated pilots

NASA Astrophysics Data System (ADS)

Zhang, Lu; Ming, Yi; Li, Jin

2017-11-01

Due to the unique phase noise (PN) characteristics in direct-detection optical OFDM (DDO-OFDM) systems, the design of PN compensator is considered as a difficult task. In this paper, a laser PN suppression scheme with low complexity for DDO-OFDM based on coherent superposition of data carrying subcarriers and their phase conjugates is proposed. Through theoretical derivation, the obvious PN suppression is observed. The effectiveness of this technique is demonstrated by simulation of a 4-QAM DDO-OFDM system over 1000 km transmission length at different laser line-width and subcarrier frequency spacing. The results show that the proposed scheme can significantly suppress both varied phase rotation term (PTR) and inter-carrier interference (ICI), and the laser line-width can be relaxed with up to 9 dB OSNR saving or even breakthrough of performance floor.

Massive MIMO-OFDM indoor visible light communication system downlink architecture design

NASA Astrophysics Data System (ADS)

Lang, Tian; Li, Zening; Chen, Gang

2014-10-01

Multiple-input multiple-output (MIMO) technique is now used in most new broadband communication system, and orthogonal frequency division multiplexing (OFDM) is also utilized within current 4th generation (4G) of mobile telecommunication technology. With MIMO and OFDM combined, visible light communication (VLC) system's diversity gain is increase, yet system capacity for dispersive channels is also enhanced. Moreover, with the emerging massive MIMO-OFDM VLC system, there are significant advantages than smaller systems' such as channel hardening, further increasing of energy efficiency (EE) and spectral efficiency (SE) based on law of large number. This paper addresses one of the major technological challenges, system architecture design, which was solved by semispherical beehive structure (SBS) receiver and so that diversity gain can be identified and applied in Massive MIMO VLC system. Simulation results shows that the proposed design clearly presents a spatial diversity over conventional VLC systems.

Implementation of orthogonal frequency division multiplexing (OFDM) and advanced signal processing for elastic optical networking in accordance with networking and transmission constraints

NASA Astrophysics Data System (ADS)

Johnson, Stanley

An increasing adoption of digital signal processing (DSP) in optical fiber telecommunication has brought to the fore several interesting DSP enabled modulation formats. One such format is orthogonal frequency division multiplexing (OFDM), which has seen great success in wireless and wired RF applications, and is being actively investigated by several research groups for use in optical fiber telecom. In this dissertation, I present three implementations of OFDM for elastic optical networking and distributed network control. The first is a field programmable gate array (FPGA) based real-time implementation of a version of OFDM conventionally known as intensity modulation and direct detection (IMDD) OFDM. I experimentally demonstrate the ability of this transmission system to dynamically adjust bandwidth and modulation format to meet networking constraints in an automated manner. To the best of my knowledge, this is the first real-time software defined networking (SDN) based control of an OFDM system. In the second OFDM implementation, I experimentally demonstrate a novel OFDM transmission scheme that supports both direct detection and coherent detection receivers simultaneously using the same OFDM transmitter. This interchangeable receiver solution enables a trade-off between bit rate and equipment cost in network deployment and upgrades. I show that the proposed transmission scheme can provide a receiver sensitivity improvement of up to 1.73 dB as compared to IMDD OFDM. I also present two novel polarization analyzer based detection schemes, and study their performance using experiment and simulation. In the third implementation, I present an OFDM pilot-tone based scheme for distributed network control. The first instance of an SDN-based OFDM elastic optical network with pilot-tone assisted distributed control is demonstrated. An improvement in spectral efficiency and a fast reconfiguration time of 30 ms have been achieved in this experiment. Finally, I

Study of dual-polarization OQAM-OFDM PON with direct detection

NASA Astrophysics Data System (ADS)

Luo, Qing-long; Feng, Min; Bai, Cheng-lin; Hu, Wei-sheng

2016-01-01

An offset quadrature amplitude modulation orthogonal frequency-division multiplexing (OQAM-OFDM) passive optical network (PON) architecture with direct detection is brought up to increase the transmission range and improve the system performance. In optical line terminal (OLT), OQAM-OFDM signals at 40 Gbit/s are transmitted as downstream. At each optical network unit (ONU), the optical OQAM-OFDM signal is demodulated with direct detection. The results show that the transmission distance can exceed 20 km with negligible penalty under the experimental conditions.

Full-subcarriers Polar-OFDM for optical spectrum-efficient transmission exploiting Polarization Multiplexing

NASA Astrophysics Data System (ADS)

Guo, Lei; Liu, Yejun; Zhou, Yufang; Wei, Xuetao; Liu, Yuying

2018-07-01

The exponential growth of the demand for broadband services has imposed great challenges on the design of spectrum-efficient optical transmission system in Passive Optical Network (PON). Recently, an innovative Orthogonal Frequency Division Multiplexing (OFDM) scheme, called Polar-OFDM (P-OFDM), has emerged as a promising solution to boost the spectral efficiency of optical transmission in PON. However, the traditional P-OFDM does not yet perform best in spectral efficiency as it only uses half of the total subcarriers. In this paper, we verify a promising complementation between Polarization Multiplexing (POLMUX) and P-OFDM aiming at higher spectral efficiency. We then propose the full-subcarriers P-OFDM by loading data on the even-indexed subcarriers of X polarization and the odd-indexed subcarriers of Y polarization, respectively. Thus, all of the subcarriers will be utilized for effective data transmission, which can double the spectral efficiency. More importantly, because the subcarriers are interlaced on different polarizations, the cross-polarization interference can be significantly mitigated, which enables the independent channel estimation and equalization at the receiver to recover the data carried on each polarization. Our evaluation results demonstrate that the proposed system realizes the double spectral efficiency of the traditional P-OFDM with reasonable Bit Error Rate (BER) performance loss.

Channel Acquisition for Massive MIMO-OFDM With Adjustable Phase Shift Pilots

NASA Astrophysics Data System (ADS)

You, Li; Gao, Xiqi; Swindlehurst, A. Lee; Zhong, Wen

2016-03-01

We propose adjustable phase shift pilots (APSPs) for channel acquisition in wideband massive multiple-input multiple-output (MIMO) systems employing orthogonal frequency division multiplexing (OFDM) to reduce the pilot overhead. Based on a physically motivated channel model, we first establish a relationship between channel space-frequency correlations and the channel power angle-delay spectrum in the massive antenna array regime, which reveals the channel sparsity in massive MIMO-OFDM. With this channel model, we then investigate channel acquisition, including channel estimation and channel prediction, for massive MIMO-OFDM with APSPs. We show that channel acquisition performance in terms of sum mean square error can be minimized if the user terminals' channel power distributions in the angle-delay domain can be made non-overlapping with proper phase shift scheduling. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The performance of APSPs is investigated for both one symbol and multiple symbol data models. Simulations demonstrate that the proposed APSP approach can provide substantial performance gains in terms of achievable spectral efficiency over the conventional phase shift orthogonal pilot approach in typical mobility scenarios.

Integration of frequency modulated constant envelope technique with ADO-OFDM to impede PAPR in VLC

NASA Astrophysics Data System (ADS)

Singh, Vinay Kumar; Dalal, U. D.

2018-07-01

A novel technique of combating the effects of high peak to average power ratio (PAPR) arising due to the non-linearity of the LED in a typical optical-OFDM (O-OFDM) for visible light communication (VLC) systems used in optical wireless channel (OWC) is proposed in this research work. The concept of constant envelope (CE) using frequency modulation (FM) for a composite O-OFDM system formed by uniting Asymmetrically Clipped Optical OFDM (ACO-OFDM) and Direct Current biased Optical OFDM (DCO-OFDM) termed as ADO-OFDM is mathematically presented with its numerical simulation results. The proposed system FM-CE-ADO-OFDM shows improvement in the PAPR with narrowing down to the least possible 0 dB theoretically. The analysis is extended to be compared with the phase modulation (PM) technique of CE-OFDM. The magnitude of phase discontinuity in the two systems is evaluated in the form of metrics yielding favorable results for the proposed system. This system is as spectrally efficient as the DCO-OFDM and as power efficient as the ACO-OFDM with the added advantage of major reduction in the effects due to PAPR arising as a result of the nonlinearity of the LED . The so formed FM-CE-ADO-OFDM is fed to the LED biased in the linear most region of its operation for simulation purpose. We also evaluate the depth of modulation required to obtain least bit error rate (BER). The frequency modulation at 30% depth has been observed to give suitable performance. The entire system is evaluated for an OWC length of 2m resembling the indoor illumination scenario. The receiver sensitivity shows an improvement of 1.2 dB at the FEC threshold for the proposed system.

Circle-16QAM for a zero-guard-interval CO-OFDM system

NASA Astrophysics Data System (ADS)

Kong, Lingyu; Yang, Aiying; Guo, Peng; Lu, Yueming; Qiao, Yaojun

2018-01-01

In this paper, we introduce circle 16 quadrature amplitude modulation (C-16QAM) modulation format in a high spectral efficiency zero-guard-interval (ZGI) coherent optical (CO) orthogonal frequency-division multiplexing (OFDM) system. At transmitter, the C-16QAM has advantages over the conventional square 16QAM in terms of transmission distance and tolerance to laser linewidth and fiber nonlinearities. ZGI CO-OFDM enables to take away the cyclic prefix (CP), so it has the benefit of higher spectral efficiency compared with the conventional CO-OFDM system. At receiver, in order to compensate chromatic dispersion (CD) and phase noise in a single channel ZGI CO-OFDM system, we studied the overlapped frequency domain equalizer (OFDE) and two carrier phase recovery (CPR) algorithms. We simulate the above systems and the results demonstrate that with the C-16QAM, a 28GBaud ZGI CO-OFDM system can have the longer transmission distance, the higher tolerance to laser linewidth and fiber nonlinearities with contrast to the conventional square 16QAM.

MAI-free performance of PMU-OFDM transceiver in time-variant environment

NASA Astrophysics Data System (ADS)

Tadjpour, Layla; Tsai, Shang-Ho; Kuo, C.-C. J.

2005-06-01

An approximately multi-user OFDM transceiver was introduced to reduce the multi-access interference (MAI ) due to the carrier frequency offset (CFO) to a negligible amount via precoding by Tsai, Lin and Kuo. In this work, we investigate the performance of this precoded multi-user (PMU) OFDM system in a time-variant channel environment. We analyze and compare the MAI effect caused by time-variant channels in the PMU-OFDM and the OFDMA systems. Generally speaking, the MAI effect consists of two parts. The first part is due to the loss of orthogonality among subchannels for all users while the second part is due to the CFO effect caused by the Doppler shift. Simulation results show that, although OFDMA outperforms the PMU-OFDM transceiver in a fast time-variant environment without CFO, PMU-OFDM outperforms OFDMA in a slow time-variant channel via the use of M/2 symmetric or anti-symmetric codewords of M Hadamard-Walsh codes.

Physical-enhanced secure strategy in an OFDM-PON.

PubMed

Zhang, Lijia; Xin, Xiangjun; Liu, Bo; Yu, Jianjun

2012-01-30

The physical layer of optical access network is vulnerable to various attacks. As the dramatic increase of users and network capacity, the issue of physical-layer security becomes more and more important. This paper proposes a physical-enhanced secure strategy for orthogonal frequency division multiplexing passive optical network (OFDM-PON) by employing frequency domain chaos scrambling. The Logistic map is adopted for the chaos mapping. The chaos scrambling strategy can dynamically allocate the scrambling matrices for different OFDM frames according to the initial condition, which enhance the confidentiality of the physical layer. A mathematical model of this secure system is derived firstly, which achieves a secure transmission at physical layer in OFDM-PON. The results from experimental implementation using Logistic mapped chaos scrambling are also given to further demonstrate the efficiency of this secure strategy. An 10.125 Gb/s 64QAM-OFDM data with Logistic mapped chaos scrambling are successfully transmitted over 25-km single mode fiber (SMF), and the experimental results show that proposed security scheme can protect the system from eavesdropper and attacker, while keep a good performance for the legal ONU.

OLT-centralized sampling frequency offset compensation scheme for OFDM-PON.

PubMed

Chen, Ming; Zhou, Hui; Zheng, Zhiwei; Deng, Rui; Chen, Qinghui; Peng, Miao; Liu, Cuiwei; He, Jing; Chen, Lin; Tang, Xionggui

2017-08-07

We propose an optical line terminal (OLT)-centralized sampling frequency offset (SFO) compensation scheme for adaptively-modulated OFDM-PON systems. By using the proposed SFO scheme, the phase rotation and inter-symbol interference (ISI) caused by SFOs between OLT and multiple optical network units (ONUs) can be centrally compensated in the OLT, which reduces the complexity of ONUs. Firstly, the optimal fast Fourier transform (FFT) size is identified in the intensity-modulated and direct-detection (IMDD) OFDM system in the presence of SFO. Then, the proposed SFO compensation scheme including phase rotation modulation (PRM) and length-adaptive OFDM frame has been experimentally demonstrated in the downlink transmission of an adaptively modulated optical OFDM with the optimal FFT size. The experimental results show that up to ± 300 ppm SFO can be successfully compensated without introducing any receiver performance penalties.

Colorless ONU implementation for WDM-PON using direct-detection optical OFDM

NASA Astrophysics Data System (ADS)

Feng, Min; Luo, Qing-long; Bai, Cheng-lin

2013-03-01

A novel architecture for the colorless optical network unit (ONU) is proposed and experimentally demonstrated with direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM). In this architecture, polarization-division multiplexing is used to reduce the cost at ONU. In optical line terminal (OLT), quadrature amplitude modulation (QAM) intensity-modulated OFDM signal with x-polarization at 10 Gbit/s is transmitted as downstream. At each ONU, the optical OFDM signal is demodulated with direct detection, and γ-polarization signal is modulated for upstream on-off keying (OOK) data at 5 Gbit/s. Simulation results show that the power penalty is negligible for both optical OFDM downstream and the on-off keying upstream signals after over 50 km single-mode fiber (SMF) transmission.

Efficient algorithms for solution of interference cancellation and channel estimation for mobile OFDM system

NASA Astrophysics Data System (ADS)

Fan, Tong-liang; Wen, Yu-cang; Kadri, Chaibou

Orthogonal frequency-division multiplexing (OFDM) is robust against frequency selective fading because of the increase of the symbol duration. However, the time-varying nature of the channel causes inter-carrier interference (ICI) which destroys the orthogonal of sub-carriers and degrades the system performance severely. To alleviate the detrimental effect of ICI, there is a need for ICI mitigation within one OFDM symbol. We propose an iterative Inter-Carrier Interference (ICI) estimation and cancellation technique for OFDM systems based on regularized constrained total least squares. In the proposed scheme, ICI aren't treated as additional additive white Gaussian noise (AWGN). The effect of Inter-Carrier Interference (ICI) and inter-symbol interference (ISI) on channel estimation is regarded as perturbation of channel. We propose a novel algorithm for channel estimation o based on regularized constrained total least squares. Computer simulations show that significant improvement can be obtained by the proposed scheme in fast fading channels.

System for Processing Coded OFDM Under Doppler and Fading

NASA Technical Reports Server (NTRS)

Tsou, Haiping; Darden, Scott; Lee, Dennis; Yan, Tsun-Yee

2005-01-01

An advanced communication system has been proposed for transmitting and receiving coded digital data conveyed as a form of quadrature amplitude modulation (QAM) on orthogonal frequency-division multiplexing (OFDM) signals in the presence of such adverse propagation-channel effects as large dynamic Doppler shifts and frequency-selective multipath fading. Such adverse channel effects are typical of data communications between mobile units or between mobile and stationary units (e.g., telemetric transmissions from aircraft to ground stations). The proposed system incorporates novel signal processing techniques intended to reduce the losses associated with adverse channel effects while maintaining compatibility with the high-speed physical layer specifications defined for wireless local area networks (LANs) as the standard 802.11a of the Institute of Electrical and Electronics Engineers (IEEE 802.11a). OFDM is a multi-carrier modulation technique that is widely used for wireless transmission of data in LANs and in metropolitan area networks (MANs). OFDM has been adopted in IEEE 802.11a and some other industry standards because it affords robust performance under frequency-selective fading. However, its intrinsic frequency-diversity feature is highly sensitive to synchronization errors; this sensitivity poses a challenge to preserve coherence between the component subcarriers of an OFDM system in order to avoid intercarrier interference in the presence of large dynamic Doppler shifts as well as frequency-selective fading. As a result, heretofore, the use of OFDM has been limited primarily to applications involving small or zero Doppler shifts. The proposed system includes a digital coherent OFDM communication system that would utilize enhanced 802.1la-compatible signal-processing algorithms to overcome effects of frequency-selective fading and large dynamic Doppler shifts. The overall transceiver design would implement a two-frequency-channel architecture (see figure

Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing.

PubMed

Benlachtar, Yannis; Watts, Philip M; Bouziane, Rachid; Milder, Peter; Rangaraj, Deepak; Cartolano, Anthony; Koutsoyannis, Robert; Hoe, James C; Püschel, Markus; Glick, Madeleine; Killey, Robert I

2009-09-28

We demonstrate a field programmable gate array (FPGA) based optical orthogonal frequency division multiplexing (OFDM) transmitter implementing real time digital signal processing at a sample rate of 21.4 GS/s. The QPSK-OFDM signal is generated using an 8 bit, 128 point inverse fast Fourier transform (IFFT) core, performing one transform per clock cycle at a clock speed of 167.2 MHz and can be deployed with either a direct-detection or a coherent receiver. The hardware design and the main digital signal processing functions are described, and we show that the main performance limitation is due to the low (4-bit) resolution of the digital-to-analog converter (DAC) and the 8-bit resolution of the IFFT core used. We analyze the back-to-back performance of the transmitter generating an 8.36 Gb/s optical single sideband (SSB) OFDM signal using digital up-conversion, suitable for direct-detection. Additionally, we use the device to transmit 8.36 Gb/s SSB OFDM signals over 200 km of uncompensated standard single mode fiber achieving an overall BER<10(-3).

Independent component analysis based channel equalization for 6 × 6 MIMO-OFDM transmission over few-mode fiber.

PubMed

He, Zhixue; Li, Xiang; Luo, Ming; Hu, Rong; Li, Cai; Qiu, Ying; Fu, Songnian; Yang, Qi; Yu, Shaohua

2016-05-02

We propose and experimentally demonstrate two independent component analysis (ICA) based channel equalizers (CEs) for 6 × 6 MIMO-OFDM transmission over few-mode fiber. Compared with the conventional channel equalizer based on training symbols (TSs-CE), the proposed two ICA-based channel equalizers (ICA-CE-I and ICA-CE-II) can achieve comparable performances, while requiring much less training symbols. Consequently, the overheads for channel equalization can be substantially reduced from 13.7% to 0.4% and 2.6%, respectively. Meanwhile, we also experimentally investigate the convergence speed of the proposed ICA-based CEs.

107 Gb/s coherent optical OFDM transmission over 1000-km SSMF fiber using orthogonal band multiplexing.

PubMed

Shieh, W; Yang, Q; Ma, Y

2008-04-28

Coherent optical OFDM (CO-OFDM) has emerged as an attractive modulation format for the forthcoming 100 Gb/s Ethernet. However, even the spectral-efficient implementation of CO-OFDM requires digital-to-analog converters (DAC) and analog-to-digital converters (ADC) to operate at the bandwidth which may not be available today or may not be cost-effective. In order to resolve the electronic bandwidth bottleneck associated with DAC/ADC devices, we propose and elucidate the principle of orthogonal-band-multiplexed OFDM (OBM-OFDM) to subdivide the entire OFDM spectrum into multiple orthogonal bands. With this scheme, the DAC/ADCs do not need to operate at extremely high sampling rate. The corresponding mapping to the mixed-signal integrated circuit (IC) design is also revealed. Additionally, we show the proof-of-concept transmission experiment through optical realization of OBM-OFDM. To the best of our knowledge, we present the first experimental demonstration of 107 Gb/s QPSK-encoded CO-OFDM signal transmission over 1000 km standard-single- mode-fiber (SSMF) without optical dispersion compensation and without Raman amplification. The demonstrated system employs 2x2 MIMO-OFDM signal processing and achieves high electrical spectral efficiency with direct-conversion at both transmitter and receiver.

PAPR-Constrained Pareto-Optimal Waveform Design for OFDM-STAP Radar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Satyabrata

We propose a peak-to-average power ratio (PAPR) constrained Pareto-optimal waveform design approach for an orthogonal frequency division multiplexing (OFDM) radar signal to detect a target using the space-time adaptive processing (STAP) technique. The use of an OFDM signal does not only increase the frequency diversity of our system, but also enables us to adaptively design the OFDM coefficients in order to further improve the system performance. First, we develop a parametric OFDM-STAP measurement model by considering the effects of signaldependent clutter and colored noise. Then, we observe that the resulting STAP-performance can be improved by maximizing the output signal-to-interference-plus-noise ratiomore » (SINR) with respect to the signal parameters. However, in practical scenarios, the computation of output SINR depends on the estimated values of the spatial and temporal frequencies and target scattering responses. Therefore, we formulate a PAPR-constrained multi-objective optimization (MOO) problem to design the OFDM spectral parameters by simultaneously optimizing four objective functions: maximizing the output SINR, minimizing two separate Cramer-Rao bounds (CRBs) on the normalized spatial and temporal frequencies, and minimizing the trace of CRB matrix on the target scattering coefficients estimations. We present several numerical examples to demonstrate the achieved performance improvement due to the adaptive waveform design.« less

An approach enabling adaptive FEC for OFDM in fiber-VLLC system

NASA Astrophysics Data System (ADS)

Wei, Yiran; He, Jing; Deng, Rui; Shi, Jin; Chen, Shenghai; Chen, Lin

2017-12-01

In this paper, we propose an orthogonal circulant matrix transform (OCT)-based adaptive frame-level-forward error correction (FEC) scheme for fiber-visible laser light communication (VLLC) system and experimentally demonstrate by Reed-Solomon (RS) Code. In this method, no extra bits are spent for adaptive message, except training sequence (TS), which is simultaneously used for synchronization and channel estimation. Therefore, RS-coding can be adaptively performed frames by frames via the last received codeword-error-rate (CER) feedback estimated by the TSs of the previous few OFDM frames. In addition, the experimental results exhibit that over 20 km standard single-mode fiber (SSMF) and 8 m visible light transmission, the costs of RS codewords are at most 14.12% lower than those of conventional adaptive subcarrier-RS-code based 16-QAM OFDM at bit error rate (BER) of 10-5.

12-mode OFDM transmission using reduced-complexity maximum likelihood detection.

PubMed

Lobato, Adriana; Chen, Yingkan; Jung, Yongmin; Chen, Haoshuo; Inan, Beril; Kuschnerov, Maxim; Fontaine, Nicolas K; Ryf, Roland; Spinnler, Bernhard; Lankl, Berthold

2015-02-01

We report the transmission of 163-Gb/s MDM-QPSK-OFDM and 245-Gb/s MDM-8QAM-OFDM transmission over 74 km of few-mode fiber supporting 12 spatial and polarization modes. A low-complexity maximum likelihood detector is employed to enhance the performance of a system impaired by mode-dependent loss.

Experimental demonstration of high spectral efficient 4 × 4 MIMO SCMA-OFDM/OQAM radio over multi-core fiber system.

PubMed

Liu, Chang; Deng, Lei; He, Jiale; Li, Di; Fu, Songnian; Tang, Ming; Cheng, Mengfan; Liu, Deming

2017-07-24

In this paper, 4 × 4 multiple-input multiple-output (MIMO) radio over 7-core fiber system based on sparse code multiple access (SCMA) and OFDM/OQAM techniques is proposed. No cyclic prefix (CP) is required by properly designing the prototype filters in OFDM/OQAM modulator, and non-orthogonally overlaid codewords by using SCMA is help to serve more users simultaneously under the condition of using equal number of time and frequency resources compared with OFDMA, resulting in the increase of spectral efficiency (SE) and system capacity. In our experiment, 11.04 Gb/s 4 × 4 MIMO SCMA-OFDM/OQAM signal is successfully transmitted over 20 km 7-core fiber and 0.4 m air distance in both uplink and downlink. As a comparison, 6.681 Gb/s traditional MIMO-OFDM signal with the same occupied bandwidth has been evaluated for both uplink and downlink transmission. The experimental results show that SE could be increased by 65.2% with no bit error rate (BER) performance degradation compared with the traditional MIMO-OFDM technique.

PMD compensation in fiber-optic communication systems with direct detection using LDPC-coded OFDM.

PubMed

Djordjevic, Ivan B

2007-04-02

The possibility of polarization-mode dispersion (PMD) compensation in fiber-optic communication systems with direct detection using a simple channel estimation technique and low-density parity-check (LDPC)-coded orthogonal frequency division multiplexing (OFDM) is demonstrated. It is shown that even for differential group delay (DGD) of 4/BW (BW is the OFDM signal bandwidth), the degradation due to the first-order PMD can be completely compensated for. Two classes of LDPC codes designed based on two different combinatorial objects (difference systems and product of combinatorial designs) suitable for use in PMD compensation are introduced.

Dispersion and nonlinear effects in OFDM-RoF system

NASA Astrophysics Data System (ADS)

Alhasson, Bader H.; Bloul, Albe M.; Matin, M.

2010-08-01

The radio-over-fiber (RoF) network has been a proven technology to be the best candidate for the wireless-access technology, and the orthogonal frequency division multiplexing (OFDM) technique has been established as the core technology in the physical layer of next generation wireless communication system, as a result OFDM-RoF has drawn attentions worldwide and raised many new research topics recently. At the present time, the trend of information industry is towards mobile, wireless, digital and broadband. The next generation network (NGN) has motivated researchers to study higher-speed wider-band multimedia communication to transmit (voice, data, and all sorts of media such as video) at a higher speed. The NGN would offer services that would necessitate broadband networks with bandwidth higher than 2Mbit/s per radio channel. Many new services emerged, such as Internet Protocol TV (IPTV), High Definition TV (HDTV), mobile multimedia and video stream media. Both speed and capacity have been the key objectives in transmission. In the meantime, the demand for transmission bandwidth increased at a very quick pace. The coming of 4G and 5G era will provide faster data transmission and higher bit rate and bandwidth. Taking advantages of both optical communication and wireless communication, OFDM Radio over Fiber (OFDM-RoF) system is characterized by its high speed, large capacity and high spectral efficiency. However, up to the present there are some problems to be solved, such as dispersion and nonlinearity effects. In this paper we will study the dispersion and nonlinearity effects and their elimination in OFDM-radio-over-fiber system.

On the capacity of MIMO-OFDM based diversity and spatial multiplexing in Radio-over-Fiber system

NASA Astrophysics Data System (ADS)

El Yahyaoui, Moussa; El Moussati, Ali; El Zein, Ghaïs

2017-11-01

This paper proposes a realistic and global simulation to predict the behavior of a Radio over Fiber (RoF) system before its realization. In this work we consider a 2 × 2 Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) RoF system at 60 GHz. This system is based on Spatial Diversity (SD) which increases reliability (decreases probability of error) and Spatial Multiplexing (SMX) which increases data rate, but not necessarily reliability. The 60 GHz MIMO channel model employed in this work based on a lot of measured data and statistical analysis named Triple-S and Valenzuela (TSV) model. To the authors best knowledge; it is the first time that this type of TSV channel model has been employed for 60 GHz MIMO-RoF system. We have evaluated and compared the performance of this system according to the diversity technique, modulation schemes, and channel coding rate for Line-Of-Sight (LOS) desktop environment. The SMX coded is proposed as an intermediate system to improve the Signal to Noise Ratio (SNR) and the data rate. The resulting 2 × 2 MIMO-OFDM SMX system achieves a higher data rate up to 70 Gb/s with 64QAM and Forward Error Correction (FEC) limit of 10-3 over 25-km fiber transmission followed by 3-m wireless transmission using 7 GHz bandwidth of millimeter wave band.

Data-aided adaptive weighted channel equalizer for coherent optical OFDM.

PubMed

Mousa-Pasandi, Mohammad E; Plant, David V

2010-02-15

We report an adaptive weighted channel equalizer (AWCE) for orthogonal frequency division multiplexing (OFDM) and study its performance for long-haul coherent optical OFDM (CO-OFDM) transmission systems. This equalizer updates the equalization parameters on a symbol-by-symbol basis thus can track slight drifts of the optical channel. This is suitable to combat polarization mode dispersion (PMD) degradation while increasing the periodicity of pilot symbols which can be translated into a significant overhead reduction. Furthermore, AWCE can increase the precision of RF-pilot enabled phase noise estimation in the presence of noise, using data-aided phase noise estimation. Simulation results corroborate the capability of AWCE in both overhead reduction and improving the quality of the phase noise compensation (PNC).

Experimental research of adaptive OFDM and OCT precoding with a high SE for VLLC system

NASA Astrophysics Data System (ADS)

Liu, Shuang-ao; He, Jing; Chen, Qinghui; Deng, Rui; Zhou, Zhihua; Chen, Shenghai; Chen, Lin

2017-09-01

In this paper, an adaptive orthogonal frequency division multiplexing (OFDM) modulation scheme with 128/64/32/16-quadrature amplitude modulation (QAM) and orthogonal circulant matrix transform (OCT) precoding is proposed and experimentally demonstrated for a visible laser light communication (VLLC) system with a cost-effective 450-nm blue-light laser diode (LD). The performance of OCT precoding is compared with conventional the adaptive Discrete Fourier Transform-spread (DFT-spread) OFDM scheme, 32 QAM OCT precoding OFDM scheme, 64 QAM OCT precoding OFDM scheme and adaptive OCT precoding OFDM scheme. The experimental results show that OCT precoding can achieve a relatively flat signal-to-noise ratio (SNR) curve, and it can provide performance improvement in bit error rate (BER). Furthermore, the BER of the proposed OFDM signal with a raw bit rate 5.04 Gb/s after 5-m free space transmission is less than 20% of soft-decision forward error correlation (SD-FEC) threshold of 2.4 × 10-2, and the spectral efficiency (SE) of 4.2 bit/s/Hz can be successfully achieved.

Performance of adaptive DD-OFDM multicore fiber links and its relation with intercore crosstalk.

PubMed

Alves, Tiago M F; Luís, Ruben S; Puttnam, Benjamin J; Cartaxo, Adolfo V T; Awaji, Yoshinari; Wada, Naoya

2017-07-10

Adaptive direct-detection (DD) orthogonal frequency-division multiplexing (OFDM) is proposed to guarantee signal quality over time in weakly-coupled homogenous multicore fiber (MCFs) links impaired by stochastic intercore crosstalk (ICXT). For the first time, the received electrical power of the ICXT and the performance of the adaptive DD-OFDM MCF link are experimentally monitored quasi-simultaneously over a 210 hour period. Experimental results show that the time evolution of the error vector magnitude due to the ICXT can be suitably estimated from the normalized power of the detected crosstalk. The detected crosstalk results from the beating between the carrier in the test core and ICXT originating from the carrier and modulated signal from interfering core. The results show that the operation of DD-OFDM systems employing fixed modulation can be severely impaired by the presence of ICXT that may unpredictable vary in both power and frequency. The system may suffer from deleterious impact of moderate ICXT levels over a time duration of several hours or from peak ICXT levels occurring over a number of minutes. Such power fluctuations can lead to large variations in bit error ratio (BER) for static modulation schemes. Here, we show that BER fluctuations may be minimized by the use of adaptive modulation techniques and that in particular, the adaptive OFDM is a viable solution to guarantee link quality in MCF-based systems. An experimental model of an adaptive DD-OFDM MCF link shows an average throughput of 12 Gb/s that represents a reduction of only 9% compared to the maximum throughput measured without ICXT and an improvement of 23% relative to throughput obtained with static modulation.

Image Transmission through OFDM System under the Influence of AWGN Channel

NASA Astrophysics Data System (ADS)

Krishna, Dharavathu; Anuradha, M. S., Dr.

2017-08-01

OFDM system is one among the modern techniques which is most abundantly used in next generation wireless communication networks for transmitting many forms of digital data in efficient manner than compared with other existing traditional techniques. In this paper, one such kind of a digital data corresponding to a two dimensional (2D) gray-scale image is used to evaluate the functionality and overall performance of an OFDM system under the influence of modeled AWGN channel in MATLAB simulation environment. Within the OFDM system, different configurations of notable modulation techniques such as M-PSK and M-QAM are considered for evaluation of the system and necessary valid conclusions are made from the comparison of several observed MATLAB simulation results.

A hybrid CATV/16-QAM-OFDM visible laser light communication system

NASA Astrophysics Data System (ADS)

Lin, Chun-Yu; Li, Chung-Yi; Lu, Hai-Han; Chen, Chia-Yi; Jhang, Tai-Wei; Ruan, Sheng-Siang; Wu, Kuan-Hung

2014-10-01

A visible laser light communication (VLLC) system employing a vertical cavity surface emitting laser and spatial light modulator with hybrid CATV/16-QAM-OFDM modulating signals over a 5 m free-space link is proposed and demonstrated. With the assistance of a push-pull scheme, low-noise amplifier, and equalizer, good performances of composite second-order and composite triple beat are obtained, accompanied by an acceptable carrier-to-noise ratio performance for a CATV signal, and a low bit error rate value and clear constellation map are achieved for a 16-QAM-OFDM signal. Such a hybrid CATV/16-QAM-OFDM VLLC system would be attractive for providing services including CATV, Internet and telecommunication services.

Nonlinear impairment compensation for DFT-S OFDM signal transmission with directly modulated laser and direct detection

NASA Astrophysics Data System (ADS)

Gou, Pengqi; Wang, Kaihui; Qin, Chaoyi; Yu, Jianjun

2017-03-01

We experimentally demonstrate a 16-ary quadrature amplitude modulation (16QAM) DFT-spread optical orthogonal frequency division multiplexing (OFDM) transmission system utilizing a cost-effective directly modulated laser (DML) and direct detection. For 20-Gbaud 16QAM-OFDM signal, with the aid of nonlinear equalization (NLE) algorithm, we respectively provide 6.2-dB and 5.2-dB receiver sensitivity improvement under the hard-decision forward-error-correction (HD-FEC) threshold of 3.8×10-3 for the back-to-back (BTB) case and after transmission over 10-km standard single mode fiber (SSMF) case, related to only adopt post-equalization scheme. To our knowledge, this is the first time to use dynamic nonlinear equalizer (NLE) based on the summation of the square of the difference between samples in one IM/DD OFDM system with DML to mitigate nonlinear distortion.

Optimization of coherent optical OFDM transmitter using DP-IQ modulator with nonlinear response

NASA Astrophysics Data System (ADS)

Chang, Sun Hyok; Kang, Hun-Sik; Moon, Sang-Rok; Lee, Joon Ki

2016-07-01

In this paper, we investigate the performance of dual polarization orthogonal frequency division multiplexing (DP-OFDM) signal generation when the signal is generated by a DP-IQ optical modulator. The DP-IQ optical modulator is made of four parallel Mach-Zehnder modulators (MZMs) which have nonlinear responses and limited extinction ratios. We analyze the effects of the MZM in the DP-OFDM signal generation by numerical simulation. The operating conditions of the DP-IQ modulator are optimized to have the best performance of the DP-OFDM signal.

Pilot self-coding applied in optical OFDM systems

NASA Astrophysics Data System (ADS)

Li, Changping; Yi, Ying; Lee, Kyesan

2015-04-01

This paper studies the frequency offset correction technique which can be applied in optical OFDM systems. Through theoretical analysis and computer simulations, we can observe that our proposed scheme named pilot self-coding (PSC) has a distinct influence for rectifying the frequency offset, which could mitigate the OFDM performance deterioration because of inter-carrier interference and common phase error. The main approach is to assign a pilot subcarrier before data subcarriers and copy this subcarrier sequence to the symmetric side. The simulation results verify that our proposed PSC is indeed effective against the high degree of frequency offset.

Phase Noise Influence in Long-range Coherent Optical OFDM Systems with Delay Detection, IFFT Multiplexing and FFT Demodulation

NASA Astrophysics Data System (ADS)

Jacobsen, Gunnar; Xu, Tianhua; Popov, Sergei; Sergeyev, Sergey; Zhang, Yimo

2012-12-01

We present a study of the influence of dispersion induced phase noise for CO-OFDM systems using FFT multiplexing/IFFT demultiplexing techniques (software based). The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) including - for the first time to our knowledge - in explicit form the effect of equalization enhanced phase noise (EEPN). This, in turns, leads to an analytic BER specification. Numerical results focus on a CO-OFDM system with 10-25 GS/s QPSK channel modulation. A worst case constellation configuration is identified for the phase noise influence and the resulting BER is compared to the BER of a conventional single channel QPSK system with the same capacity as the CO-OFDM implementation. Results are evaluated as a function of transmission distance. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. For a total capacity of 400 (1000) Gbit/s, the transmission distance to have the BER < 10-2 for the worst case CO-OFDM design is less than 800 and 460 km, respectively, whereas for a single channel QPSK system it is less than 1400 and 560 km.

Variable length adjacent partitioning for PTS based PAPR reduction of OFDM signal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibraheem, Zeyid T.; Rahman, Md. Mijanur; Yaakob, S. N.

2015-05-15

Peak-to-Average power ratio (PAPR) is a major drawback in OFDM communication. It leads the power amplifier into nonlinear region operation resulting into loss of data integrity. As such, there is a strong motivation to find techniques to reduce PAPR. Partial Transmit Sequence (PTS) is an attractive scheme for this purpose. Judicious partitioning the OFDM data frame into disjoint subsets is a pivotal component of any PTS scheme. Out of the existing partitioning techniques, adjacent partitioning is characterized by an attractive trade-off between cost and performance. With an aim of determining effects of length variability of adjacent partitions, we performed anmore » investigation into the performances of a variable length adjacent partitioning (VL-AP) and fixed length adjacent partitioning in comparison with other partitioning schemes such as pseudorandom partitioning. Simulation results with different modulation and partitioning scenarios showed that fixed length adjacent partition had better performance compared to variable length adjacent partitioning. As expected, simulation results showed a slightly better performance of pseudorandom partitioning technique compared to fixed and variable adjacent partitioning schemes. However, as the pseudorandom technique incurs high computational complexities, adjacent partitioning schemes were still seen as favorable candidates for PAPR reduction.« less

Abatement of PAPR for ACO-OFDM deployed in VLC systems by frequency modulation of the baseband signal forming a constant envelope

NASA Astrophysics Data System (ADS)

Kumar Singh, Vinay; Dalal, U. D.

2017-06-01

To inhibit the effect of non-linearity of the LEDs leading to a significant increase in the peak to average power ratio (PAPR) of the OFDM signals in the Visible light communication (VLC) we propose a frequency modulated constant envelope OFDM (FM CE-OFDM) technique. The abrupt amplitude variations in the OFDM signal are frequency modulated before being applied to the LED for electro-optical conversion resulting in a constant envelope signal. The LED is maintained in the linear region of operation by this constant envelope signal at sufficient DC bias. The proposed technique reduces the PAPR to the least possible value ≈0 dB. We theoretically analyze and perform numerical simulations to assess the enhancement of the proposed system. The optimal modulation index is found to be 0.3. The metrics pertaining to the evaluation of the phase discontinuity is derived and is found to be lesser for the FM CE-OFDM as compared to the phase modulated (PM) CE-OFDM. The receiver sensitivity is improved by 1.6 dB for a transmission distance of 2 m for the FM CE-OFDM as compared to the PM CE-OFDM at the FEC threshold. We compare the BER performance of the ideal OFDM (without the non linearity of LED), power back-off OFDM, PM CE-OFDM and FM CE-OFDM in an optical wireless channel (OWC) scenario. The FM CE-OFDM has an improvement of 2.1 dB SNR at the FEC threshold as compared to the PM CE-OFDM. It also shows an improvement of 11 dB when compared with the power back-off technique used in the VLC systems for 10 dB power back-off.

Performance Investigation of FSO-OFDM Communication Systems under the Heavy Rain Weather

NASA Astrophysics Data System (ADS)

Rashidi, Florence; He, Jing; Chen, Lin

2017-12-01

The challenge in the free-space optical (FSO) communication is the propagation of optical signal through different atmospheric conditions such as rain, snow and fog. In this paper, an orthogonal frequency-division multiplexing technique (OFDM) is proposed in the FSO communication system. Meanwhile, considering the rain attenuation models based on Marshal & Palmer and Carbonneau models, the performance of FSO communication system based on the OFDM is evaluated under the heavy-rain condition in Changsha, China. The simulation results show that, under a heavy-rainfall condition of 106.18 mm/h, with an attenuation factor of 7 dB/km based on the Marshal & Palmer model, the bit rate of 2.5 and 4.0 Gbps data can be transmitted over the FSO channels of 1.6 and 1.3 km, respectively, and the bit error rate of less than 1E - 4 can be achieved. In addition, the effect on rain attenuation over the FSO communication system based on the Marshal & Palmer model is less than that of the Carbonneau model.

The application of LDPC code in MIMO-OFDM system

NASA Astrophysics Data System (ADS)

Liu, Ruian; Zeng, Beibei; Chen, Tingting; Liu, Nan; Yin, Ninghao

2018-03-01

The combination of MIMO and OFDM technology has become one of the key technologies of the fourth generation mobile communication., which can overcome the frequency selective fading of wireless channel, increase the system capacity and improve the frequency utilization. Error correcting coding introduced into the system can further improve its performance. LDPC (low density parity check) code is a kind of error correcting code which can improve system reliability and anti-interference ability, and the decoding is simple and easy to operate. This paper mainly discusses the application of LDPC code in MIMO-OFDM system.

MIMO-OFDM System's Performance Using LDPC Codes for a Mobile Robot

NASA Astrophysics Data System (ADS)

Daoud, Omar; Alani, Omar

This work deals with the performance of a Sniffer Mobile Robot (SNFRbot)-based spatial multiplexed wireless Orthogonal Frequency Division Multiplexing (OFDM) transmission technology. The use of Multi-Input Multi-Output (MIMO)-OFDM technology increases the wireless transmission rate without increasing transmission power or bandwidth. A generic multilayer architecture of the SNFRbot is proposed with low power and low cost. Some experimental results are presented and show the efficiency of sniffing deadly gazes, sensing high temperatures and sending live videos of the monitored situation. Moreover, simulation results show the achieved performance by tackling the Peak-to-Average Power Ratio (PAPR) problem of the used technology using Low Density Parity Check (LDPC) codes; and the effect of combating the PAPR on the bit error rate (BER) and the signal to noise ratio (SNR) over a Doppler spread channel.

LDPC coded OFDM over the atmospheric turbulence channel.

PubMed

Djordjevic, Ivan B; Vasic, Bane; Neifeld, Mark A

2007-05-14

Low-density parity-check (LDPC) coded optical orthogonal frequency division multiplexing (OFDM) is shown to significantly outperform LDPC coded on-off keying (OOK) over the atmospheric turbulence channel in terms of both coding gain and spectral efficiency. In the regime of strong turbulence at a bit-error rate of 10(-5), the coding gain improvement of the LDPC coded single-side band unclipped-OFDM system with 64 sub-carriers is larger than the coding gain of the LDPC coded OOK system by 20.2 dB for quadrature-phase-shift keying (QPSK) and by 23.4 dB for binary-phase-shift keying (BPSK).

All-optical virtual private network system in OFDM based long-reach PON using RSOA re-modulation technique

NASA Astrophysics Data System (ADS)

Kim, Chang-Hun; Jung, Sang-Min; Kang, Su-Min; Han, Sang-Kook

2015-01-01

We propose an all-optical virtual private network (VPN) system in an orthogonal frequency division multiplexing (OFDM) based long reach PON (LR-PON). In the optical access network field, technologies based on fundamental upstream (U/S) and downstream (D/S) have been actively researched to accommodate explosion of data capacity. However, data transmission among the end users which is arisen from cloud computing, file-sharing and interactive game takes a large weight inside of internet traffic. Moreover, this traffic is predicted to increase more if Internet of Things (IoT) services are activated. In a conventional PON, VPN data is transmitted through ONU-OLT-ONU via U/S and D/S carriers. It leads to waste of bandwidth and energy due to O-E-O conversion in the OLT and round-trip propagation between OLT and remote node (RN). Also, it causes inevitable load to the OLT for electrical buffer, scheduling and routing. The network inefficiency becomes more critical in a LR-PON which has been researched as an effort to reduce CAPEX and OPEX through metro-access consolidation. In the proposed system, the VPN data is separated from conventional U/S and re-modulated on the D/S carrier by using RSOA in the ONUs to avoid bandwidth consumption of U/S and D/S unlike in previously reported system. Moreover, the transmitted VPN data is re-directed to the ONUs by wavelength selective reflector device in the RN without passing through the OLT. Experimental demonstration for the VPN communication system in an OFDM based LR-PON has been verified.

Performance Analysis of OFDM in Frequency Selective, Slowly Fading Nakagami Channels

DTIC Science & Technology

2001-12-01

starting with some background, then moving into how to generate an OFDM signal, and finally discussing the implementation of OFDM using one specific...application, the IEEE 802.11a standard. The application of some more general communications concepts such as the discrete Fourier transform (DFT...provide orthogonal cover to the sub-carriers, some may argue that the FFT’s complexity makes up for the loss of equalization complexity, however, as Ch

A joint swarm intelligence algorithm for multi-user detection in MIMO-OFDM system

NASA Astrophysics Data System (ADS)

Hu, Fengye; Du, Dakun; Zhang, Peng; Wang, Zhijun

2014-11-01

In the multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system, traditional multi-user detection (MUD) algorithms that usually used to suppress multiple access interference are difficult to balance system detection performance and the complexity of the algorithm. To solve this problem, this paper proposes a joint swarm intelligence algorithm called Ant Colony and Particle Swarm Optimisation (AC-PSO) by integrating particle swarm optimisation (PSO) and ant colony optimisation (ACO) algorithms. According to simulation results, it has been shown that, with low computational complexity, the MUD for the MIMO-OFDM system based on AC-PSO algorithm gains comparable MUD performance with maximum likelihood algorithm. Thus, the proposed AC-PSO algorithm provides a satisfactory trade-off between computational complexity and detection performance.

Performance Bounds on Micro-Doppler Estimation and Adaptive Waveform Design Using OFDM Signals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Satyabrata; Barhen, Jacob; Glover, Charles Wayne

We analyze the performance of a wideband orthogonal frequency division multiplexing (OFDM) signal in estimating the micro-Doppler frequency of a target having multiple rotating scatterers (e.g., rotor blades of a helicopter, propellers of a submarine). The presence of rotating scatterers introduces Doppler frequency modulation in the received signal by generating sidebands about the transmitted frequencies. This is called the micro-Doppler effects. The use of a frequency-diverse OFDM signal in this context enables us to independently analyze the micro-Doppler characteristics with respect to a set of orthogonal subcarrier frequencies. Therefore, to characterize the accuracy of micro-Doppler frequency estimation, we compute themore » Cram er-Rao Bound (CRB) on the angular-velocity estimate of the target while considering the scatterer responses as deterministic but unknown nuisance parameters. Additionally, to improve the accuracy of the estimation procedure, we formulate and solve an optimization problem by minimizing the CRB on the angular-velocity estimate with respect to the transmitting OFDM spectral coefficients. We present several numerical examples to demonstrate the CRB variations at different values of the signal-to-noise ratio (SNR) and the number of OFDM subcarriers. The CRB values not only decrease with the increase in the SNR values, but also reduce as we increase the number of subcarriers implying the significance of frequency-diverse OFDM waveforms. The improvement in estimation accuracy due to the adaptive waveform design is also numerically analyzed. Interestingly, we find that the relative decrease in the CRBs on the angular-velocity estimate is more pronounced for larger number of OFDM subcarriers.« less

Receiver sensitivity improvement in spectrally-efficient guard-band twin-SSB-OFDM using an optical IQ modulator

NASA Astrophysics Data System (ADS)

Chen, Ming; Peng, Miao; Zhou, Hui; Zheng, Zhiwei; Tang, Xionggui; Maivan, Lap

2017-12-01

To further improve receiver sensitivity of spectrally-efficient guard-band direct-detection optical orthogonal frequency-division multiplexing (OFDM) with twin single-side-band (SSB) modulation technique, an optical IQ modulator (IQM) is employed to optimize optical carrier-to-signal power ratio (CSPR). The CSPRs for the guard-band twin-SSB-OFDM signal generated by using dual-drive Mach-Zehnder modulator (DD-MZM) and optical IQM are theoretically analyzed and supported by simulations. The optimal CSPR for the two types of guard-band twin-SSB-OFDM are identified. The simulations exhibit that the error vector magnitude (EVM) performance of the IQM-enabled guard-band twin-SSB-OFDM is improved by more than 4-dB compared to that of the twin-SSB-OFDM enabled by DD-MZM after 80-km single-mode fiber (SMF) transmission. In addition, more than 3-dB and 10 dB receiver sensitivity improvements in terms of received optical power (ROP) and optical signal-to-noise ratio (OSNR) are also achieved, respectively.

Analysis of different sub-carrier allocation of M-ary QAM-OFDM downlink in RoF system

NASA Astrophysics Data System (ADS)

Shao, Yu-feng; Chen, Luo; Wang, An-rong; Zhao, Yun-jie; Long, Ying; Ji, Xing-ping

2018-01-01

In this paper, the performance of a 60 GHz radio over fiber (RoF) system with 4/16/64 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) downstream signals is studied. Delivery of 10 Gbit/s M-ary QAM (MQAM) OFDM signals through the 20-km-long single-mode fiber (SMF) is complicated in terms of intensity modulation and direct detection (IM/DD). Using self-homodyne method, the beating of two independent light waves generating the millimeter-wave at the photodetector can be down-converted to baseband in the electrical domain. Meanwhile, three kinds of sub-carrier arrangement schemes are compared and discussed, and the simulation results show that lower peak-to-average power ratio ( PAPR) can be obtained adopting the adjacent scheme. At bit error rate ( BER) of 10-3, the receiver sensitivity using 4QAM-OFDM sub-carrier signal is almost enhanced by 4 dB and 9 dB compared with those of 16QAM-OFDM signal and 64QAM-OFDM signal.

Power amplifier linearization technique with IQ imbalance and crosstalk compensation for broadband MIMO-OFDM transmitters

NASA Astrophysics Data System (ADS)

Gregorio, Fernando; Cousseau, Juan; Werner, Stefan; Riihonen, Taneli; Wichman, Risto

2011-12-01

The design of predistortion techniques for broadband multiple input multiple output-OFDM (MIMO-OFDM) systems raises several implementation challenges. First, the large bandwidth of the OFDM signal requires the introduction of memory effects in the PD model. In addition, it is usual to consider an imbalanced in-phase and quadrature (IQ) modulator to translate the predistorted baseband signal to RF. Furthermore, the coupling effects, which occur when the MIMO paths are implemented in the same reduced size chipset, cannot be avoided in MIMO transceivers structures. This study proposes a MIMO-PD system that linearizes the power amplifier response and compensates nonlinear crosstalk and IQ imbalance effects for each branch of the multiantenna system. Efficient recursive algorithms are presented to estimate the complete MIMO-PD coefficients. The algorithms avoid the high computational complexity in previous solutions based on least squares estimation. The performance of the proposed MIMO-PD structure is validated by simulations using a two-transmitter antenna MIMO system. Error vector magnitude and adjacent channel power ratio are evaluated showing significant improvement compared with conventional MIMO-PD systems.

A time and frequency synchronization method for CO-OFDM based on CMA equalizers

NASA Astrophysics Data System (ADS)

Ren, Kaixuan; Li, Xiang; Huang, Tianye; Cheng, Zhuo; Chen, Bingwei; Wu, Xu; Fu, Songnian; Ping, Perry Shum

2018-06-01

In this paper, an efficient time and frequency synchronization method based on a new training symbol structure is proposed for polarization division multiplexing (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. The coarse timing synchronization is achieved by exploiting the correlation property of the first training symbol, and the fine timing synchronization is accomplished by using the time-domain symmetric conjugate of the second training symbol. Furthermore, based on these training symbols, a constant modulus algorithm (CMA) is proposed for carrier frequency offset (CFO) estimation. Theoretical analysis and simulation results indicate that the algorithm has the advantages of robustness to poor optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD). The frequency offset estimation range can achieve [ -Nsc/2 ΔfN , + Nsc/2 ΔfN ] GHz with the mean normalized estimation error below 12 × 10-3 even under the condition of OSNR as low as 10 dB.

622-Mbps Orthogonal Frequency Division Multiplexing (OFDM) Digital Modem Implemented

NASA Technical Reports Server (NTRS)

Kifle, Muli; Bizon, Thomas P.; Nguyen, Nam T.; Tran, Quang K.; Mortensen, Dale J.

2002-01-01

Future generation space communications systems feature significantly higher data rates and relatively smaller frequency spectrum allocations than systems currently deployed. This requires the application of bandwidth- and power-efficient signal transmission techniques. There are a number of approaches to implementing such techniques, including analog, digital, mixed-signal, single-channel, or multichannel systems. In general, the digital implementations offer more advantages; however, a fully digital implementation is very difficult because of the very high clock speeds required. Multichannel techniques are used to reduce the sampling rate. One such technique, multicarrier modulation, divides the data into a number of low-rate channels that are stacked in frequency. Orthogonal frequency division multiplexing (OFDM), a form of multicarrier modulation, is being proposed for numerous systems, including mobile wireless and digital subscriber link communication systems. In response to this challenge, NASA Glenn Research Center's Communication Technology Division has developed an OFDM digital modem (modulator and demodulator) with an aggregate information throughput of 622 Mbps. The basic OFDM waveform is constructed by dividing an incoming data stream into four channels, each using either 16- ary quadrature amplitude modulation (16-QAM) or 8-phase shift keying (8-PSK). An efficient implementation for an OFDM architecture is being achieved using the combination of a discrete Fourier transform (DFT) at the transmitter to digitally stack the individual carriers, inverse DFT at the receiver to perform the frequency translations, and a polyphase filter to facilitate the pulse shaping.

Experimental demonstration of a 16.9 Gb/s link for coherent OFDM PON robust to frequency offset and timing error

NASA Astrophysics Data System (ADS)

Ma, Qian; Liu, Yu; Xiang, Yuanjiang

2018-07-01

Due to its merits of flexible bandwidth allocation and robustness towards fiber transmission impairments, coherent optical orthogonal frequency division multiplexing (CO-OFDM) technology draws a lot of attention for passive optical networks (PON). However, a CO-OFDM system is vulnerable to frequency offsets between modulated optical signals and optical local oscillators (OLO). This is particularly serious for low cost PONs where low cost lasers are used. Thus, it is of great interest to develop efficient algorithms for frequency synchronization in CO-OFDM systems. Usually frequency synchronization proposed in CO-OFDM systems are done by detecting the phase shift in time domain. In such a way, there is a trade-off between estimation accuracy and range. Considering that the integer frequency offset (IFO) contributes to the major frequency offset, a more efficient method to estimate IFO is of demand. By detecting IFO induced circular channel rotation (CCR), the frequency offset can be directly estimated after fast Fourier transforming (FFT). In this paper, circular acquisition offset frequency and timing synchronization (CAO-FTS) scheme is proposed. A specially-designed frequency domain pseudo noise (PN) sequence is used for CCR detection and timing synchronization. Full-range frequency offset compensation and non-plateau timing synchronization are experimentally demonstrated in presence of fiber dispersion. Based on CAO-FTS, 16.9 Gb/s CO-OFDM signal is successfully delivered over a span of 80-km single mode fiber.

Security scheme in IMDD-OFDM-PON system with the chaotic pilot interval and scrambling

NASA Astrophysics Data System (ADS)

Chen, Qianghua; Bi, Meihua; Fu, Xiaosong; Lu, Yang; Zeng, Ran; Yang, Guowei; Yang, Xuelin; Xiao, Shilin

2018-01-01

In this paper, a random chaotic pilot interval and permutations scheme without any requirement of redundant sideband information is firstly proposed for the physical layer security-enhanced intensity modulation direct detection orthogonal frequency division multiplexing passive optical network (IMDD-OFDM-PON) system. With the help of the position feature of inserting the pilot, a simple logistic chaos map is used to generate the random pilot interval and scramble the chaotic subcarrier allocation of each column pilot data for improving the physical layer confidentiality. Due to the dynamic chaotic permutations of pilot data, the enhanced key space of ∼103303 is achieved in OFDM-PON. Moreover, the transmission experiment of 10-Gb/s 16-QAM encrypted OFDM data is successfully demonstrated over 20-km single-mode fiber, which indicates that the proposed scheme not only improves the system security, but also can achieve the same performance as in the common IMDD-OFDM-PON system without encryption scheme.

All-optical OFDM network coding scheme for all-optical virtual private communication in PON

NASA Astrophysics Data System (ADS)

Li, Lijun; Gu, Rentao; Ji, Yuefeng; Bai, Lin; Huang, Zhitong

2014-03-01

A novel optical orthogonal frequency division multiplexing (OFDM) network coding scheme is proposed over passive optical network (PON) system. The proposed scheme for all-optical virtual private network (VPN) does not only improve transmission efficiency, but also realize full-duplex communication mode in a single fiber. Compared with the traditional all-optical VPN architectures, the all-optical OFDM network coding scheme can support higher speed, more flexible bandwidth allocation, and higher spectrum efficiency. In order to reduce the difficulty of alignment for encoding operation between inter-communication traffic, the width of OFDM subcarrier pulse is stretched in our proposed scheme. The feasibility of all-optical OFDM network coding scheme for VPN is verified, and the relevant simulation results show that the full-duplex inter-communication traffic stream can be transmitted successfully. Furthermore, the tolerance of misalignment existing in inter-ONUs traffic is investigated and analyzed for all-optical encoding operation, and the difficulty of pulse alignment is proved to be lower.

Utilization of multi-band OFDM modulation to increase traffic rate of phosphor-LED wireless VLC.

PubMed

Yeh, Chien-Hung; Chen, Hsing-Yu; Chow, Chi-Wai; Liu, Yen-Liang

2015-01-26

To increase the traffic rate in phosphor-LED visible light communication (VLC), a multi-band orthogonal frequency division multiplexed (OFDM) modulation is first proposed and demonstrated. In the measurement, we do not utilize optical blue filter to increase modulation bandwidth of phosphor-LED in the VLC system. In this proposed scheme, different bands of OFDM signals are applied to different LED chips in a LED lamp, this can avoid the power fading and nonlinearity issue by applying the same OFDM signal to all the LED chips in a LED lamp. Here, the maximum increase percentages of traffic rates are 41.1%, 17.8% and 17.8% under received illuminations of 200, 500 and 1000 Lux, respectively, when the proposed three-band OFDM modulation is used in the VLC system. In addition, the analysis and verification by experiments are also performed.

450-nm GaN laser diode enables high-speed visible light communication with 9-Gbps QAM-OFDM.

PubMed

Chi, Yu-Chieh; Hsieh, Dan-Hua; Tsai, Cheng-Ting; Chen, Hsiang-Yu; Kuo, Hao-Chung; Lin, Gong-Ru

2015-05-18

A TO-38-can packaged Gallium nitride (GaN) blue laser diode (LD) based free-space visible light communication (VLC) with 64-quadrature amplitude modulation (QAM) and 32-subcarrier orthogonal frequency division multiplexing (OFDM) transmission at 9 Gbps is preliminarily demonstrated over a 5-m free-space link. The 3-dB analog modulation bandwidth of the TO-38-can packaged GaN blue LD biased at 65 mA and controlled at 25°C is only 900 MHz, which can be extended to 1.5 GHz for OFDM encoding after throughput intensity optimization. When delivering the 4-Gbps 16-QAM OFDM data within 1-GHz bandwidth, the error vector magnitude (EVM), signal-to-noise ratio (SNR) and bit-error-rate (BER) of the received data are observed as 8.4%, 22.4 dB and 3.5 × 10(-8), respectively. By increasing the encoded bandwidth to 1.5 GHz, the TO-38-can packaged GaN blue LD enlarges its transmission capacity to 6 Gbps but degrades its transmitted BER to 1.7 × 10(-3). The same transmission capacity of 6 Gbps can also be achieved with a BER of 1 × 10(-6) by encoding 64-QAM OFDM data within 1-GHz bandwidth. Using the 1.5-GHz full bandwidth of the TO-38-can packaged GaN blue LD provides the 64-QAM OFDM transmission up to 9 Gbps, which successfully delivers data with an EVM of 5.1%, an SNR of 22 dB and a BER of 3.6 × 10(-3) passed the forward error correction (FEC) criterion.

Chaotic reconfigurable ZCMT precoder for OFDM data encryption and PAPR reduction

NASA Astrophysics Data System (ADS)

Chen, Han; Yang, Xuelin; Hu, Weisheng

2017-12-01

A secure orthogonal frequency division multiplexing (OFDM) transmission scheme precoded by chaotic Zadoff-Chu matrix transform (ZCMT) is proposed and demonstrated. It is proved that the reconfigurable ZCMT matrices after row/column permutations can be applied as an alternative precoder for peak-to-average power ratio (PAPR) reduction. The permutations and the reconfigurable parameters in ZCMT matrix are generated by a hyper digital chaos, in which a huge key space of ∼ 10800 is created for physical-layer OFDM data encryption. An encrypted data transmission of 8.9 Gb/s optical OFDM signals is successfully demonstrated over 20 km standard single-mode fiber (SSMF) for 16-QAM. The BER performance of the encrypted signals is improved by ∼ 2 dB (BER@ 10-3), which is mainly attributed to the effective reduction of PAPR via chaotic ZCMT precoding. Moreover, the chaotic ZCMT precoding scheme requires no sideband information, thus the spectrum efficiency is enhanced during transmission.

Investigation of Doppler Effects on high mobility OFDM-MIMO systems with the support of High Altitude Platforms (HAPs)

NASA Astrophysics Data System (ADS)

Mohammed, H. A.; Sibley, M. J. N.; Mather, P. J.

2012-05-01

The merging of Orthogonal Frequency Division Multiplexing (OFDM) with Multiple-input multiple-output (MIMO) is a promising mobile air interface solution for next generation wireless local area networks (WLANs) and 4G mobile cellular wireless systems. This paper details the design of a highly robust and efficient OFDM-MIMO system to support permanent accessibility and higher data rates to users moving at high speeds, such as users travelling on trains. It has high relevance for next generation wireless local area networks (WLANs) and 4G mobile cellular wireless systems. The paper begins with a comprehensive literature review focused on both technologies. This is followed by the modelling of the OFDM-MIMO physical layer based on Simulink/Matlab that takes into consideration high vehicular mobility. Then the entire system is simulated and analysed under different encoding and channel estimation algorithms. The use of High Altitude Platform system (HAPs) technology is considered and analysed.

Experimental demonstration of record high 19.125 Gb/s real-time end-to-end dual-band optical OFDM transmission over 25 km SMF in a simple EML-based IMDD system.

PubMed

Giddings, R P; Hugues-Salas, E; Tang, J M

2012-08-27

Record high 19.125 Gb/s real-time end-to-end dual-band optical OFDM (OOFDM) transmission is experimentally demonstrated, for the first time, in a simple electro-absorption modulated laser (EML)-based 25 km standard SMF system using intensity modulation and direct detection (IMDD). Adaptively modulated baseband (0-2GHz) and passband (6.125 ± 2GHz) OFDM RF sub-bands, supporting line rates of 10 Gb/s and 9.125 Gb/s respectively, are independently generated and detected with FPGA-based DSP clocked at only 100 MHz and DACs/ADCs operating at sampling speeds as low as 4GS/s. The two OFDM sub-bands are electrically frequency-division-multiplexed (FDM) for intensity modulation of a single optical carrier by an EML. To maximize and balance the signal transmission performance of each sub-band, on-line adaptive features and on-line performance monitoring is fully exploited to optimize key OOFDM transceiver and system parameters, which includes subcarrier characteristics within each individual OFDM sub-band, total and relative sub-band power as well as EML operating conditions. The achieved 19.125 Gb/s over 25 km SMF OOFDM transmission system has an optical power budget of 13.5 dB, and shows almost identical bit error rate (BER) performances for both the baseband and passband signals. In addition, experimental investigations also indicate that the maximum achievable transmission capacity of the present system is mainly determined by the EML frequency chirp-enhanced chromatic dispersion effect, and the passband BER performance is not affected by the two sub-band-induced intermixing effect, which, however, gives a 1.2dB optical power penalty to the baseband signal transmission.

A robust and scalable neuromorphic communication system by combining synaptic time multiplexing and MIMO-OFDM.

PubMed

Srinivasa, Narayan; Zhang, Deying; Grigorian, Beayna

2014-03-01

This paper describes a novel architecture for enabling robust and efficient neuromorphic communication. The architecture combines two concepts: 1) synaptic time multiplexing (STM) that trades space for speed of processing to create an intragroup communication approach that is firing rate independent and offers more flexibility in connectivity than cross-bar architectures and 2) a wired multiple input multiple output (MIMO) communication with orthogonal frequency division multiplexing (OFDM) techniques to enable a robust and efficient intergroup communication for neuromorphic systems. The MIMO-OFDM concept for the proposed architecture was analyzed by simulating large-scale spiking neural network architecture. Analysis shows that the neuromorphic system with MIMO-OFDM exhibits robust and efficient communication while operating in real time with a high bit rate. Through combining STM with MIMO-OFDM techniques, the resulting system offers a flexible and scalable connectivity as well as a power and area efficient solution for the implementation of very large-scale spiking neural architectures in hardware.

Novel toggle-rate based energy-efficient scheme for heavy load real-time IM-DD OFDM-PON with ONU LLID identification in time-domain using amplitude decision.

PubMed

Qin, Youxiang; Zhang, Junjie

2017-07-10

A novel low complexity and energy-efficient scheme by controlling the toggle-rate of ONU with time-domain amplitude identification is proposed for a heavy load downlink in an intensity-modulation and direct-detection orthogonal frequency division multiplexing passive optical network (IM-DD OFDM-PON). In a conventional OFDM-PON downlink, all ONUs have to perform demodulation for all the OFDM frames in a broadcast way no matter whether the frames are targeted to or not, which causes a huge energy waste. However, in our scheme, the optical network unit (ONU) logical link identifications (LLIDs) are inserted into each downlink OFDM frame in time-domain at the optical line terminal (OLT) side. At the ONU side, the LLID is obtained with a low complexity and high precision amplitude identification method. The ONU sets the toggle-rate of demodulation module to zero when the frames are not targeted to, which avoids unnecessary digital signal processing (DSP) energy consumption. Compared with the sleep-mode methods consisting of clock recovery and synchronization, toggle-rate shows its advantage in fast changing, which is more suitable for the heavy load scenarios. Moreover, for the first time to our knowledge, the characteristics of the proposed scheme are investigated in a real-time IM-DD OFDM system, which performs well at the received optical power as low as -21dBm. The experimental results show that 25.1% energy consumption can be saved in the receiver compared to the conventional configurations.

Experimental characterization of an all-optical wavelength converter of OFDM signals using two-mode injection-locking in a Fabry-Pérot laser.

PubMed

Dang, Juntao; Yi, Xingwen; Zhang, Jing; Ye, Taiping; Xu, Bo; Qiu, Kun

2016-07-25

While optical OFDM has been demonstrated for superior transmission performance, its analogue waveform in the time domain challenges many conventional all-optical wavelength converters (AOWC) that are needed for future flexible optical networks. There only exist a few reports on AOWC of OFDM signals, which are mainly based on the low-efficient four-wave mixing. In this paper, we propose an AOWC for OFDM signals by using two-mode injection-locking in a low-cost Fabry-Pérot laser. The control signal and the probe signal at a milliwatt power level are combined and injected into the FP laser. By a proper control, they can be injection-locked to two longitudinal modes in the FP laser and subsequently, the transmission of the probe signal is conditioned by the control signal. We conduct an experimental study on various aspects of this AOWC. Despite a vendor-specified electrical-to-optical (E/O) modulation bandwidth of 2.5 GHz, we find that the optical-to-optical (O/O) modulation bandwidth of AOWC is free from this limit and can be much wider. We examine the linear transfer curve of the AOWC by simply using the OFDM waveforms as the stimulus. The performance tolerance to the wavelength detuning and injected power ratio is also measured. The proposed AOWC can provide a linear transfer function from the control signal to the probe signal to support the random-fluctuated OFDM waveform. We also investigate the maximum capacity of the AOWC by using the adaptive bit-loading OFDM. Finally, we measure the power penalty after the AOWC at two different bit rates to show the tradeoff between the penalty and capacity.

Demodulation Algorithms for the Ofdm Signals in the Time- and Frequency-Scattering Channels

NASA Astrophysics Data System (ADS)

Bochkov, G. N.; Gorokhov, K. V.; Kolobkov, A. V.

2016-06-01

We consider a method based on the generalized maximum-likelihood rule for solving the problem of reception of the signals with orthogonal frequency division multiplexing of their harmonic components (OFDM signals) in the time- and frequency-scattering channels. The coherent and incoherent demodulators effectively using the time scattering due to the fast fading of the signal are developed. Using computer simulation, we performed comparative analysis of the proposed algorithms and well-known signal-reception algorithms with equalizers. The proposed symbolby-symbol detector with decision feedback and restriction of the number of searched variants is shown to have the best bit-error-rate performance. It is shown that under conditions of the limited accuracy of estimating the communication-channel parameters, the incoherent OFDMsignal detectors with differential phase-shift keying can ensure a better bit-error-rate performance compared with the coherent OFDM-signal detectors with absolute phase-shift keying.

CFO compensation method using optical feedback path for coherent optical OFDM system

NASA Astrophysics Data System (ADS)

Moon, Sang-Rok; Hwang, In-Ki; Kang, Hun-Sik; Chang, Sun Hyok; Lee, Seung-Woo; Lee, Joon Ki

2017-07-01

We investigate feasibility of carrier frequency offset (CFO) compensation method using optical feedback path for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Recently proposed CFO compensation algorithms provide wide CFO estimation range in electrical domain. However, their practical compensation range is limited by sampling rate of an analog-to-digital converter (ADC). This limitation has not drawn attention, since the ADC sampling rate was high enough comparing to the data bandwidth and CFO in the wireless OFDM system. For CO-OFDM, the limitation is becoming visible because of increased data bandwidth, laser instability (i.e. large CFO) and insufficient ADC sampling rate owing to high cost. To solve the problem and extend practical CFO compensation range, we propose a CFO compensation method having optical feedback path. By adding simple wavelength control for local oscillator, the practical CFO compensation range can be extended to the sampling frequency range. The feasibility of the proposed method is experimentally investigated.

OFDM-based broadband underwater wireless optical communication system using a compact blue LED

NASA Astrophysics Data System (ADS)

Xu, Jing; Kong, Meiwei; Lin, Aobo; Song, Yuhang; Yu, Xiangyu; Qu, Fengzhong; Han, Jun; Deng, Ning

2016-06-01

We propose and experimentally demonstrate an IM/DD-OFDM-based underwater wireless optical communication system. We investigate the dependence of its BER performance on the training symbol number as well as LED's bias voltage and driving voltage. With single compact blue LED and a low-cost PIN photodiode, we achieve net bit rates of 225.90 Mb/s at a BER of 1.54×10-3 using 16-QAM and 231.95 Mb/s at a BER of 3.28×10-3 using 32-QAM, respectively, over a 2-m air channel. Over a 2-m underwater channel, we achieve net bit rates of 161.36 Mb/s using 16-QAM, 156.31 Mb/s using 32-QAM, and 127.07 Mb/s using 64-QAM, respectively. The corresponding BERs are 2.5×10-3, 7.42×10-4, and 3.17×10-3, respectively, which are all below the FEC threshold.

Analysis of the Effects of Phase Noise and Frequency Offset in Orthogonal Frequency Division Multiplexing (OFDM) Systems

DTIC Science & Technology

2004-03-01

Data Communication , http://www.iec.org/, last accessed December 2003. 13. Klaus Witrisal, “Orthogonal Frequency Division Multiplexing (OFDM) for...http://ieeexplore.ieee.org, last accessed 26 February 2003. 12. The International Engineering Consortium, Web Forum Tutorials, OFDM for Mobile

Dual-LP11 mode 4×4 MIMO-OFDM transmission over a two-mode fiber.

PubMed

Al Amin, Abdullah; Li, An; Chen, Simin; Chen, Xi; Gao, Guanjun; Shieh, William

2011-08-15

We report successful transmission of dual-LP(11) mode (LP(11a) and LP(11b)), dual polarization coherent optical orthogonal frequency-division multiplexing (CO-OFDM) signals over two-mode fibers (TMF) using all-fiber mode converters. Mode converters based on mechanically induced long-period grating with better than 20 dB extinction ratios are realized and used for interfacing single-mode fiber transmitter and receivers to the TMF. We demonstrate that by using 4×4 MIMO-OFDM processing, the random coupling of the two LP(11) spatial modes can be successfully tracked and equalized with a one-tap frequency-domain equalizer. We achieve successful transmission of 35.3 Gb/s over 26-km two-mode fiber with less than 3 dB penalty. © 2011 Optical Society of America

Joint Symbol Timing and CFO Estimation for OFDM/OQAM Systems in Multipath Channels

NASA Astrophysics Data System (ADS)

Fusco, Tilde; Petrella, Angelo; Tanda, Mario

2009-12-01

The problem of data-aided synchronization for orthogonal frequency division multiplexing (OFDM) systems based on offset quadrature amplitude modulation (OQAM) in multipath channels is considered. In particular, the joint maximum-likelihood (ML) estimator for carrier-frequency offset (CFO), amplitudes, phases, and delays, exploiting a short known preamble, is derived. The ML estimators for phases and amplitudes are in closed form. Moreover, under the assumption that the CFO is sufficiently small, a closed form approximate ML (AML) CFO estimator is obtained. By exploiting the obtained closed form solutions a cost function whose peaks provide an estimate of the delays is derived. In particular, the symbol timing (i.e., the delay of the first multipath component) is obtained by considering the smallest estimated delay. The performance of the proposed joint AML estimator is assessed via computer simulations and compared with that achieved by the joint AML estimator designed for AWGN channel and that achieved by a previously derived joint estimator for OFDM systems.

Experimental demonstration of real-time adaptively modulated DDO-OFDM systems with a high spectral efficiency up to 5.76bit/s/Hz transmission over SMF links.

PubMed

Chen, Ming; He, Jing; Tang, Jin; Wu, Xian; Chen, Lin

2014-07-28

In this paper, a FPGAs-based real-time adaptively modulated 256/64/16QAM-encoded base-band OFDM transceiver with a high spectral efficiency up to 5.76bit/s/Hz is successfully developed, and experimentally demonstrated in a simple intensity-modulated direct-detection optical communication system. Experimental results show that it is feasible to transmit a raw signal bit rate of 7.19Gbps adaptively modulated real-time optical OFDM signal over 20km and 50km single mode fibers (SMFs). The performance comparison between real-time and off-line digital signal processing is performed, and the results show that there is a negligible power penalty. In addition, to obtain the best transmission performance, direct-current (DC) bias voltage for MZM and launch power into optical fiber links are explored in the real-time optical OFDM systems.

An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network.

PubMed

Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

2015-01-01

In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20-28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20-30%.

ML Frame Synchronization for OFDM Systems Using a Known Pilot and Cyclic Prefixes

NASA Astrophysics Data System (ADS)

Huh, Heon

Orthogonal frequency-division multiplexing (OFDM) is a popular air interface technology that is adopted as a standard modulation scheme for 4G communication systems owing to its excellent spectral efficiency. For OFDM systems, synchronization problems have received much attention along with peak-to-average power ratio (PAPR) reduction. In addition to frequency offset estimation, frame synchronization is a challenging problem that must be solved to achieve optimal system performance. In this paper, we present a maximum likelihood (ML) frame synchronizer for OFDM systems. The synchronizer exploits a synchronization word and cyclic prefixes together to improve the synchronization performance. Numerical results show that the performance of the proposed frame synchronizer is better than that of conventional schemes. The proposed synchronizer can be used as a reference for evaluating the performance of other suboptimal frame synchronizers. We also modify the proposed frame synchronizer to reduce the implementation complexity and propose a near-ML synchronizer for time-varying fading channels.

Proposal of ICI cancellation using opposite weightings on symmetric subcarrier pairs in CO-OFDM systems

NASA Astrophysics Data System (ADS)

Zhang, Jing; Chen, Xuemei; Deng, Mingliang; Zeng, Dengke; Yang, Heming; Qiu, Kun

2015-08-01

We propose a novel ICI cancellation using opposite weighting on symmetric subcarrier pairs to combat the linear phase noise of laser source and the nonlinear phase noise resulted from the fiber nonlinearity. We compare the proposed ICI cancellation scheme with conventional OFDM and the ICI self-cancellation at the same raw bit rate of 35.6 Gb/s. In simulations, the proposed ICI cancellation scheme shows better phase noise tolerance compared with conventional OFDM and has similar phase noise tolerance with the ICI self-cancellation. The laser linewidth is about 13 MHz at BER of 2 × 10-3 with ICI cancellation scheme while it is 5 MHz in conventional OFDM. We also study the nonlinearity tolerance and find that the proposed ICI cancellation scheme is better compared with the other two schemes which due to the first order nonlinearity mitigation. The launch power is 7 dBm for the proposed ICI cancellation scheme and its SNR improves by 4 dB or 3 dB compared with the ICI self-cancellation or conventional OFDM at BER of 1.1 × 10-3, respectively.

MIMO-OFDM WDM PON with DM-VCSEL for femtocells application.

PubMed

Othman, M B; Deng, Lei; Pang, Xiaodan; Caminos, J; Kozuch, W; Prince, K; Yu, Xianbin; Jensen, Jesper Bevensee; Monroy, I Tafur

2011-12-12

We report on experimental demonstration of 2x2 MIMO-OFDM 5.6-GHz radio over fiber signaling over 20 km WDM-PON with directly modulated (DM) VCSELs for femtocells application. MIMO-OFDM algorithms effectively compensate for impairments in the wireless link. Error-free signal demodulation of 64 subcarrier 4-QAM signals modulated at 198.5 Mb/s net data rate is achieved after fiber and 2 m indoor wireless transmission. We report BER of 7x10(-3) at the receiver for 16-QAM signals modulated at 397 Mb/s after 1 m of wireless transmission. Performance dependence on different wireless transmission path lengths, antenna separation, and number of subcarriers have been investigated. © 2011 Optical Society of America

A full-duplex optical access system with hybrid 64/16/4QAM-OFDM downlink

NASA Astrophysics Data System (ADS)

He, Chao; Tan, Ze-fu; Shao, Yu-feng; Cai, Li; Pu, He-sheng; Zhu, Yun-le; Huang, Si-si; Liu, Yu

2016-09-01

A full-duplex optical passive access scheme is proposed and verified by simulation, in which hybrid 64/16/4-quadrature amplitude modulation (64/16/4QAM) orthogonal frequency division multiplexing (OFDM) optical signal is for downstream transmission and non-return-to-zero (NRZ) optical signal is for upstream transmission. In view of the transmitting and receiving process for downlink optical signal, in-phase/quadrature-phase (I/Q) modulation based on Mach-Zehnder modulator (MZM) and homodyne coherent detection technology are employed, respectively. The simulation results show that the bit error ratio ( BER) less than hardware decision forward error correction (HD-FEC) threshold is successfully obtained over transmission path with 20-km-long standard single mode fiber (SSMF) for hybrid downlink modulation OFDM optical signal. In addition, by dividing the system bandwidth into several subchannels consisting of some continuous subcarriers, it is convenient for users to select different channels depending on requirements of communication.

The potential of FBMC over OFDM for the future 5G mobile communication technology

NASA Astrophysics Data System (ADS)

Ibrahim, A. N.; Abdullah, M. F. L.

2017-09-01

Fifth Generation (5G) is the new evolution of mobile communication technology and will be launched soon in many countries. The researchers and designers of mobile communication technology have been facing the increasing demand of the mobile consumers, high data rates and mobility requirements needed by new wireless applications. Most of the countries have started research on 5G mobile communication technology that is predictable to be launched on 2020 in conjunction with the Olympic Games in Tokyo. Filterbank Multicarrier (FBMC) is one of the modulation techniques for the future 5G mobile communication technology. It uses the multicarrier techniques that are immune to fading caused by transmission of more than one path at a time and also immune to intersymbol interference besides able to function effectively compared to Orthogonal Frequency Division Multiplexing (OFDM) which is used in Fourth Generation (4G) mobile communications technology. This paper discusses the performance of FBMC over OFDM based on the previous journals that were investigated by researchers.

A chaotic modified-DFT encryption scheme for physical layer security and PAPR reduction in OFDM-PON

NASA Astrophysics Data System (ADS)

Fu, Xiaosong; Bi, Meihua; Zhou, Xuefang; Yang, Guowei; Li, Qiliang; Zhou, Zhao; Yang, Xuelin

2018-05-01

This letter proposes a modified discrete Fourier transform (DFT) encryption scheme with multi-dimensional chaos for the physical layer security and peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing passive optical network (OFDM-PON) system. This multiple-fold encryption algorithm is mainly composed by using the column vectors permutation and the random phase encryption in the standard DFT matrix, which can create ∼10551 key space. The transmission of ∼10 Gb/s encrypted OFDM signal is verified over 20-km standard single mode fiber (SMF). Moreover, experimental results show that, the proposed scheme can achieve ∼2.6-dB PAPR reduction and ∼1-dB improvement of receiver sensitivity if compared with the common OFDM-PON.

Wired and wireless convergent extended-reach optical access network using direct-detection of all-optical OFDM super-channel signal.

PubMed

Chow, C W; Yeh, C H; Sung, J Y; Hsu, C W

2014-12-15

We propose and demonstrate the feasibility of using all-optical orthogonal frequency division multiplexing (AO-OFDM) for the convergent optical wired and wireless access networks. AO-OFDM relies on all-optically generated orthogonal subcarriers; hence, high data rate (> 100 Gb/s) can be easily achieved without hitting the speed limit of electronic digital-to-analog and analog-to-digital converters (DAC/ADC). A proof-of-concept convergent access network using AO-OFDM super-channel (SC) is demonstrated supporting 40 - 100 Gb/s wired and gigabit/s 100 GHz millimeter-wave (MMW) ROF transmissions.

Design of Optical I/Q Modulator Using Dual-drive Mach-Zehnder Modulators in Coherent Optical-OFDM System

NASA Astrophysics Data System (ADS)

Nehra, Monika; Kedia, Deepak

2018-04-01

A CO-OFDM system combines the advantages of both coherent detection and OFDM modulation for future high speed fiber transmission. In this paper, we propose an I/Q modulation technique using dual-drive MZMs for high rate 10 Gb/s CO-OFDM system. The proposed modulator provides 10.63 dBm improved optical spectra compared to a single dual-drive MZM. The simulation results in terms of BER and Q factor are quite satisfactory upto a transmission reach of 3,000 km and that to without making use of any dispersion compensation. A BER of about 8.03×10-10 and 15.06 dB Q factor have been achieved at -10.43 dBm received optical power.

Zero-overhead phase noise compensation via decision-directed phase equalizer for coherent optical OFDM.

PubMed

Mousa-Pasandi, Mohammad E; Plant, David V

2010-09-27

We report and investigate the feasibility of zero-overhead laser phase noise compensation (PNC) for long-haul coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission systems, using the decision-directed phase equalizer (DDPE). DDPE updates the equalization parameters on a symbol-by-symbol basis after an initial decision making stage and retrieves an estimation of the phase noise value by extracting and averaging the phase drift of all OFDM sub-channels. Subsequently, a second equalization is performed by using the estimated phase noise value which is followed by a final decision making stage. We numerically compare the performance of DDPE and the CO-OFDM conventional equalizer (CE) for different laser linewidth values after transmission over 2000 km of uncompensated single-mode fiber (SMF) at 40 Gb/s and investigate the effect of fiber nonlinearity and amplified spontaneous emission (ASE) noise on the received signal quality. Furthermore, we analytically analyze the complexity of DDPE versus CE in terms of the number of required complex multiplications per bit.

Low-Bit Rate Feedback Strategies for Iterative IA-Precoded MIMO-OFDM-Based Systems

PubMed Central

Teodoro, Sara; Silva, Adão; Dinis, Rui; Gameiro, Atílio

2014-01-01

Interference alignment (IA) is a promising technique that allows high-capacity gains in interference channels, but which requires the knowledge of the channel state information (CSI) for all the system links. We design low-complexity and low-bit rate feedback strategies where a quantized version of some CSI parameters is fed back from the user terminal (UT) to the base station (BS), which shares it with the other BSs through a limited-capacity backhaul network. This information is then used by BSs to perform the overall IA design. With the proposed strategies, we only need to send part of the CSI information, and this can even be sent only once for a set of data blocks transmitted over time-varying channels. These strategies are applied to iterative MMSE-based IA techniques for the downlink of broadband wireless OFDM systems with limited feedback. A new robust iterative IA technique, where channel quantization errors are taken into account in IA design, is also proposed and evaluated. With our proposed strategies, we need a small number of quantization bits to transmit and share the CSI, when comparing with the techniques used in previous works, while allowing performance close to the one obtained with perfect channel knowledge. PMID:24678274

Low-bit rate feedback strategies for iterative IA-precoded MIMO-OFDM-based systems.

PubMed

Teodoro, Sara; Silva, Adão; Dinis, Rui; Gameiro, Atílio

2014-01-01

Interference alignment (IA) is a promising technique that allows high-capacity gains in interference channels, but which requires the knowledge of the channel state information (CSI) for all the system links. We design low-complexity and low-bit rate feedback strategies where a quantized version of some CSI parameters is fed back from the user terminal (UT) to the base station (BS), which shares it with the other BSs through a limited-capacity backhaul network. This information is then used by BSs to perform the overall IA design. With the proposed strategies, we only need to send part of the CSI information, and this can even be sent only once for a set of data blocks transmitted over time-varying channels. These strategies are applied to iterative MMSE-based IA techniques for the downlink of broadband wireless OFDM systems with limited feedback. A new robust iterative IA technique, where channel quantization errors are taken into account in IA design, is also proposed and evaluated. With our proposed strategies, we need a small number of quantization bits to transmit and share the CSI, when comparing with the techniques used in previous works, while allowing performance close to the one obtained with perfect channel knowledge.

Experimental investigation of inter-core crosstalk tolerance of MIMO-OFDM/OQAM radio over multicore fiber system.

PubMed

He, Jiale; Li, Borui; Deng, Lei; Tang, Ming; Gan, Lin; Fu, Songnian; Shum, Perry Ping; Liu, Deming

2016-06-13

In this paper, the feasibility of space division multiplexing for optical wireless fronthaul systems is experimentally demonstrated by implementing high speed MIMO-OFDM/OQAM radio signals over 20km 7-core fiber and 0.4m wireless link. Moreover, the impact of optical inter-core crosstalk in multicore fibers on the proposed MIMO-OFDM/OQAM radio over fiber system is experimentally evaluated in both SISO and MIMO configurations for comparison. The experimental results show that the inter-core crosstalk tolerance of the proposed radio over fiber system can be relaxed to -10 dB by using the proposed MIMO-OFDM/OQAM processing. These results could guide high density multicore fiber design to support a large number of antenna modules and a higher density of radio-access points for potential applications in 5G cellular system.

Suppressing the relaxation oscillation noise of injection-locked WRC-FPLD for directly modulated OFDM transmission.

PubMed

Cheng, Min-Chi; Chi, Yu-Chieh; Li, Yi-Cheng; Tsai, Cheng-Ting; Lin, Gong-Ru

2014-06-30

By up-shifting the relaxation oscillation peak and suppressing its relative intensity noise in a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) under intense injection-locking, the directly modulated transmission of optical 16 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) data-stream is demonstrated. The total bit rate of up to 20 Gbit/s within 5-GHz bandwidth is achieved by using the OFDM subcarrier pre-leveling technique. With increasing the injection-locking power from -12 to -3 dBm, the effective reduction on threshold current of the WRC-FPLD significantly shifts its relaxation oscillation frequency from 5 to 7.5 GHz. This concurrently induces an up-shift of the peak relative intensity noise (RIN) of the WRC-FPLD, and effectively suppresses the background RIN level to -104 dBc/Hz within the OFDM band between 3 and 6 GHz. The enhanced signal-to-noise ratio from 16 to 20 dB leads to a significant reduction of bit-error-rate (BER) of the back-to-back transmitted 16-QAM-OFDM data from 1.3 × 10(-3) to 5 × 10(-5), which slightly degrades to 1.1 × 10(-4) after 25-km single-mode fiber (SMF) transmission. However, the enlarged injection-locking power from -12 to -3 dBm inevitably declines the modulation throughput and increases its negative throughput slope from -0.8 to -1.9 dBm/GHz. After pre-leveling the peak amplitude of the OFDM subcarriers to compensate the throughput degradation of the directly modulated WRC-FPLD, the BER under 25-km SMF transmission can be further improved to 3 × 10(-5) under a receiving power of -3 dBm.

Achievable rate maximization for decode-and-forward MIMO-OFDM networks with an energy harvesting relay.

PubMed

Du, Guanyao; Yu, Jianjun

2016-01-01

This paper investigates the system achievable rate for the multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system with an energy harvesting (EH) relay. Firstly we propose two protocols, time switching-based decode-and-forward relaying (TSDFR) and a flexible power splitting-based DF relaying (PSDFR) protocol by considering two practical receiver architectures, to enable the simultaneous information processing and energy harvesting at the relay. In PSDFR protocol, we introduce a temporal parameter to describe the time division pattern between the two phases which makes the protocol more flexible and general. In order to explore the system performance limit, we discuss the system achievable rate theoretically and formulate two optimization problems for the proposed protocols to maximize the system achievable rate. Since the problems are non-convex and difficult to solve, we first analyze them theoretically and get some explicit results, then design an augmented Lagrangian penalty function (ALPF) based algorithm for them. Numerical results are provided to validate the accuracy of our analytical results and the effectiveness of the proposed ALPF algorithm. It is shown that, PSDFR outperforms TSDFR to achieve higher achievable rate in such a MIMO-OFDM relaying system. Besides, we also investigate the impacts of the relay location, the number of antennas and the number of subcarriers on the system performance. Specifically, it is shown that, the relay position greatly affects the system performance of both protocols, and relatively worse achievable rate is achieved when the relay is placed in the middle of the source and the destination. This is different from the MIMO-OFDM DF relaying system without EH. Moreover, the optimal factor which indicates the time division pattern between the two phases in the PSDFR protocol is always above 0.8, which means that, the common division of the total transmission time into two equal phases in

Low-mobility channel tracking for MIMO-OFDM communication systems

NASA Astrophysics Data System (ADS)

Pagadarai, Srikanth; Wyglinski, Alexander M.; Anderson, Christopher R.

2013-12-01

It is now well understood that by exploiting the available additional spatial dimensions, multiple-input multiple-output (MIMO) communication systems provide capacity gains, compared to a single-input single-output systems without increasing the overall transmit power or requiring additional bandwidth. However, these large capacity gains are feasible only when the perfect knowledge of the channel is available to the receiver. Consequently, when the channel knowledge is imperfect, as is common in practical settings, the impact of the achievable capacity needs to be evaluated. In this study, we begin with a general MIMO framework at the outset and specialize it to the case of orthogonal frequency division multiplexing (OFDM) systems by decoupling channel estimation from data detection. Cyclic-prefixed OFDM systems have attracted widespread interest due to several appealing characteristics not least of which is the fact that a single-tap frequency-domain equalizer per subcarrier is sufficient due to the circulant structure of the resulting channel matrix. We consider a low-mobility wireless channel which exhibits inter-block channel variations and apply Kalman tracking when MIMO-OFDM communication is performed. Furthermore, we consider the signal transmission to contain a stream of training and information symbols followed by information symbols alone. By relying on predicted channel states when training symbols are absent, we aim to understand how the improvements in channel capacity are affected by imperfect channel knowledge. We show that the Kalman recursion procedure can be simplified by the optimal minimum mean square error training design. Using the simplified recursion, we derive capacity upper and lower bounds to evaluate the performance of the system.

15 Gb/s OFDM-based VLC using direct modulation of 450 GaN laser diode

NASA Astrophysics Data System (ADS)

Viola, Shaun; Islim, Mohamed Sufyan; Watson, Scott; Videv, Stefan; Haas, Harald; Kelly, Anthony E.

2017-10-01

A record data rate for visible light communications (VLC) using a transistor outline (TO) packaged Gallium Nitride (GaN) laser diode is reported. Using a system 3 dB bandwidth of 1.4 GHz data transmission at 15 Gb/s is reported. This is achieved due to the use of orthogonal frequency division multiplexing (OFDM) in combination with a high system signal to noise ratio (SNR) and adaptive bit loading extending the effective bandwidth to 2.5 GHz. To the best of authors knowledge this is the highest reported data rate for single channel VLC.

Performance analysis of visible light communication using the STBC-OFDM technique for intelligent transportation systems

NASA Astrophysics Data System (ADS)

Li, Changping; Yi, Ying; Lee, Kyujin; Lee, Kyesan

2014-08-01

Visible light communication (VLC) applied in an intelligent transportation system (ITS) has attracted growing attentions, but it also faces challenges, for example deep path loss and optical multi-path dispersion. In this work, we modelled an actual outdoor optical channel as a Rician channel and further proposed space-time block coding (STBC) orthogonal frequency-division multiplexing (OFDM) technology to reduce the influence of severe optical multi-path dispersion associated with such a mock channel for achieving the effective BER of 10-6 even at a low signal-to-noise ratio (SNR). In this case, the optical signals transmission distance can be extended as long as possible. Through the simulation results of STBC-OFDM and single-input-single-output (SISO) counterparts in bit error rate (BER) performance comparison, we can distinctly observe that the VLC-ITS system using STBC-OFDM technique can obtain a strongly improved BER performance due to multi-path dispersion alleviation.

Optimal Data Transmission on MIMO OFDM Channels

DTIC Science & Technology

2008-12-01

Channel State Information dB decibel DFT Discrete Fourier Transform DWTS Digital Wideband Transmission System ETSI European Telecommunications...me facultaram durante a minha infância e juventude , que em conjunto com seu permanente apoio e amor me permitiram sonhar e voar tão alto. Agradeço...transmitter, it is far simpler to build such a system using an IDFT chip, generate the overall OFDM signal in baseband and digital format, and finally

Theoretical calculation on ICI reduction using digital coherent superposition of optical OFDM subcarrier pairs in the presence of laser phase noise.

PubMed

Yi, Xingwen; Xu, Bo; Zhang, Jing; Lin, Yun; Qiu, Kun

2014-12-15

Digital coherent superposition (DCS) of optical OFDM subcarrier pairs with Hermitian symmetry can reduce the inter-carrier-interference (ICI) noise resulted from phase noise. In this paper, we show two different implementations of DCS-OFDM that have the same performance in the presence of laser phase noise. We complete the theoretical calculation on ICI reduction by using the model of pure Wiener phase noise. By Taylor expansion of the ICI, we show that the ICI power is cancelled to the second order by DCS. The fourth order term is further derived out and only decided by the ratio of laser linewidth to OFDM subcarrier symbol rate, which can greatly simplify the system design. Finally, we verify our theoretical calculations in simulations and use the analytical results to predict the system performance. DCS-OFDM is expected to be beneficial to certain optical fiber transmissions.

CSI feedback-based CS for underwater acoustic adaptive modulation OFDM system with channel prediction

NASA Astrophysics Data System (ADS)

Kuai, Xiao-yan; Sun, Hai-xin; Qi, Jie; Cheng, En; Xu, Xiao-ka; Guo, Yu-hui; Chen, You-gan

2014-06-01

In this paper, we investigate the performance of adaptive modulation (AM) orthogonal frequency division multiplexing (OFDM) system in underwater acoustic (UWA) communications. The aim is to solve the problem of large feedback overhead for channel state information (CSI) in every subcarrier. A novel CSI feedback scheme is proposed based on the theory of compressed sensing (CS). We propose a feedback from the receiver that only feedback the sparse channel parameters. Additionally, prediction of the channel state is proposed every several symbols to realize the AM in practice. We describe a linear channel prediction algorithm which is used in adaptive transmission. This system has been tested in the real underwater acoustic channel. The linear channel prediction makes the AM transmission techniques more feasible for acoustic channel communications. The simulation and experiment show that significant improvements can be obtained both in bit error rate (BER) and throughput in the AM scheme compared with the fixed Quadrature Phase Shift Keying (QPSK) modulation scheme. Moreover, the performance with standard CS outperforms the Discrete Cosine Transform (DCT) method.

A Novel Cost-effective OFDM WDM-PON Radio Over Fiber System Employing FBG to Generate Optical mm-wave

NASA Astrophysics Data System (ADS)

Nguyen, HoangViet

2015-03-01

We have investigated and demonstrated a novel scheme to generate 2.5 Gbit/s 64 QAM orthogonal frequency division multiplexing (OFDM) signals for Radio Over Fiber (ROF) systems. We employ Fiber Bragg Grating (FBG) because the repetitive frequency of the RF source and the bandwidth of the optical modulator are largely reduced and the architecture of the ROF system is simpler. Wavelength-Division-Multiplexed Passive Optical Network (WDM-PON) has been considered as a promising solution for future broadband access networks. Principle of WDM-PON access network compatible with OFDM-ROF systems is investigated. This novel scheme which has multiple double-frequency technique to generate mm-wave signal to carry OFDM signals is a practical scheme to be applied for future broadband access networks.

Decision-aided ICI mitigation with time-domain average approximation in CO-OFDM

NASA Astrophysics Data System (ADS)

Ren, Hongliang; Cai, Jiaxing; Ye, Xin; Lu, Jin; Cao, Quanjun; Guo, Shuqin; Xue, Lin-lin; Qin, Yali; Hu, Weisheng

2015-07-01

We introduce and investigate the feasibility of a novel iterative blind phase noise inter-carrier interference (ICI) mitigation scheme for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. The ICI mitigation scheme is performed through the combination of frequency-domain symbol decision-aided estimation and the ICI phase noise time-average approximation. An additional initial decision process with suitable threshold is introduced in order to suppress the decision error symbols. Our proposed ICI mitigation scheme is proved to be effective in removing the ICI for a simulated CO-OFDM with 16-QAM modulation format. With the slightly high computational complexity, it outperforms the time-domain average blind ICI (Avg-BL-ICI) algorithm at a relatively wide laser line-width and high OSNR.

Transmission over UWB channels with OFDM system using LDPC coding

NASA Astrophysics Data System (ADS)

Dziwoki, Grzegorz; Kucharczyk, Marcin; Sulek, Wojciech

2009-06-01

Hostile wireless environment requires use of sophisticated signal processing methods. The paper concerns on Ultra Wideband (UWB) transmission over Personal Area Networks (PAN) including MB-OFDM specification of physical layer. In presented work the transmission system with OFDM modulation was connected with LDPC encoder/decoder. Additionally the frame and bit error rate (FER and BER) of the system was decreased using results from the LDPC decoder in a kind of turbo equalization algorithm for better channel estimation. Computational block using evolutionary strategy, from genetic algorithms family, was also used in presented system. It was placed after SPA (Sum-Product Algorithm) decoder and is conditionally turned on in the decoding process. The result is increased effectiveness of the whole system, especially lower FER. The system was tested with two types of LDPC codes, depending on type of parity check matrices: randomly generated and constructed deterministically, optimized for practical decoder architecture implemented in the FPGA device.

Identifying and individuating cognitive systems: a task-based distributed cognition alternative to agent-based extended cognition.

PubMed

Davies, Jim; Michaelian, Kourken

2016-08-01

This article argues for a task-based approach to identifying and individuating cognitive systems. The agent-based extended cognition approach faces a problem of cognitive bloat and has difficulty accommodating both sub-individual cognitive systems ("scaling down") and some supra-individual cognitive systems ("scaling up"). The standard distributed cognition approach can accommodate a wider variety of supra-individual systems but likewise has difficulties with sub-individual systems and faces the problem of cognitive bloat. We develop a task-based variant of distributed cognition designed to scale up and down smoothly while providing a principled means of avoiding cognitive bloat. The advantages of the task-based approach are illustrated by means of two parallel case studies: re-representation in the human visual system and in a biomedical engineering laboratory.

PAPR reduction in CO-OFDM systems using IPTS and modified clipping and filtering

NASA Astrophysics Data System (ADS)

Tong, Zheng-rong; Hu, Ya-nong; Zhang, Wei-hua

2018-05-01

Aiming at the problem of the peak to average power ratio ( PAPR) in coherent optical orthogonal frequency division multiplexing (CO-OFDM), a hybrid PAPR reduction technique of the CO-OFDM system by combining iterative partial transmit sequence (IPTS) scheme with modified clipping and filtering (MCF) is proposed. The simulation results show that at the complementary cumulative distribution function ( CCDF) of 10-4, the PAPR of proposed scheme is optimized by 1.86 dB and 2.13 dB compared with those of IPTS and CF schemes, respectively. Meanwhile, when the bit error rate ( BER) is 10-3, the optical signal to noise ratio ( OSNR) are optimized by 1.57 dB and 0.66 dB compared with those of CF and IPTS-CF schemes, respectively.

Dual-polarization multi-band optical OFDM transmission and transceiver limitations for up to 500 Gb/s uncompensated long-haul links.

PubMed

Giacoumidis, E; Jarajreh, M A; Sygletos, S; Le, S T; Farjady, F; Tsokanos, A; Hamié, A; Pincemin, E; Jaouën, Y; Ellis, A D; Doran, N J

2014-05-05

A number of critical issues for dual-polarization single- and multi-band optical orthogonal-frequency division multiplexing (DP-SB/MB-OFDM) signals are analyzed in dispersion compensation fiber (DCF)-free long-haul links. For the first time, different DP crosstalk removal techniques are compared, the maximum transmission-reach is investigated, and the impact of subcarrier number and high-level modulation formats are explored thoroughly. It is shown, for a bit-error-rate (BER) of 10(-3), 2000 km of quaternary phase-shift keying (QPSK) DP-MB-OFDM transmission is feasible. At high launched optical powers (LOP), maximum-likelihood decoding can extend the LOP of 40 Gb/s QPSK DP-SB-OFDM at 2000 km by 1.5 dB compared to zero-forcing. For a 100 Gb/s DP-MB-OFDM system, a high number of subcarriers contribute to improved BER but at the cost of digital signal processing computational complexity, whilst by adapting the cyclic prefix length the BER can be improved for a low number of subcarriers. In addition, when 16-quadrature amplitude modulation (16QAM) is employed the digital-to-analogue/analogue-to-digital converter (DAC/ADC) bandwidth is relaxed with a degraded BER; while the 'circular' 8QAM is slightly superior to its 'rectangular' form. Finally, the transmission of wavelength-division multiplexing DP-MB-OFDM and single-carrier DP-QPSK is experimentally compared for up to 500 Gb/s showing great potential and similar performance at 1000 km DCF-free G.652 line.

A Fast Hartley Transform based novel optical OFDM system for VLC indoor application with constant envelope PAPR reduction technique using frequency modulation

NASA Astrophysics Data System (ADS)

Singh, Vinay Kumar; Dalal, U. D.

2017-10-01

In this research literature we present a unique optical OFDM system for Visible Light Communication (VLC) intended for indoor application which uses a non conventional transform-Fast Hartley Transform and an effective method to reduce the peak to average power ratio (PAPR) of the OFDM signal based on frequency modulation leading to a constant envelope (CE) signal. The proposed system is analyzed by a complete mathematical model and verified by the concurrent simulations results. The use of the non conventional transform makes the system computationally more desirable as it does not require the Hermitian symmetry constraint to yield real signals. The frequency modulation of the baseband signal converge random peaks into a CE signal. This leads to alleviation of the non linearity effects of the LED used in the link for electrical to optical conversion. The PAPR is reduced to 2 dB by this technique in this work. The impact of the modulation index on the performance of the system is also investigated. An optimum modulation depth of 30% gives better results. The additional phase discontinuity incurring on the demodulated signal at the receiver is also significantly reduced. A comparison of the improvement in phase discontinuity of the proposed technique of combating the PAPR with the previously known phase modulation technique is also presented in this work. Based on the channel metrics we evaluate the system performance and report an improvement of 1.2 dB at the FEC threshold. The proposed system is simple in design and computationally efficient and this can be incorporated into the present VLC system without much alteration thereby making it a cost effective solution.

Enhanced noise tolerance for 10 Gb/s Bi-directional cross-wavelength reuse colorless WDM-PON by using spectrally shaped OFDM signals

NASA Astrophysics Data System (ADS)

Choudhury, Pallab K.

2018-05-01

Spectrally shaped orthogonal frequency division multiplexing (OFDM) signal for symmetric 10 Gb/s cross-wavelength reuse reflective semiconductor optical amplifier (RSOA) based colorless wavelength division multiplexed passive optical network (WDM-PON) is proposed and further analyzed to support broadband services of next generation high speed optical access networks. The generated OFDM signal has subcarriers in separate frequency ranges for downstream and upstream, such that the re-modulation noise can be effectively minimized in upstream data receiver. Moreover, the cross wavelength reuse approach improves the tolerance against Rayleigh backscattering noise due to the propagation of different wavelengths in the same feeder fiber. The proposed WDM-PON is successfully demonstrated for 25 km fiber with 16-QAM (quadrature amplitude modulation) OFDM signal having bandwidth of 2.5 GHz for 10 Gb/s operation and subcarrier frequencies in 3-5.5 GHz and DC-2.5 GHz for downstream (DS) and upstream (US) transmission respectively. The result shows that the proposed scheme maintains a good bit error rate (BER) performance below the forward error correction (FEC) limit of 3.8 × 10-3 at acceptable receiver sensitivity and provides a high resilience against re-modulation and Rayleigh backscattering noises as well as chromatic dispersion.

A High Noise Immunity, 28 × 16-Channel Finger Touch Sensing IC Using OFDM and Frequency Translation Technique

PubMed Central

Kim, SangYun; Samadpoor Rikan, Behnam; Pu, YoungGun; Yoo, Sang-Sun; Lee, Minjae; Yang, Youngoo; Lee, Kang-Yoon

2018-01-01

In this paper, a high noise immunity, 28 × 16-channel finger touch sensing IC for an orthogonal frequency division multiplexing (OFDM) touch sensing scheme is presented. In order to increase the signal-to-noise ratio (SNR), the OFDM sensing scheme is proposed. The transmitter (TX) transmits the orthogonal signal to each channels of the panel. The receiver (RX) detects the magnitude of the orthogonal frequency to be transmitted from the TX. Due to the orthogonal characteristics, it is robust to narrowband interference and noise. Therefore, the SNR can be improved. In order to reduce the noise effect of low frequencies, a mixer and high-pass filter are proposed as well. After the noise is filtered, the touch SNR attained is 60 dB, from 20 dB before the noise is filtered. The advantage of the proposed OFDM sensing scheme is its ability to detect channels of the panel simultaneously with the use of multiple carriers. To satisfy the linearity of the signal in the OFDM system, a high-linearity mixer and a rail-to-rail amplifier in the TX driver are designed. The proposed design is implemented in 90 nm CMOS process. The SNR is approximately 60 dB. The area is 13.6 mm2, and the power consumption is 62.4 mW. PMID:29883435

Experimental demonstration of an OFDM based visible light communication system using inter-block precoding and superimposed pilots

NASA Astrophysics Data System (ADS)

Zhang, Junwei; Hong, Xuezhi; Liu, Jie; Guo, Changjian

2018-04-01

In this work, we investigate and experimentally demonstrate an orthogonal frequency division multiplexing (OFDM) based high speed wavelength-division multiplexed (WDM) visible light communication (VLC) system using an inter-block data precoding and superimposed pilots (DP-SP) based channel estimation (CE) scheme. The residual signal-to-pilot interference (SPI) can be eliminated by using inter-block data precoding, resulting in a significant improvement in estimated accuracy and the overall system performance compared with uncoded SP based CE scheme. We also study the power allocation/overhead problem of the training for DP-SP, uncoded SP and conventional preamble based CE schemes, from which we obtain the optimum signal-to-pilot power ratio (SPR)/overhead percentage for all above cases. Intra-symbol frequency-domain averaging (ISFA) is also adopted to further enhance the accuracy of CE. By using the DP-SP based CE scheme, aggregate data rates of 1.87-Gbit/s and 1.57-Gbit/s are experimentally demonstrated over 0.8-m and 2-m indoor free space transmission, respectively, using a commercially available red, green and blue (RGB) light emitting diode (LED) with WDM. Experimental results show that the DP-SP based CE scheme is comparable to the conventional preamble based CE scheme in term of received Q factor and data rate while entailing a much smaller overhead-size.

Statistical characterization of the nonlinear noise in 2.8 Tbit/s PDM-16QAM CO-OFDM system.

PubMed

Wang, Zhe; Qiao, Yaojun; Xu, Yanfei; Ji, Yuefeng

2013-07-29

We show for the first time through comprehensive simulations under both uncompensated transmission (UT) and dispersion managed transmission (DMT) systems that the statistical distribution of the nonlinear interference (NLI) within the polarization multiplexed 16-state quadrature amplitude modulation (PM-16QAM) Coherent Optical OFDM (CO-OFDM) system deviates from Gaussian distribution in the absence of amplified spontaneous emission (ASE) noise. We also observe that the dependences of the variance of the NLI noise on both the launch power and the transmission distance (logrithm) seem to be in a simple linear way.

Experimental demonstration of a real-time high-throughput digital DC blocker for compensating ADC imperfections in optical fast-OFDM receivers.

PubMed

Zhang, Lu; Ouyang, Xing; Shao, Xiaopeng; Zhao, Jian

2016-06-27

Performance degradation induced by the DC components at the output of real-time analogue-to-digital converter (ADC) is experimentally investigated for optical fast-OFDM receiver. To compensate this degradation, register transfer level (RTL) circuits for real-time digital DC blocker with 20GS/s throughput are proposed and implemented in field programmable gate array (FPGA). The performance of the proposed real-time digital DC blocker is experimentally investigated in a 15Gb/s optical fast-OFDM system with intensity modulation and direct detection over 40 km standard single-mode fibre. The results show that the fixed-point DC blocker has negligible performance penalty compared to the offline floating point one, and can overcome the error floor of the fast OFDM receiver caused by the DC components from the real-time ADC output.

Coherently wavelength injection-locking a 600-μm long cavity colorless laser diode for 16-QAM OFDM at 12 Gbit/s over 25-km SMF.

PubMed

Li, Yi-Cheng; Chi, Yu-Chieh; Cheng, Min-Chi; Lu, I-Cheng; Chen, Jason; Lin, Gong-Ru

2013-07-15

The coherent injection-locking and directly modulation of a long-cavity colorless laser diode with 1% end-facet reflectance and weak-resonant longitudinal modes is employed as an universal optical transmitter to demonstrated for optical 16-QAM OFDM transmission at 12 Gbit/s over 25 km in a DWDM-PON system. The optimized bias current of 30 mA (~1.5Ith) with corresponding extinction ratio (ER) of 6 dB and the external injection power of -9 dBm is (are) required for such a wavelength-locked universal transmitter to carry the 16-QAM and 122-subcarrier formatted OFDM and data-stream. By increasing external injection-locking from -9 dBm to 0 dBm, the peak-to-peak chirp of the OFDM data stream reduces from 7.7 to 5.4 GHz. The side mode suppression ratio (SMSR) of up to 50 dB is achieved with wider detuning range between -0.5 nm to 2.0 nm under an injection power of 0 dBm. By modulating such a colorless laser diode with an OFDM data stream of 122 subcarriers at a central carrier frequency of 1.5625 GHz and a total bandwidth of 3 GHz, the transmission data rate of up to 12 Gbit/s in standard single-mode fiber over 25 km is demonstrated to achieve an error vector magnitude (EVM) of 5.435%. Such a universal colorless DWDM-PON transmitter can deliver the optical OFDM data-stream at 12 Gbit/s QAM-OFDM data after 25-km transmission with a receiving power sensitivity of -7 dBm at BER of 3.6 × 10(-7) when pre-amplifying the OFDM data by 5 dB.

428-Gb/s single-channel coherent optical OFDM transmission over 960-km SSMF with constellation expansion and LDPC coding.

PubMed

Yang, Qi; Al Amin, Abdullah; Chen, Xi; Ma, Yiran; Chen, Simin; Shieh, William

2010-08-02

High-order modulation formats and advanced error correcting codes (ECC) are two promising techniques for improving the performance of ultrahigh-speed optical transport networks. In this paper, we present record receiver sensitivity for 107 Gb/s CO-OFDM transmission via constellation expansion to 16-QAM and rate-1/2 LDPC coding. We also show the single-channel transmission of a 428-Gb/s CO-OFDM signal over 960-km standard-single-mode-fiber (SSMF) without Raman amplification.

Opportunistic Access in Frequency Hopping Cognitive Radio Networks

DTIC Science & Technology

2014-03-27

thresholding MA multiple access MFSK M-ary frequency shift keying MIMO multiple-input/multiple-output OFDM orthogonal frequency-division multiplexing x...adaptive BER performance as a function of ISR with orthogonal frequency-division multiplexing ( OFDM ) interference present. . . . . . . . . . 41 4.15 Non...adaptive BER performance as a function of EB/N0 with OFDM interfer- ence present

An Acoustic OFDM System with Symbol-by-Symbol Doppler Compensation for Underwater Communication

PubMed Central

MinhHai, Tran; Rie, Saotome; Suzuki, Taisaku; Wada, Tomohisa

2016-01-01

We propose an acoustic OFDM system for underwater communication, specifically for vertical link communications such as between a robot in the sea bottom and a mother ship in the surface. The main contributions are (1) estimation of time varying Doppler shift using continual pilots in conjunction with monitoring the drift of Power Delay Profile and (2) symbol-by-symbol Doppler compensation in frequency domain by an ICI matrix representing nonuniform Doppler. In addition, we compare our proposal against a resampling method. Simulation and experimental results confirm that our system outperforms the resampling method when the velocity changes roughly over OFDM symbols. Overall, experimental results taken in Shizuoka, Japan, show our system using 16QAM, and 64QAM achieved a data throughput of 7.5 Kbit/sec with a transmitter moving at maximum 2 m/s, in a complicated trajectory, over 30 m vertically. PMID:27057558

Simultaneous chromatic dispersion and PMD compensation by using coded-OFDM and girth-10 LDPC codes.

PubMed

Djordjevic, Ivan B; Xu, Lei; Wang, Ting

2008-07-07

Low-density parity-check (LDPC)-coded orthogonal frequency division multiplexing (OFDM) is studied as an efficient coded modulation scheme suitable for simultaneous chromatic dispersion and polarization mode dispersion (PMD) compensation. We show that, for aggregate rate of 10 Gb/s, accumulated dispersion over 6500 km of SMF and differential group delay of 100 ps can be simultaneously compensated with penalty within 1.5 dB (with respect to the back-to-back configuration) when training sequence based channel estimation and girth-10 LDPC codes of rate 0.8 are employed.

Flexible and scalable wavelength multicast of coherent optical OFDM with tolerance against pump phase-noise using reconfigurable coherent multi-carrier pumping.

PubMed

Lu, Guo-Wei; Bo, Tianwai; Sakamoto, Takahide; Yamamoto, Naokatsu; Chan, Calvin Chun-Kit

2016-10-03

Recently the ever-growing demand for dynamic and high-capacity services in optical networks has resulted in new challenges that require improved network agility and flexibility in order for network resources to become more "consumable" and dynamic, or elastic, in response to requests from higher network layers. Flexible and scalable wavelength conversion or multicast is one of the most important technologies needed for developing agility in the physical layer. This paper will investigate how, using a reconfigurable coherent multi-carrier as a pump, the multicast scalability and the flexibility in wavelength allocation of the converted signals can be effectively improved. Moreover, the coherence in the multiple carriers prevents the phase noise transformation from the local pump to the converted signals, which is imperative for the phase-noise-sensitive multi-level single- or multi-carrier modulated signal. To verify the feasibility of the proposed scheme, we experimentally demonstrate the wavelength multicast of coherent optical orthogonal frequency division multiplexing (CO-OFDM) signals using a reconfigurable coherent multi-carrier pump, showing flexibility in wavelength allocation, scalability in multicast, and tolerance against pump phase noise. Less than 0.5 dB and 1.8 dB power penalties at a bit-error rate (BER) of 10^-3 are obtained for the converted CO-OFDM-quadrature phase-shift keying (QPSK) and CO-OFDM-16-ary quadrature amplitude modulation (16QAM) signals, respectively, even when using a distributed feedback laser (DFB) as a pump source. In contrast, with a free-running pumping scheme, the phase noise from DFB pumps severely deteriorates the CO-OFDM signals, resulting in a visible error-floor at a BER of 10^-2 in the converted CO-OFDM-16QAM signals.

The Effect of Doppler Frequency Shift, Frequency Offset of the Local Oscillators, and Phase Noise on the Performance of Coherent OFDM Receivers

NASA Technical Reports Server (NTRS)

Xiong, Fuqin; Andro, Monty

2001-01-01

This paper first shows that the Doppler frequency shift affects the frequencies of the RF carrier, subcarriers, envelope, and symbol timing by the same percentage in an Orthogonal Frequency Division Multiplexing (OFDM) signal or any other modulated signals. Then the SNR degradation of an OFDM system due to Doppler frequency shift, frequency offset of the local oscillators and phase noise is analyzed. Expressions are given and values for 4-, 16-, 64-, and 256-QAM OFDM systems are calculated and plotted. The calculations show that the Doppler shift of the D3 project is about 305 kHz, and the degradation due to it is about 0.01 to 0.04 dB, which is negligible. The degradation due to frequency offset and phase noise of local oscillators will be the main source of degradation. To keep the SNR degradation under 0.1 dB, the relative frequency offset due to local oscillators must be below 0.01 for the 16 QAM-OFDM. This translates to an offset of 1.55 MHz (0.01 x 155 MHz) or a stability of 77.5 ppm (0.01 x 155 MHz/20 GHz) for the DI project. To keep the SNR degradation under 0.1 dB, the relative linewidth (0) due to phase noise of the local oscillators must be below 0.0004 for the 16 QAM-OFDM. This translates to a linewidth of 0.062 MHz (0.0004 x 155 MHz) of the 20 GHz RIF carrier. For a degradation of 1 dB, beta = 0.04, and the linewidth can be relaxed to 6.2 MHz.

OFDM Coupled Compressive Sensing Algorithm for Stepped-Frequency Ground Penetrating Radar

DTIC Science & Technology

2014-10-01

These frequencies are combined in such a way to achieve orthogonality between the carrier frequencies, while mitigating any interference between...in such a way to achieve orthogonality between the carrier frequencies, while mitigating any interference between said frequencies. In CS, a signal...frequency tones is mitigated . Orthogonality requires that the sub-bands are spaced at = is the OFDM symbol period, and k is any

How Affectively-Based and Cognitively-Based Attitudes Drive Intergroup Behaviours: The Moderating Role of Affective-Cognitive Consistency

PubMed Central

Zhou, Jie; Dovidio, John; Wang, Erping

2013-01-01

The moderating role of affective-cognitive consistency in the effects of affectively-based and cognitively-based attitudes on consummatory and instrumental behaviors was explored using two experimental studies in the intergroup context. Study 1 revealed that affectively-based attitudes were better predictors than cognitively-based attitudes regardless of affective-cognitive consistency for consummatory behaviors (e.g., undergraduates’ supportive behaviors toward government officials). Study 2, which investigated task groups’ supportive behaviors toward an immediate supervisory group, found that for these instrumental behaviors cognitively-based attitudes were better predictors than affectively-based attitudes only when affective-cognitive consistency was high. The present research also examined the mechanism by which affective-cognitive consistency moderates the relative roles of affectively-based and cognitively-based attitudes in attitude-behavior consistency. Results indicated that attitude-behavior consistency is eroded primarily because of the weaker relationship of affective or cognitive components to behaviors than to general attitudes. The reciprocal implications of research on attitudes and work on intergroup relations are considered. PMID:24244751

Receiver IQ mismatch estimation in PDM CO-OFDM system using training symbol

NASA Astrophysics Data System (ADS)

Peng, Dandan; Ma, Xiurong; Yao, Xin; Zhang, Haoyuan

2017-07-01

Receiver in-phase/quadrature (IQ) mismatch is hard to mitigate at the receiver via using conventional method in polarization division multiplexed (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. In this paper, a novel training symbol structure is proposed to estimate IQ mismatch and channel distortion. Combined this structure with Gram Schmidt orthogonalization procedure (GSOP) algorithm, we can get lower bit error rate (BER). Meanwhile, based on this structure one estimation method is deduced in frequency domain which can achieve the estimation of IQ mismatch and channel distortion independently and improve the system performance obviously. Numerical simulation shows that the proposed two methods have better performance than compared method at 100 Gb/s after 480 km fiber transmission. Besides, the calculation complexity is also analyzed.

Development and experimental validation of downlink multiuser MIMO-OFDM in gigabit wireless LAN systems

NASA Astrophysics Data System (ADS)

Ishihara, Koichi; Asai, Yusuke; Kudo, Riichi; Ichikawa, Takeo; Takatori, Yasushi; Mizoguchi, Masato

2013-12-01

Multiuser multiple-input multiple-output (MU-MIMO) has been proposed as a means to improve spectrum efficiency for various future wireless communication systems. This paper reports indoor experimental results obtained for a newly developed and implemented downlink (DL) MU-MIMO orthogonal frequency division multiplexing (OFDM) transceiver for gigabit wireless local area network systems in the microwave band. In the transceiver, the channel state information (CSI) is estimated at each user and fed back to an access point (AP) on a real-time basis. At the AP, the estimated CSI is used to calculate the transmit beamforming weight for DL MU-MIMO transmission. This paper also proposes a recursive inverse matrix computation scheme for computing the transmit weight in real time. Experiments with the developed transceiver demonstrate its feasibility in a number of indoor scenarios. The experimental results clarify that DL MU-MIMO-OFDM transmission can achieve a 972-Mbit/s transmission data rate with simple digital signal processing of single-antenna users in an indoor environment.

A novel transmitter IQ imbalance and phase noise suppression method utilizing pilots in PDM CO-OFDM system

NASA Astrophysics Data System (ADS)

Zhang, Haoyuan; Ma, Xiurong; Li, Pengru

2018-04-01

In this paper, we develop a novel pilot structure to suppress transmitter in-phase and quadrature (Tx IQ) imbalance, phase noise and channel distortion for polarization division multiplexed (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. Compared with the conventional approach, our method not only significantly improves the system tolerance of IQ imbalance as well as phase noise, but also provides higher transmission speed. Numerical simulations of PDM CO-OFDM system is used to validate the theoretical analysis under the simulation conditions: the amplitude mismatch 3 dB, the phase mismatch 15°, the transmission bit rate 100 Gb/s and 560 km standard signal-mode fiber transmission. Moreover, the proposed method is 63% less complex than the compared method.

PHY-DLL dialogue: cross-layer design for optical-wireless OFDM downlink transmission

NASA Astrophysics Data System (ADS)

Wang, Xuguo; Li, Lee

2005-11-01

The use of radio over fiber to provide radio access has a number of advantages including the ability to deploy small, low-cost remote antenna units and ease of upgrade. And due to the great potential for increasing the capacity and quality of service, the combination of Orthogonal Frequency Division Multiplexing (OFDM) modulation and the sub-carrier multiplexed optical transmission is one of the best solutions for the future millimeter-wave mobile communication. And this makes the optimum utility of valuable radio resources essential. This paper devises a cross-layer adaptive algorithm for optical-wireless OFDM system, which takes into consideration not only transmission power limitation in the physical layer, but also traffic scheduling and user fairness at the data-link layer. According to proportional fairness principle and water-pouring theorem, we put forward the complete description of this cross-layer adaptive downlink transmission 6-step algorithm. Simulation results show that the proposed cross-layer algorithm outperforms the mere physical layer adaptive algorithm markedly. The novel scheme is able to improve performance of the packet success rate per time chip and average packet delay, support added active users.

Physically secured orthogonal frequency division multiplexing-passive optical network employing noise-based encryption and signal recovery process

NASA Astrophysics Data System (ADS)

Jin, Wei; Zhang, Chongfu; Yuan, Weicheng

2016-02-01

We propose a physically enhanced secure scheme for direct detection-orthogonal frequency division multiplexing-passive optical network (DD-OFDM-PON) and long reach coherent detection-orthogonal frequency division multiplexing-passive optical network (LRCO-OFDM-PON), by employing noise-based encryption and channel/phase estimation. The noise data generated by chaos mapping are used to substitute training sequences in preamble to realize channel estimation and frame synchronization, and also to be embedded on variable number of key-selected randomly spaced pilot subcarriers to implement phase estimation. Consequently, the information used for signal recovery is totally hidden as unpredictable noise information in OFDM frames to mask useful information and to prevent illegal users from correctly realizing OFDM demodulation, and thereby enhancing resistance to attackers. The levels of illegal-decryption complexity and implementation complexity are theoretically discussed. Through extensive simulations, the performances of the proposed channel/phase estimation and the security introduced by encrypted pilot carriers have been investigated in both DD-OFDM and LRCO-OFDM systems. In addition, in the proposed secure DD-OFDM/LRCO-OFDM PON models, both legal and illegal receiving scenarios have been considered. These results show that, by utilizing the proposed scheme, the resistance to attackers can be significantly enhanced in DD-OFDM-PON and LRCO-OFDM-PON systems without performance degradations.

Relative phase noise induced impairment in CO-OFDM optical communication system with distributed fiber Raman amplifier.

PubMed

Wu, Jiadi; Cheng, Jingchi; Tang, Ming; Deng, Lei; Songnian, Fu; Shum, Perry Ping; Liu, Deming

2014-05-15

In this Letter, we demonstrate that the interplay between Raman pump relative intensity noise and cross-phase modulation leads to a relative phase noise (RPN) that brings non-negligible performance degradation to coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission systems with co-pumped Raman amplification. By theoretical analysis and numerical simulation, we proved that RPN brings more system impairment in terms of Q-factor penalty than the single carrier system, and relatively larger walk-off between pump and signal helps to suppress the RPN induced impairment. A higher-order modulated signal is less tolerant to RPN than a lower-order signal. With the same spectral efficiency, the quadrature-amplitude modulation format shows better tolerance to RPN than phase-shift keying. The reported findings will be useful for the design and optimization of Raman amplified CO-OFDM multi-carrier transmission systems.

Improving performance of channel equalization in RSOA-based WDM-PON by QR decomposition.

PubMed

Li, Xiang; Zhong, Wen-De; Alphones, Arokiaswami; Yu, Changyuan; Xu, Zhaowen

2015-10-19

In reflective semiconductor optical amplifier (RSOA)-based wavelength division multiplexed passive optical network (WDM-PON), the bit rate is limited by low modulation bandwidth of RSOAs. To overcome the limitation, we apply QR decomposition in channel equalizer (QR-CE) to achieve successive interference cancellation (SIC) for discrete Fourier transform spreading orthogonal frequency division multiplexing (DFT-S OFDM) signal. Using an RSOA with a 3-dB modulation bandwidth of only ~800 MHz, we experimentally demonstrate a 15.5-Gb/s over 20-km SSMF DFT-S OFDM transmission with QR-CE. The experimental results show that DFTS-OFDM with QR-CE attains much better BER performance than DFTS-OFDM and OFDM with conventional channel equalizers. The impacts of several parameters on QR-CE are investigated. It is found that 2 sub-bands in one OFDM symbol and 1 pilot in each sub-band are sufficient to achieve optimal performance and maintain the high spectral efficiency.

Estimating the Volterra Series Transfer Function over coherent optical OFDM for efficient monitoring of the fiber channel nonlinearity.

PubMed

Shulkind, Gal; Nazarathy, Moshe

2012-12-17

We present an efficient method for system identification (nonlinear channel estimation) of third order nonlinear Volterra Series Transfer Function (VSTF) characterizing the four-wave-mixing nonlinear process over a coherent OFDM fiber link. Despite the seemingly large number of degrees of freedom in the VSTF (cubic in the number of frequency points) we identified a compressed VSTF representation which does not entail loss of information. Additional slightly lossy compression may be obtained by discarding very low power VSTF coefficients associated with regions of destructive interference in the FWM phased array effect. Based on this two-staged VSTF compressed representation, we develop a robust and efficient algorithm of nonlinear system identification (optical performance monitoring) estimating the VSTF by transmission of an extended training sequence over the OFDM link, performing just a matrix-vector multiplication at the receiver by a pseudo-inverse matrix which is pre-evaluated offline. For 512 (1024) frequency samples per channel, the VSTF measurement takes less than 1 (10) msec to complete with computational complexity of one real-valued multiply-add operation per time sample. Relative to a naïve exhaustive three-tone-test, our algorithm is far more tolerant of ASE additive noise and its acquisition time is orders of magnitude faster.

Demonstration of DFTS-OFDM and equalization technology using in VLC communication on the headset port of Android device

NASA Astrophysics Data System (ADS)

Wang, Fumin; Shi, Meng; Chi, Nan

2016-10-01

Visible light communication (VLC) is one of the hottest research directions in wireless communication. It is safe, fast and free of electromagnetic interference. We carry out the visible light communication using DFTS-OFDM modulation mode through the headset port to and take equalization technique to compensate the channel. In this paper, we first test the feasibility of the DFTS-OFDM modulated VLC system by analyzing the constellation and the transmission error rate via the headset interface of the smartphone. Then we change the peak value of the signal generated by the AWG as well as the static current to find the best working point. We tested the effect of changing the up-sample number on the BER performance of the communication system, and compared the BER performance of 16QAM and 8QAM modulation in different equalization method. We also do experiment to find how distance affect the performance of the communication and the maximum communication rate that can be achieved. We successfully demonstrated a visible light communication system detected by a headset port of a smart phone for a 32QAM DFTS-OFDM modulated signal of 27.5kb/s over a 3-meter free space transmission. The light source is traditional phosphorescent white LED. This result, as far as we know, is the highest data rate of VLC system via headset port detection.

An introduction to digital modulation and OFDM techniques

NASA Astrophysics Data System (ADS)

Maddocks, M. C. D.

This report differs from most BBC Research Department reports in that it does not contain details of a specific project undertaken at Kingswood Warren. While there has been a continuing development of aspects of digital modulation systems by BBC research engineers over many years, the purpose of this report is to be tutorial. That is, digital transmission techniques need to be explained in a general way if full advantage is to be obtained from other reports concerning digital broadcasting transmission systems. There are, however, references to other specialized publications if particular details are required. The text of this report is based on a paper which was prepared for an Institution of Electrical Engineers' vacation school on new broadcast standards and systems. It discusses, at a general level, the various issues and trade-offs that must be considered in the design of a digital modulation system for broadcast use. It particularly concentrates on giving a simple description of the use and benefits of OFDM systems. The particular issues can be applied to various future broadcast systems which are under development at the BBC and as part of collaborative work in international projects.

A combination of selected mapping and clipping to increase energy efficiency of OFDM systems

PubMed Central

Lee, Byung Moo; Rim, You Seung

2017-01-01

We propose an energy efficient combination design for OFDM systems based on selected mapping (SLM) and clipping peak-to-average power ratio (PAPR) reduction techniques, and show the related energy efficiency (EE) performance analysis. The combination of two different PAPR reduction techniques can provide a significant benefit in increasing EE, because it can take advantages of both techniques. For the combination, we choose the clipping and SLM techniques, since the former technique is quite simple and effective, and the latter technique does not cause any signal distortion. We provide the structure and the systematic operating method, and show the various analyzes to derive the EE gain based on the combined technique. Our analysis show that the combined technique increases the EE by 69% compared to no PAPR reduction, and by 19.34% compared to only using SLM technique. PMID:29023591

Effects of HPA-nonlinearity on a 4-DPSK/OFDM-signal for a digital sound broadcasting signal

NASA Astrophysics Data System (ADS)

Rapp, Christoph

1991-10-01

Orthogonal Frequency Division Multiplexing (OFDM) in conjunction with a 4 Differential Phase Shift Keying (DPSK) modulation format has been proposed for the future Digital Audio Broadcasting system (DAB), that should provide compact disk sound quality in portable, vehicular and fixed receivers. With properly chosen parameters, this system should be appropriate for both terrestrial and satellite transmission. The influence of the nonlinear distorsions introduced by the High Power Amplifier (HPA) of the transmitter is examined. In particular, the degradations in power efficiency due to intermodulation effects and backoff operating, as well as spectral degradations are investigated. It is shown for three different kinds of limiting amplifier models, that even with an output backoff in the region of 5 to 6 dB, the degradation of, for example a 512 carrier 4 DPSK/OFDM system relative to the linear case is below 1.7 dB (Pb = 0.0001), while the regenerated sidelobes of the transmitted spectrum are kept below -20 dB.

Terabit optical OFDM superchannel transmission via coherent carriers of a hybrid chip-scale soliton frequency comb

NASA Astrophysics Data System (ADS)

Geng, Yong; Huang, Xiatao; Cui, Wenwen; Ling, Yun; Xu, Bo; Zhang, Jin; Yi, Xingwen; Wu, Baojian; Huang, Shu-Wei; Qiu, Kun; Wong, Chee Wei; Zhou, Heng

2018-05-01

We demonstrate seamless channel multiplexing and high bitrate superchannel transmission of coherent optical orthogonal-frequency-division-multiplexing (CO-OFDM) data signals utilizing a dissipative Kerr soliton (DKS) frequency comb generated in an on-chip microcavity. Aided by comb line multiplication through Nyquist pulse modulation, the high stability and mutual coherence among mode-locked Kerr comb lines are exploited for the first time to eliminate the guard intervals between communication channels and achieve full spectral density bandwidth utilization. Spectral efficiency as high as 2.625 bit/Hz/s is obtained for 180 CO-OFDM bands encoded with 12.75 Gbaud 8-QAM data, adding up to total bitrate of 6.885 Tb/s within 2.295 THz frequency comb bandwidth. Our study confirms that high coherence is the key superiority of Kerr soliton frequency combs over independent laser diodes, as a multi-spectral coherent laser source for high-bandwidth high-spectral-density transmission networks.

Impairment assessment of orthogonal frequency division multiplexing over dispersion-managed links in backbone and backhaul networks

NASA Astrophysics Data System (ADS)

Tamilarasan, Ilavarasan; Saminathan, Brindha; Murugappan, Meenakshi

2016-04-01

The past decade has seen the phenomenal usage of orthogonal frequency division multiplexing (OFDM) in the wired as well as wireless communication domains, and it is also proposed in the literature as a future proof technique for the implementation of flexible resource allocation in cognitive optical networks. Fiber impairment assessment and adaptive compensation becomes critical in such implementations. A comprehensive analytical model for impairments in OFDM-based fiber links is developed. The proposed model includes the combined impact of laser phase fluctuations, fiber dispersion, self phase modulation, cross phase modulation, four-wave mixing, the nonlinear phase noise due to the interaction of amplified spontaneous emission with fiber nonlinearities, and the photodetector noises. The bit error rate expression for the proposed model is derived based on error vector magnitude estimation. The performance analysis of the proposed model is presented and compared for dispersion compensated and uncompensated backbone/backhaul links. The results suggest that OFDM would perform better for uncompensated links than the compensated links due to the negligible FWM effects and there is a need for flexible compensation. The proposed model can be employed in cognitive optical networks for accurate assessment of fiber-related impairments.

All optical OFDM transmission for passive optical networks

NASA Astrophysics Data System (ADS)

Kachare, Nitin; Ashik T., J.; Bai, K. Kalyani; Kumar, D. Sriram

2017-06-01

This paper demonstrates the idea of data transmission at a very higher rate (Tbits/s) through optical fibers in a passive optical network using the most efficient data transmission technique widely used in wireless communication that is orthogonal frequency division multiplexing. With an increase in internet users, data traffic has also increased significantly and the current dense wavelength division multiplexing (DWDM) systems may not support the next generation passive optical networks (PONs) requirements. The approach discussed in this paper allows to increase the downstream data rate per user and extend the standard single-mode fiber reach for future long-haul applications. All-optical OFDM is a promising solution for terabit per second capable single wavelength transmission, with high spectral efficiency and high tolerance to chromatic dispersion.

Reduction of PAPR in coded OFDM using fast Reed-Solomon codes over prime Galois fields

NASA Astrophysics Data System (ADS)

Motazedi, Mohammad Reza; Dianat, Reza

2017-02-01

In this work, two new techniques using Reed-Solomon (RS) codes over GF(257) and GF(65,537) are proposed for peak-to-average power ratio (PAPR) reduction in coded orthogonal frequency division multiplexing (OFDM) systems. The lengths of these codes are well-matched to the length of OFDM frames. Over these fields, the block lengths of codes are powers of two and we fully exploit the radix-2 fast Fourier transform algorithms. Multiplications and additions are simple modulus operations. These codes provide desirable randomness with a small perturbation in information symbols that is essential for generation of different statistically independent candidates. Our simulations show that the PAPR reduction ability of RS codes is the same as that of conventional selected mapping (SLM), but contrary to SLM, we can get error correction capability. Also for the second proposed technique, the transmission of side information is not needed. To the best of our knowledge, this is the first work using RS codes for PAPR reduction in single-input single-output systems.

Study on a low complexity adaptive modulation algorithm in OFDM-ROF system with sub-carrier grouping technology

NASA Astrophysics Data System (ADS)

Liu, Chong-xin; Liu, Bo; Zhang, Li-jia; Xin, Xiang-jun; Tian, Qing-hua; Tian, Feng; Wang, Yong-jun; Rao, Lan; Mao, Yaya; Li, Deng-ao

2018-01-01

During the last decade, the orthogonal frequency division multiplexing radio-over-fiber (OFDM-ROF) system with adaptive modulation technology is of great interest due to its capability of raising the spectral efficiency dramatically, reducing the effects of fiber link or wireless channel, and improving the communication quality. In this study, according to theoretical analysis of nonlinear distortion and frequency selective fading on the transmitted signal, a low-complexity adaptive modulation algorithm is proposed in combination with sub-carrier grouping technology. This algorithm achieves the optimal performance of the system by calculating the average combined signal-to-noise ratio of each group and dynamically adjusting the origination modulation format according to the preset threshold and user's requirements. At the same time, this algorithm takes the sub-carrier group as the smallest unit in the initial bit allocation and the subsequent bit adjustment. So, the algorithm complexity is only 1 /M (M is the number of sub-carriers in each group) of Fischer algorithm, which is much smaller than many classic adaptive modulation algorithms, such as Hughes-Hartogs algorithm, Chow algorithm, and is in line with the development direction of green and high speed communication. Simulation results show that the performance of OFDM-ROF system with the improved algorithm is much better than those without adaptive modulation, and the BER of the former achieves 10e1 to 10e2 times lower than the latter when SNR values gets larger. We can obtain that this low complexity adaptive modulation algorithm is extremely useful for the OFDM-ROF system.

Real-time experimental demonstrations of software reconfigurable optical OFDM transceivers utilizing DSP-based digital orthogonal filters for SDN PONs.

PubMed

Duan, X; Giddings, R P; Bolea, M; Ling, Y; Cao, B; Mansoor, S; Tang, J M

2014-08-11

Real-time optical OFDM (OOFDM) transceivers with on-line software-controllable channel reconfigurability and transmission performance adaptability are experimentally demonstrated, for the first time, utilizing Hilbert-pair-based 32-tap digital orthogonal filters implemented in FPGAs. By making use of an 8-bit DAC/ADC operating at 2GS/s, an oversampling factor of 2 and an EML intensity modulator, the demonstrated RF conversion-free transceiver supports end-to-end real-time simultaneous adaptive transmissions, within a 1GHz signal spectrum region, of a 2.03Gb/s in-phase OOFDM channel and a 1.41Gb/s quadrature-phase OOFDM channel over a 25km SSMF IMDD system. In addition, detailed experimental explorations are also undertaken of key physical mechanisms limiting the maximum achievable transmission performance, impacts of transceiver's channel multiplexing/demultiplexing operations on the system BER performance, and the feasibility of utilizing adaptive modulation to combat impairments associated with low-complexity digital filter designs. Furthermore, experimental results indicate that the transceiver incorporating a fixed digital orthogonal filter DSP architecture can be made transparent to various signal modulation formats up to 64-QAM.

Self-homodyne optical OFDM for broadband WDM-PONs with crosstalk-free remodulation and enhanced tolerance to Rayleigh noise

NASA Astrophysics Data System (ADS)

Lyu, WeiChao; Wang, Andong; Xie, Dequan; Zhu, Long; Guan, Xun; Wang, Jian; Xu, Jing

2018-05-01

We propose a novel architecture for wavelength-division-multiplexed passive optical network (WDM-PON) that can simultaneously circumvent both remodulation crosstalk and Rayleigh noise, based on self-homodyne detection and optical orthogonal frequency-division multiplexing (OFDM) remodulation. The proposed self-homodyne detection at optical network unit (ONU) requires neither frequency offset compensation nor phase noise compensation, and thus can significantly reduce system complexity and power consumption. Bidirectional transmission of 12.5 Gb/s down- and up-stream signals, via single 25 km single-mode fiber without dispersion compensation, is demonstrated in a proof-of-concept experiment.

Joint Transmit Power Allocation and Splitting for SWIPT Aided OFDM-IDMA in Wireless Sensor Networks

PubMed Central

Li, Shanshan; Zhou, Xiaotian; Wang, Cheng-Xiang; Yuan, Dongfeng; Zhang, Wensheng

2017-01-01

In this paper, we propose to combine Orthogonal Frequency Division Multiplexing-Interleave Division Multiple Access (OFDM-IDMA) with Simultaneous Wireless Information and Power Transfer (SWIPT), resulting in SWIPT aided OFDM-IDMA scheme for power-limited sensor networks. In the proposed system, the Receive Node (RN) applies Power Splitting (PS) to coordinate the Energy Harvesting (EH) and Information Decoding (ID) process, where the harvested energy is utilized to guarantee the iterative Multi-User Detection (MUD) of IDMA to work under sufficient number of iterations. Our objective is to minimize the total transmit power of Source Node (SN), while satisfying the requirements of both minimum harvested energy and Bit Error Rate (BER) performance from individual receive nodes. We formulate such a problem as a joint power allocation and splitting one, where the iteration number of MUD is also taken into consideration as the key parameter to affect both EH and ID constraints. To solve it, a sub-optimal algorithm is proposed to determine the power profile, PS ratio and iteration number of MUD in an iterative manner. Simulation results verify that the proposed algorithm can provide significant performance improvement. PMID:28677636

Joint Transmit Power Allocation and Splitting for SWIPT Aided OFDM-IDMA in Wireless Sensor Networks.

PubMed

Li, Shanshan; Zhou, Xiaotian; Wang, Cheng-Xiang; Yuan, Dongfeng; Zhang, Wensheng

2017-07-04

In this paper, we propose to combine Orthogonal Frequency Division Multiplexing-Interleave Division Multiple Access (OFDM-IDMA) with Simultaneous Wireless Information and Power Transfer (SWIPT), resulting in SWIPT aided OFDM-IDMA scheme for power-limited sensor networks. In the proposed system, the Receive Node (RN) applies Power Splitting (PS) to coordinate the Energy Harvesting (EH) and Information Decoding (ID) process, where the harvested energy is utilized to guarantee the iterative Multi-User Detection (MUD) of IDMA to work under sufficient number of iterations. Our objective is to minimize the total transmit power of Source Node (SN), while satisfying the requirements of both minimum harvested energy and Bit Error Rate (BER) performance from individual receive nodes. We formulate such a problem as a joint power allocation and splitting one, where the iteration number of MUD is also taken into consideration as the key parameter to affect both EH and ID constraints. To solve it, a sub-optimal algorithm is proposed to determine the power profile, PS ratio and iteration number of MUD in an iterative manner. Simulation results verify that the proposed algorithm can provide significant performance improvement.

Optimum Adaptive Modulation and Channel Coding Scheme for Frequency Domain Channel-Dependent Scheduling in OFDM Based Evolved UTRA Downlink

NASA Astrophysics Data System (ADS)

Miki, Nobuhiko; Kishiyama, Yoshihisa; Higuchi, Kenichi; Sawahashi, Mamoru; Nakagawa, Masao

In the Evolved UTRA (UMTS Terrestrial Radio Access) downlink, Orthogonal Frequency Division Multiplexing (OFDM) based radio access was adopted because of its inherent immunity to multipath interference and flexible accommodation of different spectrum arrangements. This paper presents the optimum adaptive modulation and channel coding (AMC) scheme when resource blocks (RBs) is simultaneously assigned to the same user when frequency and time domain channel-dependent scheduling is assumed in the downlink OFDMA radio access with single-antenna transmission. We start by presenting selection methods for the modulation and coding scheme (MCS) employing mutual information both for RB-common and RB-dependent modulation schemes. Simulation results show that, irrespective of the application of power adaptation to RB-dependent modulation, the improvement in the achievable throughput of the RB-dependent modulation scheme compared to that for the RB-common modulation scheme is slight, i.e., 4 to 5%. In addition, the number of required control signaling bits in the RB-dependent modulation scheme becomes greater than that for the RB-common modulation scheme. Therefore, we conclude that the RB-common modulation and channel coding rate scheme is preferred, when multiple RBs of the same coded stream are assigned to one user in the case of single-antenna transmission.

2 × 2 MIMO OFDM/OQAM radio signals over an elliptical core few-mode fiber.

PubMed

Mo, Qi; He, Jiale; Yu, Dawei; Deng, Lei; Fu, Songnian; Tang, Ming; Liu, Deming

2016-10-01

We experimentally demonstrate a 4.46  Gb/s2×2 multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM)/OQAM radio signal over a 2 km elliptical core 3-mode fiber, together with 0.4 m wireless transmission. Meanwhile, to cope with differential channel delay (DCD) among involved MIMO channels, we propose a time-offset crosstalk cancellation algorithm to extend the DCD tolerance from 10 to 60 ns without using a circle prefix (CP), leading to an 18.7% improvement of spectral efficiency. For the purpose of comparison, we also examine the transmission performance of CP-OFDM signals with different lengths of CPs, under the same system configuration. The proposed algorithm is also effective for the DCD compensation of a radio signal over a 2 km 7-core fiber. These results not only demonstrate the feasibility of space division multiplexing for RoF application but also validate that the elliptical core few-mode fiber can provide the same independent channels as the multicore fiber.

Object-Based Attention and Cognitive Tunneling

ERIC Educational Resources Information Center

Jarmasz, Jerzy; Herdman, Chris M.; Johannsdottir, Kamilla Run

2005-01-01

Simulator-based research has shown that pilots cognitively tunnel their attention on head-up displays (HUDs). Cognitive tunneling has been linked to object-based visual attention on the assumption that HUD symbology is perceptually grouped into an object that is perceived and attended separately from the external scene. The present research…

NB-PLC channel modelling with cyclostationary noise addition & OFDM implementation for smart grid

NASA Astrophysics Data System (ADS)

Thomas, Togis; Gupta, K. K.

2016-03-01

Power line communication (PLC) technology can be a viable solution for the future ubiquitous networks because it provides a cheaper alternative to other wired technology currently being used for communication. In smart grid Power Line Communication (PLC) is used to support communication with low rate on low voltage (LV) distribution network. In this paper, we propose the channel modelling of narrowband (NB) PLC in the frequency range 5 KHz to 500 KHz by using ABCD parameter with cyclostationary noise addition. Behaviour of the channel was studied by the addition of 11KV/230V transformer, by varying load location and load. Bit error rate (BER) Vs signal to noise ratio SNR) was plotted for the proposed model by employing OFDM. Our simulation results based on the proposed channel model show an acceptable performance in terms of bit error rate versus signal to noise ratio, which enables communication required for smart grid applications.

Adaptive and Cognitive Ground and Wall Penetrating Radar System

DTIC Science & Technology

2015-04-24

biosensing and active entangled photon radar. The concept behind the nonlinear biosensing is to the use the AC-GWPRS as a probe to measure the...the UVM campus that are willing to collaborate on this line of research. The active entangled photon radar concept centers around recent...Figure 44 Typical OFDM radar test results: a. Time domain OFDM signal with top trace original signal in time domain from Matlab , and bottom trace

Spectrum sensing and resource allocation for multicarrier cognitive radio systems under interference and power constraints

NASA Astrophysics Data System (ADS)

Dikmese, Sener; Srinivasan, Sudharsan; Shaat, Musbah; Bader, Faouzi; Renfors, Markku

2014-12-01

Multicarrier waveforms have been commonly recognized as strong candidates for cognitive radio. In this paper, we study the dynamics of spectrum sensing and spectrum allocation functions in cognitive radio context using very practical signal models for the primary users (PUs), including the effects of power amplifier nonlinearities. We start by sensing the spectrum with energy detection-based wideband multichannel spectrum sensing algorithm and continue by investigating optimal resource allocation methods. Along the way, we examine the effects of spectral regrowth due to the inevitable power amplifier nonlinearities of the PU transmitters. The signal model includes frequency selective block-fading channel models for both secondary and primary transmissions. Filter bank-based wideband spectrum sensing techniques are applied for detecting spectral holes and filter bank-based multicarrier (FBMC) modulation is selected for transmission as an alternative multicarrier waveform to avoid the disadvantage of limited spectral containment of orthogonal frequency-division multiplexing (OFDM)-based multicarrier systems. The optimization technique used for the resource allocation approach considered in this study utilizes the information obtained through spectrum sensing and knowledge of spectrum leakage effects of the underlying waveforms, including a practical power amplifier model for the PU transmitter. This study utilizes a computationally efficient algorithm to maximize the SU link capacity with power and interference constraints. It is seen that the SU transmission capacity depends critically on the spectral containment of the PU waveform, and these effects are quantified in a case study using an 802.11-g WLAN scenario.

PAPR reduction and receiver sensitivity improvement in 16QAM-OFDM RoF system using DMT modulation and BTN-PS technique

NASA Astrophysics Data System (ADS)

Shao, Yufeng

2016-03-01

In this letter, we present the generation, the peak-to average power ratio (PAPR) reduction, the heterodyne detection, the self-mixing reception, and the transmission performance evaluation of 16QAM-OFDM signals in 60 GHz radio over fiber (RoF) system using Discrete multitone (DMT) modulation and Better Than Nyquist pulse shaping (BTN-PS) technique. DMT modulation is introduced in the RoF system, in-phase and quadrature (IQ) will not be required using BTN-PS method, and the computation complexity is much lower than other published techniques for reduced PAPR in the RoF system. In the experiment, 5 Gb/s 16QAM-OFDM downlink signals are transmitted over 42 km SMF-28 and a 0.4 m wireless channel. The experimental results show that the receiver sensitivity is effectively enhanced using this method. Therefore, the introduced BTN-PS technique and its application is a competitive scheme for reducing PAPR, and enhancing the receiver sensitivity in future RoF system.

Cognition-Based Approaches for High-Precision Text Mining

ERIC Educational Resources Information Center

Shannon, George John

2017-01-01

This research improves the precision of information extraction from free-form text via the use of cognitive-based approaches to natural language processing (NLP). Cognitive-based approaches are an important, and relatively new, area of research in NLP and search, as well as linguistics. Cognitive approaches enable significant improvements in both…

Energy-efficient orthogonal frequency division multiplexing-based passive optical network based on adaptive sleep-mode control and dynamic bandwidth allocation

NASA Astrophysics Data System (ADS)

Zhang, Chongfu; Xiao, Nengwu; Chen, Chen; Yuan, Weicheng; Qiu, Kun

2016-02-01

We propose an energy-efficient orthogonal frequency division multiplexing-based passive optical network (OFDM-PON) using adaptive sleep-mode control and dynamic bandwidth allocation. In this scheme, a bidirectional-centralized algorithm named the receiver and transmitter accurate sleep control and dynamic bandwidth allocation (RTASC-DBA), which has an overall bandwidth scheduling policy, is employed to enhance the energy efficiency of the OFDM-PON. The RTASC-DBA algorithm is used in an optical line terminal (OLT) to control the sleep mode of an optical network unit (ONU) sleep and guarantee the quality of service of different services of the OFDM-PON. The obtained results show that, by using the proposed scheme, the average power consumption of the ONU is reduced by ˜40% when the normalized ONU load is less than 80%, compared with the average power consumption without using the proposed scheme.

Low-complexity peak-to-average power ratio reduction scheme for flip-orthogonal frequency division multiplexing visible light communication system based on μ-law mapping

NASA Astrophysics Data System (ADS)

Wang, Jianping; Zhang, Peiran; Lu, Huimin; Feng, LiFang

2017-06-01

An orthogonal frequency division multiplexing (OFDM) technique called flipped OFDM (flip-OFDM) is apposite for a visible light communication system that needs the transmitted signal to be real and positive. Flip-OFDM uses two consecutive OFDM subframes to transmit the positive and negative parts of the signal. However, peak-to-average power ratio (PAPR) for flip-OFDM is increased tremendously due to the low value of total average power that arises from many zero values in both the positive and flipped frames. We first analyze the performance of flip-OFDM and perform a comparison with the conventional DC-biased OFDM (DCO-OFDM); then we propose a flip-OFDM scheme combined with μ-law mapping to reduce the high PAPR. The simulation results show that the PAPR of the system is reduced about 17.2 and 5.9 dB when compared with the normal flip-OFDM and DCO-OFDM signals, respectively.

Affective-cognitive meta-bases versus structural bases of attitudes predict processing interest versus efficiency.

PubMed

See, Ya Hui Michelle; Petty, Richard E; Fabrigar, Leandre R

2013-08-01

We proposed that (a) processing interest for affective over cognitive information is captured by meta-bases (i.e., the extent to which people subjectively perceive themselves to rely on affect or cognition in their attitudes) and (b) processing efficiency for affective over cognitive information is captured by structural bases (i.e., the extent to which attitudes are more evaluatively congruent with affect or cognition). Because processing speed can disentangle interest from efficiency by being manifest as longer or shorter reading times, we hypothesized and found that more affective meta-bases predicted longer affective than cognitive reading time when processing efficiency was held constant (Study 1). In contrast, more affective structural bases predicted shorter affective than cognitive reading time when participants were constrained in their ability to allocate resources deliberatively (Study 2). When deliberation was neither encouraged nor constrained, effects for meta-bases and structural bases emerged (Study 3). Implications for affective-cognitive processing and other attitudes-relevant constructs are discussed.

A novel joint timing/frequency synchronization scheme based on Radon-Wigner transform of LFM signals in CO-OFDM systems

NASA Astrophysics Data System (ADS)

Liu, Jianfei; Wei, Ying; Zeng, Xiangye; Lu, Jia; Zhang, Shuangxi; Wang, Mengjun

2018-03-01

A joint timing and frequency synchronization method has been proposed for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) system in this paper. The timing offset (TO), integer frequency offset (FO) and the fractional FO can be realized by only one training symbol, which consists of two linear frequency modulation (LFM) signals with opposite chirp rates. By detecting the peak of LFM signals after Radon-Wigner transform (RWT), the TO and the integer FO can be estimated at the same time, moreover, the fractional FO can be acquired correspondingly through the self-correlation characteristic of the same training symbol. Simulation results show that the proposed method can give a more accurate TO estimation than the existing methods, especially at poor OSNR conditions; for the FO estimation, both the fractional and the integer FO can be estimated through the proposed training symbol with no extra overhead, a more accurate estimation and a large FO estimation range of [ - 5 GHz, 5GHz] can be acquired.

Security analysis of orthogonal-frequency-division-multiplexing-based continuous-variable quantum key distribution with imperfect modulation

NASA Astrophysics Data System (ADS)

Zhang, Hang; Mao, Yu; Huang, Duan; Li, Jiawei; Zhang, Ling; Guo, Ying

2018-05-01

We introduce a reliable scheme for continuous-variable quantum key distribution (CV-QKD) by using orthogonal frequency division multiplexing (OFDM). As a spectrally efficient multiplexing technique, OFDM allows a large number of closely spaced orthogonal subcarrier signals used to carry data on several parallel data streams or channels. We place emphasis on modulator impairments which would inevitably arise in the OFDM system and analyze how these impairments affect the OFDM-based CV-QKD system. Moreover, we also evaluate the security in the asymptotic limit and the Pirandola-Laurenza-Ottaviani-Banchi upper bound. Results indicate that although the emergence of imperfect modulation would bring about a slight decrease in the secret key bit rate of each subcarrier, the multiplexing technique combined with CV-QKD results in a desirable improvement on the total secret key bit rate which can raise the numerical value about an order of magnitude.

Adaptive nonlinear Volterra equalizer for mitigation of chirp-induced distortions in cost effective IMDD OFDM systems.

PubMed

André, Nuno Sequeira; Habel, Kai; Louchet, Hadrien; Richter, André

2013-11-04

We report experimental validations of an adaptive 2nd order Volterra equalization scheme for cost effective IMDD OFDM systems. This equalization scheme was applied to both uplink and downlink transmission. Downlink settings were optimized for maximum bitrate where we achieved 34 Gb/s over 10 km of SSMF using an EML with 10 GHz bandwidth. For the uplink, maximum reach was optimized achieving 14 Gb/s using a low-cost DML with 2.5 GHz bandwidth.

[Mindfulness-Based Cognitive Therapy (MBCT) and the 'Third Wave' of Cognitive-Bahavioral Therapies (CBT)].

PubMed

Garay, Cristian J; Korman, Guido P; Keegan, Eduardo G

2015-01-01

The paper presents the reasons that led to the incorporation of mindfulness as part of a cognitive therapy approach to the prevention of relapse of recurrent depressive disorders. It describes the context in which models focused on the contents of cognition gave way to models focused on cognitive processes. We highlight the problems encountered by the standard cognitive model when trying to account for the cognitive vulnerability of individuals who, having experienced a depressive episode, are in remission. We briefly describe the theoretical foundations of Mindfulness-Based Cognitive Therapy and its therapeutic approach.

[Acceptance and mindfulness-based cognitive-behavioral therapies].

PubMed

Ngô, Thanh-Lan

2013-01-01

Cognitive behavioral therapy (CBT) is one of the main approaches in psychotherapy. It teaches the patient to examine the link between dysfunctional thoughts and maladaptive behaviors and to re- evaluate the cognitive biases involved in the maintenance of symptoms by using strategies such as guided discovery. CBT is constantly evolving in part to improve its' effectiveness and accessibility. Thus in the last decade, increasingly popular approaches based on mindfulness and acceptance have emerged. These therapies do not attempt to modify cognitions even when they are biased and dysfunctional but rather seek a change in the relationship between the individual and the symptoms. This article aims to present the historical context that has allowed the emergence of this trend, the points of convergence and divergence with traditional CBT as well as a brief presentation of the different therapies based on mindfulness meditation and acceptance. Hayes (2004) described three successive waves in behavior therapy, each characterized by "dominant assumptions, methods and goals": traditional behavior therapy, cognitive therapy and therapies based on mindfulness meditation and acceptance. The latter consider that human suffering occurs when the individual lives a restricted life in order avoid pain and immediate discomfort to the detriment of his global wellbeing. These therapies combine mindfulness, experiential, acceptance strategies with traditional behavior principles in order to attain lasting results. There are significant points of convergence between traditional CBT and therapies based on mindfulness meditation and acceptance. They are both empirically validated, based upon a theoretical model postulating that avoidance is key in the maintenance of psychopathology and they recommend an approach strategy in order to overcome the identified problem. They both use behavioral techniques in the context of a collaborative relationship in order to identify precise problems and to

Blind identification of the number of sub-carriers for orthogonal frequency division multiplexing-based elastic optical networking

NASA Astrophysics Data System (ADS)

Zhao, Lei; Xu, Hengying; Bai, Chenglin

2018-03-01

In orthogonal frequency division multiplexing (OFDM)-based elastic optical networking (EON), it is imperative to identify unknown parameters of OFDM-based EON signals quickly, intelligently and robustly. Because the number of sub-carriers determines the size of the sub-carriers spacing and then affects the symbol period of the OFDM and the anti-dispersion capability of the system, the identification of the number of sub-carriers has a profound effect on the identification of other key parameters of the system. In this paper, we proposed a method of number identification for sub-carriers of OFDM-based EON signals with help of high-order cyclic cumulant. The specific fourth-order cyclic cumulant exists only at the location of its sub-carriers frequencies. So the identification of the number of sub-carriers can be implemented by detecting the cyclic-frequencies. The proposed scheme in our study can be divided into three sub-stages, i.e. estimating the spectral range, calculating the high-order cyclic cumulant and identifying the number of sub-carriers. When the optical signal-to-noise ratios (OSNR) varied from 16dB to 22dB, the number of sub-carriers (64-512) was successfully identified in the experiment, and from the statistical point of view, the average identification absolute accuracy (IAAs) exceeded 94%.

Mindfulness-Based Cognitive Hypnotherapy and Skin Disorders.

PubMed

Shenefelt, Philip D

2018-07-01

Mindfulness-based cognitive hypnotherapy integrates mindfulness, cognitive-behavioral therapy, and hypnotherapy to improve physical, emotional, mental, and/or spiritual aspects of skin disorders. Meditation, including mindfulness meditation, and hypnosis both utilize trance phenomena to help produce focalization and specific improvements in skin disorders through psycho-neuro-endocrine-immunologic mechanisms. Hypnosis, cognitive hypnotherapy, focused meditation, and mindfulness meditation are discussed with respect to improving various skin disorders including acne, acne excoriée, alopecia areata, atopic dermatitis, congenital ichthyosiform erythroderma, dyshidrotic dermatitis, erythema nodosum, erythromelalgia, furuncles, glossodynia, herpes simplex, hyperhidrosis, ichthyosis vulgaris, lichen planus, neurodermatitis, nummular dermatitis, postherpetic neuralgia, prurigo nodularis, pruritus, psoriasis, rosacea, trichotillomania, urticaria, verruca vulgaris, and vitiligo. Their integration into mindfulness-based cognitive hypnotherapy is then discussed and illustrated with improvement in a patient with systemic lupus erythematosus.

Mindfulness-Based Cognitive Therapy for Bipolar Disorder: Effects on Cognitive Functioning

PubMed Central

Stange, Jonathan P.; Eisner, Lori R.; Hölzel, Britta K.; Peckham, Andrew D.; Dougherty, Darin D.; Rauch, Scott L.; Nierenberg, Andrew A.; Lazar, Sara; Deckersbach, Thilo

2012-01-01

Bipolar disorder is associated with impairments in cognition, including difficulties in executive functioning, even when patients are euthymic (neither depressed nor manic). The purpose of this study was to assess changes in self-reported cognitive functioning in patients with bipolar disorder who participated in an open pilot trial of mindfulness-based cognitive therapy (MBCT). Following MBCT, patients reported significant improvements in executive functioning, memory, and ability to initiate and complete tasks, as measured by the Behavior Rating Inventory of Executive Function (BRIEF) and the Frontal Systems Behavior Scale (FrSBe). Changes in cognitive functioning were correlated with increases in mindful, nonjudgmental observance and awareness of thoughts, feelings, and sensations, and were not associated with decreases in depression. Improvements tended to diminish after termination of treatment, but some improvements, particularly those in executive functioning, persisted after 3 months. These results provide preliminary evidence that MBCT may be a treatment option that can be used as an adjunct to medication to improve cognitive functioning in bipolar disorder. PMID:22108398

A Chaos MIMO-OFDM Scheme for Mobile Communication with Physical-Layer Security

NASA Astrophysics Data System (ADS)

Okamoto, Eiji

Chaos communications enable a physical-layer security, which can enhance the transmission security in combining with upper-layer encryption techniques, or can omit the upper-layer secure protocol and enlarges the transmission efficiency. However, the chaos communication usually degrades the error rate performance compared to unencrypted digital modulations. To achieve both physical-layer security and channel coding gain, we have proposed a chaos multiple-input multiple-output (MIMO) scheme in which a rate-one chaos convolution is applied to MIMO multiplexing. However, in the conventional study only flat fading is considered. To apply this scheme to practical mobile environments, i.e., multipath fading channels, we propose a chaos MIMO-orthogonal frequency division multi-plexing (OFDM) scheme and show its effectiveness through computer simulations.

The Cognitive, Perceptual, and Neural Bases of Skilled Performance

DTIC Science & Technology

1994-02-01

technical report 3/15/90-3/14/93 4. TITLE AND SUBTITLE S. FUNDING NUMBERS The Cognitive , Perceptual, and Neural Bases AFOSR 90-0175 of Skilled... COGNITIVE , PERCEPTUAL, AND NEURAL BASES OF SKILLED PERFORMANCE March 15, 1990-March 14, 1993 Principal Investigator: Stephen Grossberg Wang Professor of... Cognitive and Neural Systems Professor of Mathematics, Psychology, and Biomedical Engineering Director, Center for Adaptive Systems Chairman, Department

Novel Television-Based Cognitive Training Improves Working Memory and Executive Function

PubMed Central

Shatil, Evelyn; Mikulecká, Jaroslava; Bellotti, Francesco; Bureš, Vladimír

2014-01-01

The main study objective was to investigate the effect of interactive television-based cognitive training on cognitive performance of 119 healthy older adults, aged 60–87 years. Participants were randomly allocated to a cognitive training group or to an active control group in a single-blind controlled two-group design. Before and after training interactive television cognitive performance was assessed on well validated tests of fluid, higher-order ability, and system usability was evaluated. The participants in the cognitive training group completed a television-based cognitive training programme, while the participants in the active control group completed a TV-based programme of personally benefiting activities. Significant improvements were observed in well validated working memory and executive function tasks in the cognitive training but not in the control group. None of the groups showed statistically significant improvement in life satisfaction score. Participants' reports of “adequate” to “high” system usability testify to the successful development and implementation of the interactive television-based system and compliant cognitive training contents. The study demonstrates that cognitive training delivered by means of an interactive television system can generate genuine cognitive benefits in users and these are measurable using well-validated cognitive tests. Thus, older adults who cannot use or afford a computer can easily use digital interactive television to benefit from advanced software applications designed to train cognition. PMID:24992187

Web-Based Programs Assess Cognitive Fitness

NASA Technical Reports Server (NTRS)

2009-01-01

The National Space Biomedical Research Institute, based in Houston and funded by NASA, began funding research for Harvard University researchers to design Palm software to help astronauts monitor and assess their cognitive functioning. The MiniCog Rapid Assessment Battery (MRAB) was licensed by the Criteria Corporation in Los Angeles and adapted for Web-based employment testing. The test battery assesses nine different cognitive functions and can gauge the effect of stress-related deficits, such as fatigue, on various tasks. The MRAB can be used not only for pre-employment testing but also for repeat administrations to measure day-to-day job readiness in professions where alertness is critical.

Cognitive reactivity as outcome and working mechanism of mindfulness-based cognitive therapy for recurrently depressed patients in remission.

PubMed

Cladder-Micus, M B; van Aalderen, J; Donders, A R T; Spijker, J; Vrijsen, J N; Speckens, A E M

2018-03-01

Major depressive disorder is a prevalent condition with high relapse rates. There is evidence that cognitive reactivity is an important vulnerability factor for the recurrence of depression. Mindfulness-based interventions are designed to reduce relapse rates, with cognitive reactivity as one of the proposed working mechanisms. In a randomised controlled trial we compared the effect of mindfulness-based cognitive therapy (MBCT) with treatment-as-usual (TAU) on cognitive reactivity in recurrently depressed patients (N = 115). Depressive symptoms, cognitive reactivity, and mindfulness skills were assessed pre and post treatment. Patients in the MBCT group reported a significantly greater reduction in cognitive reactivity than those in the TAU group (d = .51). The reduction of cognitive reactivity appeared to mediate the association between MBCT/TAU and decrease of depressive symptoms, using pre and post scores. The current study provides evidence that MBCT reduces cognitive reactivity and preliminary evidence that cognitive reactivity is a working mechanism of MBCT.

The neural and computational bases of semantic cognition.

PubMed

Ralph, Matthew A Lambon; Jefferies, Elizabeth; Patterson, Karalyn; Rogers, Timothy T

2017-01-01

Semantic cognition refers to our ability to use, manipulate and generalize knowledge that is acquired over the lifespan to support innumerable verbal and non-verbal behaviours. This Review summarizes key findings and issues arising from a decade of research into the neurocognitive and neurocomputational underpinnings of this ability, leading to a new framework that we term controlled semantic cognition (CSC). CSC offers solutions to long-standing queries in philosophy and cognitive science, and yields a convergent framework for understanding the neural and computational bases of healthy semantic cognition and its dysfunction in brain disorders.

Optical ranging and communication method based on all-phase FFT

NASA Astrophysics Data System (ADS)

Li, Zening; Chen, Gang

2014-10-01

This paper describes an optical ranging and communication method based on all-phase fast fourier transform (FFT). This kind of system is mainly designed for vehicle safety application. Particularly, the phase shift of the reflecting orthogonal frequency division multiplexing (OFDM) symbol is measured to determine the signal time of flight. Then the distance is calculated according to the time of flight. Several key factors affecting the phase measurement accuracy are studied. The all-phase FFT, which can reduce the effects of frequency offset, phase noise and the inter-carrier interference (ICI), is applied to measure the OFDM symbol phase shift.

A monolithic RF transceiver for DC-OFDM UWB

NASA Astrophysics Data System (ADS)

Yunfeng, Chen; Wei, Li; Haipeng, Fu; Ting, Gao; Danfeng, Chen; Feng, Zhou; Deyun, Cai; Dan, Li; Yangyang, Niu; Hanchao, Zhou; Ning, Zhu; Ning, Li; Junyan, Ren

2012-02-01

This paper presents a first monolithic RF transceiver for DC-OFDM UWB applications. The proposed direct-conversion transceiver integrates all the building blocks including two receiver (Rx) cores, two transmitter (Tx) cores and a dual-carrier frequency synthesizer (DC-FS) as well as a 3-wire serial peripheral interface (SPI) to set the operating status of the transceiver. The ESD-protected chip is fabricated by a TSMC 0.13-μm RF CMOS process with a die size of 4.5 × 3.6 mm2. The measurement results show that the wideband Rx achieves an NF of 5-6.2 dB, a max gain of 76-84 dB with 64-dB variable gain, an in-/out-of-band IIP3 of -6/+4 dBm and an input loss S11 of < -10 in all bands. The Tx achieves an LOLRR/IMGRR of -34/-33 dBc, a typical OIP3 of +6 dBm and a maximum output power of -5 dBm. The DC-FS outputs two separate carriers simultaneously with an inter-band hopping time of < 1.2 ns. The full chip consumes a maximum current of 420 mA under a 1.2-V supply.

Limitations of subjective cognitive load measures in simulation-based procedural training.

PubMed

Naismith, Laura M; Cheung, Jeffrey J H; Ringsted, Charlotte; Cavalcanti, Rodrigo B

2015-08-01

The effective implementation of cognitive load theory (CLT) to optimise the instructional design of simulation-based training requires sensitive and reliable measures of cognitive load. This mixed-methods study assessed relationships between commonly used measures of total cognitive load and the extent to which these measures reflected participants' experiences of cognitive load in simulation-based procedural skills training. Two groups of medical residents (n = 38) completed three questionnaires after participating in simulation-based procedural skills training sessions: the Paas Cognitive Load Scale; the NASA Task Load Index (TLX), and a cognitive load component (CLC) questionnaire we developed to assess total cognitive load as the sum of intrinsic load (how complex the task is), extraneous load (how the task is presented) and germane load (how the learner processes the task for learning). We calculated Pearson's correlation coefficients to assess agreement among these instruments. Group interviews explored residents' perceptions about how the simulation sessions contributed to their total cognitive load. Interviews were audio-recorded, transcribed and subjected to qualitative content analysis. Total cognitive load scores differed significantly according to the instrument used to assess them. In particular, there was poor agreement between the Paas Scale and the TLX. Quantitative and qualitative findings supported intrinsic cognitive load as synonymous with mental effort (Paas Scale), mental demand (TLX) and task difficulty and complexity (CLC questionnaire). Additional qualitative themes relating to extraneous and germane cognitive loads were not reflected in any of the questionnaires. The Paas Scale, TLX and CLC questionnaire appear to be interchangeable as measures of intrinsic cognitive load, but not of total cognitive load. A more complete understanding of the sources of extraneous and germane cognitive loads in simulation-based training contexts is

Development and initial validation of a cognitive-based work-nonwork conflict scale.

PubMed

Ezzedeen, Souha R; Swiercz, Paul M

2007-06-01

Current research related to work and life outside work specifies three types of work-nonwork conflict: time, strain, and behavior-based. Overlooked in these models is a cognitive-based type of conflict whereby individuals experience work-nonwork conflict from cognitive preoccupation with work. Four studies on six different groups (N=549) were undertaken to develop and validate an initial measure of this construct. Structural equation modeling confirmed a two-factor, nine-item scale. Hypotheses regarding cognitive-based conflict's relationship with life satisfaction, work involvement, work-nonwork conflict, and work hours were supported. The relationship with knowledge work was partially supported in that only the cognitive dimension of cognitive-based conflict was related to extent of knowledge work. Hypotheses regarding cognitive-based conflict's relationship with family demands were rejected in that the cognitive dimension correlated positively rather than negatively with number of dependent children and perceived family demands. The study provides encouraging preliminary evidence of scale validity.

Experimental Evaluation of Time Diversity Effect in Hybrid ARQ Considering Space and Path Diversity for Downlink OFDM-Based Broadband Radio Access

NASA Astrophysics Data System (ADS)

Miki, Nobuhiko; Atarashi, Hiroyuki; Higuchi, Kenichi; Sawahashi, Mamoru; Nakagawa, Masao

This paper presents experimental evaluations of the effect of time diversity obtained by hybrid automatic repeat request (HARQ) with soft combining in space and path diversity schemes on orthogonal frequency division multiplexing (OFDM)-based packet radio access in a downlink broadband multipath fading channel. The effect of HARQ is analyzed through laboratory experiments employing fading simulators and field experiments conducted in downtown Yokosuka near Tokyo. After confirming the validity of experimental results based on numerical analysis of the time diversity gain in HARQ, we show by the experimental results that, for a fixed modulation and channel coding scheme (MCS), time diversity obtained by HARQ is effective in reducing the required received signal-to-interference plus noise power ratio (SINR) according to an increase in the number of transmissions, K, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity using a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain obtained by time diversity is almost saturated at the maximum number of transmissions in HARQ, K' = 4 in Chase combining and K' = 2 in Incremental redundancy, since the improvement in the residual packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the initial packet transmission arising from appropriately selecting the optimum MCS in AMC. However, the experimental results elucidate that the time diversity in HARQ with soft combining associated with antenna diversity reception is effective in improving the throughput even in a broadband multipath channel with sufficient path diversity.

Quantification of MDL-induced signal degradation in MIMO-OFDM mode-division multiplexing systems.

PubMed

Tian, Yu; Li, Juhao; Zhu, Paikun; Wu, Zhongying; Chen, Yuanxiang; He, Yongqi; Chen, Zhangyuan

2016-08-22

Mode-division multiplexing (MDM) transmission over few-mode optical fiber has emerged as a promising technology to enhance transmission capacity, in which multiple-input-multiple-output (MIMO) digital signal processing (DSP) after coherent detection is used to demultiplex the signals. Compared with conventional single-mode systems, MIMO-MDM systems suffer non-recoverable signal degradation induced by mode-dependent loss (MDL). In this paper, the MDL-induced signal degradation in orthogonal-frequency-division-multiplexing (OFDM) MDM systems is theoretically quantified in terms of mode-average error vector magnitude (EVM) through frequency domain norm analysis. A novel scalar MDL metric is proposed considering the probability distribution of the practical MDM input signals, and a closed-form expression for EVM measured after zero-force (ZF) MIMO equalization is derived. Simulation results show that the EVM estimations utilizing the novel MDL metric remain unbiased for unrepeated links. For a 6 × 100 km 20-mode MDM transmission system, the estimation accuracy is improved by more than 90% compared with that utilizing traditional condition number (CN) based MDL metric. The proposed MDL metric can be used to predict the MDL-induced SNR penalty in a theoretical manner, which will be beneficial for the design of practical MIMO-MDM systems.

Cyberpsychology: a human-interaction perspective based on cognitive modeling.

PubMed

Emond, Bruno; West, Robert L

2003-10-01

This paper argues for the relevance of cognitive modeling and cognitive architectures to cyberpsychology. From a human-computer interaction point of view, cognitive modeling can have benefits both for theory and model building, and for the design and evaluation of sociotechnical systems usability. Cognitive modeling research applied to human-computer interaction has two complimentary objectives: (1) to develop theories and computational models of human interactive behavior with information and collaborative technologies, and (2) to use the computational models as building blocks for the design, implementation, and evaluation of interactive technologies. From the perspective of building theories and models, cognitive modeling offers the possibility to anchor cyberpsychology theories and models into cognitive architectures. From the perspective of the design and evaluation of socio-technical systems, cognitive models can provide the basis for simulated users, which can play an important role in usability testing. As an example of application of cognitive modeling to technology design, the paper presents a simulation of interactive behavior with five different adaptive menu algorithms: random, fixed, stacked, frequency based, and activation based. Results of the simulation indicate that fixed menu positions seem to offer the best support for classification like tasks such as filing e-mails. This research is part of the Human-Computer Interaction, and the Broadband Visual Communication research programs at the National Research Council of Canada, in collaboration with the Carleton Cognitive Modeling Lab at Carleton University.

Post-traumatic stress disorder: cognitive hypnotherapy, mindfulness, and acceptance-based treatment approaches.

PubMed

Lynn, Steven Jay; Malakataris, Anne; Condon, Liam; Maxwell, Reed; Cleere, Colleen

2012-04-01

In this article, we describe how cognitive hypnotherapy can be used in conjunction with evidence-based practices for the treatment of post-traumatic stress disorder (PTSD). We review cognitive-behavioral interventions for PTSD, including mindfulness and acceptance-based approaches, and contend that (a) empirical support for the use of hypnosis in treating a variety of conditions is considerable; (b) hypnosis is fundamentally a cognitive-behavioral intervention; (c) psychological interventions with a firm footing in cognitive-behavioral therapy (CBT) are well-suited to treat the symptoms of PTSD; and (d) hypnosis can be a useful adjunct to evidence-based cognitive-behavioral approaches, including mindfulness and acceptance-based interventions, for treating PTSD.

Fun cube based brain gym cognitive function assessment system.

PubMed

Zhang, Tao; Lin, Chung-Chih; Yu, Tsang-Chu; Sun, Jing; Hsu, Wen-Chuin; Wong, Alice May-Kuen

2017-05-01

The aim of this study is to design and develop a fun cube (FC) based brain gym (BG) cognitive function assessment system using the wireless sensor network and multimedia technologies. The system comprised (1) interaction devices, FCs and a workstation used as interactive tools for collecting and transferring data to the server, (2) a BG information management system responsible for managing the cognitive games and storing test results, and (3) a feedback system used for conducting the analysis of cognitive functions to assist caregivers in screening high risk groups with mild cognitive impairment. Three kinds of experiments were performed to evaluate the developed FC-based BG cognitive function assessment system. The experimental results showed that the Pearson correlation coefficient between the system's evaluation outcomes and the traditional Montreal Cognitive Assessment scores was 0.83. The average Technology Acceptance Model 2 score was close to six for 31 elderly subjects. Most subjects considered that the brain games are interesting and the FC human-machine interface is easy to learn and operate. The control group and the cognitive impairment group had statistically significant difference with respect to the accuracy of and the time taken for the brain cognitive function assessment games, including Animal Naming, Color Search, Trail Making Test, Change Blindness, and Forward / Backward Digit Span. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Mindful neuropsychology: Mindfulness-based cognitive remediation].

PubMed

Bulzacka, E; Lavault, S; Pelissolo, A; Bagnis Isnard, C

2018-02-01

Mindfulness based interventions (MBI) have recently gained much interest in western medicine. MBSR paradigm is based on teaching participants to pay complete attention to the present experience and act nonjudgmentally towards stressful events. During this mental practice the meditator focuses his or her attention on the sensations of the body. While the distractions (mental images, thoughts, emotional or somatic states) arise the participant is taught to acknowledge discursive thoughts and cultivate the state of awareness without immediate reaction. The effectiveness of these programs is well documented in the field of emotional response regulation in depression (relapse prevention), anxiety disorders, obsessive-compulsive disorder or eating disorders. Furthermore, converging lines of evidence support the hypothesis that mindfulness practice improves cognition, especially the ability to sustain attention and think in a more flexible manner. Nevertheless, formal rehabilitation programs targeting cognitive disturbances resulting from psychiatric (depression, disorder bipolar, schizophrenia) or neurologic conditions (brain injury, dementia) seldom rely on MBI principles. This review of literature aims at discussing possible links between MBI and clinical neuropsychology. We conducted a review of literature using electronic databases up to December 2016, screening studies with variants of the keywords ("Mindfulness", "MBI", "MBSR", "Meditation") OR/AND ("Cognition", "Attention", "Executive function", "Memory", "Learning") RESULTS: In the first part, we describe key concepts of the neuropsychology of attention in the light of Posner's model of attention control. We also underline the potential scope of different therapeutic contexts where disturbances of attention may be clinically relevant. Second, we review the efficacy of MBI in the field of cognition (thinking disturbances, attention biases, memory and executive processes impairment or low metacognitive abilities

Behavioral, Cognitive, or Brain-Based Training?

ERIC Educational Resources Information Center

Whitmore, Paul G.

2004-01-01

Most trainers believe there are just two scientific approaches on which to base a training technology: behavioral psychology and cognitive psychology. There is a third scientific approach currently emerging that does deal with every kind of skill, and it comes from biology rather than psychology. This new approach is based on findings from…

Efficacy analysis of LDPC coded APSK modulated differential space-time-frequency coded for wireless body area network using MB-pulsed OFDM UWB technology.

PubMed

Manimegalai, C T; Gauni, Sabitha; Kalimuthu, K

2017-12-04

Wireless body area network (WBAN) is a breakthrough technology in healthcare areas such as hospital and telemedicine. The human body has a complex mixture of different tissues. It is expected that the nature of propagation of electromagnetic signals is distinct in each of these tissues. This forms the base for the WBAN, which is different from other environments. In this paper, the knowledge of Ultra Wide Band (UWB) channel is explored in the WBAN (IEEE 802.15.6) system. The measurements of parameters in frequency range from 3.1-10.6 GHz are taken. The proposed system, transmits data up to 480 Mbps by using LDPC coded APSK Modulated Differential Space-Time-Frequency Coded MB-OFDM to increase the throughput and power efficiency.

Cognitive radio based optimal channel sensing and resources allocation

NASA Astrophysics Data System (ADS)

Vijayasarveswari, V.; Khatun, S.; Fakir, M. M.; Nayeem, M. N.; Kamarudin, L. M.; Jakaria, A.

2017-03-01

Cognitive radio (CR) is the latest type of wireless technoloy that is proposed to mitigate spectrum saturation problem. İn cognitve radio, secondary user will use primary user's spectrum during primary user's absence without interupting primary user's transmission. This paper focuses on practical cognitive radio network development process using Android based smart phone for the data transmission. Energy detector based sensing method was proposed and used here because it doesnot require primary user's information. Bluetooth and Wi-fi are the two available types of spectrum that was sensed for CR detection. Simulation showed cognitive radio network can be developed using Android based smart phones. So, a complete application was developed using Java based Android Eclipse program. Finally, the application was uploaded and run on Android based smart phone to form and verify CR network for channel sensing and resource allocation. The observed efficiency of the application was around 81%.

The temporal stability and predictive validity of affect-based and cognition-based intentions.

PubMed

Keer, Mario; Conner, Mark; Van den Putte, Bas; Neijens, Peter

2014-06-01

Recent research has revealed individual differences in the extent to which people base their intentions on affect and cognition. Two studies are presented that assess whether such differences predict the strength of individuals' intention-behaviour relationships. Participants completed measures of affect, cognition, intention, and behaviour regarding a range of health behaviours. Study 1 (N = 300) found that the strength of the intention-behaviour relationship was significantly related to the extent to which individuals based their intentions on affect, but not to the extent they based them on cognition. Study 2 (N = 387) replicated the findings of the first study. In addition, Study 2 revealed that intention stability mediated the relationship between the degree people based their intentions on affect and the strength of the intention-behaviour relationship. Thus, individuals who base their intentions strongly on affect have more stable intentions, and are therefore more likely to enact them. © 2013 The British Psychological Society.

Sprint-based exercise and cognitive function in adolescents.

PubMed

Cooper, Simon B; Bandelow, Stephan; Nute, Maria L; Dring, Karah J; Stannard, Rebecca L; Morris, John G; Nevill, Mary E

2016-12-01

Moderate intensity exercise has been shown to enhance cognition in an adolescent population, yet the effect of high-intensity sprint-based exercise remains unknown and was therefore examined in the present study. Following ethical approval and familiarisation, 44 adolescents (12.6 ± 0.6 y) completed an exercise (E) and resting (R) trial in a counter-balanced, randomised crossover design. The exercise trial comprised of 10 × 10 s running sprints, interspersed by 50 s active recovery (walking). A battery of cognitive function tests (Stroop, Digit Symbol Substitution (DSST) and Corsi blocks tests) were completed 30 min pre-exercise, immediately post-exercise and 45 min post-exercise. Data were analysed using mixed effect models with repeated measures. Response times on the simple level of the Stroop test were significantly quicker 45 min following sprint-based exercise (R: 818 ± 33 ms, E: 772 ± 26 ms; p = 0.027) and response times on the complex level of the Stroop test were quicker immediately following the sprint-based exercise (R: 1095 ± 36 ms, E: 1043 ± 37 ms; p = 0.038), while accuracy was maintained. Sprint-based exercise had no immediate or delayed effects on the number of items recalled on the Corsi blocks test (p = 0.289) or substitutions made during the DSST (p = 0.689). The effect of high intensity sprint-based exercise on adolescents' cognitive function was dependant on the component of cognitive function examined. Executive function was enhanced following exercise, demonstrated by improved response times on the Stroop test, whilst visuo-spatial memory and general psycho-motor speed were unaffected. These data support the inclusion of high-intensity sprint-based exercise for adolescents during the school day to enhance cognition.

Cognitive control predicts use of model-based reinforcement learning.

PubMed

Otto, A Ross; Skatova, Anya; Madlon-Kay, Seth; Daw, Nathaniel D

2015-02-01

Accounts of decision-making and its neural substrates have long posited the operation of separate, competing valuation systems in the control of choice behavior. Recent theoretical and experimental work suggest that this classic distinction between behaviorally and neurally dissociable systems for habitual and goal-directed (or more generally, automatic and controlled) choice may arise from two computational strategies for reinforcement learning (RL), called model-free and model-based RL, but the cognitive or computational processes by which one system may dominate over the other in the control of behavior is a matter of ongoing investigation. To elucidate this question, we leverage the theoretical framework of cognitive control, demonstrating that individual differences in utilization of goal-related contextual information--in the service of overcoming habitual, stimulus-driven responses--in established cognitive control paradigms predict model-based behavior in a separate, sequential choice task. The behavioral correspondence between cognitive control and model-based RL compellingly suggests that a common set of processes may underpin the two behaviors. In particular, computational mechanisms originally proposed to underlie controlled behavior may be applicable to understanding the interactions between model-based and model-free choice behavior.

Cognitive Control Predicts Use of Model-Based Reinforcement-Learning

PubMed Central

Otto, A. Ross; Skatova, Anya; Madlon-Kay, Seth; Daw, Nathaniel D.

2015-01-01

Accounts of decision-making and its neural substrates have long posited the operation of separate, competing valuation systems in the control of choice behavior. Recent theoretical and experimental work suggest that this classic distinction between behaviorally and neurally dissociable systems for habitual and goal-directed (or more generally, automatic and controlled) choice may arise from two computational strategies for reinforcement learning (RL), called model-free and model-based RL, but the cognitive or computational processes by which one system may dominate over the other in the control of behavior is a matter of ongoing investigation. To elucidate this question, we leverage the theoretical framework of cognitive control, demonstrating that individual differences in utilization of goal-related contextual information—in the service of overcoming habitual, stimulus-driven responses—in established cognitive control paradigms predict model-based behavior in a separate, sequential choice task. The behavioral correspondence between cognitive control and model-based RL compellingly suggests that a common set of processes may underpin the two behaviors. In particular, computational mechanisms originally proposed to underlie controlled behavior may be applicable to understanding the interactions between model-based and model-free choice behavior. PMID:25170791

Cognitive Content Engagement in Content-Based Language Teaching

ERIC Educational Resources Information Center

Kong, Stella; Hoare, Philip

2011-01-01

This article reports a study of aspects of pedagogy that can bring about students' cognitive engagement with academic content and, thus, use of the academic language in content-based language lessons in three middle schools in Xi'an, China. Two criteria--academic content level and depth of processing--were used to determine cognitive content…

Interference tables: a useful model for interference analysis in asynchronous multicarrier transmission

NASA Astrophysics Data System (ADS)

Medjahdi, Yahia; Terré, Michel; Ruyet, Didier Le; Roviras, Daniel

2014-12-01

In this paper, we investigate the impact of timing asynchronism on the performance of multicarrier techniques in a spectrum coexistence context. Two multicarrier schemes are considered: cyclic prefix-based orthogonal frequency division multiplexing (CP-OFDM) with a rectangular pulse shape and filter bank-based multicarrier (FBMC) with physical layer for dynamic spectrum access and cognitive radio (PHYDYAS) and isotropic orthogonal transform algorithm (IOTA) waveforms. First, we present the general concept of the so-called power spectral density (PSD)-based interference tables which are commonly used for multicarrier interference characterization in spectrum sharing context. After highlighting the limits of this approach, we propose a new family of interference tables called `instantaneous interference tables'. The proposed tables give the interference power caused by a given interfering subcarrier on a victim one, not only as a function of the spectral distance separating both subcarriers but also with respect to the timing misalignment between the subcarrier holders. In contrast to the PSD-based interference tables, the accuracy of the proposed tables has been validated through different simulation results. Furthermore, due to the better frequency localization of both PHYDYAS and IOTA waveforms, FBMC technique is demonstrated to be more robust to timing asynchronism compared to OFDM one. Such a result makes FBMC a potential candidate for the physical layer of future cognitive radio systems.

Association of Source of Memory Complaints and Increased Risk of Cognitive Impairment and Cognitive Decline: A Community-Based Study.

PubMed

Qi, Xue-Mei; Gu, Lin; Tang, Hui-Dong; Chen, Sheng-Di; Ma, Jian-Fang

2018-04-20

Memory complaint is common in the elderly. Recently, it was shown that self-report memory complaint was predictive of cognitive decline. This study aimed to investigate the predictive value of the source of memory complaints on the risk of cognitive impairment and cognitive decline in a community-based cohort. Data on memory complaints and cognitive function were collected among 1840 Chinese participants (aged ≥55 years old) in an urban community at baseline interview and 5-year follow-up. Incident cognitive impairment was identified based on education-adjusted Mini-Mental State Examination score. Logistic regression model was used to estimate the association between the source of memory complaints and risk of cognitive impairment conversion and cognitive decline, after adjusting for covariates. A total of 1840 participants were included into this study including 1713 normal participants and 127 cognitive impairment participants in 2009. Among 1713 normal participants in 2009, 130 participants were converted to cognitive impairment after 5 years of follow-up. In 2014, 606 participants were identified as cognitive decline. Both self- and informant-reported memory complaints were associated with an increased risk of cognitive impairment (odds ratio [OR] = 1.60, 95% confidence interval [CI]: 1.04-2.48) and cognitive decline (OR = 1.30, 95% CI: 1.01-1.68). Furthermore, this association was more significant in males (OR = 2.10, 95% CI: 1.04-4.24 for cognitive impairment and OR = 1.87, 95% CI: 1.20-2.99 for cognitive decline) and in higher education level (OR = 1.79, 95% CI: 1.02-3.15 for cognitive impairment and OR = 1.40, 95% CI: 1.02-1.91 for cognitive decline). Both self- and informant-reported memory complaints were associated with an increased risk of cognitive impairment conversion and cognitive decline, especially in persons with male gender and high educational background.

Construct Definition Using Cognitively Based Evidence: A Framework for Practice

ERIC Educational Resources Information Center

Ketterlin-Geller, Leanne R.; Yovanoff, Paul; Jung, EunJu; Liu, Kimy; Geller, Josh

2013-01-01

In this article, we highlight the need for a precisely defined construct in score-based validation and discuss the contribution of cognitive theories to accurately and comprehensively defining the construct. We propose a framework for integrating cognitively based theoretical and empirical evidence to specify and evaluate the construct. We apply…

The Effects of Metaphorical Interface on Germane Cognitive Load in Web-Based Instruction

ERIC Educational Resources Information Center

Cheon, Jongpil; Grant, Michael M.

2012-01-01

The purpose of this study was to examine the effects of a metaphorical interface on germane cognitive load in Web-based instruction. Based on cognitive load theory, germane cognitive load is a cognitive investment for schema construction and automation. A new instrument developed in a previous study was used to measure students' mental activities…

EEG Based Analysis of Cognitive Load Enhance Instructional Analysis

ERIC Educational Resources Information Center

Dan, Alex; Reiner, Miriam

2017-01-01

One of the recommended approaches in instructional design methods is to optimize the value of working memory capacity and avoid cognitive overload. Educational neuroscience offers novel processes and methodologies to analyze cognitive load based on physiological measures. Observing psychophysiological changes when they occur in response to the…

Increasing Interest in Cognitive Psychology Using Scenario-Based Assessment

ERIC Educational Resources Information Center

Cormack, Sophie

2014-01-01

Students often perceive cognitive psychology as an abstract and difficult subject with little intrinsic interest. When student feedback identified problems with the traditional essay assessment in a cognitive psychology module, action research led to the development of a forensic scenario-based assessment which successfully increased student…

The ERP Effects of Combined Cognitive Training on Intention-Based and Stimulus-Based Actions in Older Chinese Adults.

PubMed

Niu, Ya-Nan; Zhu, Xinyi; Li, Juan; Fu, Jiang-Ning

2016-01-01

Age-related decreases in action are caused by neuromuscular weakness and cognitive decline. Although physical interventions have been reported to have beneficial effects on cognitive function in older adults, whether cognitive training improves action-related function remains unclear. In this study, we investigated the effects of combined cognitive training on intention-based and stimulus-based actions in older adults using event-related potentials (ERPs). A total of 26 healthy older adults (16 in the training group and 10 in the control group) participated in the study. The training group received 16 sessions of cognitive training, including eight sessions of executive function training and eight sessions of memory strategy training. Before and after training, both groups of participants underwent cognitive assessments and ERP recordings during both the acquisition and test phases with a motor cognitive paradigm. During the acquisition phase, subjects were asked to press one of two keys, either using a self-selected (intention-based) method or based on the preceding stimulus (stimulus-based). During the test phase, subjects were asked to respond to the pre-cues with either congruent or incongruent tasks. Using ERP indices-including readiness potential, P3 and contingent negative variation to identify motor preparation, stimulus processing and interference effect, respectively-we revealed the effects of training on both intention-based and stimulus-based actions. The correlations were also computed between the improved cognitive performance and the ERP amplitudes. It was shown that the improved executive function might extend substantial benefits to both actions, whereas associative memory may be specifically related to the bidirectional action-effect association of intention-based action, although the training effect of memory was absent during the insufficient training hours. In sum, the present study provided empirical evidence demonstrating that action could

The effects of cognitive rehabilitation on Alzheimer's dementia patients' cognitive assessment reference diagnosis system performance based on level of cognitive functioning.

PubMed

Hwang, Jung-Ha; Cha, Hyun-Gyu; Cho, Hyuk-Shin

2015-09-01

[Purpose] The purpose of this study is to apply cognitive rehabilitation according to Alzheimer's disease (AD) patients' level of cognitive functioning to compare changes in Cognitive Assessment Reference Diagnosis System performance and present standards for effective intervention. [Subjects] Subjects were 30 inpatients diagnosed with AD. Subjects were grouped by Clinical Dementia Rating (CDR) class (CDR-0.5, CDR-1, or CDR-2, n = 10 per group), which is based on level of cognitive functioning, and cognitive rehabilitation was applied for 50 minutes per day, five days per week, for four weeks. [Methods] After cognitive rehabilitation intervention, CARDS tests were conducted to evaluate memory. [Results] Bonferroni tests comparing the three groups revealed that the CDR-0.5 and CDR-1 groups showed significant increases in Delayed 10 word-list, Delayed 10 object-list, Recognition 10 object, and Recent memory performance compared to the CDR-2 group. In addition, the CDR-0.5 group showed significant decreases in Recognition 10 word performance compared to the CDR-1 group. [Conclusion] Cognitive rehabilitation, CDR-0.5 or CDR-1 subjects showed significantly greater memory improvements than CDR-2 subjects. Moreover, was not effective for CDR-2 subjects.

Ontology-based automatic generation of computerized cognitive exercises.

PubMed

Leonardi, Giorgio; Panzarasa, Silvia; Quaglini, Silvana

2011-01-01

Computer-based approaches can add great value to the traditional paper-based approaches for cognitive rehabilitation. The management of a big amount of stimuli and the use of multimedia features permits to improve the patient's involvement and to reuse and recombine them to create new exercises, whose difficulty level should be adapted to the patient's performance. This work proposes an ontological organization of the stimuli, to support the automatic generation of new exercises, tailored on the patient's preferences and skills, and its integration into a commercial cognitive rehabilitation tool. The possibilities offered by this approach are presented with the help of real examples.

Toward a model-based cognitive neuroscience of mind wandering.

PubMed

Hawkins, G E; Mittner, M; Boekel, W; Heathcote, A; Forstmann, B U

2015-12-03

People often "mind wander" during everyday tasks, temporarily losing track of time, place, or current task goals. In laboratory-based tasks, mind wandering is often associated with performance decrements in behavioral variables and changes in neural recordings. Such empirical associations provide descriptive accounts of mind wandering - how it affects ongoing task performance - but fail to provide true explanatory accounts - why it affects task performance. In this perspectives paper, we consider mind wandering as a neural state or process that affects the parameters of quantitative cognitive process models, which in turn affect observed behavioral performance. Our approach thus uses cognitive process models to bridge the explanatory divide between neural and behavioral data. We provide an overview of two general frameworks for developing a model-based cognitive neuroscience of mind wandering. The first approach uses neural data to segment observed performance into a discrete mixture of latent task-related and task-unrelated states, and the second regresses single-trial measures of neural activity onto structured trial-by-trial variation in the parameters of cognitive process models. We discuss the relative merits of the two approaches, and the research questions they can answer, and highlight that both approaches allow neural data to provide additional constraint on the parameters of cognitive models, which will lead to a more precise account of the effect of mind wandering on brain and behavior. We conclude by summarizing prospects for mind wandering as conceived within a model-based cognitive neuroscience framework, highlighting the opportunities for its continued study and the benefits that arise from using well-developed quantitative techniques to study abstract theoretical constructs. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Mindfulness-based cognitive therapy for generalized anxiety disorder.

PubMed

Evans, Susan; Ferrando, Stephen; Findler, Marianne; Stowell, Charles; Smart, Colette; Haglin, Dean

2008-05-01

While cognitive behavior therapy has been found to be effective in the treatment of generalized anxiety disorder (GAD), a significant percentage of patients struggle with residual symptoms. There is some conceptual basis for suggesting that cultivation of mindfulness may be helpful for people with GAD. Mindfulness-based cognitive therapy (MBCT) is a group treatment derived from mindfulness-based stress reduction (MBSR) developed by Jon Kabat-Zinn and colleagues. MBSR uses training in mindfulness meditation as the core of the program. MBCT incorporates cognitive strategies and has been found effective in reducing relapse in patients with major depression (Teasdale, J. D., Segal, Z. V., Williams, J. M. G., Ridgeway, V., Soulsby, J., & Lau, M. (2000). Prevention of relapse/recurrence in major depression by mindfulness-based cognitive therapy. Journal of Consulting and Clinical Psychology, 6, 615-623). Eligible subjects recruited to a major academic medical center participated in the group MBCT course and completed measures of anxiety, worry, depressive symptoms, mood states and mindful awareness in everyday life at baseline and end of treatment. Eleven subjects (six female and five male) with a mean age of 49 (range=36-72) met criteria and completed the study. There were significant reductions in anxiety and depressive symptoms from baseline to end of treatment. MBCT may be an acceptable and potentially effective treatment for reducing anxiety and mood symptoms and increasing awareness of everyday experiences in patients with GAD. Future directions include development of a randomized clinical trial of MBCT for GAD.

Utilization-Based Modeling and Optimization for Cognitive Radio Networks

NASA Astrophysics Data System (ADS)

Liu, Yanbing; Huang, Jun; Liu, Zhangxiong

The cognitive radio technique promises to manage and allocate the scarce radio spectrum in the highly varying and disparate modern environments. This paper considers a cognitive radio scenario composed of two queues for the primary (licensed) users and cognitive (unlicensed) users. According to the Markov process, the system state equations are derived and an optimization model for the system is proposed. Next, the system performance is evaluated by calculations which show the rationality of our system model. Furthermore, discussions among different parameters for the system are presented based on the experimental results.

Big-Data Based Decision-Support Systems to Improve Clinicians' Cognition.

PubMed

Roosan, Don; Samore, Matthew; Jones, Makoto; Livnat, Yarden; Clutter, Justin

2016-01-01

Complex clinical decision-making could be facilitated by using population health data to inform clinicians. In two previous studies, we interviewed 16 infectious disease experts to understand complex clinical reasoning. For this study, we focused on answers from the experts on how clinical reasoning can be supported by population-based Big-Data. We found cognitive strategies such as trajectory tracking, perspective taking, and metacognition has the potential to improve clinicians' cognition to deal with complex problems. These cognitive strategies could be supported by population health data, and all have important implications for the design of Big-Data based decision-support tools that could be embedded in electronic health records. Our findings provide directions for task allocation and design of decision-support applications for health care industry development of Big data based decision-support systems.

Design and performance investigation of LDPC-coded upstream transmission systems in IM/DD OFDM-PONs

NASA Astrophysics Data System (ADS)

Gong, Xiaoxue; Guo, Lei; Wu, Jingjing; Ning, Zhaolong

2016-12-01

In Intensity-Modulation Direct-Detection (IM/DD) Orthogonal Frequency Division Multiplexing Passive Optical Networks (OFDM-PONs), aside from Subcarrier-to-Subcarrier Intermixing Interferences (SSII) induced by square-law detection, the same laser frequency for data sending from Optical Network Units (ONUs) results in ONU-to-ONU Beating Interferences (OOBI) at the receiver. To mitigate those interferences, we design a Low-Density Parity Check (LDPC)-coded and spectrum-efficient upstream transmission system. A theoretical channel model is also derived, in order to analyze the detrimental factors influencing system performances. Simulation results demonstrate that the receiver sensitivity is improved 3.4 dB and 2.5 dB under QPSK and 8QAM, respectively, after 100 km Standard Single-Mode Fiber (SSMF) transmission. Furthermore, the spectrum efficiency can be improved by about 50%.

Localization and cooperative communication methods for cognitive radio

NASA Astrophysics Data System (ADS)

Duval, Olivier

We study localization of nearby nodes and cooperative communication for cognitive radios. Cognitive radios sensing their environment to estimate the channel gain between nodes can cooperate and adapt their transmission power to maximize the capacity of the communication between two nodes. We study the end-to-end capacity of a cooperative relaying scheme using orthogonal frequency-division modulation (OFDM) modulation, under power constraints for both the base station and the relay station. The relay uses amplify-and-forward and decode-and-forward cooperative relaying techniques to retransmit messages on a subset of the available subcarriers. The power used in the base station and the relay station transmitters is allocated to maximize the overall system capacity. The subcarrier selection and power allocation are obtained based on convex optimization formulations and an iterative algorithm. Additionally, decode-and-forward relaying schemes are allowed to pair source and relayed subcarriers to increase further the capacity of the system. The proposed techniques outperforms non-selective relaying schemes over a range of relay power budgets. Cognitive radios can be used for opportunistic access of the radio spectrum by detecting spectrum holes left unused by licensed primary users. We introduce a spectrum holes detection approach, which combines blind modulation classification, angle of arrival estimation and number of sources detection. We perform eigenspace analysis to determine the number of sources, and estimate their angles of arrival (AOA). In addition, we classify detected sources as primary or secondary users with their distinct second-orde one-conjugate cyclostationarity features. Extensive simulations carried out indicate that the proposed system identifies and locates individual sources correctly, even at -4 dB signal-to-noise ratios (SNR). In environments with a high density of scatterers, several wireless channels experience nonline-of-sight (NLOS

Exploring Music-Based Rehabilitation for Parkinsonism through Embodied Cognitive Science.

PubMed

Schiavio, Andrea; Altenmüller, Eckart

2015-01-01

Recent embodied approaches in cognitive sciences emphasize the constitutive roles of bodies and environment in driving cognitive processes. Cognition is thus seen as a distributed system based on the continuous interaction of bodies, brains, and environment. These categories, moreover, do not relate only causally, through a sequential input-output network of computations; rather, they are dynamically enfolded in each other, being mutually implemented by the concrete patterns of actions adopted by the cognitive system. However, while this claim has been widely discussed across various disciplines, its relevance and potential beneficial applications for music therapy remain largely unexplored. With this in mind, we provide here an overview of the embodied approaches to cognition, discussing their main tenets through the lenses of music therapy. In doing so, we question established methodological and theoretical paradigms and identify possible novel strategies for intervention. In particular, we refer to the music-based rehabilitative protocols adopted for Parkinson's disease patients. Indeed, in this context, it has recently been observed that music therapy not only affects movement-related skills but that it also contributes to stabilizing physiological functions and improving socio-affective behaviors. We argue that these phenomena involve previously unconsidered aspects of cognition and (motor) behavior, which are rooted in the action-perception cycle characterizing the whole living system.

Decreasing Cognitive Load for Learners: Strategy of Web-Based Foreign Language Learning

ERIC Educational Resources Information Center

Zhang, Jianfeng

2013-01-01

Cognitive load is one of the important factors that influence the effectiveness and efficiency of web-based foreign language learning. Cognitive load theory assumes that human's cognitive capacity in working memory is limited and if it overloads, learning will be hampered, so that high level of cognitive load can affect the performance of learning…

Assessment of Fiber Chromatic Dispersion Based on Elimination of Second-Order Harmonics in Optical OFDM Single Sideband Modulation Using Mach Zehnder Modulator

NASA Astrophysics Data System (ADS)

Patel, Dhananjay; Singh, Vinay Kumar; Dalal, U. D.

2016-07-01

This work addresses the analytical and numerical investigations of the transmission performance of an optical Single Sideband (SSB) modulation technique generated by a Mach Zehnder Modulator (MZM) with a 90° and 120° hybrid coupler. It takes into account the problem of chromatic dispersion in single mode fibers in Passive Optical Networks (PON), which severely degrades the performance of the system. Considering the transmission length of the fiber, the SSB modulation generated by maintaining a phase shift of π/2 between the two electrodes of the MZM provides better receiver sensitivity. However, the power of higher-order harmonics generated due to the nonlinearity of the MZM is directly proportional to the modulation index, making the SSB look like a quasi-double sideband (DSB) and causing power fading due to chromatic dispersion. To eliminate one of the second-order harmonics, the SSB signal based on an MZM with a 120° hybrid coupler is simulated. An analytical model of conventional SSB using 90° and 120° hybrid couplers is established. The latter suppresses unwanted (upper/lower) first-order and second-order (lower/upper) sidebands. For the analysis, a varying quadrature amplitude modulation (QAM) Orthogonal Frequency Division Multiplexing (OFDM) signal with a data rate of 5 Gb/s is upconverted using both of the SSB techniques and is transmitted over a distance of 75 km in Single Mode Fiber (SMF). The simulation results show that the SSB with 120° hybrid coupler proves to be more immune to chromatic dispersion as compared to the conventional SSB technique. This is in tandem with the theoretical analysis presented in the article.

Improved Processing Speed: Online Computer-Based Cognitive Training in Older Adults

ERIC Educational Resources Information Center

Simpson, Tamara; Camfield, David; Pipingas, Andrew; Macpherson, Helen; Stough, Con

2012-01-01

In an increasingly aging population, a number of adults are concerned about declines in their cognitive abilities. Online computer-based cognitive training programs have been proposed as an accessible means by which the elderly may improve their cognitive abilities; yet, more research is needed in order to assess the efficacy of these programs. In…

The influence of affective and cognitive arguments on message judgement and attitude change: The moderating effects of meta-bases and structural bases.

PubMed

Keer, Mario; van den Putte, Bas; Neijens, Peter; de Wit, John

2013-01-01

This study investigated whether the efficacy of affective vs. cognitive persuasive messages was moderated by (1) individuals' subjective assessments of whether their attitudes were based on affect or cognition (i.e. meta-bases) and (2) the degree individuals' attitudes were correlated with affect and cognition (i.e. structural bases). Participants (N = 97) were randomly exposed to a message containing either affective or cognitive arguments discouraging binge drinking. The results demonstrated that meta-bases and not structural bases moderated the influence of argument type on message judgement. Affective (cognitive) messages were judged more positively when individuals' meta-bases were more affective (cognitive). In contrast, structural bases and not meta-bases moderated the influence of argument type on attitude and intention change following exposure to the message. Surprisingly, change was greater among individuals who read a message that mismatched their structural attitude base. Affective messages were more effective as attitudes were more cognition-based, and vice versa. Thus, although individuals prefer messages that match their meta-base, attitude and intention change regarding binge drinking are best established by mismatching their structural base.

Science Teaching Based on Cognitive Load Theory: Engaged Students, but Cognitive Deficiencies

ERIC Educational Resources Information Center

Meissner, Barbara; Bogner, Franz X.

2012-01-01

To improve science learning under demanding conditions, we designed an out-of-school lesson in compliance with cognitive load theory (CLT). We extracted student clusters based on individual effectiveness, and compared instructional efficiency, mental effort, and persistence of learning. The present study analyses students' engagement. 50.0% of our…

Developmental issues in school-based aggression prevention from a social-cognitive perspective.

PubMed

Boxer, Paul; Goldstein, Sara E; Musher-Eizenman, Dara; Dubow, Eric F; Heretick, Donna

2005-09-01

Contemporary research on the development and prevention of aggressive behavior in childhood and adolescence emphasizes the importance of social-cognitive factors such as perceptual biases, problem-solving skills, and social-moral beliefs in the maintenance of aggression. Indeed, school-based social-cognitive intervention approaches have been identified as best practices by the Centers for Disease Control and Prevention. However, because child age is an important covariate of both intervention effectiveness and social-cognitive ability, school-based prevention program designers should keep in mind a number of issues identified through developmental research. In this paper, we review the social-cognitive model of aggressive behavior development as applied to prevention programming. We then discuss some of the ways in which the broader developmental research base can inform the design of aggression prevention programs. EDITORS' STRATEGIC IMPLICATIONS: Educational administrators and policy makers will find evidence in this review that school-based programs that employ a social-cognitive model represent a strategy that works for preventing violence. Prevention researchers will also benefit from the authors' insights regarding theoretical mediating processes and the importance of a developmental view.

Cognitive Support for Learning Computer-Based Tasks Using Animated Demonstration

ERIC Educational Resources Information Center

Chen, Chun-Ying

2016-01-01

This study investigated the influence of cognitive support for learning computer-based tasks using animated demonstration (AD) on instructional efficiency. Cognitive support included (1) segmentation and learner control introducing interactive devices that allow content sequencing through a navigational menu, and content pacing through stop and…

Web-Based Learning Programs: Use by Learners with Various Cognitive Styles

ERIC Educational Resources Information Center

Chen, Ling-Hsiu

2010-01-01

To consider how Web-based learning program is utilized by learners with different cognitive styles, this study presents a Web-based learning system (WBLS) and analyzes learners' browsing data recorded in the log file to identify how learners' cognitive styles and learning behavior are related. In order to develop an adapted WBLS, this study also…

Big-Data Based Decision-Support Systems to Improve Clinicians’ Cognition

PubMed Central

Roosan, Don; Samore, Matthew; Jones, Makoto; Livnat, Yarden; Clutter, Justin

2016-01-01

Complex clinical decision-making could be facilitated by using population health data to inform clinicians. In two previous studies, we interviewed 16 infectious disease experts to understand complex clinical reasoning. For this study, we focused on answers from the experts on how clinical reasoning can be supported by population-based Big-Data. We found cognitive strategies such as trajectory tracking, perspective taking, and metacognition has the potential to improve clinicians’ cognition to deal with complex problems. These cognitive strategies could be supported by population health data, and all have important implications for the design of Big-Data based decision-support tools that could be embedded in electronic health records. Our findings provide directions for task allocation and design of decision-support applications for health care industry development of Big data based decision-support systems. PMID:27990498

Blood Glucose, Diet-Based Glycemic Load and Cognitive Aging Among Dementia-Free Older Adults

PubMed Central

Andel, Ross; McEvoy, Cathy; Dahl Aslan, Anna K.; Finkel, Deborah; Pedersen, Nancy L.

2015-01-01

Background. Although evidence indicates that Type II Diabetes is related to abnormal brain aging, the influence of elevated blood glucose on long-term cognitive change is unclear. In addition, the relationship between diet-based glycemic load and cognitive aging has not been extensively studied. The focus of this study was to investigate the influence of diet-based glycemic load and blood glucose on cognitive aging in older adults followed for up to 16 years. Methods. Eight-hundred and thirty-eight cognitively healthy adults aged ≥50 years (M = 63.1, SD = 8.3) from the Swedish Adoption/Twin Study of Aging were studied. Mixed effects growth models were utilized to assess overall performance and change in general cognitive functioning, perceptual speed, memory, verbal ability, and spatial ability as a function of baseline blood glucose and diet-based glycemic load. Results. High blood glucose was related to poorer overall performance on perceptual speed as well as greater rates of decline in general cognitive ability, perceptual speed, verbal ability, and spatial ability. Diet-based glycemic load was related to poorer overall performance in perceptual speed and spatial ability. Conclusion. Diet-based glycemic load and, in particular, elevated blood glucose appear important for cognitive performance/cognitive aging. Blood glucose control (perhaps through low glycemic load diets) may be an important target in the detection and prevention of age-related cognitive decline. PMID:25149688

Music-Based Cognitive Remediation Therapy for Patients with Traumatic Brain Injury

PubMed Central

Hegde, Shantala

2014-01-01

Traumatic brain injury (TBI) is one of the common causes of disability in physical, psychological, and social domains of functioning leading to poor quality of life. TBI leads to impairment in sensory, motor, language, and emotional processing, and also in cognitive functions such as attention, information processing, executive functions, and memory. Cognitive impairment plays a central role in functional recovery in TBI. Innovative methods such as music therapy to alleviate cognitive impairments have been investigated recently. The role of music in cognitive rehabilitation is evolving, based on newer findings emerging from the fields of neuromusicology and music cognition. Research findings from these fields have contributed significantly to our understanding of music perception and cognition, and its neural underpinnings. From a neuroscientific perspective, indulging in music is considered as one of the best cognitive exercises. With “plasticity” as its veritable nature, brain engages in producing music indulging an array of cognitive functions and the product, the music, in turn permits restoration and alters brain functions. With scientific findings as its basis, “neurologic music therapy” (NMT) has been developed as a systematic treatment method to improve sensorimotor, language, and cognitive domains of functioning via music. A preliminary study examining the effect of NMT in cognitive rehabilitation has reported promising results in improving executive functions along with improvement in emotional adjustment and decreasing depression and anxiety following TBI. The potential usage of music-based cognitive rehabilitation therapy in various clinical conditions including TBI is yet to be fully explored. There is a need for systematic research studies to bridge the gap between increasing theoretical understanding of usage of music in cognitive rehabilitation and application of the same in a heterogeneous condition such as TBI. PMID:24715887

Smartphone-based system to improve transportation access for the cognitively impaired.

PubMed

Anderson, Shane M; Riehle, Timothy H; Lichter, Patrick A; Brown, Allen W; Panescu, Dorin

2015-01-01

This project developed and evaluated a smartphone-based system to improve mobility and transportation access for the cognitively impaired. The proposed system is intended to allow the cognitively impaired to use public transportation systems, community transportation and dedicated transportation services for the disabled with greater ease and safety. Individuals with cognitive disabilities are often unable to operate an automobile, or may require a prolonged recovery period before resuming driving. Public transportation systems represent a significant means to allow these individuals to maintain independence. Yet public transportation systems can pose significant challenges to individuals with cognitive impairment. The goal of this project is to develop a system to reduce these barriers via a technological solution consisting of components developed both for the cognitively impaired user and their caregiver or family member. The first component consists of a cognitive prosthetic device featuring traditional memory cueing and reminders as well as custom location-based transportation specific functions. This cognitive mobility assistant will leverage the computing power and GPS location determination capabilities of inexpensive, powerful smart phones. The second component consists of a management application which offers caregivers the ability to configure and program the reminder and transit functions remotely via the Internet. Following completion of the prototype system a pilot human test was performed with cognitively disabled individuals and family members or caregivers to assess the usability and acceptability of both system components.

Cognitive Transfer Outcomes for a Simulation-Based Introductory Statistics Curriculum

ERIC Educational Resources Information Center

Backman, Matthew D.; Delmas, Robert C.; Garfield, Joan

2017-01-01

Cognitive transfer is the ability to apply learned skills and knowledge to new applications and contexts. This investigation evaluates cognitive transfer outcomes for a tertiary-level introductory statistics course using the CATALST curriculum, which exclusively used simulation-based methods to develop foundations of statistical inference. A…

Designing an Adaptive Web-Based Learning System Based on Students' Cognitive Styles Identified Online

ERIC Educational Resources Information Center

Lo, Jia-Jiunn; Chan, Ya-Chen; Yeh, Shiou-Wen

2012-01-01

This study developed an adaptive web-based learning system focusing on students' cognitive styles. The system is composed of a student model and an adaptation model. It collected students' browsing behaviors to update the student model for unobtrusively identifying student cognitive styles through a multi-layer feed-forward neural network (MLFF).…

Cognitive performance modeling based on general systems performance theory.

PubMed

Kondraske, George V

2010-01-01

General Systems Performance Theory (GSPT) was initially motivated by problems associated with quantifying different aspects of human performance. It has proved to be invaluable for measurement development and understanding quantitative relationships between human subsystem capacities and performance in complex tasks. It is now desired to bring focus to the application of GSPT to modeling of cognitive system performance. Previous studies involving two complex tasks (i.e., driving and performing laparoscopic surgery) and incorporating measures that are clearly related to cognitive performance (information processing speed and short-term memory capacity) were revisited. A GSPT-derived method of task analysis and performance prediction termed Nonlinear Causal Resource Analysis (NCRA) was employed to determine the demand on basic cognitive performance resources required to support different levels of complex task performance. This approach is presented as a means to determine a cognitive workload profile and the subsequent computation of a single number measure of cognitive workload (CW). Computation of CW may be a viable alternative to measuring it. Various possible "more basic" performance resources that contribute to cognitive system performance are discussed. It is concluded from this preliminary exploration that a GSPT-based approach can contribute to defining cognitive performance models that are useful for both individual subjects and specific groups (e.g., military pilots).

Exploring Music-Based Rehabilitation for Parkinsonism through Embodied Cognitive Science

PubMed Central

Schiavio, Andrea; Altenmüller, Eckart

2015-01-01

Recent embodied approaches in cognitive sciences emphasize the constitutive roles of bodies and environment in driving cognitive processes. Cognition is thus seen as a distributed system based on the continuous interaction of bodies, brains, and environment. These categories, moreover, do not relate only causally, through a sequential input–output network of computations; rather, they are dynamically enfolded in each other, being mutually implemented by the concrete patterns of actions adopted by the cognitive system. However, while this claim has been widely discussed across various disciplines, its relevance and potential beneficial applications for music therapy remain largely unexplored. With this in mind, we provide here an overview of the embodied approaches to cognition, discussing their main tenets through the lenses of music therapy. In doing so, we question established methodological and theoretical paradigms and identify possible novel strategies for intervention. In particular, we refer to the music-based rehabilitative protocols adopted for Parkinson’s disease patients. Indeed, in this context, it has recently been observed that music therapy not only affects movement-related skills but that it also contributes to stabilizing physiological functions and improving socio-affective behaviors. We argue that these phenomena involve previously unconsidered aspects of cognition and (motor) behavior, which are rooted in the action-perception cycle characterizing the whole living system. PMID:26539155

Cognition-based and affect-based trust as mediators of leader behavior influences on team performance.

PubMed

Schaubroeck, John; Lam, Simon S K; Peng, Ann Chunyan

2011-07-01

We develop a model in which cognitive and affective trust in the leader mediate the relationship between leader behavior and team psychological states that, in turn, drive team performance. The model is tested on a sample of 191 financial services teams in Hong Kong and the U.S. Servant leadership influenced team performance through affect-based trust and team psychological safety. Transformational leadership influenced team performance indirectly through cognition-based trust. Cognition-based trust directly influenced team potency and indirectly (through affect-based trust) influenced team psychological safety. The effects of leader behavior on team performance were fully mediated through the trust in leader variables and the team psychological states. Servant leadership explained an additional 10% of the variance in team performance beyond the effect of transformational leadership. We discuss implications of these results for research on the relationship between leader behavior and team performance, and for efforts to enhance leader development by combining knowledge from different leadership theories.

Digital Game-Based Learning Supports Student Motivation, Cognitive Success, and Performance Outcomes

ERIC Educational Resources Information Center

Woo, Jeng-Chung

2014-01-01

Traditional multimedia learning is primarily based on the cognitive load concept of information processing theory. Recent digital game-based learning (DGBL) studies have focused on exploring content support for learning motivation and related game characteristics. Motivation, volition, and performance (MVP) theory indicates that cognitive load and…

Embedded assessment algorithms within home-based cognitive computer game exercises for elders.

PubMed

Jimison, Holly; Pavel, Misha

2006-01-01

With the recent consumer interest in computer-based activities designed to improve cognitive performance, there is a growing need for scientific assessment algorithms to validate the potential contributions of cognitive exercises. In this paper, we present a novel methodology for incorporating dynamic cognitive assessment algorithms within computer games designed to enhance cognitive performance. We describe how this approach works for variety of computer applications and describe cognitive monitoring results for one of the computer game exercises. The real-time cognitive assessments also provide a control signal for adapting the difficulty of the game exercises and providing tailored help for elders of varying abilities.

Using the Cognitive Apprenticeship Web-Based Argumentation System to Improve Argumentation Instruction

ERIC Educational Resources Information Center

Tsai, Chun-Yen; Jack, Brady Michael; Huang, Tai-Chu; Yang, Jin-Tan

2012-01-01

This study investigated how the instruction of argumentation skills could be promoted by using an online argumentation system. This system entitled "Cognitive Apprenticeship Web-based Argumentation" (CAWA) system was based on cognitive apprenticeship model. One hundred eighty-nine fifth grade students took part in this study. A quasi-experimental…

Evidence-based Assessment of Cognitive Functioning in Pediatric Psychology

PubMed Central

Brown, Ronald T.; Cavanagh, Sarah E.; Vess, Sarah F.; Segall, Mathew J.

2008-01-01

Objective To review the evidence base for measures of cognitive functioning frequently used within the field of pediatric psychology. Methods From a list of 47 measures identified by the Society of Pediatric Psychology (Division 54) Evidence-Based Assessment Task Force Workgroup, 27 measures were included in the review. Measures were organized, reviewed, and evaluated according to general domains of functioning (e.g., attention/executive functioning, memory). Results Twenty-two of 27 measures reviewed demonstrated psychometric properties that met “Well-established” criteria as set forth by the Assessment Task Force. Psychometric properties were strongest for measures of general cognitive ability and weakest for measures of visual-motor functioning and attention. Conclusions We report use of “Well-established” measures of overall cognitive functioning, nonverbal intelligence, academic achievement, language, and memory and learning. For several specific tests in the domains of visual-motor functioning and attention, additional psychometric data are needed for measures to meet criteria as “Well established.” PMID:18194973

The influence of computer-based cognitive flexibility training on subjective cognitive well-being after stroke: A multi-center randomized controlled trial

PubMed Central

Murre, Jaap M. J.; Buitenweg, Jessika I. V.; Veltman, Dick J.; Aaronson, Justine A.; Nijboer, Tanja C. W.; Kruiper-Doesborgh, Suzanne J. C.; van Bennekom, Coen A. M.; Ridderinkhof, K. Richard; Schmand, Ben

2017-01-01

Background Stroke can result in cognitive complaints that can have a large impact on quality of life long after its occurrence. A number of computer-based training programs have been developed with the aim to improve cognitive functioning. Most studies investigating their efficacy used only objective outcome measures, whereas a reduction of subjective cognitive complaints may be equally important for improving quality of life. A few studies used subjective outcome measures but were inconclusive, partly due to methodological shortcomings such as lack of proper active and passive control groups. Objective The aim of the current study was to investigate whether computer-based cognitive flexibility training can improve subjective cognitive functioning and quality of life after stroke. Methods We performed a randomized controlled double blind trial (RCT). Adults (30–80 years old) who had a stroke 3 months to 5 years ago, were randomly assigned to either an intervention group (n = 38), an active control group (i.e., mock training; n = 35), or a waiting list control group (n = 24). The intervention and mock training consisted of 58 half-hour sessions within 12 weeks. The primary subjective outcome measures were cognitive functioning (Cognitive Failure Questionnaire), executive functioning (Dysexecutive Functioning Questionnaire), quality of life (Short Form Health Survey), instrumental activities of daily living (IADL; Lawton & Brody IADL scale), and participation in society (Utrecht Scale for Evaluation of Rehabilitation-Participation). Secondary subjective outcome measures were recovery after stroke, depressive symptoms (Hospital Anxiety Depression Scale—depression subscale), fatigue (Checklist Individual Strength—Fatigue subscale), and subjective cognitive improvement (exit list). Finally, a proxy of the participant rated the training effects in subjective cognitive functioning, subjective executive functioning, and IADL. Results and conclusions All groups

The influence of computer-based cognitive flexibility training on subjective cognitive well-being after stroke: A multi-center randomized controlled trial.

PubMed

van de Ven, Renate M; Murre, Jaap M J; Buitenweg, Jessika I V; Veltman, Dick J; Aaronson, Justine A; Nijboer, Tanja C W; Kruiper-Doesborgh, Suzanne J C; van Bennekom, Coen A M; Ridderinkhof, K Richard; Schmand, Ben

2017-01-01

Stroke can result in cognitive complaints that can have a large impact on quality of life long after its occurrence. A number of computer-based training programs have been developed with the aim to improve cognitive functioning. Most studies investigating their efficacy used only objective outcome measures, whereas a reduction of subjective cognitive complaints may be equally important for improving quality of life. A few studies used subjective outcome measures but were inconclusive, partly due to methodological shortcomings such as lack of proper active and passive control groups. The aim of the current study was to investigate whether computer-based cognitive flexibility training can improve subjective cognitive functioning and quality of life after stroke. We performed a randomized controlled double blind trial (RCT). Adults (30-80 years old) who had a stroke 3 months to 5 years ago, were randomly assigned to either an intervention group (n = 38), an active control group (i.e., mock training; n = 35), or a waiting list control group (n = 24). The intervention and mock training consisted of 58 half-hour sessions within 12 weeks. The primary subjective outcome measures were cognitive functioning (Cognitive Failure Questionnaire), executive functioning (Dysexecutive Functioning Questionnaire), quality of life (Short Form Health Survey), instrumental activities of daily living (IADL; Lawton & Brody IADL scale), and participation in society (Utrecht Scale for Evaluation of Rehabilitation-Participation). Secondary subjective outcome measures were recovery after stroke, depressive symptoms (Hospital Anxiety Depression Scale-depression subscale), fatigue (Checklist Individual Strength-Fatigue subscale), and subjective cognitive improvement (exit list). Finally, a proxy of the participant rated the training effects in subjective cognitive functioning, subjective executive functioning, and IADL. All groups improved on the two measures of subjective cognitive functioning

Blood glucose, diet-based glycemic load and cognitive aging among dementia-free older adults.

PubMed

Seetharaman, Shyam; Andel, Ross; McEvoy, Cathy; Dahl Aslan, Anna K; Finkel, Deborah; Pedersen, Nancy L

2015-04-01

Although evidence indicates that Type II Diabetes is related to abnormal brain aging, the influence of elevated blood glucose on long-term cognitive change is unclear. In addition, the relationship between diet-based glycemic load and cognitive aging has not been extensively studied. The focus of this study was to investigate the influence of diet-based glycemic load and blood glucose on cognitive aging in older adults followed for up to 16 years. Eight-hundred and thirty-eight cognitively healthy adults aged ≥50 years (M = 63.1, SD = 8.3) from the Swedish Adoption/Twin Study of Aging were studied. Mixed effects growth models were utilized to assess overall performance and change in general cognitive functioning, perceptual speed, memory, verbal ability, and spatial ability as a function of baseline blood glucose and diet-based glycemic load. High blood glucose was related to poorer overall performance on perceptual speed as well as greater rates of decline in general cognitive ability, perceptual speed, verbal ability, and spatial ability. Diet-based glycemic load was related to poorer overall performance in perceptual speed and spatial ability. Diet-based glycemic load and, in particular, elevated blood glucose appear important for cognitive performance/cognitive aging. Blood glucose control (perhaps through low glycemic load diets) may be an important target in the detection and prevention of age-related cognitive decline. © The Author 2014. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Impact of Learning Model Based on Cognitive Conflict toward Student’s Conceptual Understanding

NASA Astrophysics Data System (ADS)

Mufit, F.; Festiyed, F.; Fauzan, A.; Lufri, L.

2018-04-01

The problems that often occur in the learning of physics is a matter of misconception and low understanding of the concept. Misconceptions do not only happen to students, but also happen to college students and teachers. The existing learning model has not had much impact on improving conceptual understanding and remedial efforts of student misconception. This study aims to see the impact of cognitive-based learning model in improving conceptual understanding and remediating student misconceptions. The research method used is Design / Develop Research. The product developed is a cognitive conflict-based learning model along with its components. This article reports on product design results, validity tests, and practicality test. The study resulted in the design of cognitive conflict-based learning model with 4 learning syntaxes, namely (1) preconception activation, (2) presentation of cognitive conflict, (3) discovery of concepts & equations, (4) Reflection. The results of validity tests by some experts on aspects of content, didactic, appearance or language, indicate very valid criteria. Product trial results also show a very practical product to use. Based on pretest and posttest results, cognitive conflict-based learning models have a good impact on improving conceptual understanding and remediating misconceptions, especially in high-ability students.

Cognitive Remediation: Potential Novel Brain-Based Treatment for Bipolar Disorder in Children and Adolescents

PubMed Central

Dickstein, Daniel P.; Cushman, Grace K.; Kim, Kerri L.; Weissman, Alexandra B.; Wegbreit, Ezra

2015-01-01

Bipolar disorder (BD) is among the most impairing psychiatric disorders affecting children and adolescents, despite our best psychopharmacological and psychotherapeutic treatments. Cognitive remediation, defined as a behavioral intervention designed to improve cognitive functions so as to reduce psychiatric illness, is an emerging brain-based treatment approach that has thus far not been studied in pediatric BD. The present article reviews the basic principles of cognitive remediation, describes what is known about cognitive remediation in psychiatric disorders, and delineates potential brain/behavior alterations implicated in pediatric BD that might be targets for cognitive remediation. Emerging data shows that cognitive remediation may be useful in children and adults with schizophrenia, ADHD, and anxiety disorders, and in adults with BD. Potential targets for cognitive remediation in pediatric BD include face processing, response inhibition, frustration, and cognitive flexibility. Further study is warranted to determine if cognitive remediation for these targets, or others, may serve as a novel, brain-based treatment for pediatric BD. PMID:26135596

Cognitive training on stroke patients via virtual reality-based serious games.

PubMed

Gamito, Pedro; Oliveira, Jorge; Coelho, Carla; Morais, Diogo; Lopes, Paulo; Pacheco, José; Brito, Rodrigo; Soares, Fabio; Santos, Nuno; Barata, Ana Filipa

2017-02-01

Use of virtual reality environments in cognitive rehabilitation offers cost benefits and other advantages. In order to test the effectiveness of a virtual reality application for neuropsychological rehabilitation, a cognitive training program using virtual reality was applied to stroke patients. A virtual reality-based serious games application for cognitive training was developed, with attention and memory tasks consisting of daily life activities. Twenty stroke patients were randomly assigned to two conditions: exposure to the intervention, and waiting list control. The results showed significant improvements in attention and memory functions in the intervention group, but not in the controls. Overall findings provide further support for the use of VR cognitive training applications in neuropsychological rehabilitation. Implications for Rehabilitation Improvements in memory and attention functions following a virtual reality-based serious games intervention. Training of daily-life activities using a virtual reality application. Accessibility to training contents.

Evaluation of a Web-Based Cognitive Rehabilitation Program in Cancer Survivors Reporting Cognitive Symptoms After Chemotherapy.

PubMed

Bray, Victoria J; Dhillon, Haryana M; Bell, Melanie L; Kabourakis, Michael; Fiero, Mallorie H; Yip, Desmond; Boyle, Frances; Price, Melanie A; Vardy, Janette L

2017-01-10

Purpose Cognitive impairment is reported frequently by cancer survivors. There are no proven treatments. We evaluated a cognitive rehabilitation program (Insight) and compared it with standard care in cancer survivors self-reporting cognitive symptoms. Patients and Methods We recruited adult cancer survivors with a primary malignancy (excluding central nervous system malignancies) who had completed three or more cycles of adjuvant chemotherapy in the previous 6 to 60 months and reported persistent cognitive symptoms. All participants received a 30-minute telephone consultation and were then randomly assigned to the 15-week, home-based intervention or to standard care. Primary outcome was self-reported cognitive function (Functional Assessment of Cancer Therapy Cognitive Function [FACT-COG] perceived cognitive impairment [PCI] subscale): difference between groups after intervention (T2) and 6 months later (T3). Results A total of 242 participants were randomly assigned: median age, 53 years; 95% female. The primary outcome of difference in FACT-COG PCI was significant, with less PCI in the intervention group at T2 ( P < .001). This difference was sustained at T3 ( P < .001). At T2, there was a significant difference in all FACT-COG subscales, favoring the intervention. Neuropsychological results were not significantly different between the groups at T2 or T3. There were significantly lower levels of anxiety/depression and fatigue in the intervention group at T2. There were significant improvements in stress in the intervention group at both time points. There was no significant difference in quality of life between the groups at T2, but the intervention group had better quality of life at T3. Conclusion The intervention, Insight, led to improvements in cognitive symptoms compared with standard care. To our knowledge, this is the first large randomized controlled trial showing an improvement in self-reported cognitive function in cancer survivors, indicating that

Effects of a computer-based cognitive exercise program on age-related cognitive decline.

PubMed

Bozoki, Andrea; Radovanovic, Mirjana; Winn, Brian; Heeter, Carrie; Anthony, James C

2013-01-01

We developed a 'senior friendly' suite of online 'games for learning' with interactive calibration for increasing difficulty, and evaluated the feasibility of a randomized clinical trial to test the hypothesis that seniors aged 60-80 can improve key aspects of cognitive ability with the aid of such games. Sixty community-dwelling senior volunteers were randomized to either an online game suite designed to train multiple cognitive abilities, or to a control arm with online activities that simulated the look and feel of the games but with low level interactivity and no calibration of difficulty. Study assessment included measures of recruitment, retention and play-time. Cognitive change was measured with a computerized assessment battery administered just before and within two weeks after completion of the six-week intervention. Impediments to feasibility included: limited access to in-home high-speed internet, large variations in the amount of time devoted to game play, and a reluctance to pursue more challenging levels. Overall analysis was negative for assessed performance (transference effects) even though subjects improved on the games themselves. Post hoc analyses suggest that some types of games may have more value than others, but these effects would need to be replicated in a study designed for that purpose. We conclude that a six-week, moderate-intensity computer game-based cognitive intervention can be implemented with high-functioning seniors, but the effect size is relatively small. Our findings are consistent with Owen et al. (2010), but there are open questions about whether more structured, longer duration or more intensive 'games for learning' interventions might yield more substantial cognitive improvement in seniors. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

A Memory-Based Theory of Verbal Cognition

ERIC Educational Resources Information Center

Dennis, Simon

2005-01-01

The syntagmatic paradigmatic model is a distributed, memory-based account of verbal processing. Built on a Bayesian interpretation of string edit theory, it characterizes the control of verbal cognition as the retrieval of sets of syntagmatic and paradigmatic constraints from sequential and relational long-term memory and the resolution of these…

Security management based on trust determination in cognitive radio networks

NASA Astrophysics Data System (ADS)

Li, Jianwu; Feng, Zebing; Wei, Zhiqing; Feng, Zhiyong; Zhang, Ping

2014-12-01

Security has played a major role in cognitive radio networks. Numerous researches have mainly focused on attacking detection based on source localization and detection probability. However, few of them took the penalty of attackers into consideration and neglected how to implement effective punitive measures against attackers. To address this issue, this article proposes a novel penalty mechanism based on cognitive trust value. The main feature of this mechanism has been realized by six functions: authentication, interactive, configuration, trust value collection, storage and update, and punishment. Data fusion center (FC) and cluster heads (CHs) have been put forward as a hierarchical architecture to manage trust value of cognitive users. Misbehaving users would be punished by FC by declining their trust value; thus, guaranteeing network security via distinguishing attack users is of great necessity. Simulation results verify the rationality and effectiveness of our proposed mechanism.

Differential effects of water-based exercise on the cognitive function in independent elderly adults.

PubMed

Sato, Daisuke; Seko, Chihiro; Hashitomi, Tatsuya; Sengoku, Yasuo; Nomura, Takeo

2015-04-01

Physical exercise has been reported to be the most effective method to improve cognitive function and brain health, but there is as yet no research on the effect of water-based exercise. The aim of the present study was to compare the effects of water-based exercise with and without cognitive stimuli on cognitive and physical functions. The design is a single-blind randomized controlled study. Twenty-one participants were randomly assigned to a normal water-based exercise (Nor-WE) group or a cognitive water-based exercise (Cog-WE) group. The exercise sessions were divided into two exercise series: a 10-min series of land-based warm-up, consisting of flexibility exercises, and a 50-min series of exercises in water. The Nor-WE consisted of 10 min of walking, 30 min of strength and stepping exercise, including stride over, and 10 min of stretching and relaxation in water. The Cog-WE consisted of 10 min of walking, 30 min of water-cognitive exercises, and 10 min of stretching and relaxation in water. Cognitive function, physical function, and ADL were measured before the exercise intervention (pre-intervention) and 10 weeks after the intervention (post-intervention). Participation in the Cog-WE performed significantly better on the pegboard test and the choice stepping reaction test and showed a significantly improved attention, memory, and learning, and in the general cognitive function (measured as the total score in the 5-Cog test). Participation in the Nor-WE dramatically improved walking ability and lower limb muscle strength. Our results reveal that the benefits elderly adults may obtain from water-based exercise depend on the characteristics of each specific exercise program. These findings highlight the importance of prescription for personalized water-based exercises to elderly adults to improve cognitive function.

Cognitive-Based Interventions to Improve Mobility: A Systematic Review and Meta-analysis.

PubMed

Marusic, Uros; Verghese, Joe; Mahoney, Jeannette R

2018-06-01

A strong relation between cognition and mobility has been identified in aging, supporting a role for enhancement mobility through cognitive-based interventions. However, a critical evaluation of the consistency of treatment effects of cognitive-based interventions is currently lacking. The objective of this study was 2-fold: (1) to review the existing literature on cognitive-based interventions aimed at improving mobility in older adults and (2) to assess the clinical effectiveness of cognitive interventions on gait performance. A systematic review of randomized controlled trials (RCT) of cognitive training interventions for improving simple (normal walking) and complex (dual task walking) gait was conducted in February 2018. Older adults without major cognitive, psychiatric, neurologic, and/or sensory impairments were included. Random effect meta-analyses and a subsequent meta-regression were performed to generate overall cognitive intervention effects on single- and dual-task walking conditions. Ten RCTs met inclusion criteria, with a total of 351 participants included in this meta-analysis. Cognitive training interventions revealed a small effect of intervention on complex gait [effect size (ES) = 0.47, 95% confidence interval (CI) 0.13 to 0.81, P = .007, I 2  = 15.85%], but not simple gait (ES = 0.35, 95% CI -0.01 to 0.71, P = .057, I 2  = 57.32%). Moreover, a meta-regression analysis revealed that intervention duration, training frequency, total number of sessions, and total minutes spent in intervention were not significant predictors of improvement in dual-task walking speed, though there was a suggestive trend toward a negative association between dual-task walking speed improvements and individual training session duration (P = .067). This meta-analysis provides support for the fact that cognitive training interventions can improve mobility-related outcomes, especially during challenging walking conditions requiring higher-order executive

Virtual reality-based cognitive training for drug abusers: A randomised controlled trial.

PubMed

Man, David W K

2018-05-08

Non-pharmacological means are being developed to enhance cognitive abilities in drug abusers. This study evaluated virtual reality (VR) as an intervention tool for enhancing cognitive and vocational outcomes in 90 young ketamine users (KU) randomly assigned to a treatment group (virtual reality group, VRG; tutor-administered group, TAG) or wait-listed control group (CG). Two training programmes with similar content but different delivery modes (VR-based and manual-based) were applied using a virtual boutique as a training scenario. Outcome assessments comprised the Digit Vigilance Test, Rivermead Behavioural Memory Test, Wisconsin Cart Sorting Test, work-site test and self-efficacy pre- and post-test and during 3- and 6-month follow-ups. The VRG exhibited significant improvements in attention and improvements in memory that were maintained after 3 months. Both the VRG and TAG exhibited significantly improved vocational skills after training which were maintained during follow-up, and improved self-efficacy. VR-based cognitive training might target cognitive problems in KU.

The Cognitive Assessment Interview (CAI): development and validation of an empirically derived, brief interview-based measure of cognition.

PubMed

Ventura, Joseph; Reise, Steven P; Keefe, Richard S E; Baade, Lyle E; Gold, James M; Green, Michael F; Kern, Robert S; Mesholam-Gately, Raquelle; Nuechterlein, Keith H; Seidman, Larry J; Bilder, Robert M

2010-08-01

Practical, reliable "real world" measures of cognition are needed to supplement neurocognitive performance data to evaluate possible efficacy of new drugs targeting cognitive deficits associated with schizophrenia. Because interview-based measures of cognition offer one possible approach, data from the MATRICS initiative (n=176) were used to examine the psychometric properties of the Schizophrenia Cognition Rating Scale (SCoRS) and the Clinical Global Impression of Cognition in Schizophrenia (CGI-CogS). We used classical test theory methods and item response theory to derive the 10-item Cognitive Assessment Interview (CAI) from the SCoRS and CGI-CogS ("parent instruments"). Sources of information for CAI ratings included the patient and an informant. Validity analyses examined the relationship between the CAI and objective measures of cognitive functioning, intermediate measures of cognition, and functional outcome. The rater's score from the newly derived CAI (10 items) correlate highly (r=.87) with those from the combined set of the SCoRS and CGI-CogS (41 items). Both the patient (r=.82) and the informant (r=.95) data were highly correlated with the rater's score. The CAI was modestly correlated with objectively measured neurocognition (r=-.32), functional capacity (r=-.44), and functional outcome (r=-.32), which was comparable to the parent instruments. The CAI allows for expert judgment in evaluating a patient's cognitive functioning and was modestly correlated with neurocognitive functioning, functional capacity, and functional outcome. The CAI is a brief, repeatable, and potentially valuable tool for rating cognition in schizophrenia patients who are participating in clinical trials. Copyright 2010 Elsevier B.V. All rights reserved.

Web-based cognitive rehabilitation for survivors of adult cancer: A randomised controlled trial.

PubMed

Mihuta, Mary E; Green, Heather J; Shum, David H K

2018-04-01

Cognitive dysfunction associated with cancer is frequently reported and can reduce quality of life. This study evaluated a Web-based cognitive rehabilitation therapy program (eReCog) in cancer survivors compared with a waitlist control group. Adult cancer survivors with self-reported cognitive symptoms who had completed primary treatment at least 6 months prior were recruited. Participants completed telephone screening and were randomly allocated to the 4-week online intervention or waitlist. Primary outcome was perceived cognitive impairment assessed with the Functional Assessment of Cancer Therapy-Cognitive Function version 3. Secondary outcomes were additional measures of subjective cognitive functioning, objective cognitive functioning, and psychosocial variables. Seventy-six women were allocated to the intervention (n = 40) or waitlist (n = 36). A significant interaction was found on the instrumental activities of daily living measure of self-reported prospective memory whereby the intervention group reported a greater reduction in prospective memory failures than the waitlist group. Interaction trends were noted on perceived cognitive impairments (P = .089) and executive functioning (P = .074). No significant interactions were observed on other measures of objective cognitive functioning or psychosocial variables. The Web-based intervention shows promise for improving self-reported cognitive functioning in adult cancer survivors. Further research is warranted to better understand the mechanisms by which the intervention might contribute to improved self-reported cognition. Copyright © 2017 John Wiley & Sons, Ltd.

Cognitive and Cognate-Based Treatments for Bilingual Aphasia: A Case Study

ERIC Educational Resources Information Center

Kohnert, Kathryn

2004-01-01

Two consecutive treatments were conducted to investigate skill learning and generalization within and across cognitive-linguistic domains in a 62-year-old Spanish-English bilingual man with severe non-fluent aphasia. Treatment 1 was a cognitive-based treatment that emphasized non-linguistic skills, such as visual scanning, categorization, and…

Design of cognitive engine for cognitive radio based on the rough sets and radial basis function neural network

NASA Astrophysics Data System (ADS)

Yang, Yanchao; Jiang, Hong; Liu, Congbin; Lan, Zhongli

2013-03-01

Cognitive radio (CR) is an intelligent wireless communication system which can dynamically adjust the parameters to improve system performance depending on the environmental change and quality of service. The core technology for CR is the design of cognitive engine, which introduces reasoning and learning methods in the field of artificial intelligence, to achieve the perception, adaptation and learning capability. Considering the dynamical wireless environment and demands, this paper proposes a design of cognitive engine based on the rough sets (RS) and radial basis function neural network (RBF_NN). The method uses experienced knowledge and environment information processed by RS module to train the RBF_NN, and then the learning model is used to reconfigure communication parameters to allocate resources rationally and improve system performance. After training learning model, the performance is evaluated according to two benchmark functions. The simulation results demonstrate the effectiveness of the model and the proposed cognitive engine can effectively achieve the goal of learning and reconfiguration in cognitive radio.

Plant Based Extracts and Cognition

ClinicalTrials.gov

2014-07-28

Change in Cognitive Function and Fatigue During Extended Performance of the Cognitive Demand Battery (CDB) at 1, 3 and 6 Hours Post Consumption; Change in Long Term Declarative Memory at 1, 3 and 6 Hours Post-intervention.

Manual-based cognitive behavioral and cognitive rehabilitation therapy for young-onset dementia: a case report.

PubMed

Tonga, Johanne Bjoernstad; Arnevik, Espen Ajo; Werheid, Katja; Ulstein, Ingun Dina

2016-03-01

There is a growing attention worldwide to young-onset dementia (YOD) and this group's special challenges and needs. The literature on psychosocial interventions for this population is scarce, and little is known about the specific challenges and benefits of working therapeutically with this group of patients. The aim of this study was to explore if a manual-based structured cognitive behavioral/cognitive rehabilitation program would be beneficial for these patients. One case, a 63-year-old woman with YOD, is presented to illustrate how this intervention can be applied to individual patients to manage depressive symptoms in YOD.

Cognitive Correlates of Functional Abilities in Individuals with Mild Cognitive Impairment: Comparison of Questionnaire, Direct Observation and Performance-based Measures

PubMed Central

Schmitter-Edgecombe, Maureen; Parsey, Carolyn M.

2014-01-01

The relationship between and the cognitive correlates of several proxy measures of functional status were studied in a population with mild cognitive impairment (MCI). Participants were 51 individuals diagnosed with MCI and 51 cognitively healthy older adults (OA). Participants completed performance-based functional status tests, standardized neuropsychological tests, and performed eight activities of daily living (e.g., watered plants, filled medication dispenser) while under direct observation in a campus apartment. An informant interview about everyday functioning was also conducted. Compared to the OA control group, the MCI group performed more poorly on all proxy measures of everyday functioning. The informant-report of instrumental activities of daily living (IADL) did not correlate with the two performance-based measures; however, both the informant-report IADL and the performance-based everyday problem-solving test correlated with the direct observation measure. After controlling for age and education, cognitive predictors did not explain a significant amount of variance in the performance-based measures; however, performance on a delayed memory task was a unique predictor for the informant-report IADL, and processing speed predicted unique variance for the direct observation score. These findings indicate that differing methods for evaluating functional status are not assessing completely overlapping aspects of everyday functioning in the MCI population. PMID:24766574

Cognitive correlates of functional abilities in individuals with mild cognitive impairment: comparison of questionnaire, direct observation, and performance-based measures.

PubMed

Schmitter-Edgecombe, Maureen; Parsey, Carolyn M

2014-01-01

The relationship between, and the cognitive correlates of, several proxy measures of functional status were studied in a population with mild cognitive impairment (MCI). Participants were 51 individuals diagnosed with MCI and 51 cognitively healthy older adults (OA). Participants completed performance-based functional status tests and standardized neuropsychological tests, and performed eight activities of daily living (e.g., watered plants, filled medication dispenser) while under direct observation in a campus apartment. An informant interview about everyday functioning was also conducted. Compared to the OA control group, the MCI group performed more poorly on all proxy measures of everyday functioning. The informant report of instrumental activities of daily living (IADL) did not correlate with the two performance-based measures; however, both the informant-report IADL and the performance-based everyday problem-solving test correlated with the direct observation measure. After controlling for age and education, cognitive predictors did not explain a significant amount of variance in the performance-based measures; however, performance on a delayed memory task was a unique predictor for the informant-report IADL, and processing speed predicted unique variance for the direct observation score. These findings indicate that differing methods for evaluating functional status are not assessing completely overlapping aspects of everyday functioning in the MCI population.

Improving the learning of clinical reasoning through computer-based cognitive representation.

PubMed

Wu, Bian; Wang, Minhong; Johnson, Janice M; Grotzer, Tina A

2014-01-01

Clinical reasoning is usually taught using a problem-solving approach, which is widely adopted in medical education. However, learning through problem solving is difficult as a result of the contextualization and dynamic aspects of actual problems. Moreover, knowledge acquired from problem-solving practice tends to be inert and fragmented. This study proposed a computer-based cognitive representation approach that externalizes and facilitates the complex processes in learning clinical reasoning. The approach is operationalized in a computer-based cognitive representation tool that involves argument mapping to externalize the problem-solving process and concept mapping to reveal the knowledge constructed from the problems. Twenty-nine Year 3 or higher students from a medical school in east China participated in the study. Participants used the proposed approach implemented in an e-learning system to complete four learning cases in 4 weeks on an individual basis. For each case, students interacted with the problem to capture critical data, generate and justify hypotheses, make a diagnosis, recall relevant knowledge, and update their conceptual understanding of the problem domain. Meanwhile, students used the computer-based cognitive representation tool to articulate and represent the key elements and their interactions in the learning process. A significant improvement was found in students' learning products from the beginning to the end of the study, consistent with students' report of close-to-moderate progress in developing problem-solving and knowledge-construction abilities. No significant differences were found between the pretest and posttest scores with the 4-week period. The cognitive representation approach was found to provide more formative assessment. The computer-based cognitive representation approach improved the learning of clinical reasoning in both problem solving and knowledge construction.

The Cognitive Assessment Interview (CAI): Development and Validation of an Empirically Derived, Brief Interview-Based Measure of Cognition

PubMed Central

Ventura, Joseph; Reise, Steven P.; Keefe, Richard S. E.; Baade, Lyle E.; Gold, James M.; Green, Michael F.; Kern, Robert S.; Mesholam-Gately, Raquelle; Nuechterlein, Keith H.; Seidman, Larry J.; Bilder, Robert M.

2011-01-01

Background Practical, reliable “real world” measures of cognition are needed to supplement neurocognitive performance data to evaluate possible efficacy of new drugs targeting cognitive deficits associated with schizophrenia. Because interview-based measures of cognition offer one possible approach, data from the MATRICS initiative (n=176) were used to examine the psychometric properties of the Schizophrenia Cognition Rating Scale (SCoRS) and the Clinical Global Impression of Cognition in Schizophrenia (CGI-CogS). Method We used classical test theory methods and item response theory to derive the 10 item Cognitive Assessment Interview (CAI) from the SCoRS and CGI-Cogs (“parent instruments”). Sources of information for CAI ratings included the patient and an informant. Validity analyses examined the relationship between the CAI and objective measures of cognitive functioning, intermediate measures of cognition, and functional outcome. Results The rater’s score from the newly derived CAI (10-items) correlate highly (r = .87) with those from the combined set of the SCoRS and CGI-CogS (41 items). Both the patient (r= .82) and the informant (r= .95) data were highly correlated with the rater’s score. The CAI was modestly correlated with objectively measured neurocognition (r = −.32), functional capacity (r = −.44), and functional outcome (r = −.32), which was comparable to the parent instruments. Conclusions The CAI allows for expert judgment in evaluating a patient’s cognitive functioning and was modestly correlated with neurocognitive functioning, functional capacity, and functional outcome. The CAI is a brief, repeatable, and potentially valuable tool for rating cognition in schizophrenia patients who are participating in clinical trials. PMID:20542412

Using EEG to Discriminate Cognitive Workload and Performance Based on Neural Activation and Connectivity

DTIC Science & Technology

2016-05-31

auditory working memory task to vary cognitive workload by altering the number of digits held in memory during the simultaneous retention of a sentence...in memory . Cognitive efficacy is assessed based on accuracy in recalling digits from memory . A Gaussian classifier is used to discriminate cognitive...effectiveness of cognition under the existing load. One major factor that impacts cognitive load is the amount of working memory required in a task

Effects of a process-based cognitive training intervention for patients with stress-related exhaustion.

PubMed

Gavelin, Hanna Malmberg; Boraxbekk, Carl-Johan; Stenlund, Therese; Järvholm, Lisbeth Slunga; Neely, Anna Stigsdotter

2015-08-13

Stress-related exhaustion has been linked to a pattern of selective cognitive impairments, mainly affecting executive functioning, attention and episodic memory. Little is known about potential treatments of these cognitive deficits. The purpose of this study was to evaluate the effects of a process-based cognitive training intervention, designed to target the specific cognitive impairments associated with stress-related exhaustion. To this end, patients diagnosed with exhaustion disorder (ED) were randomized to either a multimodal stress rehabilitation program with the addition of a process-based cognitive training intervention (training group, n = 27) or a treatment-as-usual control condition, consisting of multimodal stress rehabilitation with no additional training (control group, n = 32). Treatment effects were evaluated through an extensive cognitive test battery, assessing both near and far transfer effects, as well as self-report forms regarding subjective cognitive complaints and burnout levels. Results showed pronounced training-related improvements on the criterion updating task (p < 0.001). Further, evidence was found of selective near transfer effects to updating (p = 0.01) and episodic memory (p = 0.04). Also, the trained group reported less subjective memory complaints (p = 0.02) and levels of burnout decreased for both groups, but more so for the trained group (p = 0.04), following the intervention. These findings suggest that process-based cognitive training may be a viable method to address the cognitive impairments associated with ED.

Effects of a process-based cognitive training intervention for patients with stress-related exhaustion.

PubMed

Gavelin, Hanna Malmberg; Boraxbekk, Carl-Johan; Stenlund, Therese; Järvholm, Lisbeth Slunga; Neely, Anna Stigsdotter

2015-01-01

Stress-related exhaustion has been linked to a pattern of selective cognitive impairments, mainly affecting executive functioning, attention and episodic memory. Little is known about potential treatments of these cognitive deficits. The purpose of this study was to evaluate the effects of a process-based cognitive training intervention, designed to target the specific cognitive impairments associated with stress-related exhaustion. To this end, patients diagnosed with exhaustion disorder (ED) were randomized to either a multimodal stress rehabilitation program with the addition of a process-based cognitive training intervention (training group, n = 27) or a treatment-as-usual control condition, consisting of multimodal stress rehabilitation with no additional training (control group, n = 32). Treatment effects were evaluated through an extensive cognitive test battery, assessing both near and far transfer effects, as well as self-report forms regarding subjective cognitive complaints and burnout levels. Results showed pronounced training-related improvements on the criterion updating task (p < 0.001). Further, evidence was found of selective near transfer effects to updating (p = 0.01) and episodic memory (p = 0.04). Also, the trained group reported less subjective memory complaints (p = 0.02) and levels of burnout decreased for both groups, but more so for the trained group (p = 0.04), following the intervention. These findings suggest that process-based cognitive training may be a viable method to address the cognitive impairments associated with ED.

Evidence-based practice for pain identification in cognitively impaired nursing home residents.

PubMed

Sacoco, Christina; Ishikawa, Sally

2014-09-01

Pain identification of cognitively impaired elderly is very challenging. This project aimed to identify best practices for pain assessment in nursing home residents with cognitive impairment and to establish a standardized pain assessment guide to optimize nursing practice and resident outcomes. The Iowa Model of Evidence-Based Practice to Promote Quality of Care guided the project's process. Phase I of the project analyzed data gained from chart reviews on current practices of pain assessment, and Phase II used the results of Phase I to develop, implement, and evaluate an evidence-based practice standard for nursing assessment of pain for cognitively impaired residents. Copyright © 2014 Elsevier Inc. All rights reserved.

Efficacy of cognitive rehabilitation therapies for mild cognitive impairment (MCI) in older adults: Working toward a theoretical model and evidence-based interventions

PubMed Central

Huckans, Marilyn; Hutson, Lee; Twamley, Elizabeth; Jak, Amy; Kaye, Jeffrey; Storzbach, Daniel

2013-01-01

Objective To evaluate the efficacy of cognitive rehabilitation therapies (CRTs) for mild cognitive impairment (MCI). Our review revealed a need for evidence-based treatments for MCI and a lack of a theoretical rehabilitation model to guide the development and evaluation of these interventions. We have thus proposed a theoretical rehabilitation model of MCI that yields key intervention targets - cognitive compromise, functional compromise, neuropsychiatric symptoms, and modifiable risk and protective factors known to be associated with MCI and dementia. Our model additionally defines specific cognitive rehabilitation approaches that may directly or indirectly target key outcomes - restorative cognitive training, compensatory cognitive training, lifestyle interventions, and psychotherapeutic techniques. Methods Fourteen randomized controlled trials met inclusion criteria and were reviewed. Results Studies markedly varied in terms of intervention approaches and selected outcome measures and were frequently hampered by design limitations. The bulk of the evidence suggested that CRTs can change targeted behaviors in individuals with MCI and that CRTs are associated with improvements in objective cognitive performance, but the pattern of effects on specific cognitive domains was inconsistent across studies. Other important outcomes (i.e., daily functioning, quality of life, neuropsychiatric symptom severity) were infrequently assessed across studies. Few studies evaluated long-term outcomes or the impact of CRTs on conversion rates from MCI to dementia or normal cognition. Conclusions Overall, results from trials are promising but inconclusive. Additional well-designed and adequately powered trials are warranted and required before CRTs for MCI can be considered evidence based. PMID:23471631

Combined peak-to-average power ratio reduction and physical layer security enhancement in optical orthogonal frequency division multiplexing visible-light communication systems

NASA Astrophysics Data System (ADS)

Wang, Zhongpeng; Chen, Shoufa

2016-07-01

A physical encryption scheme for discrete Hartley transform (DHT) precoded orthogonal frequency division multiplexing (OFDM) visible-light communication (VLC) systems using frequency domain chaos scrambling is proposed. In the scheme, the chaos scrambling, which is generated by a modified logistic mapping, is utilized to enhance the physical layer of security, and the DHT precoding is employed to reduce of OFDM signal for OFDM-based VLC. The influence of chaos scrambling on peak-to-average power ratio (PAPR) and bit error rate (BER) of systems is studied. The experimental simulation results prove the efficiency of the proposed encryption method for DHT-precoded, OFDM-based VLC systems. Furthermore, the influence of the proposed encryption to the PAPR and BER of systems is evaluated. The experimental results show that the proposed security scheme can protect the DHT-precoded, OFDM-based VLC from eavesdroppers, while keeping the good BER performance of DHT-precoded systems. The BER performance of the encrypted and DHT-precoded system is almost the same as that of the conventional DHT-precoded system without encryption.

Quantifying the cognitive cost of laparo-endoscopic single-site surgeries: Gaze-based indices.

PubMed

Di Stasi, Leandro L; Díaz-Piedra, Carolina; Ruiz-Rabelo, Juan Francisco; Rieiro, Héctor; Sanchez Carrion, Jose M; Catena, Andrés

2017-11-01

Despite the growing interest concerning the laparo-endoscopic single-site surgery (LESS) procedure, LESS presents multiple difficulties and challenges that are likely to increase the surgeon's cognitive cost, in terms of both cognitive load and performance. Nevertheless, there is currently no objective index capable of assessing the surgeon cognitive cost while performing LESS. We assessed if gaze-based indices might offer unique and unbiased measures to quantify LESS complexity and its cognitive cost. We expect that the assessment of surgeon's cognitive cost to improve patient safety by measuring fitness-for-duty and reducing surgeons overload. Using a wearable eye tracker device, we measured gaze entropy and velocity of surgical trainees and attending surgeons during two surgical procedures (LESS vs. multiport laparoscopy surgery [MPS]). None of the participants had previous experience with LESS. They performed two exercises with different complexity levels (Low: Pattern Cut vs. High: Peg Transfer). We also collected performance and subjective data. LESS caused higher cognitive demand than MPS, as indicated by increased gaze entropy in both surgical trainees and attending surgeons (exploration pattern became more random). Furthermore, gaze velocity was higher (exploration pattern became more rapid) for the LESS procedure independently of the surgeon's expertise. Perceived task complexity and laparoscopic accuracy confirmed gaze-based results. Gaze-based indices have great potential as objective and non-intrusive measures to assess surgeons' cognitive cost and fitness-for-duty. Furthermore, gaze-based indices might play a relevant role in defining future guidelines on surgeons' examinations to mark their achievements during the entire training (e.g. analyzing surgical learning curves). Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of Clipping Based Iterative PAPR Reduction Techniques for FBMC Systems

PubMed Central

Kollár, Zsolt

2014-01-01

This paper investigates filter bankmulticarrier (FBMC), a multicarrier modulation technique exhibiting an extremely low adjacent channel leakage ratio (ACLR) compared to conventional orthogonal frequency division multiplexing (OFDM) technique. The low ACLR of the transmitted FBMC signal makes it especially favorable in cognitive radio applications, where strict requirements are posed on out-of-band radiation. Large dynamic range resulting in high peak-to-average power ratio (PAPR) is characteristic of all sorts of multicarrier signals. The advantageous spectral properties of the high-PAPR FBMC signal are significantly degraded if nonlinearities are present in the transceiver chain. Spectral regrowth may appear, causing harmful interference in the neighboring frequency bands. This paper presents novel clipping based PAPR reduction techniques, evaluated and compared by simulations and measurements, with an emphasis on spectral aspects. The paper gives an overall comparison of PAPR reduction techniques, focusing on the reduction of the dynamic range of FBMC signals without increasing out-of-band radiation. An overview is presented on transmitter oriented techniques employing baseband clipping, which can maintain the system performance with a desired bit error rate (BER). PMID:24558338

Responsible Adult Culture (RAC): Cognitive and Behavioral Changes at a Community-Based Correctional Facility

ERIC Educational Resources Information Center

Devlin, Renee S.; Gibbs, John C.

2010-01-01

This article examined cognitive and behavioral changes among participants in Responsible Adult Culture (RAC), a cognitive-behavioral (especially, cognitive restructuring) treatment program in use at the Franklin County Community-Based Correctional Facility (CBCF). Participants were adult felony offenders (approximately three-fourths male). A…

Mindfulness-based cognitive therapy for recurrent major depression: A 'best buy' for health care?

PubMed

Shawyer, Frances; Enticott, Joanne C; Özmen, Mehmet; Inder, Brett; Meadows, Graham N

2016-10-01

While mindfulness-based cognitive therapy is effective in reducing depressive relapse/recurrence, relatively little is known about its health economic properties. We describe the health economic properties of mindfulness-based cognitive therapy in relation to its impact on depressive relapse/recurrence over 2 years of follow-up. Non-depressed adults with a history of three or more major depressive episodes were randomised to mindfulness-based cognitive therapy + depressive relapse active monitoring (n = 101) or control (depressive relapse active monitoring alone) (n = 102) and followed up for 2 years. Structured self-report instruments for service use and absenteeism provided cost data items for health economic analyses. Treatment utility, expressed as disability-adjusted life years, was calculated by adjusting the number of days an individual was depressed by the relevant International Classification of Diseases 12-month severity of depression disability weight from the Global Burden of Disease 2010. Intention-to-treat analysis assessed the incremental cost-utility ratios of the interventions across mental health care, all of health-care and whole-of-society perspectives. Per protocol and site of usual care subgroup analyses were also conducted. Probabilistic uncertainty analysis was completed using cost-utility acceptability curves. Mindfulness-based cognitive therapy participants had significantly less major depressive episode days compared to controls, as supported by the differential distributions of major depressive episode days (modelled as Poisson, p < 0.001). Average major depressive episode days were consistently less in the mindfulness-based cognitive therapy group compared to controls, e.g., 31 and 55 days, respectively. From a whole-of-society perspective, analyses of patients receiving usual care from all sectors of the health-care system demonstrated dominance (reduced costs, demonstrable health gains). From a mental health

Improving the learning of clinical reasoning through computer-based cognitive representation.

PubMed

Wu, Bian; Wang, Minhong; Johnson, Janice M; Grotzer, Tina A

2014-01-01

Objective Clinical reasoning is usually taught using a problem-solving approach, which is widely adopted in medical education. However, learning through problem solving is difficult as a result of the contextualization and dynamic aspects of actual problems. Moreover, knowledge acquired from problem-solving practice tends to be inert and fragmented. This study proposed a computer-based cognitive representation approach that externalizes and facilitates the complex processes in learning clinical reasoning. The approach is operationalized in a computer-based cognitive representation tool that involves argument mapping to externalize the problem-solving process and concept mapping to reveal the knowledge constructed from the problems. Methods Twenty-nine Year 3 or higher students from a medical school in east China participated in the study. Participants used the proposed approach implemented in an e-learning system to complete four learning cases in 4 weeks on an individual basis. For each case, students interacted with the problem to capture critical data, generate and justify hypotheses, make a diagnosis, recall relevant knowledge, and update their conceptual understanding of the problem domain. Meanwhile, students used the computer-based cognitive representation tool to articulate and represent the key elements and their interactions in the learning process. Results A significant improvement was found in students' learning products from the beginning to the end of the study, consistent with students' report of close-to-moderate progress in developing problem-solving and knowledge-construction abilities. No significant differences were found between the pretest and posttest scores with the 4-week period. The cognitive representation approach was found to provide more formative assessment. Conclusions The computer-based cognitive representation approach improved the learning of clinical reasoning in both problem solving and knowledge construction.

Improving the learning of clinical reasoning through computer-based cognitive representation

PubMed Central

Wu, Bian; Wang, Minhong; Johnson, Janice M.; Grotzer, Tina A.

2014-01-01

Objective Clinical reasoning is usually taught using a problem-solving approach, which is widely adopted in medical education. However, learning through problem solving is difficult as a result of the contextualization and dynamic aspects of actual problems. Moreover, knowledge acquired from problem-solving practice tends to be inert and fragmented. This study proposed a computer-based cognitive representation approach that externalizes and facilitates the complex processes in learning clinical reasoning. The approach is operationalized in a computer-based cognitive representation tool that involves argument mapping to externalize the problem-solving process and concept mapping to reveal the knowledge constructed from the problems. Methods Twenty-nine Year 3 or higher students from a medical school in east China participated in the study. Participants used the proposed approach implemented in an e-learning system to complete four learning cases in 4 weeks on an individual basis. For each case, students interacted with the problem to capture critical data, generate and justify hypotheses, make a diagnosis, recall relevant knowledge, and update their conceptual understanding of the problem domain. Meanwhile, students used the computer-based cognitive representation tool to articulate and represent the key elements and their interactions in the learning process. Results A significant improvement was found in students’ learning products from the beginning to the end of the study, consistent with students’ report of close-to-moderate progress in developing problem-solving and knowledge-construction abilities. No significant differences were found between the pretest and posttest scores with the 4-week period. The cognitive representation approach was found to provide more formative assessment. Conclusions The computer-based cognitive representation approach improved the learning of clinical reasoning in both problem solving and knowledge construction. PMID:25518871

Positive Effects of Computer-Based Cognitive Training in Adults with Mild Cognitive Impairment

ERIC Educational Resources Information Center

Herrera, C.; Chambon, C.; Michel, B. F.; Paban, V.; Alescio-Lautier, B.

2012-01-01

Considering the high risk for individuals with amnestic Mild Cognitive Impairment (A-MCI) to progress towards Alzheimer's disease (AD), we investigated the efficacy of a non-pharmacological intervention, that is, cognitive training that could reduce cognitive difficulties and delay the cognitive decline. For this, we evaluated the efficacy of a…

Computer-based cognitive training for ADHD: a review of current evidence.

PubMed

Sonuga-Barke, Edmund; Brandeis, Daniel; Holtmann, Martin; Cortese, Samuele

2014-10-01

There has been an increasing interest in and the use of computer-based cognitive training as a treatment of attention-deficit/hyperactivity disorder (ADHD). The authors' review of current evidence, based partly on a stringent meta-analysis of 6 randomized controlled trials (RCTs) published in 2013, and an overview of 8 recently published RCTs highlights the inconsistency of findings between trials and across blinded and nonblinded ADHD measures within trials. Based on this, they conclude that more evidence from well-blinded studies is required before cognitive training can be supported as a frontline treatment of core ADHD symptoms. Copyright © 2014 Elsevier Inc. All rights reserved.

Identifying Mobility Types in Cognitively Heterogeneous Older Adults Based on GPS-Tracking: What Discriminates Best?

PubMed

Wettstein, Markus; Wahl, Hans-Werner; Shoval, Noam; Auslander, Gail; Oswald, Frank; Heinik, Jeremia

2015-12-01

Heterogeneity in older adults' mobility and its correlates have rarely been investigated based on objective mobility data and in samples including cognitively impaired individuals. We analyzed mobility profiles within a cognitively heterogeneous sample of N = 257 older adults from Israel and Germany based on GPS tracking technology. Participants were aged between 59 and 91 years (M = 72.9; SD = 6.4) and were either cognitively healthy (CH, n = 146), mildly cognitively impaired (MCI, n = 76), or diagnosed with an early-stage dementia of the Alzheimer's type (DAT, n = 35). Based on cluster analysis, we identified three mobility types ("Mobility restricted," "Outdoor oriented," "Walkers"), which could be predicted based on socio-demographic indicators, activity, health, and cognitive impairment status using discriminant analysis. Particularly demented individuals and persons with worse health exhibited restrictions in mobility. Our findings contribute to a better understanding of heterogeneity in mobility in old age. © The Author(s) 2013.

Crosstalk mitigation using pilot assisted least square algorithm in OFDM-carrying orbital angular momentum multiplexed free-space-optical communication links.

PubMed

Sun, Tengfen; Liu, Minwen; Li, Yingchun; Wang, Min

2017-10-16

In this paper, we experimentally investigate the performance of crosstalk mitigation for 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing (16QAM-OFDM) signals carrying orbital angular momentum (OAM) multiplexed free-space-optical communication (FSO) links using the pilot assisted Least Square (LS) algorithm. At the demodulating spatial light modulators (SLMs), we launch the distorted phase holograms which have the information of atmospheric turbulence obeying the modified Hill spectrum. And crosstalk can be introduced by these holograms with the experimental verification. The pilot assisted LS algorithm can efficiently improve the quality of system performance, the points of constellations get closer to the reference points and around two orders of magnitude improvement of bit-error rate (BER) is obtained.

Effect of Neuroscience-Based Cognitive Skill Training on Growth of Cognitive Deficits Associated with Learning Disabilities in Children Grades 2-4

ERIC Educational Resources Information Center

Avtzon, Sarah Abitbol

2012-01-01

Working memory, executive functions, and cognitive processes associated with specific academic areas, are empirically identified as being the core underlying cognitive deficits in students with specific learning disabilities. Using Hebb's theory of neuroplasticity and the principle of automaticity as theoretical bases, this experimental study…

Going beyond the unitary curve: incorporating richer cognition into agent-based water resources models

NASA Astrophysics Data System (ADS)

Kock, B. E.

2008-12-01

The increased availability and understanding of agent-based modeling technology and techniques provides a unique opportunity for water resources modelers, allowing them to go beyond traditional behavioral approaches from neoclassical economics, and add rich cognition to social-hydrological models. Agent-based models provide for an individual focus, and the easier and more realistic incorporation of learning, memory and other mechanisms for increased cognitive sophistication. We are in an age of global change impacting complex water resources systems, and social responses are increasingly recognized as fundamentally adaptive and emergent. In consideration of this, water resources models and modelers need to better address social dynamics in a manner beyond the capabilities of neoclassical economics theory and practice. However, going beyond the unitary curve requires unique levels of engagement with stakeholders, both to elicit the richer knowledge necessary for structuring and parameterizing agent-based models, but also to make sure such models are appropriately used. With the aim of encouraging epistemological and methodological convergence in the agent-based modeling of water resources, we have developed a water resources-specific cognitive model and an associated collaborative modeling process. Our cognitive model emphasizes efficiency in architecture and operation, and capacity to adapt to different application contexts. We describe a current application of this cognitive model and modeling process in the Arkansas Basin of Colorado. In particular, we highlight the potential benefits of, and challenges to, using more sophisticated cognitive models in agent-based water resources models.

A first approach to a neuropsychological screening tool using eye-tracking for bedside cognitive testing based on the Edinburgh Cognitive and Behavioural ALS Screen.

PubMed

Keller, Jürgen; Krimly, Amon; Bauer, Lisa; Schulenburg, Sarah; Böhm, Sarah; Aho-Özhan, Helena E A; Uttner, Ingo; Gorges, Martin; Kassubek, Jan; Pinkhardt, Elmar H; Abrahams, Sharon; Ludolph, Albert C; Lulé, Dorothée

2017-08-01

Reliable assessment of cognitive functions is a challenging task in amyotrophic lateral sclerosis (ALS) patients unable to speak and write. We therefore present an eye-tracking based neuropsychological screening tool based on the Edinburgh Cognitive and Behavioural ALS Screen (ECAS), a standard screening tool for cognitive deficits in ALS. In total, 46 ALS patients and 50 healthy controls matched for age, gender and education were tested with an oculomotor based and a standard paper-and-pencil version of the ECAS. Significant correlation between both versions was observed for ALS patients and healthy controls in the ECAS total score and in all of its ALS-specific domains (all r > 0.3; all p < 0.05). The eye-tracking version of the ECAS reliably distinguished between ALS patients and healthy controls in the ECAS total score (p < 0.05). Also, cognitively impaired and non-impaired patients could be reliably distinguished with a specificity of 95%. This study provides first evidence that the eye-tracking based ECAS version is a promising approach for assessing cognitive deficits in ALS patients who are unable to speak or write.

Web-Based Learning: Cognitive Styles and Instructional Strategies

ERIC Educational Resources Information Center

Alomyan, Hesham Raji

2016-01-01

This paper reports a study, which investigated whether different instructional strategies might interact with individual's cognitive style in learning. A web-based learning package was designed employing three strategies, Interactive Concept Maps, Illustration with Embedded Text and Text-Only. Group Embedded Figure Test was administered to 178…

Classroom-Based Physical Activity Breaks and Children's Attention: Cognitive Engagement Works!

PubMed Central

Schmidt, Mirko; Benzing, Valentin; Kamer, Mario

2016-01-01

Classroom-based physical activity breaks are postulated to positively impact children's attention during their school day. However, empirical evidence for this claim is scarce and the role of cognitive engagement in enhancing children's attentional performance is unexplored in studies on physical activity breaks. The aim of the present study was therefore to disentangle the separate and/or combined effects of physical exertion and cognitive engagement induced by physical activity breaks on primary school children's attention. In addition, the role of children's affective reactions to acute interventions at school was investigated. Using a 2 × 2 between-subjects experimental design, 92 children between the ages of 11 and 12 years (M = 11.77, SD = 0.41) were randomly assigned to one of four experimental conditions: (1) combo group (physical activity with high cognitive demands), (2) cognition group (sedentary with high cognitive demands), (3) physical group (physical activity with low cognitive demands), and (4) control group (sedentary with low cognitive demands). Attention and affect were measured before and immediately after a 10-min intervention. ANCOVAs revealed that whereas physical exertion had no effect on any measure of children's attentional performance, cognitive engagement was the crucial factor leading to increased focused attention and enhanced processing speed. Mediational analyses showed that changes in positive affect during the interventions mediated the effect between cognitive engagement and focused attention as well as between cognitive engagement and processing speed. These surprising results are discussed in the light of theories predicting both facilitating and deteriorative effects of positive affect on attention. PMID:27757088

Factors Influencing the Use of Cognitive Tools in Web-Based Learning Environments: A Case Study

ERIC Educational Resources Information Center

Ozcelik, Erol; Yildirim, Soner

2005-01-01

High demands on learners in Web-based learning environments and constraints of the human cognitive system cause disorientation and cognitive overload. These problems could be inhibited if appropriate cognitive tools are provided to support learners' cognitive processes. The purpose of this study was to explore the factors influencing the use of…

Studying distributed cognition of simulation-based team training with DiCoT.

PubMed

Rybing, Jonas; Nilsson, Heléne; Jonson, Carl-Oscar; Bang, Magnus

2016-03-01

Health care organizations employ simulation-based team training (SBTT) to improve skill, communication and coordination in a broad range of critical care contexts. Quantitative approaches, such as team performance measurements, are predominantly used to measure SBTTs effectiveness. However, a practical evaluation method that examines how this approach supports cognition and teamwork is missing. We have applied Distributed Cognition for Teamwork (DiCoT), a method for analysing cognition and collaboration aspects of work settings, with the purpose of assessing the methodology's usefulness for evaluating SBTTs. In a case study, we observed and analysed four Emergo Train System® simulation exercises where medical professionals trained emergency response routines. The study suggests that DiCoT is an applicable and learnable tool for determining key distributed cognition attributes of SBTTs that are of importance for the simulation validity of training environments. Moreover, we discuss and exemplify how DiCoT supports design of SBTTs with a focus on transfer and validity characteristics. Practitioner Summary: In this study, we have evaluated a method to assess simulation-based team training environments from a cognitive ergonomics perspective. Using a case study, we analysed Distributed Cognition for Teamwork (DiCoT) by applying it to the Emergo Train System®. We conclude that DiCoT is useful for SBTT evaluation and simulator (re)design.

Beliefs About Appearance, Cognitive Distraction and Sexual Functioning in Men and Women: A Mediation Model Based on Cognitive Theory.

PubMed

Silva, Elizabet; Pascoal, Patrícia M; Nobre, Pedro

2016-09-01

Dysfunctional beliefs about body appearance and cognitive distraction from body appearance during sexual activity have been associated with sexual problems, particularly in women. However, there are no studies examining the interplay between these dimensions and the mechanisms by which they affect sexual functioning. To examine the mediating role of cognitive distraction with body appearance on the relation between beliefs about appearance and sexual functioning. The study sample consisted of 426 heterosexual participants (129 men and 297 women) involved in an exclusive dyadic committed relationship who answered an online questionnaire. The Body Appearance Cognitive Distraction Scale, the Beliefs About Appearance Scale, the International Index of Erectile Function, and the Female Sexual Function Index. The findings indicated that cognitive distraction with body appearance fully mediated the relation between beliefs about appearance and sexual functioning in men and women. The results support the role of beliefs about appearance and cognitive distraction based on body appearance in predicting sexual functioning, reaffirming the role of cognitive models in explaining sexual functioning in men and women. Copyright © 2016 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Cognition in school-aged children with "active" epilepsy: A population-based study.

PubMed

Reilly, Colin; Atkinson, Patricia; Das, Krishna B; Chin, Richard F M; Aylett, Sarah E; Burch, Victoria; Gillberg, Christopher; Scott, Rod C; Neville, Brian G R

2015-01-01

There is a lack of population-based data on specific cognitive profiles in childhood epilepsy. This study sought to determine the frequency of impairments in global cognition and aspects of working memory and processing speed in a population-based sample of children with "active" epilepsy (on antiepileptic Drugs (AEDs), and/or had a seizure in the last year). Factors significantly associated with global and specific difficulties in cognition were also identified. A total of 85 (74% of eligible population) school-aged children (5-15 years) with "active" epilepsy underwent comprehensive psychological assessment including assessment of global cognition, working memory, and processing speed. Scores on cognitive subtests were compared via paired-samples t tests. The factors associated with cognitive difficulties were analyzed via linear regression. A total of 24% of children were functioning below IQ 50, and 40% had IQ scores below 70. Scores on the Processing Speed Index were significantly lower than scores on the Verbal or Performance indexes on Wechsler instruments. The Coding subtest was a significant weakness compared with the other Wechsler subtests. A total of 58% of children displayed "memory underachievement" (memory score 1 SD below assessed IQ) on at least one of the four administered working memory subtests. Factors significantly associated with globally impaired cognition included being on polytherapy (β = -13.0; 95% CI [-19.3, -6.6], p = .000) and having attention-deficit/hyperactivity disorder (ADHD; β = -11.1, 95% CI [-3.0, -19.3], p = .008). Being on polytherapy was also associated with lower scores on the working memory and processing speed composite scores. Having developmental coordination disorder (DCD) was associated with a lower score on the processing speed composite. There is a high rate of global and specific cognitive difficulties in childhood epilepsy. Difficulties are most pronounced in aspects of working memory and processing speed

PERFORMANCE OF A COMPUTER-BASED ASSESSMENT OF COGNITIVE FUNCTION MEASURES IN TWO COHORTS OF SENIORS

PubMed Central

Espeland, Mark A.; Katula, Jeffrey A.; Rushing, Julia; Kramer, Arthur F.; Jennings, Janine M.; Sink, Kaycee M.; Nadkarni, Neelesh K.; Reid, Kieran F.; Castro, Cynthia M.; Church, Timothy; Kerwin, Diana R.; Williamson, Jeff D.; Marottoli, Richard A.; Rushing, Scott; Marsiske, Michael; Rapp, Stephen R.

2013-01-01

Background Computer-administered assessment of cognitive function is being increasingly incorporated in clinical trials, however its performance in these settings has not been systematically evaluated. Design The Seniors Health and Activity Research Program (SHARP) pilot trial (N=73) developed a computer-based tool for assessing memory performance and executive functioning. The Lifestyle Interventions and Independence for Seniors (LIFE) investigators incorporated this battery in a full scale multicenter clinical trial (N=1635). We describe relationships that test scores have with those from interviewer-administered cognitive function tests and risk factors for cognitive deficits and describe performance measures (completeness, intra-class correlations). Results Computer-based assessments of cognitive function had consistent relationships across the pilot and full scale trial cohorts with interviewer-administered assessments of cognitive function, age, and a measure of physical function. In the LIFE cohort, their external validity was further demonstrated by associations with other risk factors for cognitive dysfunction: education, hypertension, diabetes, and physical function. Acceptable levels of data completeness (>83%) were achieved on all computer-based measures, however rates of missing data were higher among older participants (odds ratio=1.06 for each additional year; p<0.001) and those who reported no current computer use (odds ratio=2.71; p<0.001). Intra-class correlations among clinics were at least as low (ICC≤0.013) as for interviewer measures (ICC≤0.023), reflecting good standardization. All cognitive measures loaded onto the first principal component (global cognitive function), which accounted for 40% of the overall variance. Conclusion Our results support the use of computer-based tools for assessing cognitive function in multicenter clinical trials of older individuals. PMID:23589390

Cognitive components underpinning the development of model-based learning.

PubMed

Potter, Tracey C S; Bryce, Nessa V; Hartley, Catherine A

2017-06-01

Reinforcement learning theory distinguishes "model-free" learning, which fosters reflexive repetition of previously rewarded actions, from "model-based" learning, which recruits a mental model of the environment to flexibly select goal-directed actions. Whereas model-free learning is evident across development, recruitment of model-based learning appears to increase with age. However, the cognitive processes underlying the development of model-based learning remain poorly characterized. Here, we examined whether age-related differences in cognitive processes underlying the construction and flexible recruitment of mental models predict developmental increases in model-based choice. In a cohort of participants aged 9-25, we examined whether the abilities to infer sequential regularities in the environment ("statistical learning"), maintain information in an active state ("working memory") and integrate distant concepts to solve problems ("fluid reasoning") predicted age-related improvements in model-based choice. We found that age-related improvements in statistical learning performance did not mediate the relationship between age and model-based choice. Ceiling performance on our working memory assay prevented examination of its contribution to model-based learning. However, age-related improvements in fluid reasoning statistically mediated the developmental increase in the recruitment of a model-based strategy. These findings suggest that gradual development of fluid reasoning may be a critical component process underlying the emergence of model-based learning. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Spectrum sensing algorithm based on autocorrelation energy in cognitive radio networks

NASA Astrophysics Data System (ADS)

Ren, Shengwei; Zhang, Li; Zhang, Shibing

2016-10-01

Cognitive radio networks have wide applications in the smart home, personal communications and other wireless communication. Spectrum sensing is the main challenge in cognitive radios. This paper proposes a new spectrum sensing algorithm which is based on the autocorrelation energy of signal received. By taking the autocorrelation energy of the received signal as the statistics of spectrum sensing, the effect of the channel noise on the detection performance is reduced. Simulation results show that the algorithm is effective and performs well in low signal-to-noise ratio. Compared with the maximum generalized eigenvalue detection (MGED) algorithm, function of covariance matrix based detection (FMD) algorithm and autocorrelation-based detection (AD) algorithm, the proposed algorithm has 2 11 dB advantage.

Distinct and shared cognitive functions mediate event- and time-based prospective memory impairment in normal ageing

PubMed Central

Gonneaud, Julie; Kalpouzos, Grégoria; Bon, Laetitia; Viader, Fausto; Eustache, Francis; Desgranges, Béatrice

2011-01-01

Prospective memory (PM) is the ability to remember to perform an action at a specific point in the future. Regarded as multidimensional, PM involves several cognitive functions that are known to be impaired in normal aging. In the present study, we set out to investigate the cognitive correlates of PM impairment in normal aging. Manipulating cognitive load, we assessed event- and time-based PM, as well as several cognitive functions, including executive functions, working memory and retrospective episodic memory, in healthy subjects covering the entire adulthood. We found that normal aging was characterized by PM decline in all conditions and that event-based PM was more sensitive to the effects of aging than time-based PM. Whatever the conditions, PM was linked to inhibition and processing speed. However, while event-based PM was mainly mediated by binding and retrospective memory processes, time-based PM was mainly related to inhibition. The only distinction between high- and low-load PM cognitive correlates lays in an additional, but marginal, correlation between updating and the high-load PM condition. The association of distinct cognitive functions, as well as shared mechanisms with event- and time-based PM confirms that each type of PM relies on a different set of processes. PMID:21678154

Cognitive Components Underpinning the Development of Model-Based Learning

PubMed Central

Potter, Tracey C.S.; Bryce, Nessa V.; Hartley, Catherine A.

2016-01-01

Reinforcement learning theory distinguishes “model-free” learning, which fosters reflexive repetition of previously rewarded actions, from “model-based” learning, which recruits a mental model of the environment to flexibly select goal-directed actions. Whereas model-free learning is evident across development, recruitment of model-based learning appears to increase with age. However, the cognitive processes underlying the development of model-based learning remain poorly characterized. Here, we examined whether age-related differences in cognitive processes underlying the construction and flexible recruitment of mental models predict developmental increases in model-based choice. In a cohort of participants aged 9–25, we examined whether the abilities to infer sequential regularities in the environment (“statistical learning”), maintain information in an active state (“working memory”) and integrate distant concepts to solve problems (“fluid reasoning”) predicted age-related improvements in model-based choice. We found that age-related improvements in statistical learning performance did not mediate the relationship between age and model-based choice. Ceiling performance on our working memory assay prevented examination of its contribution to model-based learning. However, age-related improvements in fluid reasoning statistically mediated the developmental increase in the recruitment of a model-based strategy. These findings suggest that gradual development of fluid reasoning may be a critical component process underlying the emergence of model-based learning. PMID:27825732

The Effectiveness of Computer-Based Cognitive Training Programs

ERIC Educational Resources Information Center

Walcott, Christy M.; Phillips, Miranda E.

2013-01-01

The purpose of this article is to summarize empirical findings for school-age computer-based cognitive training (CCT) programs and to provide specific guidelines to practitioners who may be consulting with parents and schools about the utility of such programs. CCT programs vary in nature and in their targeted functions, but they share similar…

Screening for cognitive impairment in older individuals. Validation study of a computer-based test.

PubMed

Green, R C; Green, J; Harrison, J M; Kutner, M H

1994-08-01

This study examined the validity of a computer-based cognitive test that was recently designed to screen the elderly for cognitive impairment. Criterion-related validity was examined by comparing test scores of impaired patients and normal control subjects. Construct-related validity was computed through correlations between computer-based subtests and related conventional neuropsychological subtests. University center for memory disorders. Fifty-two patients with mild cognitive impairment by strict clinical criteria and 50 unimpaired, age- and education-matched control subjects. Control subjects were rigorously screened by neurological, neuropsychological, imaging, and electrophysiological criteria to identify and exclude individuals with occult abnormalities. Using a cut-off total score of 126, this computer-based instrument had a sensitivity of 0.83 and a specificity of 0.96. Using a prevalence estimate of 10%, predictive values, positive and negative, were 0.70 and 0.96, respectively. Computer-based subtests correlated significantly with conventional neuropsychological tests measuring similar cognitive domains. Thirteen (17.8%) of 73 volunteers with normal medical histories were excluded from the control group, with unsuspected abnormalities on standard neuropsychological tests, electroencephalograms, or magnetic resonance imaging scans. Computer-based testing is a valid screening methodology for the detection of mild cognitive impairment in the elderly, although this particular test has important limitations. Broader applications of computer-based testing will require extensive population-based validation. Future studies should recognize that normal control subjects without a history of disease who are typically used in validation studies may have a high incidence of unsuspected abnormalities on neurodiagnostic studies.

Prevalence of Dementia and Cognitive Complaints in the Context of High Cognitive Reserve: A Population-Based Study.

PubMed

Perquin, Magali; Diederich, Nico; Pastore, Jessica; Lair, Marie-Lise; Stranges, Saverio; Vaillant, Michel

2015-01-01

This study aimed to assess the prevalence of dementia and cognitive complaints in a cross-sectional sample of Luxembourg seniors, and to discuss the results in the societal context of high cognitive reserve resulting from multilingualism. A population sample of 1,377 people representative of Luxembourg residents aged over 64 years was initially identified via the national social insurance register. There were three different levels of contribution: full participation in the study, partial participation, and non-participation. We examined the profiles of these three different samples so that we could infer the prevalence estimates in the Luxembourgish senior population as a whole using the prevalence estimates obtained in this study. After careful attention to the potential bias and of the possibility of underestimation, we considered the obtained prevalence estimates of 3.8% for dementia (with corresponding 95% confidence limits (CL) of 2.8% and 4.8%) and 26.1% for cognitive complaints (CL = [17.8-34.3]) as trustworthy. Based on these findings, we postulate that high cognitive reserve may result in surprisingly low prevalence estimates of cognitive complaints and dementia in adults over the age of 64 years, which thereby corroborates the longer disability-free life expectancy observed in the Luxembourg population. To the best of our knowledge, this study is the first to report such Luxembourgish public health data.

Prevalence of Dementia and Cognitive Complaints in the Context of High Cognitive Reserve: A Population-Based Study

PubMed Central

Perquin, Magali; Diederich, Nico; Pastore, Jessica; Lair, Marie-Lise; Stranges, Saverio; Vaillant, Michel

2015-01-01

Objectives This study aimed to assess the prevalence of dementia and cognitive complaints in a cross-sectional sample of Luxembourg seniors, and to discuss the results in the societal context of high cognitive reserve resulting from multilingualism. Methods A population sample of 1,377 people representative of Luxembourg residents aged over 64 years was initially identified via the national social insurance register. There were three different levels of contribution: full participation in the study, partial participation, and non-participation. We examined the profiles of these three different samples so that we could infer the prevalence estimates in the Luxembourgish senior population as a whole using the prevalence estimates obtained in this study. Results After careful attention to the potential bias and of the possibility of underestimation, we considered the obtained prevalence estimates of 3.8% for dementia (with corresponding 95% confidence limits (CL) of 2.8% and 4.8%) and 26.1% for cognitive complaints (CL = [17.8–34.3]) as trustworthy. Conclusion Based on these findings, we postulate that high cognitive reserve may result in surprisingly low prevalence estimates of cognitive complaints and dementia in adults over the age of 64 years, which thereby corroborates the longer disability-free life expectancy observed in the Luxembourg population. To the best of our knowledge, this study is the first to report such Luxembourgish public health data. PMID:26390288

Combining computerized social cognitive training with neuroplasticity-based auditory training in schizophrenia.

PubMed

Sacks, Stephanie; Fisher, Melissa; Garrett, Coleman; Alexander, Phillip; Holland, Christine; Rose, Demian; Hooker, Christine; Vinogradov, Sophia

2013-01-01

Social cognitive deficits are an important treatment target in schizophrenia, but it is unclear to what degree they require specialized interventions and which specific components of behavioral interventions are effective. In this pilot study, we explored the effects of a novel computerized neuroplasticity-based auditory training delivered in conjunction with computerized social cognition training (SCT) in patients with schizophrenia. Nineteen clinically stable schizophrenia subjects performed 50 hours of computerized exercises that place implicit, increasing demands on auditory perception, plus 12 hours of computerized training in emotion identification, social perception, and theory of mind tasks. All subjects were assessed with MATRICS-recommended measures of neurocognition and social cognition, plus a measure of self-referential source memory before and after the computerized training. Subjects showed significant improvements on multiple measures of neurocognition. Additionally, subjects showed significant gains on measures of social cognition, including the MSCEIT Perceiving Emotions, MSCEIT Managing Emotions, and self-referential source memory, plus a significant decrease in positive symptoms. Computerized training of auditory processing/verbal learning in schizophrenia results in significant basic neurocognitive gains. Further, addition of computerized social cognition training results in significant gains in several social cognitive outcome measures. Computerized cognitive training that directly targets social cognitive processes can drive improvements in these crucial functions.

Distinguishing the affective and cognitive bases of implicit attitudes to improve prediction of food choices.

PubMed

Trendel, Olivier; Werle, Carolina O C

2016-09-01

Eating behaviors largely result from automatic processes. Yet, in existing research, automatic or implicit attitudes toward food often fail to predict eating behaviors. Applying findings in cognitive neuroscience research, we propose and find that a central reason why implicit attitudes toward food are not good predictors of eating behaviors is that implicit attitudes are driven by two distinct constructs that often have diverging evaluative consequences: the automatic affective reactions to food (e.g., tastiness; the affective basis of implicit attitudes) and the automatic cognitive reactions to food (e.g., healthiness; the cognitive basis of implicit attitudes). More importantly, we find that the affective and cognitive bases of implicit attitudes directly and uniquely influence actual food choices under different conditions. While the affective basis of implicit attitude is the main driver of food choices, it is the only driver when cognitive resources during choice are limited. The cognitive basis of implicit attitudes uniquely influences food choices when cognitive resources during choice are plentiful but only for participants low in impulsivity. Researchers interested in automatic processes in eating behaviors could thus benefit by distinguishing between the affective and cognitive bases of implicit attitudes. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effect of telephone-based cognitive-behavioural therapy on parenting stress: A randomised controlled trial.

PubMed

Ngai, Fei Wan; Wong, Paul Wai-Ching; Chung, Ka Fai; Leung, Kwok Yin

2016-07-01

Objective Stress related to parenting has detrimental effects on the well-being of children, parents and the family system as a whole. There are limited studies about the efficacy of cognitive-behavioural therapy delivered by telephone in reducing parenting stress. The present study investigates the effect of telephone-based cognitive-behavioural therapy on parenting stress at six weeks and six months postpartum. This is a multi-site randomised controlled trial. A total of 397 Chinese mothers at risk of postnatal depression were randomly assigned to receive either telephone-based cognitive-behavioural therapy or routine postpartum care. Parental stress was assessed by the Parenting Stress Index Short Form at six weeks and six months postpartum. The findings revealed that mothers who had received telephone-based cognitive-behavioural therapy showed significantly lower levels of parenting stress than women only receiving routine postpartum care at six weeks (mean difference=9.42, 95% confidence interval 5.85-12.99, p<0.001, Cohen's d=0.52) and six months postpartum (mean difference=3.58, 95% confidence interval 0.07-7.09, p=0.046, Cohen's d=0.20). Telephone-based cognitive-behavioural therapy is a promising treatment modality for supporting parenting and reducing stress during the transition period. Integration of telephone-based cognitive-behavioural therapy into routine postpartum care might facilitate positive adaptation in particular for mothers at risk of postnatal depression. Copyright © 2016. Published by Elsevier Inc.

Active Cooperation Between Primary Users and Cognitive Radio Users in Heterogeneous Ad-Hoc Networks

DTIC Science & Technology

2012-04-01

processing to wireless communications and networking, including space-time coding and modulation for MIMO wireless communications, MIMO - OFDM systems, and...multiinput-multioutput ( MIMO ) system that can significantly increase the link capacity and realize a new form of spatial diversity which has been termed

UMTS base station-like exposure, well-being, and cognitive performance.

PubMed

Regel, Sabine J; Negovetic, Sonja; Röösli, Martin; Berdiñas, Veronica; Schuderer, Jürgen; Huss, Anke; Lott, Urs; Kuster, Niels; Achermann, Peter

2006-08-01

Radio-frequency electromagnetic fields (RF EMF) of mobile communication systems are widespread in the living environment, yet their effects on humans are uncertain despite a growing body of literature. We investigated the influence of a Universal Mobile Telecommunications System (UMTS) base station-like signal on well-being and cognitive performance in subjects with and without self-reported sensitivity to RF EMF. We performed a controlled exposure experiment (45 min at an electric field strength of 0, 1, or 10 V/m, incident with a polarization of 45 degrees from the left back side of the subject, weekly intervals) in a randomized, double-blind crossover design. A total of 117 healthy subjects (33 self-reported sensitive, 84 nonsensitive subjects) participated in the study. We assessed well-being, perceived field strength, and cognitive performance with questionnaires and cognitive tasks and conducted statistical analyses using linear mixed models. Organ-specific and brain tissue-specific dosimetry including uncertainty and variation analysis was performed. In both groups, well-being and perceived field strength were not associated with actual exposure levels. We observed no consistent condition-induced changes in cognitive performance except for two marginal effects. At 10 V/m we observed a slight effect on speed in one of six tasks in the sensitive subjects and an effect on accuracy in another task in nonsensitive subjects. Both effects disappeared after multiple end point adjustment. In contrast to a recent Dutch study, we could not confirm a short-term effect of UMTS base station-like exposure on well-being. The reported effects on brain functioning were marginal and may have occurred by chance. Peak spatial absorption in brain tissue was considerably smaller than during use of a mobile phone. No conclusions can be drawn regarding short-term effects of cell phone exposure or the effects of long-term base station-like exposure on human health.

Reward-based training of recurrent neural networks for cognitive and value-based tasks

PubMed Central

Song, H Francis; Yang, Guangyu R; Wang, Xiao-Jing

2017-01-01

Trained neural network models, which exhibit features of neural activity recorded from behaving animals, may provide insights into the circuit mechanisms of cognitive functions through systematic analysis of network activity and connectivity. However, in contrast to the graded error signals commonly used to train networks through supervised learning, animals learn from reward feedback on definite actions through reinforcement learning. Reward maximization is particularly relevant when optimal behavior depends on an animal’s internal judgment of confidence or subjective preferences. Here, we implement reward-based training of recurrent neural networks in which a value network guides learning by using the activity of the decision network to predict future reward. We show that such models capture behavioral and electrophysiological findings from well-known experimental paradigms. Our work provides a unified framework for investigating diverse cognitive and value-based computations, and predicts a role for value representation that is essential for learning, but not executing, a task. DOI: http://dx.doi.org/10.7554/eLife.21492.001 PMID:28084991

Evidenced-based cognitive rehabilitation for persons with multiple sclerosis: a review of the literature.

PubMed

O'Brien, Amanda R; Chiaravalloti, Nancy; Goverover, Yael; Deluca, John

2008-04-01

To conduct evidence-based review of cognitive rehabilitation intervention research conducted in persons with multiple sclerosis (MS), to classify level of evidence, and to generate recommendations for interventions in this area. An open (no year limits set) search of Medline, PsychInfo, and CINAHL (eliminating repetitions) using combinations of the following terms: attention, awareness, cognition, cognitive, communication, executive, executive function, language, learning, memory, perception, problem solving, reasoning, rehabilitation, remediation, training, and working memory. Reference sections of articles found through the sites were also searched. Studies were chosen based on criteria from previous evidence-based reviews such that articles are excluded from the review if (1) the study was not an intervention, (2) it was a theoretic article, (3) it was a review article, (4) detail was lacking to fully evaluate the intervention, (5) it was not MS-specific, (6) it included a pediatric sample, (7) it was a case report without empirical data to evaluate outcomes, (8) it was not peer-reviewed (also excludes book chapters), (9) it was a pharmacologic intervention, or (10) it was not available for review in English. Articles were categorized into interventions for attention, learning and memory, executive functioning, or nonspecified/combined cognitive domains. There were 4 reviewers in the current study. All articles were reviewed independently by at least 2 persons and abstracted according to predetermined criteria. There was a final total of 16 articles, which underwent a full review and classification of a level of evidence based on previously published peer-reviewed methodology used for evidence-based reviews. The current review yielded 16 studies of cognitive rehabilitation for persons with MS, including 4 class I studies, 5 class II studies, 2 class III studies, and 5 class IV studies. Two intervention methodologies in the area of verbal learning and memory

Applying Cognitive Psychology Based Instructional Design Principles in Mathematics Teaching and Learning: Introduction

ERIC Educational Resources Information Center

Verschaffel, Lieven; Van Dooren, W.; Star, J.

2017-01-01

This special issue comprises contributions that address the breadth of current lines of recent research from cognitive psychology that appear promising for positively impacting students' learning of mathematics. More specifically, we included contributions (a) that refer to cognitive psychology based principles and techniques, such as explanatory…

Effect of elastic band-based high-speed power training on cognitive function, physical performance and muscle strength in older women with mild cognitive impairment.

PubMed

Yoon, Dong Hyun; Kang, Dongheon; Kim, Hee-Jae; Kim, Jin-Soo; Song, Han Sol; Song, Wook

2017-05-01

The effectiveness of resistance training in improving cognitive function in older adults is well demonstrated. In particular, unconventional high-speed resistance training can improve muscle power development. In the present study, the effectiveness of 12 weeks of elastic band-based high-speed power training (HSPT) was examined. Participants were randomly assigned into a HSPT group (n = 14, age 75.0 ± 0.9 years), a low-speed strength training (LSST) group (n = 9, age 76.0 ± 1.3 years) and a control group (CON; n = 7, age 78.0 ± 1.0 years). A 1-h exercise program was provided twice a week for 12 weeks for the HSPT and LSST groups, and balance and tone exercises were carried out by the CON group. Significant increases in levels of cognitive function, physical function, and muscle strength were observed in both the HSPT and LSST groups. In cognitive function, significant improvements in the Mini-Mental State Examination and Montreal Cognitive Assessment were seen in both the HSPT and LSST groups compared with the CON group. In physical functions, Short Physical Performance Battery scores were increased significantly in the HSPT and LSST groups compared with the CON group. In the 12 weeks of elastic band-based training, the HSPT group showed greater improvements in older women with mild cognitive impairment than the LSST group, although both regimens were effective in improving cognitive function, physical function and muscle strength. We conclude that elastic band-based HSPT, as compared with LSST, is more efficient in helping older women with mild cognitive impairment to improve cognitive function, physical performance and muscle strength. Geriatr Gerontol Int 2017; 17: 765-772. © 2016 Japan Geriatrics Society.

A social cognitive-based model for condom use among college students.

PubMed

Dilorio, C; Dudley, W N; Soet, J; Watkins, J; Maibach, E

2000-01-01

Social cognitive theory has been used extensively to explain health behaviors. Although the influence of one construct in this model-self-efficacy-has been well established, the role of other social cognitive constructs has not received as much attention in human immunodeficiency virus (HIV) prevention research. More complete understanding of how social cognitive constructs operate together to explain condom use behaviors would be useful in developing HIV and sexually transmitted disease (STD) prevention programs for college students. The primary aim of this study was to test a social cognitive-based model of condom use behaviors among college students. Data were collected from a sample of college students attending six different colleges and universities. Participants were 18 to 25 years of age, single, and sexually active. For the sample of 1,380 participants, the mean age was 20.6 years (SD = 1.76). Most participants reported having had vaginal intercourse (95.8%) and oral sex (86.5%); 16% reported anal sex. Self-efficacy was related directly to condom use behaviors and indirectly through its effect on outcome expectancies. As predicted, self-efficacy was related to anxiety, but anxiety was not related to condom use. Substance use during sexual encounters was related to outcome expectancies but not to condom use as predicted. Overall, the findings lend support to a condom use model based on social cognitive theory and provide implications for HIV interventions. Interventions that focus on self-efficacy are more likely to reduce anxiety related to condom use, increase positive perceptions about condoms, and increase the likelihood of adopting condom use behaviors.

Cognitively Stimulating Leisure Activity and Subsequent Cognitive Function: A SHARE-based Analysis.

PubMed

Litwin, Howard; Schwartz, Ella; Damri, Noam

2017-10-01

The aim of the inquiry was to examine whether cognitively stimulating leisure activity (CSLA) can delay or reduce cognitive decline in late life and whether its effect is moderated by education, age, or activity pattern. Employing secondary analysis of data on respondents aged 65 and older from the 4th and 5th waves of the Survey of Health, Ageing and Retirement in Europe (N = 16,572), the inquiry regressed cognitive function (memory, numeracy, and fluency) at Time 2 on frequency of engagement in CSLA at baseline, controlling for cognitive function scores at baseline and a range of confounders. The study also considered education by CSLA and age by CSLA interactions, as well as the effect of CSLA patterns. CSLA frequency was found to be positively related to subsequent cognitive functioning on all measures, 2 years later. The effect of CSLA on memory and fluency was stronger among those with lower education, whereas the age by CSLA interaction was not significant. Respondents who started CSLA after baseline showed better cognitive functioning at Time 2 than those who did not engage in CSLA at all and those who had engaged in such activity at baseline but stopped. The study documents that CSLAs constitute a potential source for the delay or reduction of cognitive decline, regardless of one's age. As such, practitioners should recognize the value of this medium and encourage its greater use in appropriate settings. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Cognitive Load Measurement in a Virtual Reality-based Driving System for Autism Intervention

PubMed Central

Zhang, Lian; Wade, Joshua; Bian, Dayi; Fan, Jing; Swanson, Amy; Weitlauf, Amy; Warren, Zachary; Sarkar, Nilanjan

2016-01-01

Autism Spectrum Disorder (ASD) is a highly prevalent neurodevelopmental disorder with enormous individual and social cost. In this paper, a novel virtual reality (VR)-based driving system was introduced to teach driving skills to adolescents with ASD. This driving system is capable of gathering eye gaze, electroencephalography, and peripheral physiology data in addition to driving performance data. The objective of this paper is to fuse multimodal information to measure cognitive load during driving such that driving tasks can be individualized for optimal skill learning. Individualization of ASD intervention is an important criterion due to the spectrum nature of the disorder. Twenty adolescents with ASD participated in our study and the data collected were used for systematic feature extraction and classification of cognitive loads based on five well-known machine learning methods. Subsequently, three information fusion schemes—feature level fusion, decision level fusion and hybrid level fusion—were explored. Results indicate that multimodal information fusion can be used to measure cognitive load with high accuracy. Such a mechanism is essential since it will allow individualization of driving skill training based on cognitive load, which will facilitate acceptance of this driving system for clinical use and eventual commercialization. PMID:28966730

Cognitive Load Measurement in a Virtual Reality-based Driving System for Autism Intervention.

PubMed

Zhang, Lian; Wade, Joshua; Bian, Dayi; Fan, Jing; Swanson, Amy; Weitlauf, Amy; Warren, Zachary; Sarkar, Nilanjan

2017-01-01

Autism Spectrum Disorder (ASD) is a highly prevalent neurodevelopmental disorder with enormous individual and social cost. In this paper, a novel virtual reality (VR)-based driving system was introduced to teach driving skills to adolescents with ASD. This driving system is capable of gathering eye gaze, electroencephalography, and peripheral physiology data in addition to driving performance data. The objective of this paper is to fuse multimodal information to measure cognitive load during driving such that driving tasks can be individualized for optimal skill learning. Individualization of ASD intervention is an important criterion due to the spectrum nature of the disorder. Twenty adolescents with ASD participated in our study and the data collected were used for systematic feature extraction and classification of cognitive loads based on five well-known machine learning methods. Subsequently, three information fusion schemes-feature level fusion, decision level fusion and hybrid level fusion-were explored. Results indicate that multimodal information fusion can be used to measure cognitive load with high accuracy. Such a mechanism is essential since it will allow individualization of driving skill training based on cognitive load, which will facilitate acceptance of this driving system for clinical use and eventual commercialization.

Cognitive lifestyle in older persons: the population-based Sydney Memory and Ageing Study.

PubMed

Valenzuela, Michael J; Leon, Irene; Suo, Chao; Piamba, Diana Martinez; Kochan, Nicole; Brodaty, Henry; Sachdev, Perminder

2013-01-01

Cognitive lifestyle may be an important modifiable risk factor for dementia but has not yet been comprehensively studied in healthy elderly. To examine gender- and lifespan-related differences in cognitive lifestyle in a population-based cohort. 872 individuals from the second wave of the Sydney Memory and Ageing Study (MAS) cohort were invited to complete the Lifetime of Experiences Questionnaire (LEQ), a validated measure of cognitive lifestyle. Of 555 questionnaires returned (64%), 253 were excluded due to prior diagnosis of mild cognitive impairment, leaving n = 302 cognitively-intact elders (mean age 80.1 years, ±SD 4.7, 40.1% men). Total LEQ was significantly higher in men (97.9 ± 20.0) than women (90.0 ± 24.5), resulting mainly from midlife LEQ differences. Men were more likely to have worked in managerial or professional jobs (73.8% versus 39.5% women), and twice as likely to have supervised large groups of workers. In late life, women were significantly more likely to be living alone (68.1% versus 25.4% men), but otherwise significantly more engaged in specific cognitive activities, including reading novels (72.3% versus 52.0% men) and incorporating volunteer work (31.9% versus 19.7% men) and socializing (59.0% versus 37.0% men) into their typical day. Over the adult lifespan, it was more common for men and women to transition between LEQ tertiles than remain the same. Cognitive lifestyle changes over the adult lifespan and exhibits a range of gender-based differences. While older women are more likely to be living alone they generally lead a more active current cognitive lifestyle.

All-optical VPN utilizing DSP-based digital orthogonal filters access for PONs

NASA Astrophysics Data System (ADS)

Zhang, Xiaoling; Zhang, Chongfu; Chen, Chen; Jin, Wei; Qiu, Kun

2018-04-01

Utilizing digital filtering-enabled signal multiplexing and de-multiplexing, a cost-effective all-optical virtual private network (VPN) system is proposed, for the first time to our best knowledge, in digital filter multiple access passive optical networks (DFMA-PONs). Based on the DFMA technology, the proposed system can be easily designed to meet the requirements of next generation network's flexibility, elasticity, adaptability and compatibility. Through dynamic digital filter allocation and recycling, the proposed all-optical VPN system can provide dynamic establishments and cancellations of multiple VPN communications with arbitrary traffic volumes. More importantly, due to the employment of DFMA technology, the system is not limited to a fixed signal format and different signal formats such as pulse amplitude modulation (PAM), quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM) can be used. Moreover, one transceiver is sufficient to simultaneously transmit upstream (US)/VPN data to optical line terminal (OLT) or other VPN optical network units (ONUs), thus leading to great reduction in network constructions and operation expenditures. The proposed all-optical VPN system is demonstrated with the transceiver incorporating the formats of QAM and OFDM, which can be made transparent to downstream (DS), US and VPN communications. The bit error rates (BERs) of DS, US and VPN for OFDM signals are below the forward-error-correction (FEC) limit of 3 . 8 × 10-3 when the received optical powers are about -16.8 dBm, -14.5 dBm and -15.7 dBm, respectively.

A Computer Based Cognitive Simulation of Cataract Surgery

DTIC Science & Technology

2011-12-01

for zonular absence, assess for notable lenticular astigmatism ** How and when do you decide to use a capsular tension ring? (Expert) Zonular...INTRODUCTION The Virtual Mentor Cataract Surgery Trainer is a computer based, cognitive simulation of phacoemulsification cataract surgery. It is...the Cataract Trainer. BODY Phacoemulsification cataract surgery (phaco) is a difficult procedure to learn, with little margin for error. As in other

Data-Dependent Fingerprints for Wireless Device Authentication

DTIC Science & Technology

2014-05-20

enhanced when using a modulation based on orthogonal frequency division multiplexing ( OFDM ) that has a large range of signal levels. However, in...at 70 MHz. The radios use OFDM with 64-point FFT block sizes for transmission so that the bandwidth is divided into Nd = 64 data and Nc = 5 cyclic...τℓTs) (1) where Ts is the OFDM symbol period (and therefore discrete-time sampling period) and L is the number of multipaths in the channel with

Implementing Filters to Identify and Prioritize Industrial Base Risk: Rules of Thumb to Reduce Cognitive Overload

DTIC Science & Technology

2015-04-30

Thumb to Reduce Cognitive Overload Sally Sleeper, ODASD[M&IBP] John F. Starns, Northrop Grumman Published April 30, 2015 Disclaimer: The views...Prioritize Industrial Base Risk: Rules of Thumb to Reduce Cognitive Overload 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6... Cognitive Overload Sally Sleeper—joined the Office of the Deputy Assistant Secretary of Defense for Manufacturing and Industrial Base Policy as Senior

Acquisition and Development of a Cognitive Radio Based Wireless Monitoring and Surveillance Testbed for Future Battlefield Communications Research

DTIC Science & Technology

2015-03-01

for Public Release; Distribution Unlimited Final Report: Acquisition and Development of A Cognitive Radio based Wireless Monitoring and Surveillance...journals: Final Report: Acquisition and Development of A Cognitive Radio based Wireless Monitoring and Surveillance Testbed for Future Battlefield...Opeyemi Oduola, Nan Zou, Xiangfang Li, Husheng Li, Lijun Qian. Distributed Spectrum Monitoring and Surveillance using a Cognitive Radio based Testbed

Independent component analysis based digital signal processing in coherent optical fiber communication systems

NASA Astrophysics Data System (ADS)

Li, Xiang; Luo, Ming; Qiu, Ying; Alphones, Arokiaswami; Zhong, Wen-De; Yu, Changyuan; Yang, Qi

2018-02-01

In this paper, channel equalization techniques for coherent optical fiber transmission systems based on independent component analysis (ICA) are reviewed. The principle of ICA for blind source separation is introduced. The ICA based channel equalization after both single-mode fiber and few-mode fiber transmission for single-carrier and orthogonal frequency division multiplexing (OFDM) modulation formats are investigated, respectively. The performance comparisons with conventional channel equalization techniques are discussed.

Analysis of Mathematics Critical Thinking Students in Junior High School Based on Cognitive Style

NASA Astrophysics Data System (ADS)

Agoestanto, A.; Sukestiyarno, YL; Rochmad

2017-04-01

The purpose of this research was to determine the critical thinking ability of mathematics from junior high school students based on FI and FD cognitive style. Data of this research were taken from students grade VIII at SMPN 2 Ambarawa. The research method used a descriptive qualitative approach. Data was taken with a testing method; the critical thinking was measured with WGCTA which is modified with mathematical problems, the cognitive style was measured with GEFT. The student’s test result was analysed, then four students were selected, the two of them are FI cognitive style, and the others are FD cognitive style, for qualitative analysis. The result showed that the ability of mathematics critical thinking students with FI cognitive style is better than FD cognitive style on the ability of inference, assumption, deduction, and interpretation. While on the aspect of argument evaluation, mathematics critical thinking ability of students with FD cognitive style is a little better than students with FI cognitive style.

Treatment-resistant depressed patients show a good response to Mindfulness-based Cognitive Therapy

PubMed Central

Kenny, M.A.; Williams, J.M.G.

2007-01-01

Mindfulness-based Cognitive Therapy (MBCT) is a class-based programme designed for use in the prevention of relapse of major depression. Its aim is to teach participants to disengage from those cognitive processes that may render them vulnerable to future episodes. These same cognitive processes are also known to maintain depression once established, hence a clinical audit was conducted to explore the use of MBCT in patients who were currently actively depressed, and who had not responded fully to standard treatments. The study showed that it was acceptable to these patients and resulted in an improvement in depression scores (pre-post Effect Size=1.04), with a significant proportion of patients returning to normal or near-normal levels of mood. PMID:16797486

Cognitive Effects of Mindfulness Training: Results of a Pilot Study Based on a Theory Driven Approach

PubMed Central

Wimmer, Lena; Bellingrath, Silja; von Stockhausen, Lisa

2016-01-01

The present paper reports a pilot study which tested cognitive effects of mindfulness practice in a theory-driven approach. Thirty-four fifth graders received either a mindfulness training which was based on the mindfulness-based stress reduction approach (experimental group), a concentration training (active control group), or no treatment (passive control group). Based on the operational definition of mindfulness by Bishop et al. (2004), effects on sustained attention, cognitive flexibility, cognitive inhibition, and data-driven as opposed to schema-based information processing were predicted. These abilities were assessed in a pre-post design by means of a vigilance test, a reversible figures test, the Wisconsin Card Sorting Test, a Stroop test, a visual search task, and a recognition task of prototypical faces. Results suggest that the mindfulness training specifically improved cognitive inhibition and data-driven information processing. PMID:27462287

Cognitive Effects of Mindfulness Training: Results of a Pilot Study Based on a Theory Driven Approach.

PubMed

Wimmer, Lena; Bellingrath, Silja; von Stockhausen, Lisa

2016-01-01

The present paper reports a pilot study which tested cognitive effects of mindfulness practice in a theory-driven approach. Thirty-four fifth graders received either a mindfulness training which was based on the mindfulness-based stress reduction approach (experimental group), a concentration training (active control group), or no treatment (passive control group). Based on the operational definition of mindfulness by Bishop et al. (2004), effects on sustained attention, cognitive flexibility, cognitive inhibition, and data-driven as opposed to schema-based information processing were predicted. These abilities were assessed in a pre-post design by means of a vigilance test, a reversible figures test, the Wisconsin Card Sorting Test, a Stroop test, a visual search task, and a recognition task of prototypical faces. Results suggest that the mindfulness training specifically improved cognitive inhibition and data-driven information processing.

A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-VLLC integration

NASA Astrophysics Data System (ADS)

Tsai, Wen-Shing; Lu, Hai-Han; Li, Chung-Yi; Chen, Bo-Rui; Lin, Hung-Hsien; Lin, Dai-Hua

2016-04-01

A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-visible laser light communication (VLLC) integration is proposed and experimentally demonstrated. To be the first one of its kind in employing light injection and optoelectronic feedback techniques in a fiber-VLLC integration lightwave transmission system, the light is successfully directly modulated with Community Access Television (CATV), 16-QAM, and 16-QAM-OFDM signals. Over a 40 km SMF and a 10 m free-space VLLC transport, good performances of carrier-to-noise ratio (CNR)/composite second-order (CSO)/composite triple-beat (CTB)/bit error rate (BER) are achieved for CATV/16-QAM/16-QAM-OFDM signals transmission. Such a hybrid lightwave transmission system would be very useful since it can provide broadband integrated services including CATV, Internet, and telecommunication services over both distribute fiber and in-building networks.

A randomized trial to measure the impact of a community-based cognitive training intervention on balance and gait in cognitively intact Black older adults.

PubMed

Smith-Ray, Renae L; Makowski-Woidan, Beth; Hughes, Susan L

2014-10-01

Fall prevention is important for maintaining mobility and independence into old age. Approaches for reducing falls include exercise, tai chi, and home modifications; however, causes of falling are multifactorial and include not just physical but cognitive factors. Cognitive decline occurs with age, but older adults with the greatest declines in executive function experience more falls. The purpose of this study was twofold: to demonstrate the feasibility of a community-based cognitive training program for cognitively intact Black older adults and to analyze its impact on gait and balance in this population. This pilot study used a pretest/posttest randomized trial design with assignment to an intervention or control group. Participants assigned to the intervention completed a computer-based cognitive training class that met 2 days a week for 60 min over 10 weeks. Classes were held at senior/community centers. Primary outcomes included balance as measured by the Berg Balance Scale (BBS), 10-meter gait speed, and 10-meter gait speed under visuospatial dual-task condition. All measures were assessed at baseline and immediately post-intervention. Participants were community-dwelling Black adults with a mean age of 72.5 and history of falls (N = 45). Compared to controls, intervention participants experienced statistically significant improvements in BBS and gait speed. Mean performance on distracted gait speed also improved more for intervention participants compared to controls. Findings from this pilot randomized trial demonstrate the feasibility of a community-based cognitive training intervention. They provide initial evidence that cognitive training may be an efficacious approach toward improving balance and gait in older adults known to have a history of falls. © 2014 Society for Public Health Education.

Understanding the Effects of Databases as Cognitive Tools in a Problem-Based Multimedia Learning Environment

ERIC Educational Resources Information Center

Li, Rui; Liu, Min

2007-01-01

The purpose of this study is to examine the potential of using computer databases as cognitive tools to share learners' cognitive load and facilitate learning in a multimedia problem-based learning (PBL) environment designed for sixth graders. Two research questions were: (a) can the computer database tool share sixth-graders' cognitive load? and…

Effectiveness of music-based interventions on motricity or cognitive functioning in neurological populations: a systematic review.

PubMed

Moumdjian, Lousin; Sarkamo, Teppo; Leone, Carmela; Leman, Marc; Feys, Peter

2017-06-01

Motor and cognitive symptoms are frequent in persons with neurological disorders and often require extensive long-term rehabilitation. Recently, a variety of music-based interventions have been introduced into neurological rehabilitation as training tools. This review aims to 1) describe and define music-based intervention modalities and content which are applied in experimental studies; and 2) describe the effects of these interventions on motor and/or cognitive symptoms in the neurological population. The databases PubMed and Web of Science were searched. Cited references of included articles where screened for potential inclusion. A systematic literature search up to 20th of June 2016 was conducted to include controlled trials and cohort studies that have used music-based interventions for ≥3 weeks in the neurological population (in- and outpatients) targeting motor and/or cognitive symptoms. No limitations to publication date was set. EVIDENCE SYNTHESISː Nineteen articles comprising thirteen randomized controlled trials (total participants Nexp=241, Nctrl=269), four controlled trials (Nexp=59, Nctrl=53) and two cohort studies (N.=27) were included. Fourteen studies were conducted in stroke, three in Parkinson's disease, and two in multiple sclerosis population. Modalities of music-based interventions were clustered into four groups: instrument-based, listening-based, rhythm-based, and multicomponent-based music interventions. Overall, studies consistently showed that music-based interventions had similar or larger effects than conventional rehabilitation on upper limb function (N.=16; fine motricity, hand and arm capacity, finger and hand tapping velocity/variability), mobility (N.=7; gait parameters), and cognition (N.=4; verbal memory and focused attention). CONCLUSIONSː Variety of modalities using music-based interventions has been identified and grouped into four clusters. Effects of interventions demonstrate an improvement in the domains assessed

Codebook-based electrooculography data analysis towards cognitive activity recognition.

PubMed

Lagodzinski, P; Shirahama, K; Grzegorzek, M

2018-04-01

With the advancement in mobile/wearable technology, people started to use a variety of sensing devices to track their daily activities as well as health and fitness conditions in order to improve the quality of life. This work addresses an idea of eye movement analysis, which due to the strong correlation with cognitive tasks can be successfully utilized in activity recognition. Eye movements are recorded using an electrooculographic (EOG) system built into the frames of glasses, which can be worn more unobtrusively and comfortably than other devices. Since the obtained information is low-level sensor data expressed as a sequence representing values in constant intervals (100 Hz), the cognitive activity recognition problem is formulated as sequence classification. However, it is unclear what kind of features are useful for accurate cognitive activity recognition. Thus, a machine learning algorithm like a codebook approach is applied, which instead of focusing on feature engineering is using a distribution of characteristic subsequences (codewords) to describe sequences of recorded EOG data, where the codewords are obtained by clustering a large number of subsequences. Further, statistical analysis of the codeword distribution results in discovering features which are characteristic to a certain activity class. Experimental results demonstrate good accuracy of the codebook-based cognitive activity recognition reflecting the effective usage of the codewords. Copyright © 2017 Elsevier Ltd. All rights reserved.

Building simplification algorithms based on user cognition in mobile environment

NASA Astrophysics Data System (ADS)

Shen, Jie; Shi, Junfei; Wang, Meizhen; Wu, Chenyan

2008-10-01

With the development of LBS, mobile map should adaptively satisfy the cognitive requirement of user. User cognition in mobile environment is much more objective oriented and also seem to be a heavier burden than the user in static environment. The holistic idea and methods of map generalization can not fully suitable for the mobile map. This paper took the building simplification in habitation generalization as example, analyzed the characteristic of user cognition in mobile environment and the basic rules of building simplification, collected and studied the state-of-the-art of algorithms of building simplification in the static and mobile environment, put forward the idea of hierarchical building simplification based on user cognition. This paper took Hunan road business district of Nanjing as test area and took the building data with shapfile format of ESRI as test data and realized the simplification algorithm. The method took user as center, calculated the distance between user and the building which will be simplified and took the distance as the basis for choosing different simplification algorithm for different spaces. This contribution aimed to hierarchically present the building in different level of detail by real-time simplification.

Student Characteristics, Sense of Community, and Cognitive Achievement in Web-Based and Lab-Based Learning Environments

ERIC Educational Resources Information Center

Overbaugh, Richard C.; Lin, ShinYi

2006-01-01

This study investigated differential effects of learning styles and learning orientation on sense of community and cognitive achievement in Web-based and lab-based university course formats. Students in the Web-based sections achieved higher scores at the "remember" and "understand" levels, but not at the "apply" or "analyze" levels. In terms of…

Multi-Objective Reinforcement Learning for Cognitive Radio-Based Satellite Communications

NASA Technical Reports Server (NTRS)

Ferreira, Paulo Victor R.; Paffenroth, Randy; Wyglinski, Alexander M.; Hackett, Timothy M.; Bilen, Sven G.; Reinhart, Richard C.; Mortensen, Dale J.

2016-01-01

Previous research on cognitive radios has addressed the performance of various machine-learning and optimization techniques for decision making of terrestrial link properties. In this paper, we present our recent investigations with respect to reinforcement learning that potentially can be employed by future cognitive radios installed onboard satellite communications systems specifically tasked with radio resource management. This work analyzes the performance of learning, reasoning, and decision making while considering multiple objectives for time-varying communications channels, as well as different cross-layer requirements. Based on the urgent demand for increased bandwidth, which is being addressed by the next generation of high-throughput satellites, the performance of cognitive radio is assessed considering links between a geostationary satellite and a fixed ground station operating at Ka-band (26 GHz). Simulation results show multiple objective performance improvements of more than 3.5 times for clear sky conditions and 6.8 times for rain conditions.

Multi-Objective Reinforcement Learning for Cognitive Radio Based Satellite Communications

NASA Technical Reports Server (NTRS)

Ferreira, Paulo; Paffenroth, Randy; Wyglinski, Alexander; Hackett, Timothy; Bilen, Sven; Reinhart, Richard; Mortensen, Dale John

2016-01-01

Previous research on cognitive radios has addressed the performance of various machine learning and optimization techniques for decision making of terrestrial link properties. In this paper, we present our recent investigations with respect to reinforcement learning that potentially can be employed by future cognitive radios installed onboard satellite communications systems specifically tasked with radio resource management. This work analyzes the performance of learning, reasoning, and decision making while considering multiple objectives for time-varying communications channels, as well as different crosslayer requirements. Based on the urgent demand for increased bandwidth, which is being addressed by the next generation of high-throughput satellites, the performance of cognitive radio is assessed considering links between a geostationary satellite and a fixed ground station operating at Ka-band (26 GHz). Simulation results show multiple objective performance improvements of more than 3:5 times for clear sky conditions and 6:8 times for rain conditions.

Interdisciplinary Project-Based Learning: Technology for Improving Student Cognition

ERIC Educational Resources Information Center

Stozhko, Natalia; Bortnik, Boris; Mironova, Ludmila; Tchernysheva, Albina; Podshivalova, Ekaterina

2015-01-01

The article studies a way of enhancing student cognition by using interdisciplinary project-based learning (IPBL) in a higher education institution. IPBL is a creative pedagogic approach allowing students of one area of specialisation to develop projects for students with different academic profiles. The application of this approach in the Ural…

Image secure transmission for optical orthogonal frequency-division multiplexing visible light communication systems using chaotic discrete cosine transform

NASA Astrophysics Data System (ADS)

Wang, Zhongpeng; Zhang, Shaozhong; Chen, Fangni; Wu, Ming-Wei; Qiu, Weiwei

2017-11-01

A physical encryption scheme for orthogonal frequency-division multiplexing (OFDM) visible light communication (VLC) systems using chaotic discrete cosine transform (DCT) is proposed. In the scheme, the row of the DCT matrix is permutated by a scrambling sequence generated by a three-dimensional (3-D) Arnold chaos map. Furthermore, two scrambling sequences, which are also generated from a 3-D Arnold map, are employed to encrypt the real and imaginary parts of the transmitted OFDM signal before the chaotic DCT operation. The proposed scheme enhances the physical layer security and improves the bit error rate (BER) performance for OFDM-based VLC. The simulation results prove the efficiency of the proposed encryption method. The experimental results show that the proposed security scheme not only protects image data from eavesdroppers but also keeps the good BER and peak-to-average power ratio performances for image-based OFDM-VLC systems.

Cognitive Perspectives on SLA: The Associative-Cognitive CREED

ERIC Educational Resources Information Center

Ellis, Nick C.

2006-01-01

This paper outlines current cognitive perspectives on second language acquisition (SLA). The Associative-Cognitive CREED holds that SLA is governed by the same principles of associative and cognitive learning that underpin the rest of human knowledge. The major principles of the framework are that SLA is Construction-based, Rational,…

Feasibility of the evidence-based cognitive telerehabilitation program Remind for patients with primary brain tumors.

PubMed

van der Linden, Sophie D; Sitskoorn, Margriet M; Rutten, Geert-Jan M; Gehring, Karin

2018-05-01

Many patients with primary brain tumors experience cognitive deficits. Cognitive rehabilitation programs focus on alleviating these deficits, but availability of such programs is limited. Our large randomized controlled trial (RCT) demonstrated positive effects of the cognitive rehabilitation program developed by our group. We converted the program into the iPad-based cognitive rehabilitation program ReMind, to increase its accessibility. The app incorporates psychoeducation, strategy training and retraining. This pilot study in patients with primary brain tumors evaluates the feasibility of the use of the ReMind-app in a clinical (research) setting in terms of accrual, attrition, adherence and patient satisfaction. The intervention commenced 3 months after resective surgery and patients were advised to spend 3 h per week on the program for 10 weeks. Of 28 eligible patients, 15 patients with presumed low-grade glioma or meningioma provided informed consent. Most important reason for decline was that patients (7) experienced no cognitive complaints. Participants completed on average 71% of the strategy training and 76% of the retraining. Some patients evaluated the retraining as too easy. Overall, 85% of the patients evaluated the intervention as "good" or "excellent". All patients indicated that they would recommend the program to other patients with brain tumors. The ReMind-app is the first evidence-based cognitive telerehabilitation program for adult patients with brain tumors and this pilot study suggests that postoperative cognitive rehabilitation via this app is feasible. Based on patients' feedback, we have expanded the retraining with more difficult exercises. We will evaluate the efficacy of ReMind in an RCT.

Cognitive load and task condition in event- and time-based prospective memory: an experimental investigation.

PubMed

Khan, Azizuddin; Sharma, Narendra K; Dixit, Shikha

2008-09-01

Prospective memory is memory for the realization of delayed intention. Researchers distinguish 2 kinds of prospective memory: event- and time-based (G. O. Einstein & M. A. McDaniel, 1990). Taking that distinction into account, the present authors explored participants' comparative performance under event- and time-based tasks. In an experimental study of 80 participants, the authors investigated the roles of cognitive load and task condition in prospective memory. Cognitive load (low vs. high) and task condition (event- vs. time-based task) were the independent variables. Accuracy in prospective memory was the dependent variable. Results showed significant differential effects under event- and time-based tasks. However, the effect of cognitive load was more detrimental in time-based prospective memory. Results also revealed that time monitoring is critical in successful performance of time estimation and so in time-based prospective memory. Similarly, participants' better performance on the event-based prospective memory task showed that they acted on the basis of environment cues. Event-based prospective memory was environmentally cued; time-based prospective memory required self-initiation.

UMTS Base Station-like Exposure, Well-Being, and Cognitive Performance

PubMed Central

Regel, Sabine J.; Negovetic, Sonja; Röösli, Martin; Berdiñas, Veronica; Schuderer, Jürgen; Huss, Anke; Lott, Urs; Kuster, Niels; Achermann, Peter

2006-01-01

Background Radio-frequency electromagnetic fields (RF EMF) of mobile communication systems are widespread in the living environment, yet their effects on humans are uncertain despite a growing body of literature. Objectives We investigated the influence of a Universal Mobile Telecommunications System (UMTS) base station-like signal on well-being and cognitive performance in subjects with and without self-reported sensitivity to RF EMF. Methods We performed a controlled exposure experiment (45 min at an electric field strength of 0, 1, or 10 V/m, incident with a polarization of 45° from the left back side of the subject, weekly intervals) in a randomized, double-blind crossover design. A total of 117 healthy subjects (33 self-reported sensitive, 84 nonsensitive subjects) participated in the study. We assessed well-being, perceived field strength, and cognitive performance with questionnaires and cognitive tasks and conducted statistical analyses using linear mixed models. Organ-specific and brain tissue–specific dosimetry including uncertainty and variation analysis was performed. Results In both groups, well-being and perceived field strength were not associated with actual exposure levels. We observed no consistent condition-induced changes in cognitive performance except for two marginal effects. At 10 V/m we observed a slight effect on speed in one of six tasks in the sensitive subjects and an effect on accuracy in another task in nonsensitive subjects. Both effects disappeared after multiple end point adjustment. Conclusions In contrast to a recent Dutch study, we could not confirm a short-term effect of UMTS base station-like exposure on well-being. The reported effects on brain functioning were marginal and may have occurred by chance. Peak spatial absorption in brain tissue was considerably smaller than during use of a mobile phone. No conclusions can be drawn regarding short-term effects of cell phone exposure or the effects of long-term base station

Test Accuracy of Informant-Based Cognitive Screening Tests for Diagnosis of Dementia and Multidomain Cognitive Impairment in Stroke.

PubMed

McGovern, Aine; Pendlebury, Sarah T; Mishra, Nishant K; Fan, Yuhua; Quinn, Terence J

2016-02-01

Poststroke cognitive assessment can be performed using standardized questionnaires designed for family or care givers. We sought to describe the test accuracy of such informant-based assessments for diagnosis of dementia/multidomain cognitive impairment in stroke. We performed a systematic review using a sensitive search strategy across multidisciplinary electronic databases. We created summary test accuracy metrics and described reporting and quality using STARDdem and Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tools, respectively. From 1432 titles, we included 11 studies. Ten papers used the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). Four studies described IQCODE for diagnosis of poststroke dementia (n=1197); summary sensitivity: 0.81 (95% confidence interval, 0.60-0.93); summary specificty: 0.83 (95% confidence interval, 0.64-0.93). Five studies described IQCODE as tool for predicting future dementia (n=837); summary sensitivity: 0.60 (95% confidence interval, 0.32-0.83); summary specificity: 0.97 (95% confidence interval, 0.70-1.00). All papers had issues with at least 1 aspect of study reporting or quality. There is a limited literature on informant cognitive assessments in stroke. IQCODE as a diagnostic tool has test properties similar to other screening tools, IQCODE as a prognostic tool is specific but insensitive. We found no papers describing test accuracy of informant tests for diagnosis of prestroke cognitive decline, few papers on poststroke dementia and all included papers had issues with potential bias. © 2015 American Heart Association, Inc.

The Effect of Occupation-based Cognitive Rehabilitation for Traumatic Brain Injury: A Meta-analysis of Randomized Controlled Trials.

PubMed

Park, Hae Yean; Maitra, Kinsuk; Martinez, Kristina Marie

2015-06-01

Traumatic brain injury (TBI) is the leading cause of death and disability among people younger than 35 years in the United States. Cognitive difficulty is a common consequence of TBI. To address cognitive deficits of patients with TBI, various cognitive rehabilitation approaches have been used for the clinical setting. The purpose of this study was to investigate the overall effect of occupation-based cognitive rehabilitation on patients' improvement in cognitive performance components, activity of daily living (ADL) performance, and values, beliefs and spirituality functions of patients with TBI. The papers used in this study were retrieved from the Cochrane Database, EBSCO (CINAHL), PsycINFO, PubMed and Web of Science published between 1997 and 2014. The keywords for searching were cognitive, rehabilitation, occupation, memory, attention, problem-solving, executive function, ADL, values, beliefs, spirituality, randomized controlled trials and TBI. For the meta-analysis, we examined 60 effect sizes from nine studies that are related to the occupation-based cognitive rehabilitation on persons with TBI. In persons with TBI, overall mental functions, ADL, and values, beliefs and spirituality were significantly improved in the groups that received occupation-based cognitive rehabilitation compared with comparison groups (mean d = 0.19, p < .05). Evidence from the present meta-analytic study suggests that occupation-based cognitive rehabilitation would be beneficial for individuals with TBI for improving daily functioning and positively be able to affect their psychosocial functions. Collecting many outcome measures in studies with relatively few participants and the final data are less reliable than the whole instrument itself. Future research should evaluate the effectiveness of specific occupation-based cognitive rehabilitations programmes in order to improve consistency among rehabilitation providers. Copyright © 2015 John Wiley & Sons, Ltd.

Wavelength reused bidirectional transmission of adaptively modulated optical OFDM signals in WDM-PONs incorporating SOA and RSOA intensity modulators.

PubMed

Wei, J L; Hugues-Salas, E; Giddings, R P; Jin, X Q; Zheng, X; Mansoor, S; Tang, J M

2010-05-10

Detailed numerical investigations are undertaken of wavelength reused bidirectional transmission of adaptively modulated optical OFDM (AMOOFDM) signals over a single SMF in a colorless WDM-PON incorporating a semiconductor optical amplifier (SOA) intensity modulator and a reflective SOA (RSOA) intensity modulator in the optical line termination and optical network unit, respectively. A comprehensive theoretical model describing the performance of such network scenarios is, for the first time, developed, taking into account dynamic optical characteristics of SOA and RSOA intensity modulators as well as the effects of Rayleigh backscattering (RB) and residual downstream signal-induced crosstalk. The developed model is rigorously verified experimentally in RSOA-based real-time end-to-end OOFDM systems at 7.5 Gb/s. It is shown that the RB noise and crosstalk effects are dominant factors limiting the maximum achievable downstream and upstream transmission performance. Under optimum SOA and RSOA operating conditions as well as practical downstream and upstream optical launch powers, 10 Gb/s downstream and 6 Gb/s upstream over 40 km SMF transmissions of conventional double sideband AMOOFDM signals are feasible without utilizing in-line optical amplification and chromatic dispersion compensation. In particular, the aforementioned transmission performance can be improved to 23 Gb/s downstream and 8 Gb/s upstream over 40 km SMFs when single sideband subcarrier modulation is adopted in the downstream systems. (c) 2010 Optical Society of America.

Mindfulness-Based Cognitive Approach for Seniors (MBCAS): Program Development and Implementation.

PubMed

Zellner Keller, Brigitte; Singh, Nirbhay N; Winton, Alan S W

2014-01-01

A number of cognitive interventions have been developed to enhance cognitive functioning in the growing population of the elderly. We describe the Mindfulness-Based Cognitive Approach for Seniors (MBCAS), a new training program designed especially for seniors. It was conceived in the context of self-development for seniors who wish to enhance their relationship with their inner and outer selves in order to navigate their aging process more easily and fluently. Physical and psychosocial problems related to aging, as well as some temporal issues, were taken into account in developing this program. Unlike clinically oriented mindfulness-based programs, which are generally delivered during an 8-week period, the MBCAS training program is presented over a period of 8 months. The main objectives of this program are to teach seniors to observe current experiences with nonjudgmental awareness, to identify automatic behaviors or reactions to current experiences that are potentially nonadaptive, and to enhance and reinforce positive coping with typical difficulties that they face in their daily lives. Details of the program development and initial implementation are presented, with suggestions for evaluating the program's effectiveness.

Improving clinical cognitive testing

PubMed Central

Gale, Seth A.; Barrett, A.M.; Boeve, Bradley F.; Chatterjee, Anjan; Coslett, H. Branch; D'Esposito, Mark; Finney, Glen R.; Gitelman, Darren R.; Hart, John J.; Lerner, Alan J.; Meador, Kimford J.; Pietras, Alison C.; Voeller, Kytja S.; Kaufer, Daniel I.

2015-01-01

Objective: To evaluate the evidence basis of single-domain cognitive tests frequently used by behavioral neurologists in an effort to improve the quality of clinical cognitive assessment. Methods: Behavioral Neurology Section members of the American Academy of Neurology were surveyed about how they conduct clinical cognitive testing, with a particular focus on the Neurobehavioral Status Exam (NBSE). In contrast to general screening cognitive tests, an NBSE consists of tests of individual cognitive domains (e.g., memory or language) that provide a more comprehensive diagnostic assessment. Workgroups for each of 5 cognitive domains (attention, executive function, memory, language, and spatial cognition) conducted evidence-based reviews of frequently used tests. Reviews focused on suitability for office-based clinical practice, including test administration time, accessibility of normative data, disease populations studied, and availability in the public domain. Results: Demographic and clinical practice data were obtained from 200 respondents who reported using a wide range of cognitive tests. Based on survey data and ancillary information, between 5 and 15 tests in each cognitive domain were reviewed. Within each domain, several tests are highlighted as being well-suited for an NBSE. Conclusions: We identified frequently used single-domain cognitive tests that are suitable for an NBSE to help make informed choices about clinical cognitive assessment. Some frequently used tests have limited normative data or have not been well-studied in common neurologic disorders. Utilizing standardized cognitive tests, particularly those with normative data based on the individual's age and educational level, can enhance the rigor and utility of clinical cognitive assessment. PMID:26163433

Implementing software based on relation frame theory to develop and increase relational cognitive skills

NASA Astrophysics Data System (ADS)

Presti, Giovambattista; Messina, Concetta; Mongelli, Francesca; Sireci, Maria Josè; Collotta, Mario

2017-11-01

Relational Frame Theory is a post-skinnerian theory of language and cognition based on more than thirty years of basic and applied research. It defines language and cognitive skills as an operant repertoire of responses to arbitrarily related stimuli specific, as far as is now known, of the human species. RFT has been proved useful in addressing cognitive barriers to human action in psychotherapy and also improving children skills in reading, IQ testing, and in metaphoric and categorical repertoires. We present a frame of action where RFT can be used in programming software to help autistic children to develop cognitive skills within a developmental vision.

Spatial cognition

NASA Technical Reports Server (NTRS)

Kaiser, Mary Kister; Remington, Roger

1988-01-01

Spatial cognition is the ability to reason about geometric relationships in the real (or a metaphorical) world based on one or more internal representations of those relationships. The study of spatial cognition is concerned with the representation of spatial knowledge, and our ability to manipulate these representations to solve spatial problems. Spatial cognition is utilized most critically when direct perceptual cues are absent or impoverished. Examples are provided of how human spatial cognitive abilities impact on three areas of space station operator performance: orientation, path planning, and data base management. A videotape provides demonstrations of relevant phenomena (e.g., the importance of orientation for recognition of complex, configural forms). The presentation is represented by abstract and overhead visuals only.

Exploring the Cognitive Loads of High-School Students as They Learn Concepts in Web-Based Environments

ERIC Educational Resources Information Center

Chang, Cheng-Chieh; Yang, Fang-Ying

2010-01-01

This study measured high-school learners' cognitive load as they interacted with different web-based curriculum components, and examined the interactions between cognitive load and web-based concept learning. Participants in this study were 105 11th graders from an academic senior high school in Taiwan. An online, multimedia curriculum on the…

The Use of Task-based Cognitive Tests for Defining Vocational Aptness of Individuals with Disabilities.

PubMed

Kwon, Jae-Sung; Oh, Duck-Won

2015-06-01

The purpose of this study was to demonstrate the use of task-based cognitive tests to detect potential problems in the assessment of work training for vocational rehabilitation. Eleven participants with a normal range of cognitive functioning scores were recruited for this study. Participants were all trainees who participated in a vocational training program. The Rey Complex Figure Test and the Allen Cognitive Level Screen were randomly administered to all participants. Responses to the tests were qualitatively analyzed with matrix and scatter charts. Observational outcomes derived from the tests indicated that response errors, distortions, and behavioral problems occurred in most participants. These factors may impede occupational performance despite normal cognitive function. These findings suggest that the use of task-based tests may be beneficial for detecting potential problems associated with the work performance of people with disabilities. Specific analysis using the task-based tests may be necessary to complete the decision-making process for vocational aptness. Furthermore, testing should be led by professionals with a higher specialization in this field.

Senior-driven design and development of tablet-based cognitive games.

PubMed

Marques, João; Vasconcelos, Ana; Teixeira, Luís F

2013-01-01

This paper describes the design and development of a tablet-based gaming platform targeting the senior population, aiming at improving their overall wellbeing by stimulating their cognitive capabilities and promoting social interaction between players. To achieve these goals, we started by performing a study of the specific characteristics of the senior user as well as what makes a game appealing to the player. Furthermore we investigated why the tablet proves to be an advantageous device to our target audience. Based on the results of our research, we developed a solution that incorporates cognitive and social mechanisms into its games, while performing iterative evaluations together with the final user by adopting a user-centered design methodology. In each design phase, a pre-selected group of senior participants experimented with the game platform and provided feedback to improve its features and usability. Through a series of short-term and a long-term evaluation, the game platform proved to be appealing to its intended users, providing an enjoyable gaming experience.

Simulation-Based Assessment Identifies Longitudinal Changes in Cognitive Skills in an Anesthesiology Residency Training Program.

PubMed

Sidi, Avner; Gravenstein, Nikolaus; Vasilopoulos, Terrie; Lampotang, Samsun

2017-06-02

We describe observed improvements in nontechnical or "higher-order" deficiencies and cognitive performance skills in an anesthesia residency cohort for a 1-year time interval. Our main objectives were to evaluate higher-order, cognitive performance and to demonstrate that simulation can effectively serve as an assessment of cognitive skills and can help detect "higher-order" deficiencies, which are not as well identified through more traditional assessment tools. We hypothesized that simulation can identify longitudinal changes in cognitive skills and that cognitive performance deficiencies can then be remediated over time. We used 50 scenarios evaluating 35 residents during 2 subsequent years, and 18 of those 35 residents were evaluated in both years (post graduate years 3 then 4) in the same or similar scenarios. Individual basic knowledge and cognitive performance during simulation-based scenarios were assessed using a 20- to 27-item scenario-specific checklist. Items were labeled as basic knowledge/technical (lower-order cognition) or advanced cognitive/nontechnical (higher-order cognition). Identical or similar scenarios were repeated annually by a subset of 18 residents during 2 successive academic years. For every scenario and item, we calculated group error scenario rate (frequency) and individual (resident) item success. Grouped individuals' success rates are calculated as mean (SD), and item success grade and group error rates are calculated and presented as proportions. For all analyses, α level is 0.05. Overall PGY4 residents' error rates were lower and success rates higher for the cognitive items compared with technical item performance in the operating room and resuscitation domains. In all 3 clinical domains, the cognitive error rate by PGY4 residents was fairly low (0.00-0.22) and the cognitive success rate by PGY4 residents was high (0.83-1.00) and significantly better compared with previous annual assessments (P < 0.05). Overall, there was an

The effect of cognitive-based training for the healthy older people: A meta-analysis of randomized controlled trials

PubMed Central

Chiu, Huei-Ling; Chu, Hsin; Tsai, Jui-Chen; Liu, Doresses; Chen, Ying-Ren; Yang, Hui-Ling

2017-01-01

Background From the perspective of disease prevention, the enhancement of cognitive function among the healthy older people has become an important issue in many countries lately. This study aim to investigate the effect of cognitive-based training on the overall cognitive function, memory, attention, executive function, and visual-spatial ability of the healthy older people. Methods Cochrane, PubMed, EMBASE, MEDLINE, PsycINFO, and CINAHL of selected randomized controlled trials (RCTs), and previous systematic reviews were searched for eligible studies. The population focused on this study were healthy older people who participated in randomized controlled trials that investigated the effectiveness of cognitive-based training. The outcomes including change in overall cognitive function, memory, attention, executive function, and visual-spatial ability. Results We collected a total of 31 RCTs, the results showed that cognitive-based training has a moderate effect on overall cognitive function (g = 0.419; 95%CI = 0.205–0.634) and executive function (g = 0.420; 95%CI = 0.239–0.602), and a small effect on the memory (g = 0.354; 95%CI = 0.244–0.465), attention (g = 0.218; 95%CI = 0.125–0.311), and visual-spatial ability (g = 0.183;95%CI = 0.015–0.352) in healthy older people. Subgroup analysis indicated the intervention characteristics of ≧3 times each week (p = 0.042), ≧8 total training weeks (p = 0.003) and ≧24 total training sessions (p = 0.040) yields a greater effect size. Conclusions Cognitive-based training is effective for the healthy older people. This improvement can represent a clinically important benefit, provide information about the use of cognitive-based training in healthy older people, and help the healthy older people obtain the greatest possible benefit in health promotion and disease prevention. PMID:28459873

Effects of Cognitive Load on Driving Performance: The Cognitive Control Hypothesis.

PubMed

Engström, Johan; Markkula, Gustav; Victor, Trent; Merat, Natasha

2017-08-01

The objective of this paper was to outline an explanatory framework for understanding effects of cognitive load on driving performance and to review the existing experimental literature in the light of this framework. Although there is general consensus that taking the eyes off the forward roadway significantly impairs most aspects of driving, the effects of primarily cognitively loading tasks on driving performance are not well understood. Based on existing models of driver attention, an explanatory framework was outlined. This framework can be summarized in terms of the cognitive control hypothesis: Cognitive load selectively impairs driving subtasks that rely on cognitive control but leaves automatic performance unaffected. An extensive literature review was conducted wherein existing results were reinterpreted based on the proposed framework. It was demonstrated that the general pattern of experimental results reported in the literature aligns well with the cognitive control hypothesis and that several apparent discrepancies between studies can be reconciled based on the proposed framework. More specifically, performance on nonpracticed or inherently variable tasks, relying on cognitive control, is consistently impaired by cognitive load, whereas the performance on automatized (well-practiced and consistently mapped) tasks is unaffected and sometimes even improved. Effects of cognitive load on driving are strongly selective and task dependent. The present results have important implications for the generalization of results obtained from experimental studies to real-world driving. The proposed framework can also serve to guide future research on the potential causal role of cognitive load in real-world crashes.

Processes of change in a school-based mindfulness programme: cognitive reactivity and self-coldness as mediators.

PubMed

Van der Gucht, Katleen; Takano, Keisuke; Raes, Filip; Kuppens, Peter

2018-05-01

The underlying mechanisms of the effectiveness of mindfulness-based interventions for emotional well-being remain poorly understood. Here, we examined the potential mediating effects of cognitive reactivity and self-compassion on symptoms of depression, anxiety and stress using data from an earlier randomised controlled school trial. A moderated time-lagged mediation model based on multilevel modelling was used to analyse the data. The findings showed that post-treatment changes in cognitive reactivity and self-coldness, an aspect of self-compassion, mediated subsequent changes in symptoms of depression, anxiety and stress. These results suggest that cognitive reactivity and self-coldness may be considered as transdiagnostic mechanisms of change of a mindfulness-based intervention programme for youth.

Problem Based Learning: Cognitive and Metacognitive Processes during Problem Analysis.

ERIC Educational Resources Information Center

De Grave, W. S.; And Others

1996-01-01

To investigate whether problem-based learning leads to conceptual change, the cognitive and metacognitive processes of a group of medical students were studied during the problem analysis phase, and their verbal communication and thinking processes were analyzed. Stimulated recall of the thinking process during the discussion detected a conceptual…

Fault Diagnosis for Rolling Bearings under Variable Conditions Based on Visual Cognition

PubMed Central

Cheng, Yujie; Zhou, Bo; Lu, Chen; Yang, Chao

2017-01-01

Fault diagnosis for rolling bearings has attracted increasing attention in recent years. However, few studies have focused on fault diagnosis for rolling bearings under variable conditions. This paper introduces a fault diagnosis method for rolling bearings under variable conditions based on visual cognition. The proposed method includes the following steps. First, the vibration signal data are transformed into a recurrence plot (RP), which is a two-dimensional image. Then, inspired by the visual invariance characteristic of the human visual system (HVS), we utilize speed up robust feature to extract fault features from the two-dimensional RP and generate a 64-dimensional feature vector, which is invariant to image translation, rotation, scaling variation, etc. Third, based on the manifold perception characteristic of HVS, isometric mapping, a manifold learning method that can reflect the intrinsic manifold embedded in the high-dimensional space, is employed to obtain a low-dimensional feature vector. Finally, a classical classification method, support vector machine, is utilized to realize fault diagnosis. Verification data were collected from Case Western Reserve University Bearing Data Center, and the experimental result indicates that the proposed fault diagnosis method based on visual cognition is highly effective for rolling bearings under variable conditions, thus providing a promising approach from the cognitive computing field. PMID:28772943

Detection of Subtle Cognitive Changes after mTBI Using a Novel Tablet-Based Task.

PubMed

Fischer, Tara D; Red, Stuart D; Chuang, Alice Z; Jones, Elizabeth B; McCarthy, James J; Patel, Saumil S; Sereno, Anne B

2016-07-01

This study examined the potential for novel tablet-based tasks, modeled after eye tracking techniques, to detect subtle sensorimotor and cognitive deficits after mild traumatic brain injury (mTBI). Specifically, we examined whether performance on these tablet-based tasks (Pro-point and Anti-point) was able to correctly categorize concussed versus non-concussed participants, compared with performance on other standardized tests for concussion. Patients admitted to the emergency department with mTBI were tested on the Pro-point and Anti-point tasks, a current standard cognitive screening test (i.e., the Standard Assessment of Concussion [SAC]), and another eye movement-based tablet test, the King-Devick(®) (KD). Within hours after injury, mTBI patients showed significant slowing in response times, compared with both orthopedic and age-matched control groups, in the Pro-point task, demonstrating deficits in sensorimotor function. Mild TBI patients also showed significant slowing, compared with both control groups, on the Anti-point task, even when controlling for sensorimotor slowing, indicating deficits in cognitive function. Performance on the SAC test revealed similar deficits of cognitive function in the mTBI group, compared with the age-matched control group; however, the KD test showed no evidence of cognitive slowing in mTBI patients, compared with either control group. Further, measuring the sensitivity and specificity of these tasks to accurately predict mTBI with receiver operating characteristic analysis indicated that the Anti-point and Pro-point tasks reached excellent levels of accuracy and fared better than current standardized tools for assessment of concussion. Our findings suggest that these rapid tablet-based tasks are able to reliably detect and measure functional impairment in cognitive and sensorimotor control within hours after mTBI. These tasks may provide a more sensitive diagnostic measure for functional deficits that could prove key to

Detection of Subtle Cognitive Changes after mTBI Using a Novel Tablet-Based Task

PubMed Central

Red, Stuart D.; Chuang, Alice Z.; Jones, Elizabeth B.; McCarthy, James J.; Patel, Saumil S.; Sereno, Anne B.

2016-01-01

Abstract This study examined the potential for novel tablet-based tasks, modeled after eye tracking techniques, to detect subtle sensorimotor and cognitive deficits after mild traumatic brain injury (mTBI). Specifically, we examined whether performance on these tablet-based tasks (Pro-point and Anti-point) was able to correctly categorize concussed versus non-concussed participants, compared with performance on other standardized tests for concussion. Patients admitted to the emergency department with mTBI were tested on the Pro-point and Anti-point tasks, a current standard cognitive screening test (i.e., the Standard Assessment of Concussion [SAC]), and another eye movement–based tablet test, the King-Devick® (KD). Within hours after injury, mTBI patients showed significant slowing in response times, compared with both orthopedic and age-matched control groups, in the Pro-point task, demonstrating deficits in sensorimotor function. Mild TBI patients also showed significant slowing, compared with both control groups, on the Anti-point task, even when controlling for sensorimotor slowing, indicating deficits in cognitive function. Performance on the SAC test revealed similar deficits of cognitive function in the mTBI group, compared with the age-matched control group; however, the KD test showed no evidence of cognitive slowing in mTBI patients, compared with either control group. Further, measuring the sensitivity and specificity of these tasks to accurately predict mTBI with receiver operating characteristic analysis indicated that the Anti-point and Pro-point tasks reached excellent levels of accuracy and fared better than current standardized tools for assessment of concussion. Our findings suggest that these rapid tablet-based tasks are able to reliably detect and measure functional impairment in cognitive and sensorimotor control within hours after mTBI. These tasks may provide a more sensitive diagnostic measure for functional deficits that could prove

[User friendliness of computer-based cognitive training for psychogeriatric patients with mild to moderate cognitive impairments].

PubMed

van der Ploeg, Eva S; Hoorweg, Angela; van der Lee, Jacqueline

2016-04-01

Cognitive impairment associated with dementia is characterized by a continuous decline. Cognitive training is a method to train specific brain functions such as memory and attention to prevent or slow down cognitive decline. A small number of studies has shown that cognitive training on a computer has a positive effect on both cognition and mood in people with cognitive impairment. This pilot study tested if serious games could be integrated in a psychogeriatric rehabilitation center. Fourteen psychogeriatric patients participated twice weekly in cognitive training sessions on a computer. Both the participants and the facilitator reported positive interactions and outcomes. However, after five weeks only half of the sample still participated in the training. This was partly because of patient turn-over as well as incorporating this new task in the facilitators' daily work. Fear of failure, physical limitations and rapidly decreasing cognitive function led to drop out according to the facilitator. The engagement of patients in the games and the role of the facilitator seemed essential for success, especially monitoring (and adjusting) the difficulty level of the program for every individual participant.

Feasibility, reliability, and validity of a smartphone based application for the assessment of cognitive function in the elderly.

PubMed

Brouillette, Robert M; Foil, Heather; Fontenot, Stephanie; Correro, Anthony; Allen, Ray; Martin, Corby K; Bruce-Keller, Annadora J; Keller, Jeffrey N

2013-01-01

While considerable knowledge has been gained through the use of established cognitive and motor assessment tools, there is a considerable interest and need for the development of a battery of reliable and validated assessment tools that provide real-time and remote analysis of cognitive and motor function in the elderly. Smartphones appear to be an obvious choice for the development of these "next-generation" assessment tools for geriatric research, although to date no studies have reported on the use of smartphone-based applications for the study of cognition in the elderly. The primary focus of the current study was to assess the feasibility, reliability, and validity of a smartphone-based application for the assessment of cognitive function in the elderly. A total of 57 non-demented elderly individuals were administered a newly developed smartphone application-based Color-Shape Test (CST) in order to determine its utility in measuring cognitive processing speed in the elderly. Validity of this novel cognitive task was assessed by correlating performance on the CST with scores on widely accepted assessments of cognitive function. Scores on the CST were significantly correlated with global cognition (Mini-Mental State Exam: r = 0.515, p<0.0001) and multiple measures of processing speed and attention (Digit Span: r = 0.427, p<0.0001; Trail Making Test: r = -0.651, p<0.00001; Digit Symbol Test: r = 0.508, p<0.0001). The CST was not correlated with naming and verbal fluency tasks (Boston Naming Test, Vegetable/Animal Naming) or memory tasks (Logical Memory Test). Test re-test reliability was observed to be significant (r = 0.726; p = 0.02). Together, these data are the first to demonstrate the feasibility, reliability, and validity of using a smartphone-based application for the purpose of assessing cognitive function in the elderly. The importance of these findings for the establishment of smartphone-based assessment batteries of cognitive

Cortical and subcortical gray matter bases of cognitive deficits in REM sleep behavior disorder.

PubMed

Rahayel, Shady; Postuma, Ronald B; Montplaisir, Jacques; Génier Marchand, Daphné; Escudier, Frédérique; Gaubert, Malo; Bourgouin, Pierre-Alexandre; Carrier, Julie; Monchi, Oury; Joubert, Sven; Blanc, Frédéric; Gagnon, Jean-François

2018-05-15

To investigate cortical and subcortical gray matter abnormalities underlying cognitive impairment in patients with REM sleep behavior disorder (RBD) with or without mild cognitive impairment (MCI). Fifty-two patients with RBD, including 17 patients with MCI, were recruited and compared to 41 controls. All participants underwent extensive clinical assessments, neuropsychological examination, and 3-tesla MRI acquisition of T1 anatomical images. Vertex-based cortical analyses of volume, thickness, and surface area were performed to investigate cortical abnormalities between groups, whereas vertex-based shape analysis was performed to investigate subcortical structure surfaces. Correlations were performed to investigate associations between cortical and subcortical metrics, cognitive domains, and other markers of neurodegeneration (color discrimination, olfaction, and autonomic measures). Patients with MCI had cortical thinning in the frontal, cingulate, temporal, and occipital cortices, and abnormal surface contraction in the lenticular nucleus and thalamus. Patients without MCI had cortical thinning restricted to the frontal cortex. Lower patient performance in cognitive domains was associated with cortical and subcortical abnormalities. Moreover, impaired performance on olfaction, color discrimination, and autonomic measures was associated with thinning in the occipital lobe. Cortical and subcortical gray matter abnormalities are associated with cognitive status in patients with RBD, with more extensive patterns in patients with MCI. Our results highlight the importance of distinguishing between subgroups of patients with RBD according to cognitive status in order to better understand the neurodegenerative process in this population. © 2018 American Academy of Neurology.

Prevalence of Mild Cognitive Impairment and Dementia in Saudi Arabia: A Community-Based Study.

PubMed

Alkhunizan, Muath; Alkhenizan, Abdullah; Basudan, Loay

2018-01-01

The age of the population in Saudi Arabia is shifting toward elderly, which can lead to an increased risk of mild cognitive impairment (MCI) and dementia. The aim of this study is to determine the prevalence of cognitive impairment (MCI and dementia) among elderly patients in a community-based setting in Riyadh, Saudi Arabia. In this cross-sectional study, we included patients aged 60 years and above who were seen in the Family Medicine Clinics affiliated with King Faisal Specialist Hospital and Research Centre. Patients with delirium, active depression, and patients with a history of severe head trauma in the past 3 months were excluded. Patients were interviewed during their regular visit by a trained physician to collect demographic data and to administer the validated Arabic version of the Montreal Cognitive Assessment (MoCA) test. One hundred seventy-one Saudi patients were recruited based on a calculated sample size for the aim of this study. The mean age of included sample was 67 ± 6 years. The prevalence of cognitive impairment was 45%. The prevalence of MCI was 38.6% and the prevalence of dementia was 6.4%. Age, low level of education, hypertension, and cardiovascular disease were risk factors for cognitive impairment. Prevalence of MCI and dementia in Saudi Arabia using MoCA were in the upper range compared to developed and developing countries. The high rate of risk factors for cognitive impairment in Saudi Arabia is contributing to this finding.

Layout Design of Human-Machine Interaction Interface of Cabin Based on Cognitive Ergonomics and GA-ACA.

PubMed

Deng, Li; Wang, Guohua; Yu, Suihuai

2016-01-01

In order to consider the psychological cognitive characteristics affecting operating comfort and realize the automatic layout design, cognitive ergonomics and GA-ACA (genetic algorithm and ant colony algorithm) were introduced into the layout design of human-machine interaction interface. First, from the perspective of cognitive psychology, according to the information processing process, the cognitive model of human-machine interaction interface was established. Then, the human cognitive characteristics were analyzed, and the layout principles of human-machine interaction interface were summarized as the constraints in layout design. Again, the expression form of fitness function, pheromone, and heuristic information for the layout optimization of cabin was studied. The layout design model of human-machine interaction interface was established based on GA-ACA. At last, a layout design system was developed based on this model. For validation, the human-machine interaction interface layout design of drilling rig control room was taken as an example, and the optimization result showed the feasibility and effectiveness of the proposed method.

Layout Design of Human-Machine Interaction Interface of Cabin Based on Cognitive Ergonomics and GA-ACA

PubMed Central

Deng, Li; Wang, Guohua; Yu, Suihuai

2016-01-01

In order to consider the psychological cognitive characteristics affecting operating comfort and realize the automatic layout design, cognitive ergonomics and GA-ACA (genetic algorithm and ant colony algorithm) were introduced into the layout design of human-machine interaction interface. First, from the perspective of cognitive psychology, according to the information processing process, the cognitive model of human-machine interaction interface was established. Then, the human cognitive characteristics were analyzed, and the layout principles of human-machine interaction interface were summarized as the constraints in layout design. Again, the expression form of fitness function, pheromone, and heuristic information for the layout optimization of cabin was studied. The layout design model of human-machine interaction interface was established based on GA-ACA. At last, a layout design system was developed based on this model. For validation, the human-machine interaction interface layout design of drilling rig control room was taken as an example, and the optimization result showed the feasibility and effectiveness of the proposed method. PMID:26884745

Can mindfulness-based interventions influence cognitive functioning in older adults? A review and considerations for future research.

PubMed

Berk, Lotte; van Boxtel, Martin; van Os, Jim

2017-11-01

An increased need exists to examine factors that protect against age-related cognitive decline. There is preliminary evidence that meditation can improve cognitive function. However, most studies are cross-sectional and examine a wide variety of meditation techniques. This review focuses on the standard eight-week mindfulness-based interventions (MBIs) such as mindfulness-based stress reduction (MBSR) and mindfulness-based cognitive therapy (MBCT). We searched the PsychINFO, CINAHL, Web of Science, COCHRANE, and PubMed databases to identify original studies investigating the effects of MBI on cognition in older adults. Six reports were included in the review of which three were randomized controlled trials. Studies reported preliminary positive effects on memory, executive function and processing speed. However, most reports had a high risk of bias and sample sizes were small. The only study with low risk of bias, large sample size and active control group reported no significant findings. We conclude that eight-week MBI for older adults are feasible, but results on cognitive improvement are inconclusive due a limited number of studies, small sample sizes, and a high risk of bias. Rather than a narrow focus on cognitive training per se, future research may productively shift to investigate MBI as a tool to alleviate suffering in older adults, and to prevent cognitive problems in later life already in younger target populations.

Development and Evaluation of a Cognitive Training Game for Older People: A Design-based Approach.

PubMed

Lu, Ming-Hsin; Lin, Weijane; Yueh, Hsiu-Ping

2017-01-01

In the research field of cognitive aging, games have gained attention as training interventions to remediate age-related deficits. Cognitive training games on computer, video and mobile platforms have shown ample and positive support. However, the generalized effects are not agreed upon unanimously, and the game tasks are usually simple and decontextualized due to the limitations of measurements. This study adopted a qualitative approach of design-based research (DBR) to systematically review and pragmatically examine the regime, presentation and feedback design of a cognitive training game for older adults. An overview of the literature of cognitive aging and training games was conducted to form the theoretical conjectures of the design, and an iterative cycle and process were employed to develop a mobile game for older adults who are homebound or receiving care in a nursing home. Stakeholders, i.e., elderly users and institutional administrators, were invited to participate in the design process. Using two cycles of design and evaluation, a working prototype of an iPad-based app that accounted for the needs of elderly adults in terms of form, appearance and working function was developed and tested in the actual contexts of the participants' homes and an assisted living facility. The results showed that the cognitive training game developed in this study was accepted by the participants, and a high degree of satisfaction was noted. Moreover, the elements of the interface, including its size, layout and control flow, were tested and found to be suitable for use. This study contributes to the literature by providing design suggestions for such games, including the designs of the cognitive training structure, interface, interaction, instructions and feedback, based on empirical evidence collected in natural settings. This study further suggests that the effectiveness of cognitive training in mobile games be evaluated through field and physical testing on a larger

Development and Evaluation of a Cognitive Training Game for Older People: A Design-based Approach

PubMed Central

Lu, Ming-Hsin; Lin, Weijane; Yueh, Hsiu-Ping

2017-01-01

In the research field of cognitive aging, games have gained attention as training interventions to remediate age-related deficits. Cognitive training games on computer, video and mobile platforms have shown ample and positive support. However, the generalized effects are not agreed upon unanimously, and the game tasks are usually simple and decontextualized due to the limitations of measurements. This study adopted a qualitative approach of design-based research (DBR) to systematically review and pragmatically examine the regime, presentation and feedback design of a cognitive training game for older adults. An overview of the literature of cognitive aging and training games was conducted to form the theoretical conjectures of the design, and an iterative cycle and process were employed to develop a mobile game for older adults who are homebound or receiving care in a nursing home. Stakeholders, i.e., elderly users and institutional administrators, were invited to participate in the design process. Using two cycles of design and evaluation, a working prototype of an iPad-based app that accounted for the needs of elderly adults in terms of form, appearance and working function was developed and tested in the actual contexts of the participants' homes and an assisted living facility. The results showed that the cognitive training game developed in this study was accepted by the participants, and a high degree of satisfaction was noted. Moreover, the elements of the interface, including its size, layout and control flow, were tested and found to be suitable for use. This study contributes to the literature by providing design suggestions for such games, including the designs of the cognitive training structure, interface, interaction, instructions and feedback, based on empirical evidence collected in natural settings. This study further suggests that the effectiveness of cognitive training in mobile games be evaluated through field and physical testing on a larger

Telephone-Based Cognitive-Behavioral Screening for Frontotemporal Changes in Patients with Amyotrophic Lateral Sclerosis (ALS)

PubMed Central

Christodoulou, Georgia; Gennings, Chris; Hupf, Jonathan; Factor-Litvak, Pam; Murphy, Jennifer; Goetz, Raymond R.; Mitsumoto, Hiroshi

2017-01-01

Objective To establish a valid and reliable battery of measures to evaluate frontotemporal dementia (FTD) in patients with ALS over the phone. Methods Thirty-one subjects were administered either in-person or telephone-based screening followed by the opposite mode of testing two weeks later, using a modified version of the UCSF Cognitive Screening Battery. Results Equivalence testing was performed for in-person and telephone-based tests. The standard ALS Cognitive Behavioral Screen (ALS-CBS) showed statistical equivalence at the 5% significance level when compared to a revised phone-version of the ALS-CBS. In addition, the Controlled Oral Word Association Test (COWAT) and Center for Neurologic Study-Lability Scale (CNS-LS) were also found to be equivalent at the 5% and 10% significance level respectively. Similarly, the Mini-Mental State Examination (MMSE) and the well-established Telephone Interview for Cognitive Status (TICS) were also statistically equivalent. Equivalence could not be claimed for the ALS-Frontal Behavioral Inventory (ALS-FBI) caregiver interview and the Written Verbal Fluency Index (WVFI). Conclusions Our study suggests that telephone-based versions of the ALS-CBS, COWAT, and CNS-LS may offer clinicians valid tools to detect frontotemporal changes in the ALS population. Development of telephone-based cognitive testing for ALS could become an integral resource for population-based research in the future. PMID:27121545

Telephone based cognitive-behavioral screening for frontotemporal changes in patients with amyotrophic lateral sclerosis (ALS).

PubMed

Christodoulou, Georgia; Gennings, Chris; Hupf, Jonathan; Factor-Litvak, Pam; Murphy, Jennifer; Goetz, Raymond R; Mitsumoto, Hiroshi

Our objective was to establish a valid and reliable battery of measures to evaluate frontotemporal dementia (FTD) in patients with ALS over the telephone. Thirty-one subjects were administered either in-person or by telephone-based screening followed by the opposite mode of testing two weeks later, using a modified version of the UCSF Cognitive Screening Battery. Equivalence testing was performed for in-person and telephone based tests. The standard ALS Cognitive Behavioral Screen (ALS-CBS) showed statistical equivalence at the 5% significance level compared to a revised phone version of the ALS-CBS. In addition, the Controlled Oral Word Association Test (COWAT) and Center for Neurologic Study-Lability Scale (CNS-LS) were also found to be equivalent at the 5% and 10% significance level, respectively. Similarly, the Mini-Mental State Examination (MMSE) and the well-established Telephone Interview for Cognitive Status (TICS) were also statistically equivalent. Equivalence could not be claimed for the ALS-Frontal Behavioral Inventory (ALS-FBI) caregiver interview and the Written Verbal Fluency Index (WVFI). In conclusion, our study suggests that telephone-based versions of the ALS-CBS, COWAT, and CNS-LS may offer clinicians valid tools to detect frontotemporal changes in the ALS population. Development of telephone based cognitive testing for ALS could become an integral resource for population based research in the future.

Technology and Cognition Merge with Challenge-Based Learning Cycles Online

ERIC Educational Resources Information Center

Cobbett, Shelley L.

2013-01-01

Teaching and learning in Web-based courses has become a global phenomenon. Educators are grappling with merging cognition and technology to offer students quality, relevant online courses. The development of social presence in the online environment is of paramount importance and requires individuals to engage in meaningful interactions about, and…

Cognition in multiple sclerosis

PubMed Central

Benedict, Ralph; Enzinger, Christian; Filippi, Massimo; Geurts, Jeroen J.; Hamalainen, Paivi; Hulst, Hanneke; Inglese, Matilde; Leavitt, Victoria M.; Rocca, Maria A.; Rosti-Otajarvi, Eija M.; Rao, Stephen

2018-01-01

Cognitive decline is recognized as a prevalent and debilitating symptom of multiple sclerosis (MS), especially deficits in episodic memory and processing speed. The field aims to (1) incorporate cognitive assessment into standard clinical care and clinical trials, (2) utilize state-of-the-art neuroimaging to more thoroughly understand neural bases of cognitive deficits, and (3) develop effective, evidence-based, clinically feasible interventions to prevent or treat cognitive dysfunction, which are lacking. There are obstacles to these goals. Our group of MS researchers and clinicians with varied expertise took stock of the current state of the field, and we identify several important practical and theoretical challenges, including key knowledge gaps and methodologic limitations related to (1) understanding and measurement of cognitive deficits, (2) neuroimaging of neural bases and correlates of deficits, and (3) development of effective treatments. This is not a comprehensive review of the extensive literature, but instead a statement of guidelines and priorities for the field. For instance, we provide recommendations for improving the scientific basis and methodologic rigor for cognitive rehabilitation research. Toward this end, we call for multidisciplinary collaborations toward development of biologically based theoretical models of cognition capable of empirical validation and evidence-based refinement, providing the scientific context for effective treatment discovery. PMID:29343470

Reducing the PAPR in FBMC-OQAM systems with low-latency trellis-based SLM technique

NASA Astrophysics Data System (ADS)

Bulusu, S. S. Krishna Chaitanya; Shaiek, Hmaied; Roviras, Daniel

2016-12-01

Filter-bank multi-carrier (FBMC) modulations, and more specifically FBMC-offset quadrature amplitude modulation (OQAM), are seen as an interesting alternative to orthogonal frequency division multiplexing (OFDM) for the 5th generation radio access technology. In this paper, we investigate the problem of peak-to-average power ratio (PAPR) reduction for FBMC-OQAM signals. Recently, it has been shown that FBMC-OQAM with trellis-based selected mapping (TSLM) scheme not only is superior to any scheme based on symbol-by-symbol approach but also outperforms that of the OFDM with classical SLM scheme. This paper is an extension of that work, where we analyze the TSLM in terms of computational complexity, required hardware memory, and latency issues. We have proposed an improvement to the TSLM, which requires very less hardware memory, compared to the originally proposed TSLM, and also have low latency. Additionally, the impact of the time duration of partial PAPR on the performance of TSLM is studied, and its lower bound has been identified by proposing a suitable time duration. Also, a thorough and fair comparison of performance has been done with an existing trellis-based scheme proposed in literature. The simulation results show that the proposed low-latency TSLM yields better PAPR reduction performance with relatively less hardware memory requirements.

Cognitive training in Parkinson disease: cognition-specific vs nonspecific computer training.

PubMed

Zimmermann, Ronan; Gschwandtner, Ute; Benz, Nina; Hatz, Florian; Schindler, Christian; Taub, Ethan; Fuhr, Peter

2014-04-08

In this study, we compared a cognition-specific computer-based cognitive training program with a motion-controlled computer sports game that is not cognition-specific for their ability to enhance cognitive performance in various cognitive domains in patients with Parkinson disease (PD). Patients with PD were trained with either a computer program designed to enhance cognition (CogniPlus, 19 patients) or a computer sports game with motion-capturing controllers (Nintendo Wii, 20 patients). The effect of training in 5 cognitive domains was measured by neuropsychological testing at baseline and after training. Group differences over all variables were assessed with multivariate analysis of variance, and group differences in single variables were assessed with 95% confidence intervals of mean difference. The groups were similar regarding age, sex, and educational level. Patients with PD who were trained with Wii for 4 weeks performed better in attention (95% confidence interval: -1.49 to -0.11) than patients trained with CogniPlus. In our study, patients with PD derived at least the same degree of cognitive benefit from non-cognition-specific training involving movement as from cognition-specific computerized training. For patients with PD, game consoles may be a less expensive and more entertaining alternative to computer programs specifically designed for cognitive training. This study provides Class III evidence that, in patients with PD, cognition-specific computer-based training is not superior to a motion-controlled computer game in improving cognitive performance.

TENI: A comprehensive battery for cognitive assessment based on games and technology.

PubMed

Delgado, Marcela Tenorio; Uribe, Paulina Arango; Alonso, Andrés Aparicio; Díaz, Ricardo Rosas

2016-01-01

TENI (Test de Evaluación Neuropsicológica Infantil) is an instrument developed to assess cognitive abilities in children between 3 and 9 years of age. It is based on a model that incorporates games and technology as tools to improve the assessment of children's capacities. The test was standardized with two Chilean samples of 524 and 82 children living in urban zones. Evidence of reliability and validity based on current standards is presented. Data show good levels of reliability for all subtests. Some evidence of validity in terms of content, test structure, and association with other variables is presented. This instrument represents a novel approach and a new frontier in cognitive assessment. Further studies with clinical, rural, and cross-cultural populations are required.

Cognitive Activity-based Design Methodology for Novice Visual Communication Designers

ERIC Educational Resources Information Center

Kim, Hyunjung; Lee, Hyunju

2016-01-01

The notion of design thinking is becoming more concrete nowadays, as design researchers and practitioners study the thinking processes involved in design and employ the concept of design thinking to foster better solutions to complex and ill-defined problems. The goal of the present research is to develop a cognitive activity-based design…

[Establishment and practice of traditional Chinese medicine property cognitive model based on three elements].

PubMed

Zhang, Bing; Jin, Rui; Huang, Jianmei; Liu, Xiaoqing; Xue, Chunmiao; Lin, Zhijian

2012-08-01

Traditional Chinese medicine (TCM) property theory is believed to be a key and difficult point of basic theory studies of TCM. Complex concepts, components and characteristics of TCM property have long puzzled researchers and urged them to develop new angles and approaches. In the view of cognitive science, TCM property theory is a cognitive process of storing, extracting, rebuilding and summarizing the sensory information about TCMs and their effects during the medical practice struggling against diseases under the guidance of traditional Chinese philosophical thinking. The cognitive process of TCM property has particular cognitive elements and strategies. Taking into account clinical application characteristics of TCMs, this study defines the particular cognitive elements. In the combination of research methods of modern chemistry, biology and mathematics, and on the basis early-stage work for five years, we have built a TCM property cognition model based on three elements and practiced with drugs with pungent and hot properties as example, in the hope of interpreting TCM properties with modern science and providing thoughts for the nature of medical properties and instruction for rational clinical prescription.

Developing an international scoring system for a consensus-based social cognition measure: MSCEIT-managing emotions.

PubMed

Hellemann, G S; Green, M F; Kern, R S; Sitarenios, G; Nuechterlein, K H

2017-10-01

Measures of social cognition are increasingly being applied to psychopathology, including studies of schizophrenia and other psychotic disorders. Tests of social cognition present unique challenges for international adaptations. The Mayer-Salovey-Caruso Emotional Intelligence Test, Managing Emotions Branch (MSCEIT-ME) is a commonly-used social cognition test that involves the evaluation of social scenarios presented in vignettes. This paper presents evaluations of translations of this test in six different languages based on representative samples from the relevant countries. The goal was to identify items from the MSCEIT-ME that show different response patterns across countries using indices of discrepancy and content validity criteria. An international version of the MSCEIT-ME scoring was developed that excludes items that showed undesirable properties across countries. We then confirmed that this new version had better performance (i.e. less discrepancy across regions) in international samples than the version based on the original norms. Additionally, it provides scores that are comparable to ratings based on local norms. This paper shows that it is possible to adapt complex social cognitive tasks so they can provide valid data across different cultural contexts.

Mindfulness-based cognitive therapy for prevention of recurrence of suicidal behavior.

PubMed

Williams, J Mark G; Duggan, Danielle S; Crane, Catherine; Fennell, Melanie J V

2006-02-01

Once suicidal thoughts have emerged as a feature of depression they are likely to be reactivated as part of a suicidal mode of mind whenever sad mood reappears. This article reviews the methods and the usefulness of mindfulness-based cognitive therapy (MBCT) as a treatment for the prevention of the reactivation of the suicidal mode. MBCT integrates mindfulness meditation practices and cognitive therapy techniques. It teaches participants to develop moment-by-moment awareness, approaching ongoing experience with an attitude of nonjudgment and acceptance. Participants are increasingly able to see their thoughts as mental events rather than facts (metacognitive awareness). A case example illustrates how mindfulness skills develop with MBCT and how they relate to the cognitive processes that fuel suicidal crises. An ongoing controlled trial will provide further evidence, but pilot work suggests that MBCT is a promising intervention for those who have experienced suicidal ideation in the past. (c) 2005 Wiley Periodicals, Inc.

Early Childhood OCD: Preliminary Findings from a Family-Based Cognitive-Behavioral Approach

ERIC Educational Resources Information Center

Freeman, Jennifer B.; Garcia, Abbe M.; Coyne, Lisa; Ale, Chelsea; Prezeworski, Amy; Himle, Michael; Compton, Scott; Leonard, Henrietta L.

2008-01-01

A study was conducted to compare the relative usefulness of family-based cognitive-behavioral therapy (CBT) against family-based relaxation treatment for children with obsessive-compulsive disorder (OCD). Results showed that children with early childhood-onset OCD benefited from the CBT program as it effectively decreased OCD symptoms and helped…

Towards a model-based cognitive neuroscience of stopping - a neuroimaging perspective.

PubMed

Sebastian, Alexandra; Forstmann, Birte U; Matzke, Dora

2018-07-01

Our understanding of the neural correlates of response inhibition has greatly advanced over the last decade. Nevertheless the specific function of regions within this stopping network remains controversial. The traditional neuroimaging approach cannot capture many processes affecting stopping performance. Despite the shortcomings of the traditional neuroimaging approach and a great progress in mathematical and computational models of stopping, model-based cognitive neuroscience approaches in human neuroimaging studies are largely lacking. To foster model-based approaches to ultimately gain a deeper understanding of the neural signature of stopping, we outline the most prominent models of response inhibition and recent advances in the field. We highlight how a model-based approach in clinical samples has improved our understanding of altered cognitive functions in these disorders. Moreover, we show how linking evidence-accumulation models and neuroimaging data improves the identification of neural pathways involved in the stopping process and helps to delineate these from neural networks of related but distinct functions. In conclusion, adopting a model-based approach is indispensable to identifying the actual neural processes underlying stopping. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Evident cognitive impairments in seemingly recovered patients after midazolam-based light sedation during diagnostic endoscopy.

PubMed

Hsu, Yen-Hsuan; Lin, Feng-Sheng; Yang, Chi-Cheng; Lin, Chih-Peng; Hua, Mau-Sun; Sun, Wei-Zen

2015-06-01

Midazolam is a widely used sedative agent during colonoscopy, with cognitive toxicity. However, the potential cognitive hazard of midazolam-based light sedation has not been sufficiently examined. We aimed to examine the cognitive safety and vulnerability profile under midazolam light sedation, with a particular focus on individual variations. We conducted a prospective case-controlled study in an academic hospital. In total, 30 patients undergoing sedative colonoscopy as part of a health check-up were recruited. Neuropsychological testing on the full cognitive spectrum was evaluated at 15 minutes and 120 minutes after low-dose midazolam administration. The modified reliable change index (RCI) was used for intrapersonal comparisons and controlling for practice effects. Midazolam affected psychomotor speed (48%), memory (40%), learning (32%), working memory (17%), and sustained attention (11%), while sparing orientation and the fluency aspect of executive function at the acute stage. Residual memory (10%) and learning (10%) impairments at 2 hours after administration were evidenced in some patients. The three object recall and digit symbol coding tests can serve as useful screening tools. Midazolam-based light sedation induced selective cognitive impairments and prolonged cognitive impairments occurred in patients with advanced age. A longer observation time and further screening were recommended for patients due to their at risk state. Copyright © 2013. Published by Elsevier B.V.

Speaking and cognitive distractions during EEG-based brain control of a virtual neuroprosthesis-arm.

PubMed

Foldes, Stephen T; Taylor, Dawn M

2013-12-21

Brain-computer interface (BCI) systems have been developed to provide paralyzed individuals the ability to command the movements of an assistive device using only their brain activity. BCI systems are typically tested in a controlled laboratory environment were the user is focused solely on the brain-control task. However, for practical use in everyday life people must be able to use their brain-controlled device while mentally engaged with the cognitive responsibilities of daily activities and while compensating for any inherent dynamics of the device itself. BCIs that use electroencephalography (EEG) for movement control are often assumed to require significant mental effort, thus preventing users from thinking about anything else while using their BCI. This study tested the impact of cognitive load as well as speaking on the ability to use an EEG-based BCI. Six participants controlled the two-dimensional (2D) movements of a simulated neuroprosthesis-arm under three different levels of cognitive distraction. The two higher cognitive load conditions also required simultaneously speaking during BCI use. On average, movement performance declined during higher levels of cognitive distraction, but only by a limited amount. Movement completion time increased by 7.2%, the percentage of targets successfully acquired declined by 11%, and path efficiency declined by 8.6%. Only the decline in percentage of targets acquired and path efficiency were statistically significant (p < 0.05). People who have relatively good movement control of an EEG-based BCI may be able to speak and perform other cognitively engaging activities with only a minor drop in BCI-control performance.

Mindfulness-Based Cognitive Therapy to Prevent Relapse in Recurrent Depression

ERIC Educational Resources Information Center

Kuyken, Willem; Byford, Sarah; Taylor, Rod S.; Watkins, Ed; Holden, Emily; White, Kat; Barrett, Barbara; Byng, Richard; Evans, Alison; Mullan, Eugene; Teasdale, John D.

2008-01-01

For people at risk of depressive relapse, mindfulness-based cognitive therapy (MBCT) has an additive benefit to usual care (H. F. Coelho, P. H. Canter, & E. Ernst, 2007). This study asked if, among patients with recurrent depression who are treated with antidepressant medication (ADM), MBCT is comparable to treatment with maintenance ADM (m-ADM)…

D Visibility Analysis in Urban Environment - Cognition Research Based on Vge

NASA Astrophysics Data System (ADS)

Lin, T. P.; Lin, H.; Hu, M. Y.

2013-09-01

The author in this research attempts to illustrate a measurable relationship between the physical environment and human's visual perception, including the distance, visual angle impact and visual field (a 3D isovist conception) against human's cognition way, by using a 3D visibility analysis method based on the platform of Virtual Geographic Environment (VGE). The whole project carries out in the CUHK campus (the Chinese University of Hong Kong), by adopting a virtual 3D model of the whole campus and survey in real world. A possible model for the simulation of human cognition in urban spaces is expected to be the output of this research, such as what the human perceive from the environment, how their feelings and behaviours are and how they affect the surrounding world. Kevin Lynch raised 5 elements of urban design in 1960s, which are "vitality, sense, fit, access and control". As the development of urban design, several problems around the human's cognitive and behaviour have come out. Due to the restriction of sensing knowledge in urban spaces, the research among the "sense" and the "fit" of urban design were not quite concerned in recent decades. The geo-spatial cognition field comes into being in 1997 and developed in recent 15 years, which made great effort in way-finding and urban behaviour simulation based on the platform of GIS (geographic information system) or VGE. The platform of VGE is recognized as a proper tool for the analysis of human's perception in urban places, because of its efficient 3D spatial data management and excellent 3D visualization for output result. This article will generally describe the visibility analysis method based on the 3D VGE platform. According to the uncertainty and variety of human perception existed in this research, the author attempts to arrange a survey of observer investigation and validation for the analysis results. Four figures related with space and human's perception will be mainly concerned in this proposal

Regional Gray Matter Density Associated with Cognitive Reflectivity–Impulsivity: Evidence from Voxel-Based Morphometry

PubMed Central

Yokoyama, Ryoichi; Nozawa, Takayuki; Takeuchi, Hikaru; Taki, Yasuyuki; Sekiguchi, Atsushi; Nouchi, Rui; Kotozaki, Yuka; Nakagawa, Seishu; Miyauchi, Carlos Makoto; Iizuka, Kunio; Shinada, Takamitsu; Yamamoto, Yuki; Hanawa, Sugiko; Araki, Tsuyoshi; Hashizume, Hiroshi; Kunitoki, Keiko; Hanihara, Mayu; Sassa, Yuko; Kawashima, Ryuta

2015-01-01

When faced with a problem or choice, humans can use two different strategies: “cognitive reflectivity,” which involves slow responses and fewer mistakes, or “cognitive impulsivity,” which comprises of quick responses and more mistakes. Different individuals use these two strategies differently. To our knowledge, no study has directly investigated the brain regions involved in reflectivity–impulsivity; therefore, this study focused on associations between these cognitive strategies and the gray matter structure of several brain regions. In order to accomplish this, we enrolled 776 healthy, right-handed individuals (432 men and 344 women; 20.7 ± 1.8 years) and used voxel-based morphometry with administration of a cognitive reflectivity–impulsivity questionnaire. We found that high cognitive reflectivity was associated with greater regional gray matter density in the ventral medial prefrontal cortex. Our finding suggests that this area plays an important role in defining an individual’s trait associated with reflectivity and impulsivity. PMID:25803809

Neurotoxic Effects of Anthracycline- vs Nonanthracycline-Based Chemotherapy on Cognition in Breast Cancer Survivors.

PubMed

Kesler, Shelli R; Blayney, Douglas W

2016-02-01

Chemotherapy exposure is a known risk factor for cancer-related cognitive impairments. Anthracycline-based regimens are commonly used chemotherapies that have been shown to be associated with cognitive impairment and brain changes in clinical studies. To directly compare the effects of anthracycline and nonanthracycline regimens on cognitive status and functional brain connectivity. In this observational study, we retrospectively examined cognitive and resting state functional magnetic resonance imaging data acquired from 62 primary breast cancer survivors (mean [SD] age, 54.7 [8.5] years) who were more than 2 years off-therapy, on average. Twenty of these women received anthracycline-based chemotherapy as part of their primary treatment, 19 received nonanthracycline regimens, and 23 did not receive any chemotherapy. Participants were enrolled at a single academic institution (Stanford University) from 2008 to 2014, and the study analyses were performed at this time. Cognitive status was measured using standardized neuropsychological tests, and functional brain connectivity was evaluated using resting state functional magnetic resonance imaging with a focus on the brain's default mode network. The anthracycline group demonstrated significantly lower verbal memory performance including immediate recall (F = 3.73; P = .03) and delayed recall (F = 11.11; P < .001) as well as lower left precuneus connectivity (F = 7.48; P = .001) compared with the other 2 groups. Patient-reported outcomes related to cognitive dysfunction (F = 7.27; P = .002) and psychological distress (F = 5.64; P = .006) were similarly elevated in both chemotherapy groups compared with the non-chemotherapy-treated controls. These results suggest that anthracyclines may have greater negative effects than nonanthracycline regimens on particular cognitive domains and brain network connections. Both anthracycline and nonanthracycline regimens may have nonspecific effects on other cognitive

Cognitive Assessment of Movement-Based Computer Games

NASA Technical Reports Server (NTRS)

Kearney, Paul

2008-01-01

This paper examines the possibility that dance games such as Dance Dance Revolution or StepMania enhance the cognitive abilities that are critical to academic achievement. These games appear to place a high cognitive load on working memory requiring the player to convert a visual signal to a physical movement up to 7 times per second. Players see a pattern of directions displayed on the screen and they memorise these as a dance sequence. Other researchers have found that attention span and memory ability, both cognitive abilities required for academic achievement, are improved through the use of physical movement and exercise. This paper reviews these claims and documents tool development for on-going research by the author.

An OFDM System Using Polyphase Filter and DFT Architecture for Very High Data Rate Applications

NASA Technical Reports Server (NTRS)

Kifle, Muli; Andro, Monty; Vanderaar, Mark J.

2001-01-01

This paper presents a conceptual architectural design of a four-channel Orthogonal Frequency Division Multiplexing (OFDM) system with an aggregate information throughput of 622 megabits per second (Mbps). Primary emphasis is placed on the generation and detection of the composite waveform using polyphase filter and Discrete Fourier Transform (DFT) approaches to digitally stack and bandlimit the individual carriers. The four-channel approach enables the implementation of a system that can be both power and bandwidth efficient, yet enough parallelism exists to meet higher data rate goals. It also enables a DC power efficient transmitter that is suitable for on-board satellite systems, and a moderately complex receiver that is suitable for low-cost ground terminals. The major advantage of the system as compared to a single channel system is lower complexity and DC power consumption. This is because the highest sample rate is half that of the single channel system and synchronization can occur at most, depending on the synchronization technique, a quarter of the rate of a single channel system. The major disadvantage is the increased peak-to-average power ratio over the single channel system. Simulation results in a form of bit-error-rate (BER) curves are presented in this paper.

60-GHz optical/wireless MIMO system integrated with optical subcarrier multiplexing and 2x2 wireless communication.

PubMed

Lin, Chi-Hsiang; Lin, Chun-Ting; Huang, Hou-Tzu; Zeng, Wei-Siang; Chiang, Shou-Chih; Chang, Hsi-Yu

2015-05-04

This paper proposes a 2x2 MIMO OFDM Radio-over-Fiber scheme based on optical subcarrier multiplexing and 60-GHz MIMO wireless transmission. We also schematically investigated the principle of optical subcarrier multiplexing, which is based on a dual-parallel Mach-Zehnder modulator (DP-MZM). In our simulation result, combining two MIMO OFDM signals to drive DP-MZM gives rise to the PAPR augmentation of less than 0.4 dB, which mitigates nonlinear distortion. Moreover, we applied a Levin-Campello bit-loading algorithm to compensate for the uneven frequency responses in the V-band. The resulting system achieves OFDM signal rates of 61.5-Gbits/s with BER of 10(-3) over 25-km SMF transmission followed by 3-m wireless transmission.

How to Train an Injured Brain? A Pilot Feasibility Study of Home-Based Computerized Cognitive Training.

PubMed

Verhelst, Helena; Vander Linden, Catharine; Vingerhoets, Guy; Caeyenberghs, Karen

2017-02-01

Computerized cognitive training programs have previously shown to be effective in improving cognitive abilities in patients suffering from traumatic brain injury (TBI). These studies often focused on a single cognitive function or required expensive hardware, making it difficult to be used in a home-based environment. This pilot feasibility study aimed to evaluate the feasibility of a newly developed, home-based, computerized cognitive training program for adolescents who suffered from TBI. Additionally, feasibility of study design, procedures, and measurements were examined. Case series, longitudinal, pilot, feasibility intervention study with one baseline and two follow-up assessments. Nine feasibility outcome measures and criteria for success were defined, including accessibility, training motivation/user experience, technical smoothness, training compliance, participation willingness, participation rates, loss to follow-up, assessment timescale, and assessment procedures. Five adolescent patients (four boys, mean age = 16 years 7 months, standard deviation = 9 months) with moderate to severe TBI in the chronic stage were recruited and received 8 weeks of cognitive training with BrainGames. Effect sizes (Cohen's d) were calculated to determine possible training-related effects. The new cognitive training intervention, BrainGames, and study design and procedures proved to be feasible; all nine feasibility outcome criteria were met during this pilot feasibility study. Estimates of effect sizes showed small to very large effects on cognitive measures and questionnaires, which were retained after 6 months. Our pilot study shows that a longitudinal intervention study comprising our novel, computerized cognitive training program and two follow-up assessments is feasible in adolescents suffering from TBI in the chronic stage. Future studies with larger sample sizes will evaluate training-related effects on cognitive functions and underlying brain structures.

Using cognitive architectures to study issues in team cognition in a complex task environment

NASA Astrophysics Data System (ADS)

Smart, Paul R.; Sycara, Katia; Tang, Yuqing

2014-05-01

Cognitive social simulation is a computer simulation technique that aims to improve our understanding of the dynamics of socially-situated and socially-distributed cognition. This makes cognitive social simulation techniques particularly appealing as a means to undertake experiments into team cognition. The current paper reports on the results of an ongoing effort to develop a cognitive social simulation capability that can be used to undertake studies into team cognition using the ACT-R cognitive architecture. This capability is intended to support simulation experiments using a team-based problem solving task, which has been used to explore the effect of different organizational environments on collective problem solving performance. The functionality of the ACT-R-based cognitive social simulation capability is presented and a number of areas of future development work are outlined. The paper also describes the motivation for adopting cognitive architectures in the context of social simulation experiments and presents a number of research areas where cognitive social simulation may be useful in developing a better understanding of the dynamics of team cognition. These include the use of cognitive social simulation to study the role of cognitive processes in determining aspects of communicative behavior, as well as the impact of communicative behavior on the shaping of task-relevant cognitive processes (e.g., the social shaping of individual and collective memory as a result of communicative exchanges). We suggest that the ability to perform cognitive social simulation experiments in these areas will help to elucidate some of the complex interactions that exist between cognitive, social, technological and informational factors in the context of team-based problem-solving activities.

Future Cognitive Ability: US IQ Prediction until 2060 Based on NAEP.

PubMed

Rindermann, Heiner; Pichelmann, Stefan

2015-01-01

The US National Assessment of Educational Progress (NAEP) measures cognitive competences in reading and mathematics of US students (last 2012 survey N = 50,000). The long-term development based on results from 1971 to 2012 allows a prediction of future cognitive trends. For predicting US averages also demographic trends have to be considered. The largest groups' (White) average of 1978/80 was set at M = 100 and SD = 15 and was used as a benchmark. Based on two past NAEP development periods for 17-year-old students, 1978/80 to 2012 (more optimistic) and 1992 to 2012 (more pessimistic), and demographic projections from the US Census Bureau, cognitive trends until 2060 for the entire age cohort and ethnic groups were estimated. Estimated population averages for 2060 are 103 (optimistic) or 102 (pessimistic). The average rise per decade is dec = 0.76 or 0.45 IQ points. White-Black and White-Hispanic gaps are declining by half, Asian-White gaps treble. The catch-up of minorities (their faster ability growth) contributes around 2 IQ to the general rise of 3 IQ; however, their larger demographic increase reduces the general rise at about the similar amount (-1.4 IQ). Because minorities with faster ability growth also rise in their population proportion the interactive term is positive (around 1 IQ). Consequences for economic and societal development are discussed.

Future Cognitive Ability: US IQ Prediction until 2060 Based on NAEP

PubMed Central

2015-01-01

The US National Assessment of Educational Progress (NAEP) measures cognitive competences in reading and mathematics of US students (last 2012 survey N = 50,000). The long-term development based on results from 1971 to 2012 allows a prediction of future cognitive trends. For predicting US averages also demographic trends have to be considered. The largest groups’ (White) average of 1978/80 was set at M = 100 and SD = 15 and was used as a benchmark. Based on two past NAEP development periods for 17-year-old students, 1978/80 to 2012 (more optimistic) and 1992 to 2012 (more pessimistic), and demographic projections from the US Census Bureau, cognitive trends until 2060 for the entire age cohort and ethnic groups were estimated. Estimated population averages for 2060 are 103 (optimistic) or 102 (pessimistic). The average rise per decade is dec = 0.76 or 0.45 IQ points. White-Black and White-Hispanic gaps are declining by half, Asian-White gaps treble. The catch-up of minorities (their faster ability growth) contributes around 2 IQ to the general rise of 3 IQ; however, their larger demographic increase reduces the general rise at about the similar amount (-1.4 IQ). Because minorities with faster ability growth also rise in their population proportion the interactive term is positive (around 1 IQ). Consequences for economic and societal development are discussed. PMID:26460731

Validation of a Smartphone-Based Approach to In Situ Cognitive Fatigue Assessment

PubMed Central

Linden, Mark

2017-01-01

The most highly correlated results were from the PVT, which showed a positive correlation with those from the prevalidated MFS, measuring 0.342 (P<.008). Scores from the cognitive tests were entered into a regression model and showed that only reaction time in the PVT was a significant predictor of fatigue (P=.016, F=2.682, 95% CI 9.0-84.2). Higher scores on the MFS were related to increases in reaction time during our mobile variant of the PVT. Conclusions The results show that the PVT mobile cognitive test developed for this study could be used as a valid and reliable method for measuring cognitive fatigue in situ. This test would remove the subjectivity associated with established self-assessment approaches and the need for assessments to be performed in a medical setting. Based on our findings, future work could explore delivering a small set of tests with increased duration to further improve measurement reliability. Moreover, as the smartphone assessment tool can be used as part of everyday life, additional sources of data relating to physiological, psychological, and environmental context could be included within the analysis to improve the nature and precision of the assessment process. PMID:28818818

Validation of a Smartphone-Based Approach to In Situ Cognitive Fatigue Assessment.

PubMed

Price, Edward; Moore, George; Galway, Leo; Linden, Mark

2017-08-17

were from the PVT, which showed a positive correlation with those from the prevalidated MFS, measuring 0.342 (P<.008). Scores from the cognitive tests were entered into a regression model and showed that only reaction time in the PVT was a significant predictor of fatigue (P=.016, F=2.682, 95% CI 9.0-84.2). Higher scores on the MFS were related to increases in reaction time during our mobile variant of the PVT. The results show that the PVT mobile cognitive test developed for this study could be used as a valid and reliable method for measuring cognitive fatigue in situ. This test would remove the subjectivity associated with established self-assessment approaches and the need for assessments to be performed in a medical setting. Based on our findings, future work could explore delivering a small set of tests with increased duration to further improve measurement reliability. Moreover, as the smartphone assessment tool can be used as part of everyday life, additional sources of data relating to physiological, psychological, and environmental context could be included within the analysis to improve the nature and precision of the assessment process. ©Edward Price, George Moore, Leo Galway, Mark Linden. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 17.08.2017.

The Design and the Formative Evaluation of an Adaptive Educational System Based on Cognitive Styles

ERIC Educational Resources Information Center

Triantafillou, Evangelos; Pomportsis, Andreas; Demetriadis, Stavros

2003-01-01

Adaptive Hypermedia Systems (AHS) can be developed to accommodate a variety of individual differences, including learning style and cognitive style. The current research is an attempt to examine some of the critical variables, which may be important in the design of an Adaptive Educational System (AES) based on student's cognitive style. Moreover,…

Baseline Predictors for Success Following Strategy-Based Cognitive Remediation Group Training in Schizophrenia.

PubMed

Farreny, Aida; Aguado, Jaume; Corbera, Silvia; Ochoa, Susana; Huerta-Ramos, Elena; Usall, Judith

2016-08-01

Our aim was to examine predictive variables associated with the improvement in cognitive, clinical, and functional outcomes after outpatient participation in REPYFLEC strategy-based Cognitive Remediation (CR) group training. In addition, we investigated which factors might be associated with some long-lasting effects at 6 months' follow-up. Predictors of improvement after CR were studied in a sample of 29 outpatients with schizophrenia. Partial correlations were computed between targeted variables and outcomes of response to explore significant associations. Subsequently, we built linear regression models for each outcome variable and predictors of improvement. The improvement in negative symptoms at posttreatment was linked to faster performance in the Trail Making Test B. Disorganization and cognitive symptoms were related to changes in executive function at follow-up. Lower levels of positive symptoms were related to durable improvements in life skills. Levels of symptoms and cognition were associated with improvements following CR, but the pattern of resulting associations was nonspecific.