Science.gov

Sample records for hoc cognitive radio

  1. Reinforcement learning for routing in cognitive radio ad hoc networks.

    PubMed

    Al-Rawi, Hasan A A; Yau, Kok-Lim Alvin; Mohamad, Hafizal; Ramli, Nordin; Hashim, Wahidah

    2014-01-01

    Cognitive radio (CR) enables unlicensed users (or secondary users, SUs) to sense for and exploit underutilized licensed spectrum owned by the licensed users (or primary users, PUs). Reinforcement learning (RL) is an artificial intelligence approach that enables a node to observe, learn, and make appropriate decisions on action selection in order to maximize network performance. Routing enables a source node to search for a least-cost route to its destination node. While there have been increasing efforts to enhance the traditional RL approach for routing in wireless networks, this research area remains largely unexplored in the domain of routing in CR networks. This paper applies RL in routing and investigates the effects of various features of RL (i.e., reward function, exploitation, and exploration, as well as learning rate) through simulation. New approaches and recommendations are proposed to enhance the features in order to improve the network performance brought about by RL to routing. Simulation results show that the RL parameters of the reward function, exploitation, and exploration, as well as learning rate, must be well regulated, and the new approaches proposed in this paper improves SUs' network performance without significantly jeopardizing PUs' network performance, specifically SUs' interference to PUs.

  2. Reinforcement Learning for Routing in Cognitive Radio Ad Hoc Networks

    PubMed Central

    Al-Rawi, Hasan A. A.; Mohamad, Hafizal; Hashim, Wahidah

    2014-01-01

    Cognitive radio (CR) enables unlicensed users (or secondary users, SUs) to sense for and exploit underutilized licensed spectrum owned by the licensed users (or primary users, PUs). Reinforcement learning (RL) is an artificial intelligence approach that enables a node to observe, learn, and make appropriate decisions on action selection in order to maximize network performance. Routing enables a source node to search for a least-cost route to its destination node. While there have been increasing efforts to enhance the traditional RL approach for routing in wireless networks, this research area remains largely unexplored in the domain of routing in CR networks. This paper applies RL in routing and investigates the effects of various features of RL (i.e., reward function, exploitation, and exploration, as well as learning rate) through simulation. New approaches and recommendations are proposed to enhance the features in order to improve the network performance brought about by RL to routing. Simulation results show that the RL parameters of the reward function, exploitation, and exploration, as well as learning rate, must be well regulated, and the new approaches proposed in this paper improves SUs' network performance without significantly jeopardizing PUs' network performance, specifically SUs' interference to PUs. PMID:25140350

  3. Opportunistic Hybrid Transport Protocol (OHTP) for Cognitive Radio Ad Hoc Sensor Networks.

    PubMed

    Bin Zikria, Yousaf; Nosheen, Summera; Ishmanov, Farruh; Kim, Sung Won

    2015-12-15

    The inefficient assignment of spectrum for different communications purposes, plus technology enhancements and ever-increasing usage of wireless technology is causing spectrum scarcity. To address this issue, one of the proposed solutions in the literature is to access the spectrum dynamically or opportunistically. Therefore, the concept of cognitive radio appeared, which opens up a new research paradigm. There is extensive research on the physical, medium access control and network layers. The impact of the transport layer on the performance of cognitive radio ad hoc sensor networks is still unknown/unexplored. The Internet's de facto transport protocol is not well suited to wireless networks because of its congestion control mechanism. We propose an opportunistic hybrid transport protocol for cognitive radio ad hoc sensor networks. We developed a new congestion control mechanism to differentiate true congestion from interruption loss. After such detection and differentiation, we propose methods to handle them opportunistically. There are several benefits to window- and rate-based protocols. To exploit the benefits of both in order to enhance overall system performance, we propose a hybrid transport protocol. We empirically calculate the optimal threshold value to switch between window- and rate-based mechanisms. We then compare our proposed transport protocol to Transmission Control Protocol (TCP)-friendly rate control, TCP-friendly rate control for cognitive radio, and TCP-friendly window-based control. We ran an extensive set of simulations in Network Simulator 2. The results indicate that the proposed transport protocol performs better than all the others.

  4. A Sensitive Secondary Users Selection Algorithm for Cognitive Radio Ad Hoc Networks

    PubMed Central

    Li, Aohan; Han, Guangjie; Wan, Liangtian; Shu, Lei

    2016-01-01

    Secondary Users (SUs) are allowed to use the temporarily unused licensed spectrum without disturbing Primary Users (PUs) in Cognitive Radio Ad Hoc Networks (CRAHNs). Existing architectures for CRAHNs impose energy-consuming Cognitive Radios (CRs) on SUs. However, the advanced CRs will increase energy cost for their cognitive functionalities, which is undesirable for the battery powered devices. A new architecture referred to as spectral Requirement-based CRAHN (RCRAHN) is proposed to enhance energy efficiency for CRAHNs in this paper. In RCRAHNs, only parts of SUs are equipped with CRs. SUs equipped with CRs are referred to as Cognitive Radio Users (CRUs). To further enhance energy efficiency of CRAHNs, we aim to select minimum CRUs to sense available spectrum. A non-linear programming problem is mathematically formulated under the constraints of energy efficiency and real-time. Considering the NP-hardness of the problem, a framework of a heuristic algorithm referred to as Sensitive Secondary Users Selection (SSUS) was designed to compute the near-optimal solutions. The simulation results demonstrate that SSUS not only improves the energy efficiency, but also achieves satisfied performances in end-to-end delay and communication reliability. PMID:27023562

  5. Space Telecommunications Radio System STRS Cognitive Radio

    NASA Technical Reports Server (NTRS)

    Briones, Janette C.; Handler, Louis M.

    2013-01-01

    Radios today are evolving from awareness toward cognition. A software defined radio (SDR) provides the most capability for integrating autonomic decision making ability and allows the incremental evolution toward a cognitive radio. This cognitive radio technology will impact NASA space communications in areas such as spectrum utilization, interoperability, network operations, and radio resource management over a wide range of operating conditions. NASAs cognitive radio will build upon the infrastructure being developed by Space Telecommunication Radio System (STRS) SDR technology. This paper explores the feasibility of inserting cognitive capabilities in the NASA STRS architecture and the interfaces between the cognitive engine and the STRS radio. The STRS architecture defines methods that can inform the cognitive engine about the radio environment so that the cognitive engine can learn autonomously from experience, and take appropriate actions to adapt the radio operating characteristics and optimize performance.

  6. Cognitive Radio Wireless Sensor Networks: Applications, Challenges and Research Trends

    PubMed Central

    Joshi, Gyanendra Prasad; Nam, Seung Yeob; Kim, Sung Won

    2013-01-01

    A cognitive radio wireless sensor network is one of the candidate areas where cognitive techniques can be used for opportunistic spectrum access. Research in this area is still in its infancy, but it is progressing rapidly. The aim of this study is to classify the existing literature of this fast emerging application area of cognitive radio wireless sensor networks, highlight the key research that has already been undertaken, and indicate open problems. This paper describes the advantages of cognitive radio wireless sensor networks, the difference between ad hoc cognitive radio networks, wireless sensor networks, and cognitive radio wireless sensor networks, potential application areas of cognitive radio wireless sensor networks, challenges and research trend in cognitive radio wireless sensor networks. The sensing schemes suited for cognitive radio wireless sensor networks scenarios are discussed with an emphasis on cooperation and spectrum access methods that ensure the availability of the required QoS. Finally, this paper lists several open research challenges aimed at drawing the attention of the readers toward the important issues that need to be addressed before the vision of completely autonomous cognitive radio wireless sensor networks can be realized. PMID:23974152

  7. Cognitive radio wireless sensor networks: applications, challenges and research trends.

    PubMed

    Joshi, Gyanendra Prasad; Nam, Seung Yeob; Kim, Sung Won

    2013-08-22

    A cognitive radio wireless sensor network is one of the candidate areas where cognitive techniques can be used for opportunistic spectrum access. Research in this area is still in its infancy, but it is progressing rapidly. The aim of this study is to classify the existing literature of this fast emerging application area of cognitive radio wireless sensor networks, highlight the key research that has already been undertaken, and indicate open problems. This paper describes the advantages of cognitive radio wireless sensor networks, the difference between ad hoc cognitive radio networks, wireless sensor networks, and cognitive radio wireless sensor networks, potential application areas of cognitive radio wireless sensor networks, challenges and research trend in cognitive radio wireless sensor networks. The sensing schemes suited for cognitive radio wireless sensor networks scenarios are discussed with an emphasis on cooperation and spectrum access methods that ensure the availability of the required QoS. Finally, this paper lists several open research challenges aimed at drawing the attention of the readers toward the important issues that need to be addressed before the vision of completely autonomous cognitive radio wireless sensor networks can be realized.

  8. 75 FR 10439 - Cognitive Radio Technologies and Software Defined Radios

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-08

    ... COMMISSION 47 CFR Part 2 Cognitive Radio Technologies and Software Defined Radios AGENCY: Federal... implement security features in software defined radios (SDRs). While, the Commission dismisses this petition... Order 1. On March 17, 2005, the Commission adopted the Cognitive Radio Report and Order, 70 FR...

  9. Assessing Routing Strategies for Cognitive Radio Sensor Networks

    PubMed Central

    Zubair, Suleiman; Fisal, Norsheila; Baguda, Yakubu S.; Saleem, Kashif

    2013-01-01

    Interest in the cognitive radio sensor network (CRSN) paradigm has gradually grown among researchers. This concept seeks to fuse the benefits of dynamic spectrum access into the sensor network, making it a potential player in the next generation (NextGen) network, which is characterized by ubiquity. Notwithstanding its massive potential, little research activity has been dedicated to the network layer. By contrast, we find recent research trends focusing on the physical layer, the link layer and the transport layers. The fact that the cross-layer approach is imperative, due to the resource-constrained nature of CRSNs, can make the design of unique solutions non-trivial in this respect. This paper seeks to explore possible design opportunities with wireless sensor networks (WSNs), cognitive radio ad-hoc networks (CRAHNs) and cross-layer considerations for implementing viable CRSN routing solutions. Additionally, a detailed performance evaluation of WSN routing strategies in a cognitive radio environment is performed to expose research gaps. With this work, we intend to lay a foundation for developing CRSN routing solutions and to establish a basis for future work in this area. PMID:24077319

  10. Cognitive Radio will revolutionize American transportation

    ScienceCinema

    None

    2016-07-12

    Cognitive Radio will revolutionize American transportation. Through smart technology, it will anticipate user needs; detect available bandwidths and frequencies then seamlessly connect vehicles, infrastructures, and consumer devices; and it will support the Department of Transportation IntelliDrive Program, helping researchers, auto manufacturers, and Federal and State officials advance the connectivity of US transportation systems for improved safety, mobility, and environmental conditions. Using cognitive radio, a commercial vehicle will know its driver, onboard freight and destination route. Drivers will save time and resources communicating with automatic toll booths and know ahead of time whether to stop at a weigh station or keep rolling. At accident scenes, cognitive radio sensors on freight and transportation modes can alert emergency personnel and measure on-site, real-time conditions such as a chemical leak. The sensors will connect freight to industry, relaying shipment conditions and new delivery schedules. For industry or military purposes, cognitive radio will enable real-time freight tracking around the globe and its sensory technology can help prevent cargo theft or tampering by alerting shipper and receiver if freight is tampered with while en route. For the average consumer, a vehicle will tailor the transportation experience to the passenger such as delivering age-appropriate movies via satellite. Cognitive radio will enhance transportation safety by continually sensing what is important to the user adapting to its environment and incoming information, and proposing solutions that improve mobility and quality of life.

  11. Cognitive Radio will revolutionize American transportation

    SciTech Connect

    2013-07-22

    Cognitive Radio will revolutionize American transportation. Through smart technology, it will anticipate user needs; detect available bandwidths and frequencies then seamlessly connect vehicles, infrastructures, and consumer devices; and it will support the Department of Transportation IntelliDrive Program, helping researchers, auto manufacturers, and Federal and State officials advance the connectivity of US transportation systems for improved safety, mobility, and environmental conditions. Using cognitive radio, a commercial vehicle will know its driver, onboard freight and destination route. Drivers will save time and resources communicating with automatic toll booths and know ahead of time whether to stop at a weigh station or keep rolling. At accident scenes, cognitive radio sensors on freight and transportation modes can alert emergency personnel and measure on-site, real-time conditions such as a chemical leak. The sensors will connect freight to industry, relaying shipment conditions and new delivery schedules. For industry or military purposes, cognitive radio will enable real-time freight tracking around the globe and its sensory technology can help prevent cargo theft or tampering by alerting shipper and receiver if freight is tampered with while en route. For the average consumer, a vehicle will tailor the transportation experience to the passenger such as delivering age-appropriate movies via satellite. Cognitive radio will enhance transportation safety by continually sensing what is important to the user adapting to its environment and incoming information, and proposing solutions that improve mobility and quality of life.

  12. Reconfigurable, Cognitive Software-Defined Radio

    NASA Technical Reports Server (NTRS)

    Bhat, Arvind

    2015-01-01

    Software-defined radio (SDR) technology allows radios to be reconfigured to perform different communication functions without using multiple radios to accomplish each task. Intelligent Automation, Inc., has developed SDR platforms that switch adaptively between different operation modes. The innovation works by modifying both transmit waveforms and receiver signal processing tasks. In Phase I of the project, the company developed SDR cognitive capabilities, including adaptive modulation and coding (AMC), automatic modulation recognition (AMR), and spectrum sensing. In Phase II, these capabilities were integrated into SDR platforms. The reconfigurable transceiver design employs high-speed field-programmable gate arrays, enabling multimode operation and scalable architecture. Designs are based on commercial off-the-shelf (COTS) components and are modular in nature, making it easier to upgrade individual components rather than redesigning the entire SDR platform as technology advances.

  13. Pliable Cognitive MAC for Heterogeneous Adaptive Cognitive Radio Sensor Networks

    PubMed Central

    Ali, Borhanuddin Mohd; Sali, Aduwati

    2016-01-01

    The rapid expansion of wireless monitoring and surveillance applications in several domains reinforces the trend of exploiting emerging technologies such as the cognitive radio. However, these technologies have to adjust their working concepts to consider the common characteristics of conventional wireless sensor networks (WSNs). The cognitive radio sensor network (CRSN), still an immature technology, has to deal with new networks that might have different types of data, traffic patterns, or quality of service (QoS) requirements. In this paper, we design and model a new cognitive radio-based medium access control (MAC) algorithm dealing with the heterogeneous nature of the developed networks in terms of either the traffic pattern or the required QoS for the node applications. The proposed algorithm decreases the consumed power on several fronts, provides satisfactory levels of latency and spectrum utilization with efficient scheduling, and manages the radio resources for various traffic conditions. An intensive performance evaluation is conducted to study the impact of key parameters such as the channel idle time length, node density, and the number of available channels. The performance evaluation of the proposed algorithm shows a better performance than the comparable protocols. Moreover, the results manifest that the proposed algorithm is suitable for real time monitoring applications. PMID:27257964

  14. Cognitive Radio Networks for Tactical Wireless Communications

    DTIC Science & Technology

    2014-12-01

    the international defence scientific community in this area, and describe our own approach to security solutions for cognitive radio networks. Our...communications. DRDC-RDDC-2014-R185 i Résumé …….. Le champ de bataille moderne est un environnement exigeant pour les réseaux de...et la réduction de l’encombrement du spectre, une résilience accrue des communications dans des environnements hétérogènes dynamiques, en plus de

  15. Software defined radio based multi-carrier multi-function waveform for cognitive radio

    NASA Astrophysics Data System (ADS)

    Zhou, Ruolin; Li, Xue; Chakravarthy, Vasu; Wu, Zhiqiang

    2010-04-01

    In this paper, we demonstrate an adaptive multicarrier multi-function waveform generator for cognitive radio via software defined radio. Using a USRP (universal software radio peripheral) software defined radio boards and GNU radio software, we implement a multi-carrier waveform generator which can generate multi-function waveforms such as OFDM, NC-OFDM, MC-CDMA, NC-MC-CDMA, CI/MC-CDMA, NCCI/ MC-CDMA, TDCS for cognitive radio. Additionally, we demonstrate a portable overlay cognitive radio using this multicarrier multi-function waveform generator. This cognitive radio is capable of detecting primary users in real time and adaptively adjusting its transmission parameters to avoid interference to primary users. More importantly, this cognitive radio can take advantage of multiple spectrum holes by employing non-contiguous multi-carrier transmission technologies. Additionally, we demonstrate that when the primary user transmission changes, the cognitive radio dynamically adjusts its transmission accordingly. We also demonstrate seamless real time video transmission between two cognitive radio nodes, while avoiding interference from primary users and interference to primary users operating in the same spectrum.

  16. Test and Evaluation Enhancements for Cognitive Radio Technologies

    DTIC Science & Technology

    2015-05-13

    Radio Technologies The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued as an official...Final Report: Test and Evaluation Enhancements for Cognitive Radio Technologies Report Title This document serves as the final report for the...Instrumentation Grant (W911NF-14-1-0042) TEST & EVALUATION ENHANCEMENTS FOR COGNITIVE RADIO TECHNOLOGIES Final Report Dr. Willie L. Thompson, II

  17. Optimal Consensus Based Decentralized Cooperative Spectrum Sensing in Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Shen, Liang; Xu, Yuhua; Gao, Zhan; Wu, Qihui

    2013-03-01

    We study the problem of decentralized cooperative spectrum sensing in cognitive radio ad hoc networks without a fusion center, using a consensus based solution. First, the received logarithmic likelihood ratio (LLR) is employed as the local detection outcome; then, it is exchanged between neighboring CR users and is updated based on the LLR received from the neighbors. It is proved that with the proposed decentralized algorithm, the optimal sensing performance is achieved via just local information exchange between neighbors. In addition, it is shown that the proposed algorithm outperforms previous work in which the received energy was employed as the local detection outcome.

  18. Performance evaluation of cognitive radio in advanced metering infrastructure communication

    NASA Astrophysics Data System (ADS)

    Hiew, Yik-Kuan; Mohd Aripin, Norazizah; Din, Norashidah Md

    2016-03-01

    Smart grid is an intelligent electricity grid system. A reliable two-way communication system is required to transmit both critical and non-critical smart grid data. However, it is difficult to locate a huge chunk of dedicated spectrum for smart grid communications. Hence, cognitive radio based communication is applied. Cognitive radio allows smart grid users to access licensed spectrums opportunistically with the constraint of not causing harmful interference to licensed users. In this paper, a cognitive radio based smart grid communication framework is proposed. Smart grid framework consists of Home Area Network (HAN) and Advanced Metering Infrastructure (AMI), while AMI is made up of Neighborhood Area Network (NAN) and Wide Area Network (WAN). In this paper, the authors only report the findings for AMI communication. AMI is smart grid domain that comprises smart meters, data aggregator unit, and billing center. Meter data are collected by smart meters and transmitted to data aggregator unit by using cognitive 802.11 technique; data aggregator unit then relays the data to billing center using cognitive WiMAX and TV white space. The performance of cognitive radio in AMI communication is investigated using Network Simulator 2. Simulation results show that cognitive radio improves the latency and throughput performances of AMI. Besides, cognitive radio also improves spectrum utilization efficiency of WiMAX band from 5.92% to 9.24% and duty cycle of TV band from 6.6% to 10.77%.

  19. A Method for Dynamic Reconfiguration of a Cognitive Radio System

    DTIC Science & Technology

    2006-01-01

    17 2.1.4 Virtual Radios/VANU Inc . . . . . . . . . . . . . . . . . . . . . . 17 2.1.5 End to End Reconfiguratility (E2R...DARPA neXt Generation 2004 Vanu Inc . GSM Basestation Figure 2.1: Timeline of Software-Defined and Cognitive Radio Developments 2.1.1 SPEAKeasy: Military...modulation type, and data rate. 2.1.4 Virtual Radios/VANU Inc . Around 1995 there was a large amount of interest in the transition from special- ized

  20. 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%.

  1. Reconfigurable Antenna and Cognitive Radio for Space Applications

    NASA Technical Reports Server (NTRS)

    Hwu, Shian U.

    2012-01-01

    This presentation briefly discusses a research effort on mitigation techniques of radio frequency interference (RFI) on communication systems for possible space applications. This problem is of considerable interest in the context of providing reliable communications to the space vehicle which might suffer severe performance degradation due to RFI sources such as visiting spacecrafts and various ground radar systems. This study proposes a communication system with Reconfigurable Antenna (RA) and Cognitive Radio (CR) to mitigate the RFI impact. A cognitive radio is an intelligent radio that is able to learn from the environment and adapt to the variations in its surrounding by adjusting the transmit power, carrier frequency, modulation strategy or transmission data rate. Therefore, the main objective of a cognitive radio system is to ensure highly reliable communication whenever and wherever needed. To match the intelligent adaptability of the cognitive radio, a reconfigurable antenna system will be required to ensure the system performance. The technical challenges in design such a system will be discussed in this presentation.

  2. Intelligent cognitive radio jamming - a game-theoretical approach

    NASA Astrophysics Data System (ADS)

    Dabcevic, Kresimir; Betancourt, Alejandro; Marcenaro, Lucio; Regazzoni, Carlo S.

    2014-12-01

    Cognitive radio (CR) promises to be a solution for the spectrum underutilization problems. However, security issues pertaining to cognitive radio technology are still an understudied topic. One of the prevailing such issues are intelligent radio frequency (RF) jamming attacks, where adversaries are able to exploit on-the-fly reconfigurability potentials and learning mechanisms of cognitive radios in order to devise and deploy advanced jamming tactics. In this paper, we use a game-theoretical approach to analyze jamming/anti-jamming behavior between cognitive radio systems. A non-zero-sum game with incomplete information on an opponent's strategy and payoff is modelled as an extension of Markov decision process (MDP). Learning algorithms based on adaptive payoff play and fictitious play are considered. A combination of frequency hopping and power alteration is deployed as an anti-jamming scheme. A real-life software-defined radio (SDR) platform is used in order to perform measurements useful for quantifying the jamming impacts, as well as to infer relevant hardware-related properties. Results of these measurements are then used as parameters for the modelled jamming/anti-jamming game and are compared to the Nash equilibrium of the game. Simulation results indicate, among other, the benefit provided to the jammer when it is employed with the spectrum sensing algorithm in proactive frequency hopping and power alteration schemes.

  3. Linear QoS goals of additive and concave metrics in ad hoc cognitive packet routing.

    PubMed

    Lent, Ricardo

    2006-12-01

    This paper addresses two scalability problems related to the cognitive map of packets in ad hoc cognitive packet networks and proposes a solution. Previous works have included latency as part of the routing goal of smart packets, which requires packets to collect their arrival time at each node in a path. Such a requirement resulted in a packet overhead proportional to the path length. The second problem is that the multiplicative form of path availability, which was employed to measure resources, loses accuracy in long paths. To solve these problems, new goals are proposed in this paper. These goals are linear functions of low-overhead metrics and can provide similar performance results with lower cost. One direct result shown in simulation is that smart packets driven by a linear function of path length and buffer occupancy can effectively balance the traffic of multiple flows without the large overhead that would be needed if round-trip delay was used. In addition, energy-aware routing is also studied under this scheme as well as link selection based on their expected level of security.

  4. A Test Methodology for Evaluating Cognitive Radio Systems

    DTIC Science & Technology

    2014-03-27

    radio network CRS cognitive radio system CUT component under test d- OFDM dis-contiguous OFDM DSA dynamic spectrum access DYSE dynamic spectrum...array FSK frequency shift keying OFDM orthogonal frequency division multiplexing OODA Observe-Orient-Decide-Act OSA Opportunistic Spectrum Access PER...waveforms are used in this experiment: frequency shift keying (FSK), orthogonal frequency division multiplexing ( OFDM ), and dis-contiguous OFDM (d- OFDM

  5. Effective Management of Secondary User's Density in Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Jiang, Chunxiao; Fan, Shuai; Chen, Canfeng; Ma, Jian; Ren, Yong

    Cognitive radio has emerged as an efficient approach to reusing the licensed spectrums. How to appropriately set parameters of secondary user (SU) plays a rather important role in constructing cognitive radio networks. In this letter, we have analyzed the theoretical value of SUs' density, which provides a standard for controlling the number of SUs around one primary receiver, in order to guarantee that primary communication links do not experience excessive interference. The simulation result of secondary density well matches with the theoretical result derived from our analysis. Additionally, the achievable rate of secondary user under density control is also analyzed and simulated.

  6. Optimal satisfaction degree in energy harvesting cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Li, Zan; Liu, Bo-Yang; Si, Jiang-Bo; Zhou, Fu-Hui

    2015-12-01

    A cognitive radio (CR) network with energy harvesting (EH) is considered to improve both spectrum efficiency and energy efficiency. A hidden Markov model (HMM) is used to characterize the imperfect spectrum sensing process. In order to maximize the whole satisfaction degree (WSD) of the cognitive radio network, a tradeoff between the average throughput of the secondary user (SU) and the interference to the primary user (PU) is analyzed. We formulate the satisfaction degree optimization problem as a mixed integer nonlinear programming (MINLP) problem. The satisfaction degree optimization problem is solved by using differential evolution (DE) algorithm. The proposed optimization problem allows the network to adaptively achieve the optimal solution based on its required quality of service (Qos). Numerical results are given to verify our analysis. Project supported by the National Natural Science Foundation of China (Grant No. 61301179), the Doctorial Programs Foundation of the Ministry of Education of China (Grant No. 20110203110011), and the 111 Project (Grant No. B08038).

  7. High fidelity wireless network evaluation for heterogeneous cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Ding, Lei; Sagduyu, Yalin; Yackoski, Justin; Azimi-Sadjadi, Babak; Li, Jason; Levy, Renato; Melodia, Tammaso

    2012-06-01

    We present a high fidelity cognitive radio (CR) network emulation platform for wireless system tests, measure- ments, and validation. This versatile platform provides the configurable functionalities to control and repeat realistic physical channel effects in integrated space, air, and ground networks. We combine the advantages of scalable simulation environment with reliable hardware performance for high fidelity and repeatable evaluation of heterogeneous CR networks. This approach extends CR design only at device (software-defined-radio) or lower-level protocol (dynamic spectrum access) level to end-to-end cognitive networking, and facilitates low-cost deployment, development, and experimentation of new wireless network protocols and applications on frequency- agile programmable radios. Going beyond the channel emulator paradigm for point-to-point communications, we can support simultaneous transmissions by network-level emulation that allows realistic physical-layer inter- actions between diverse user classes, including secondary users, primary users, and adversarial jammers in CR networks. In particular, we can replay field tests in a lab environment with real radios perceiving and learning the dynamic environment thereby adapting for end-to-end goals over distributed spectrum coordination channels that replace the common control channel as a single point of failure. CR networks offer several dimensions of tunable actions including channel, power, rate, and route selection. The proposed network evaluation platform is fully programmable and can reliably evaluate the necessary cross-layer design solutions with configurable op- timization space by leveraging the hardware experiments to represent the realistic effects of physical channel, topology, mobility, and jamming on spectrum agility, situational awareness, and network resiliency. We also provide the flexibility to scale up the test environment by introducing virtual radios and establishing seamless signal

  8. Radio Implementation of a Testbed For Cognitive Radio Source Localization Using USRPS and GNU Radio

    DTIC Science & Technology

    2014-09-01

    pp. 116–130, 2009. [4] R.A. Rashid , M.A. Sarijari, N. Fisal, S.K.S. Yusof and N.H. Mahalin, “Spectrum sensing measurement using GNU Radio and...USRP software radio platform,” in Proc. 7th Int. Conf. Wireless and Mobile Commun., Luxembourg, 2011. [5] R.A. Rashid , M.A. Sarijari, N. Fisal...Sarijari, A. Marwanto, N. Fisal, S.K.S. Yusof and R.A Rashid , “Energy detection sensing based on GNU Radio and USRP: An analysis study,” in Proc

  9. An Examination of Application of Artificial Neural Network in Cognitive Radios

    NASA Astrophysics Data System (ADS)

    Bello Salau, H.; Onwuka, E. N.; Aibinu, A. M.

    2013-12-01

    Recent advancement in software radio technology has led to the development of smart device known as cognitive radio. This type of radio fuses powerful techniques taken from artificial intelligence, game theory, wideband/multiple antenna techniques, information theory and statistical signal processing to create an outstanding dynamic behavior. This cognitive radio is utilized in achieving diverse set of applications such as spectrum sensing, radio parameter adaptation and signal classification. This paper contributes by reviewing different cognitive radio implementation that uses artificial intelligence such as the hidden markov models, metaheuristic algorithm and artificial neural networks (ANNs). Furthermore, different areas of application of ANNs and their performance metrics based approach are also examined.

  10. 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.

  11. SETI reloaded: Next generation radio telescopes, transients and cognitive computing

    NASA Astrophysics Data System (ADS)

    Garrett, Michael A.

    2015-08-01

    The Search for Extra-terrestrial Intelligence (SETI) using radio telescopes is an area of research that is now more than 50 years old. Thus far, both targeted and wide-area surveys have yet to detect artificial signals from intelligent civilisations. In this paper, I argue that the incidence of co-existing intelligent and communicating civilisations is probably small in the Milky Way. While this makes successful SETI searches a very difficult pursuit indeed, the huge impact of even a single detection requires us to continue the search. A substantial increase in the overall performance of radio telescopes (and in particular future wide-field instruments such as the Square Kilometre Array - SKA), provide renewed optimism in the field. Evidence for this is already to be seen in the success of SETI researchers in acquiring observations on some of the world's most sensitive radio telescope facilities via open, peer-reviewed processes. The increasing interest in the dynamic radio sky, and our ability to detect new and rapid transient phenomena such as Fast Radio Bursts (FRB) is also greatly encouraging. While the nature of FRBs is not yet fully understood, I argue they are unlikely to be the signature of distant extra-terrestrial civilisations. As astronomers face a data avalanche on all sides, advances made in related areas such as advanced Big Data analytics, and cognitive computing are crucial to enable serendipitous discoveries to be made. In any case, as the era of the SKA fast approaches, the prospects of a SETI detection have never been better.

  12. Exploring Cognition Using Software Defined Radios for NASA Missions

    NASA Technical Reports Server (NTRS)

    Mortensen, Dale J.; Reinhart, Richard C.

    2016-01-01

    NASA missions typically operate using a communication infrastructure that requires significant schedule planning with limited flexibility when the needs of the mission change. Parameters such as modulation, coding scheme, frequency, and data rate are fixed for the life of the mission. This is due to antiquated hardware and software for both the space and ground assets and a very complex set of mission profiles. Automated techniques in place by commercial telecommunication companies are being explored by NASA to determine their usability by NASA to reduce cost and increase science return. Adding cognition the ability to learn from past decisions and adjust behavior is also being investigated. Software Defined Radios are an ideal way to implement cognitive concepts. Cognition can be considered in many different aspects of the communication system. Radio functions, such as frequency, modulation, data rate, coding and filters can be adjusted based on measurements of signal degradation. Data delivery mechanisms and route changes based on past successes and failures can be made to more efficiently deliver the data to the end user. Automated antenna pointing can be added to improve gain, coverage, or adjust the target. Scheduling improvements and automation to reduce the dependence on humans provide more flexible capabilities. The Cognitive Communications project, funded by the Space Communication and Navigation Program, is exploring these concepts and using the SCaN Testbed on board the International Space Station to implement them as they evolve. The SCaN Testbed contains three Software Defined Radios and a flight computer. These four computing platforms, along with a tracking antenna system and the supporting ground infrastructure, will be used to implement various concepts in a system similar to those used by missions. Multiple universities and SBIR companies are supporting this investigation. This paper will describe the cognitive system ideas under consideration and

  13. 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

  14. Circuit techniques for cognitive radio receiver front-ends

    NASA Astrophysics Data System (ADS)

    Sadhu, Bodhisatwa

    This thesis discusses the design of the receiver front-end for software defined radio (SDR) based cognitive radio applications. Two aspects of SDRs for cognitive radios are distinguished: signaling and spectrum sensing. Narrowband wide tuning signaling architectures and instantaneous wideband spectrum sensing architectures are identified as candidates for feasible SDR implementations. Several architectures and circuit implementations are reviewed. Wide tuning range, low phase noise frequency synthesizers for signaling, and RF samplers and signal processors for spectrum sensing are identified as critical circuit design blocks. A number of voltage controlled oscillator (VCO) techniques for wide-tuning range, and low phase noise frequency synthesis techniques are developed. Wide-tuning range techniques based on switched inductors are proposed as a way to design inductor-capacitor (LC) VCOs with wide-tuning ranges that maintain a good phase noise and power dissipation performance over the entire tuning range. Switched inductor VCOs are analyzed in detail, and a design framework is developed. Optimized capacitor array design techniques for wide-tuning ranges are discussed. Based on these techniques, measurements from two prototype designs are presented, that achieve tuning ranges of 87% and 157% in measurement. They also maintain good phase noise, power consumption, and figure of merit (FOM) over the entire tuning range. In addition, a new family of VCOs that achieve superior phase noise is introduced. This set of novel topologies are based on linearized transconductance using capacitive feedback techniques. They achieve higher amplitudes of oscillation, and consequently, a superior phase noise performance. A wide tuning range is also maintained. The VCOs are analyzed, and detailed measurement results from a design prototype are presented. For spectrum sensing, the design of CRAFT (Charge Re-use Analog Fourier Transform): an RF front-end channelizer for software defined

  15. Performance comparison of modulation techniques for underlay cognitive radio transceivers

    NASA Astrophysics Data System (ADS)

    Khan, Imtiyaz; Singh, Poonam

    2013-01-01

    In this paper, we present a quantitative comparison of two agile modulation techniques employed by cognitive radio transceivers operating in a dynamic spectrum access (DSA) network. One of the modulation techniques is single carrier frequency division multiple access (SC-FDMA). The other modulation technique under study is a variant of multicarrier code division multiple access (MCCDMA). Although several studies comparing conventional OFDM and MC-CDMA has been conducted in literature to justify robust error performance of MC-CDMA, a quantitative performance evaluation of these schemes has not been performed when employed in a DSA network. In this paper we show that their performances can be significantly different from the conventional setup. Analytical expressions for the error probability of an SC-FDMA transceiver have been derived and compared with computer simulation results. The results show that the error robustness of SC-FDMA is relatively better then MC-CDMA in underlay communication.

  16. On the Connectivity and Multihop Delay of Ad Hoc Cognitive Radio Networks

    DTIC Science & Technology

    2010-05-01

    depends on the density of SUs and the traffic load of PUs. 9 Connectivity: Static Case When PTxs/ PRxs are static over time: PSfrag replacements λ P T...Connectivity: Dynamic Case When temporal dynamics of PTxs/ PRxs are sufficiently rich: PSfrag replacements λ P T (D en si ty of P T xs ) λS (Density of SUs)λ

  17. On the Connectivity and Multihop Delay of Ad Hoc Cognitive Radio Networks

    DTIC Science & Technology

    2011-04-01

    that we can move fast enough such that the driving time on the road is negligible. When the secondary network is instantaneously connected, there...and receiving activities of the primary users. Without loss of generality, we set TS = 1. At the beginning of each slot, the primary transmitters are...the transmission/interference range is a function of the pass- loss exponent. Thus, the pass- loss exponent affects the topology of the secondary

  18. Temporal Traffic Dynamics Improve the Connectivity of Ad Hoc Cognitive Radio Networks

    DTIC Science & Technology

    2014-02-12

    of nearby primary users. Using theories and techniques from continuum percolation and ergodicity, we analytically characterize the con- nectivity of...users depends on the transmitting and receiving activities of nearby primary users. Using theories and techniques from continuum percolation and...connectivity of homogeneous net- works (i.e., secondary network only) have been well studied in [6]–[14] and references therein. The theory of continuum 3Since

  19. A New SIR-Based Sigmoid Power Control Game in Cognitive Radio Networks

    PubMed Central

    Al-Gumaei, Yousef Ali; Noordin, Kamarul Ariffin; Reza, Ahmed Wasif; Dimyati, Kaharudin

    2014-01-01

    Interference resulting from Cognitive Radios (CRs) is the most important aspect of cognitive radio networks that leads to degradation in Quality of Service (QoS) in both primary and CR systems. Power control is one of the efficient techniques that can be used to reduce interference and satisfy the Signal-to-Interference Ratio (SIR) constraint among CRs. This paper proposes a new distributed power control algorithm based on game theory approach in cognitive radio networks. The proposal focuses on the channel status of cognitive radio users to improve system performance. A new cost function for SIR-based power control via a sigmoid weighting factor is introduced. The existence of Nash Equilibrium and convergence of the algorithm are also proved. The advantage of the proposed algorithm is the possibility to utilize and implement it in a distributed manner. Simulation results show considerable savings on Nash Equilibrium power compared to relevant algorithms while reduction in achieved SIR is insignificant. PMID:25286044

  20. A new SIR-based sigmoid power control game in cognitive radio networks.

    PubMed

    Al-Gumaei, Yousef Ali; Noordin, Kamarul Ariffin; Reza, Ahmed Wasif; Dimyati, Kaharudin

    2014-01-01

    Interference resulting from Cognitive Radios (CRs) is the most important aspect of cognitive radio networks that leads to degradation in Quality of Service (QoS) in both primary and CR systems. Power control is one of the efficient techniques that can be used to reduce interference and satisfy the Signal-to-Interference Ratio (SIR) constraint among CRs. This paper proposes a new distributed power control algorithm based on game theory approach in cognitive radio networks. The proposal focuses on the channel status of cognitive radio users to improve system performance. A new cost function for SIR-based power control via a sigmoid weighting factor is introduced. The existence of Nash Equilibrium and convergence of the algorithm are also proved. The advantage of the proposed algorithm is the possibility to utilize and implement it in a distributed manner. Simulation results show considerable savings on Nash Equilibrium power compared to relevant algorithms while reduction in achieved SIR is insignificant.

  1. Novel Spectrum Sensing Algorithms for OFDM Cognitive Radio Networks

    PubMed Central

    Shi, Zhenguo; Wu, Zhilu; Yin, Zhendong; Cheng, Qingqing

    2015-01-01

    Spectrum sensing technology plays an increasingly important role in cognitive radio networks. Consequently, several spectrum sensing algorithms have been proposed in the literature. In this paper, we present a new spectrum sensing algorithm “Differential Characteristics-Based OFDM (DC-OFDM)” for detecting OFDM signal on account of differential characteristics. We put the primary value on channel gain θ around zero to detect the presence of primary user. Furthermore, utilizing the same method of differential operation, we improve two traditional OFDM sensing algorithms (cyclic prefix and pilot tones detecting algorithms), and propose a “Differential Characteristics-Based Cyclic Prefix (DC-CP)” detector and a “Differential Characteristics-Based Pilot Tones (DC-PT)” detector, respectively. DC-CP detector is based on auto-correlation vector to sense the spectrum, while the DC-PT detector takes the frequency-domain cross-correlation of PT as the test statistic to detect the primary user. Moreover, the distributions of the test statistics of the three proposed methods have been derived. Simulation results illustrate that all of the three proposed methods can achieve good performance under low signal to noise ratio (SNR) with the presence of timing delay. Specifically, the DC-OFDM detector gets the best performance among the presented detectors. Moreover, both of the DC-CP and DC-PT detector achieve significant improvements compared with their corresponding original detectors. PMID:26083226

  2. Threshold optimization of cooperative spectrum sensing in cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Jia, Min; Tan, Xuezhi

    2013-01-01

    We consider the threshold optimization problem of cooperative spectrum sensing for cognitive radio (CR) and investigate the threshold optimization algorithm for both single-channel and multichannel cooperative spectrum sensing. In order to obtain the optimal threshold for single-channel cooperative spectrum sensing, we deploy the fusion rules AND Logic, OR Logic, and K-OUT-N Logic. Moreover, an iterative optimization algorithm is proposed to obtain optimal CRs in cooperative spectrum sensing and their optimal thresholds. In multichannel cooperative spectrum sensing, two threshold optimization methods—namely nonrestrained multichannel threshold optimization (NRMTO) and restrained multichannel threshold optimization (RMTO)—have been proposed in order to decrease the total error detection probability of all the subchannels. The simulation results show that in single-channel cooperative spectrum sensing the proposed algorithm outperforms traditional cooperative spectrum sensing with the uniform threshold if the SNR is different, while decreasing the detection performance slightly if the SNR is identical. The results also indicate that the NRMTO can achieve the minimal total error detection probability of multichannel cooperative spectrum sensing, while the RMTO can guarantee the detection performance of each subchannel but with a higher total error detection probability.

  3. Novel Spectrum Sensing Algorithms for OFDM Cognitive Radio Networks.

    PubMed

    Shi, Zhenguo; Wu, Zhilu; Yin, Zhendong; Cheng, Qingqing

    2015-06-15

    Spectrum sensing technology plays an increasingly important role in cognitive radio networks. Consequently, several spectrum sensing algorithms have been proposed in the literature. In this paper, we present a new spectrum sensing algorithm "Differential Characteristics-Based OFDM (DC-OFDM)" for detecting OFDM signal on account of differential characteristics. We put the primary value on channel gain θ around zero to detect the presence of primary user. Furthermore, utilizing the same method of differential operation, we improve two traditional OFDM sensing algorithms (cyclic prefix and pilot tones detecting algorithms), and propose a "Differential Characteristics-Based Cyclic Prefix (DC-CP)" detector and a "Differential Characteristics-Based Pilot Tones (DC-PT)" detector, respectively. DC-CP detector is based on auto-correlation vector to sense the spectrum, while the DC-PT detector takes the frequency-domain cross-correlation of PT as the test statistic to detect the primary user. Moreover, the distributions of the test statistics of the three proposed methods have been derived. Simulation results illustrate that all of the three proposed methods can achieve good performance under low signal to noise ratio (SNR) with the presence of timing delay. Specifically, the DC-OFDM detector gets the best performance among the presented detectors. Moreover, both of the DC-CP and DC-PT detector achieve significant improvements compared with their corresponding original detectors.

  4. A virus spreading model for cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Hou, L.; Yeung, K. H.; Wong, K. Y.

    2012-12-01

    Since cognitive radio (CR) networks could solve the spectrum scarcity problem, they have drawn much research in recent years. Artificial intelligence(AI) is introduced into CRs to learn from and adapt to their environment. Nonetheless, AI brings in a new kind of attacks specific to CR networks. The most powerful one is a self-propagating AI virus. And no spreading properties specific to this virus have been reported in the literature. To fill this research gap, we propose a virus spreading model of an AI virus by considering the characteristics of CR networks and the behavior of CR users. Several important observations are made from the simulation results based on the model. Firstly, the time taken to infect the whole network increases exponentially with the network size. Based on this result, CR network designers could calculate the optimal network size to slow down AI virus propagation rate. Secondly, the anti-virus performance of static networks to an AI virus is better than dynamic networks. Thirdly, if the CR devices with the highest degree are initially infected, the AI virus propagation rate will be increased substantially. Finally, it is also found that in the area with abundant spectrum resource, the AI virus propagation speed increases notably but the variability of the spectrum does not affect the propagation speed much.

  5. Biogeography-based optimisation of Cognitive Radio system

    NASA Astrophysics Data System (ADS)

    Kaur, Kiranjot; Rattan, Munish; Singh Patterh, Manjeet

    2014-01-01

    Biogeography-based optimisation (BBO) is a novel population-based global optimisation algorithm that is stimulated by the science of biogeography. The mathematical models of biogeography describe how a species arises, migrates from one habitat (Island) to another or gets extinct. BBO searches for the global optimum mainly through two steps: migration and mutation. These steps are controlled by immigration and emigration rates of the species in the habitat which are also used to share information between the habitats. In this paper, BBO has been applied to Cognitive Radio (CR) system for optimising its various transmission parameters to meet the quality of service (QoS) that is defined by the user in terms of minimum transmit power, minimum bit error rate (BER), maximum throughput, minimum interference and maximum spectral efficiency. To confirm the capability of biogeography-based optimisation algorithm, the results obtained by BBO are compared with that obtained by using genetic algorithm (GA) for the various QoS parameters, and it has been observed that BBO outperforms GA in system optimisation.

  6. Implementation of Software Programmable Radios to Form Ad-Hoc Meshed Networks to Enhance Maritime Interception Operations

    DTIC Science & Technology

    2010-09-01

    Networks, Software Programmable Radios, MIMO , Ultra-wideband, MIO, VBSS 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT Unclassified 18...locations where it was never possible before: in crowded urban environments, massive buildings, subway tunnels, - virtually anywhere.  Networks can be...Multiple Input / Multiple Output ( MIMO )  Network-Controlled Robotics (Unmanned Vehicles) 2. Possible Combination of TW220 and Small Satellites Software

  7. Outage Probability Minimization for Energy Harvesting Cognitive Radio Sensor Networks

    PubMed Central

    Zhang, Fan; Jing, Tao; Huo, Yan; Jiang, Kaiwei

    2017-01-01

    The incorporation of cognitive radio (CR) capability in wireless sensor networks yields a promising network paradigm known as CR sensor networks (CRSNs), which is able to provide spectrum efficient data communication. However, due to the high energy consumption results from spectrum sensing, as well as subsequent data transmission, the energy supply for the conventional sensor nodes powered by batteries is regarded as a severe bottleneck for sustainable operation. The energy harvesting technique, which gathers energy from the ambient environment, is regarded as a promising solution to perpetually power-up energy-limited devices with a continual source of energy. Therefore, applying the energy harvesting (EH) technique in CRSNs is able to facilitate the self-sustainability of the energy-limited sensors. The primary concern of this study is to design sensing-transmission policies to minimize the long-term outage probability of EH-powered CR sensor nodes. We formulate this problem as an infinite-horizon discounted Markov decision process and propose an ϵ-optimal sensing-transmission (ST) policy through using the value iteration algorithm. ϵ is the error bound between the ST policy and the optimal policy, which can be pre-defined according to the actual need. Moreover, for a special case that the signal-to-noise (SNR) power ratio is sufficiently high, we present an efficient transmission (ET) policy and prove that the ET policy achieves the same performance with the ST policy. Finally, extensive simulations are conducted to evaluate the performance of the proposed policies and the impaction of various network parameters. PMID:28125023

  8. Outage Probability Minimization for Energy Harvesting Cognitive Radio Sensor Networks.

    PubMed

    Zhang, Fan; Jing, Tao; Huo, Yan; Jiang, Kaiwei

    2017-01-24

    The incorporation of cognitive radio (CR) capability in wireless sensor networks yields a promising network paradigm known as CR sensor networks (CRSNs), which is able to provide spectrum efficient data communication. However, due to the high energy consumption results from spectrum sensing, as well as subsequent data transmission, the energy supply for the conventional sensor nodes powered by batteries is regarded as a severe bottleneck for sustainable operation. The energy harvesting technique, which gathers energy from the ambient environment, is regarded as a promising solution to perpetually power-up energy-limited devices with a continual source of energy. Therefore, applying the energy harvesting (EH) technique in CRSNs is able to facilitate the self-sustainability of the energy-limited sensors. The primary concern of this study is to design sensing-transmission policies to minimize the long-term outage probability of EH-powered CR sensor nodes. We formulate this problem as an infinite-horizon discounted Markov decision process and propose an ϵ-optimal sensing-transmission (ST) policy through using the value iteration algorithm. ϵ is the error bound between the ST policy and the optimal policy, which can be pre-defined according to the actual need. Moreover, for a special case that the signal-to-noise (SNR) power ratio is sufficiently high, we present an efficient transmission (ET) policy and prove that the ET policy achieves the same performance with the ST policy. Finally, extensive simulations are conducted to evaluate the performance of the proposed policies and the impaction of various network parameters.

  9. Optimal throughput for cognitive radio with energy harvesting in fading wireless channel.

    PubMed

    Vu-Van, Hiep; Koo, Insoo

    2014-01-01

    Energy resource management is a crucial problem of a device with a finite capacity battery. In this paper, cognitive radio is considered to be a device with an energy harvester that can harvest energy from a non-RF energy resource while performing other actions of cognitive radio. Harvested energy will be stored in a finite capacity battery. At the start of the time slot of cognitive radio, the radio needs to determine if it should remain silent or carry out spectrum sensing based on the idle probability of the primary user and the remaining energy in order to maximize the throughput of the cognitive radio system. In addition, optimal sensing energy and adaptive transmission power control are also investigated in this paper to effectively utilize the limited energy of cognitive radio. Finding an optimal approach is formulated as a partially observable Markov decision process. The simulation results show that the proposed optimal decision scheme outperforms the myopic scheme in which current throughput is only considered when making a decision.

  10. 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.

  11. Efficient Cooperative Spectrum Sensing with Minimum Sensing Error Probability in Heterogeneous Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Hu, Hang; Li, Ning; Xu, Youyun

    2012-06-01

    To improve the sensing performance, cooperation among secondary users can be utilized to collect space diversity. We focus on the optimization of cooperative spectrum sensing in which multiple secondary users efficiently cooperate to achieve superior detection accuracy with minimum sensing error probability in heterogeneous cognitive radio (CR) networks. Rayleigh fading and Nakagami fading are considered respectively in cognitive network I and cognitive network II. For each cognitive network, we derive the optimal randomized rule for different decision threshold. Then, the optimal decision threshold is derived according to the rule of minimum sensing error (MSE). MSE rule shows better performance on improving the final false alarm and detection probability simultaneously. By simulations, our proposed strategy optimizes the sensing performance for each secondary user which is randomly distributed in the heterogeneous cognitive radio networks.

  12. Design and Implementation of an Underlay Control Channel for Cognitive Radios

    SciTech Connect

    Daryl Wasden; Hussein Moradi; Behrouz Farhang-Boroujeny

    2012-11-01

    Implementation of any cognitive radio network requires an effective control channel that can operate under various modes of activity from the primary users. This paper reports the design and implementation of a filter bank multicarrier spread spectrum (FBMC-SS) system for use as the control channel in cognitive radio networks. The proposed design is based on a filtered multitone (FMT) implementation. Carrier and timing acquisition and tracking methods as well as a blind channel estimation method are developed for the proposed control channel. We also report an implementation of the proposed FBMC-SS system on a hardware platform; a FlexRIO FPGA module from National Instruments.

  13. A robust and energy-efficient transport protocol for cognitive radio sensor networks.

    PubMed

    Salim, Shelly; Moh, Sangman

    2014-10-20

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. CRSNs benefit from cognitive radio capabilities such as dynamic spectrum access and transmission parameters reconfigurability; but cognitive radio also brings additional challenges and leads to higher energy consumption. Motivated to improve the energy efficiency in CRSNs, we propose a robust and energy-efficient transport protocol (RETP). The novelties of RETP are two-fold: (I) it combines distributed channel sensing and channel decision with centralized schedule-based data transmission; and (II) it differentiates the types of data transmission on the basis of data content and adopts different acknowledgment methods for different transmission types. To the best of our knowledge, no transport layer protocols have yet been designed for CRSNs. Simulation results show that the proposed protocol achieves remarkably longer network lifetime and shorter event-detection delay compared to those achieved with a conventional transport protocol, while simultaneously preserving event-detection reliability.

  14. Effects of levomilnacipran extended-release on major depressive disorder patients with cognitive impairments: post-hoc analysis of a phase III study.

    PubMed

    Wesnes, Keith A; Gommoll, Carl; Chen, Changzheng; Sambunaris, Angelo; McIntyre, Roger S; Harvey, Philip D

    2017-03-01

    Performance-based cognitive data were collected using the Cognitive Drug Research System in a study of levomilnacipran extended-release (ER) 40-120 mg/day (NCT01034462) in adults with major depressive disorder. These data were analyzed post-hoc to explore the relationship between cognitive measures, depression symptoms (Montgomery-Åsberg Depression Rating Scale, MADRS), and self-reported psychosocial functioning (Sheehan Disability Scale; SDS). Changes from baseline were analyzed in the intent-to-treat population and subgroups with impaired attention, as indicated by baseline Cognitive Drug Research System scores for Power of Attention and Continuity of Attention. Path analyses evaluated the direct and indirect effects of levomilnacipran ER on SDS total score change. Significantly greater improvements were observed for levomilnacipran ER versus placebo for Power of Attention, Continuity of Attention, MADRS, and SDS score changes; the mean differences were larger in the impaired subgroups than in the overall intent-to-treat population. Path analyses showed that the majority of SDS total score improvement (≥50%) was attributable to an indirect treatment effect through MADRS total score change; some direct effect of levomilnacipran ER on SDS total score improvement was also observed. In adults with major depressive disorder, levomilnacipran ER effectively improved measures of depression and cognition, which contributed toward reductions in self-reported functional impairment.

  15. Effects of levomilnacipran extended-release on major depressive disorder patients with cognitive impairments: post-hoc analysis of a phase III study

    PubMed Central

    Gommoll, Carl; Chen, Changzheng; Sambunaris, Angelo; McIntyre, Roger S.; Harvey, Philip D.

    2017-01-01

    Performance-based cognitive data were collected using the Cognitive Drug Research System in a study of levomilnacipran extended-release (ER) 40–120 mg/day (NCT01034462) in adults with major depressive disorder. These data were analyzed post-hoc to explore the relationship between cognitive measures, depression symptoms (Montgomery–Åsberg Depression Rating Scale, MADRS), and self-reported psychosocial functioning (Sheehan Disability Scale; SDS). Changes from baseline were analyzed in the intent-to-treat population and subgroups with impaired attention, as indicated by baseline Cognitive Drug Research System scores for Power of Attention and Continuity of Attention. Path analyses evaluated the direct and indirect effects of levomilnacipran ER on SDS total score change. Significantly greater improvements were observed for levomilnacipran ER versus placebo for Power of Attention, Continuity of Attention, MADRS, and SDS score changes; the mean differences were larger in the impaired subgroups than in the overall intent-to-treat population. Path analyses showed that the majority of SDS total score improvement (≥50%) was attributable to an indirect treatment effect through MADRS total score change; some direct effect of levomilnacipran ER on SDS total score improvement was also observed. In adults with major depressive disorder, levomilnacipran ER effectively improved measures of depression and cognition, which contributed toward reductions in self-reported functional impairment. PMID:27861191

  16. 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.

  17. Joint Spectrum Allocation and Scheduling in Multi-Radio Multi-Channel Cognitive Radio Wireless Networks

    DTIC Science & Technology

    2010-04-01

    radios in node y. The time required to solve this problem can be significantly decreased if a greedy clique decomposition of the conflict graph is...performed. Specifically, a set of cliques © Qi, i = 1, 2, ...Q ª are found such that if yj ∈ χ (xk), then there is a clique Qi such that xk ∈ Qi and yj ∈ Qi...and trace files. The propagation simulator is based on ray -tracing and accounts for reflections off of the ground and off of buildings, transmission

  18. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks.

    PubMed

    Salim, Shelly; Moh, Sangman

    2016-06-30

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead.

  19. 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.

  20. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks

    PubMed Central

    Salim, Shelly; Moh, Sangman

    2016-01-01

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290

  1. Game theoretic wireless resource allocation for H.264 MGS video transmission over cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Fragkoulis, Alexandros; Kondi, Lisimachos P.; Parsopoulos, Konstantinos E.

    2015-03-01

    We propose a method for the fair and efficient allocation of wireless resources over a cognitive radio system network to transmit multiple scalable video streams to multiple users. The method exploits the dynamic architecture of the Scalable Video Coding extension of the H.264 standard, along with the diversity that OFDMA networks provide. We use a game-theoretic Nash Bargaining Solution (NBS) framework to ensure that each user receives the minimum video quality requirements, while maintaining fairness over the cognitive radio system. An optimization problem is formulated, where the objective is the maximization of the Nash product while minimizing the waste of resources. The problem is solved by using a Swarm Intelligence optimizer, namely Particle Swarm Optimization. Due to the high dimensionality of the problem, we also introduce a dimension-reduction technique. Our experimental results demonstrate the fairness imposed by the employed NBS framework.

  2. Cognitive radio adaptation for power consumption minimization using biogeography-based optimization

    NASA Astrophysics Data System (ADS)

    Qi, Pei-Han; Zheng, Shi-Lian; Yang, Xiao-Niu; Zhao, Zhi-Jin

    2016-12-01

    Adaptation is one of the key capabilities of cognitive radio, which focuses on how to adjust the radio parameters to optimize the system performance based on the knowledge of the radio environment and its capability and characteristics. In this paper, we consider the cognitive radio adaptation problem for power consumption minimization. The problem is formulated as a constrained power consumption minimization problem, and the biogeography-based optimization (BBO) is introduced to solve this optimization problem. A novel habitat suitability index (HSI) evaluation mechanism is proposed, in which both the power consumption minimization objective and the quality of services (QoS) constraints are taken into account. The results show that under different QoS requirement settings corresponding to different types of services, the algorithm can minimize power consumption while still maintaining the QoS requirements. Comparison with particle swarm optimization (PSO) and cat swarm optimization (CSO) reveals that BBO works better, especially at the early stage of the search, which means that the BBO is a better choice for real-time applications. Project supported by the National Natural Science Foundation of China (Grant No. 61501356), the Fundamental Research Funds of the Ministry of Education, China (Grant No. JB160101), and the Postdoctoral Fund of Shaanxi Province, China.

  3. A Survey of MAC Protocols for Cognitive Radio Body Area Networks

    PubMed Central

    Bhandari, Sabin; Moh, Sangman

    2015-01-01

    The advancement in electronics, wireless communications and integrated circuits has enabled the development of small low-power sensors and actuators that can be placed on, in or around the human body. A wireless body area network (WBAN) can be effectively used to deliver the sensory data to a central server, where it can be monitored, stored and analyzed. For more than a decade, cognitive radio (CR) technology has been widely adopted in wireless networks, as it utilizes the available spectra of licensed, as well as unlicensed bands. A cognitive radio body area network (CRBAN) is a CR-enabled WBAN. Unlike other wireless networks, CRBANs have specific requirements, such as being able to automatically sense their environments and to utilize unused, licensed spectra without interfering with licensed users, but existing protocols cannot fulfill them. In particular, the medium access control (MAC) layer plays a key role in cognitive radio functions, such as channel sensing, resource allocation, spectrum mobility and spectrum sharing. To address various application-specific requirements in CRBANs, several MAC protocols have been proposed in the literature. In this paper, we survey MAC protocols for CRBANs. We then compare the different MAC protocols with one another and discuss challenging open issues in the relevant research. PMID:25903551

  4. 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.

  5. Acquisition and Development of a Cognitive Radio Based Wireless Monitoring and Surveillance Testbed for Future Battlefield Communications Research

    DTIC Science & Technology

    2015-03-01

    SECURITY CLASSIFICATION OF: During the funding period, a set of state-of-the-art software defined radio platforms are acquired, including 10 NI USRP...2932 (400MHz~4.4GHz + GPS Clock) Software Radio Kit, 3 NI USRP-2942R (400MHZ~4.4GHz with KINTEX-7 FPGA), and 3 NI USRP-2952R (400MHZ~4.4GHZ with GPS...These software defined radio platforms provide the much needed infrastructure support for cognitive radio research. In addition, a commercial grade

  6. Elaborate analysis and design of filter-bank-based sensing for wideband cognitive radios

    NASA Astrophysics Data System (ADS)

    Maliatsos, Konstantinos; Adamis, Athanasios; Kanatas, Athanasios G.

    2014-12-01

    The successful operation of a cognitive radio system strongly depends on its ability to sense the radio environment. With the use of spectrum sensing algorithms, the cognitive radio is required to detect co-existing licensed primary transmissions and to protect them from interference. This paper focuses on filter-bank-based sensing and provides a solid theoretical background for the design of these detectors. Optimum detectors based on the Neyman-Pearson theorem are developed for uniform discrete Fourier transform (DFT) and modified DFT filter banks with root-Nyquist filters. The proposed sensing framework does not require frequency alignment between the filter bank of the sensor and the primary signal. Each wideband primary channel is spanned and monitored by several sensor subchannels that analyse it in narrowband signals. Filter-bank-based sensing is proved to be robust and efficient under coloured noise. Moreover, the performance of the weighted energy detector as a sensing technique is evaluated. Finally, based on the Locally Most Powerful and the Generalized Likelihood Ratio test, real-world sensing algorithms that do not require a priori knowledge are proposed and tested.

  7. Improved cooperative spectrum sensing based on the reputation in cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Lu, Jianqi; Wei, Ping

    2015-05-01

    Cognitive radio (CR) is a promising technology to improve the utilisation of wireless spectrum resources. Spectrum sensing is the core functionality in CR networks (CRN). When there exist malicious users (MUs) in CRN and MUs start to attack the network after accumulating reputation to some extent, the performance is deteriorated. In this paper, a scheme is proposed by employing Orthogonalized Gnanadesikan-Kettenring (OGK) to mitigate the effect of MUs without the assistance of trusted nodes, and it can improve the robustness of CRN. Simulations verify the effectiveness of the proposed scheme.

  8. 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.

  9. Outage Probability of SINR for Underlay Cognitive Radio Systems in Nakagami Fading

    NASA Astrophysics Data System (ADS)

    Jarrouj, Jiana; Blagojevic, Vesna; Ivanis, Predrag

    2014-11-01

    In this paper underlay cognitive radio system is analyzed in Nakagami fading environment, for the case when the available channel state information (CSI) of the link from the secondary transmitter to the primary receiver is outdated. We considered the case when both interference and transmit power constraints are applied. The impact of the co-channel interference that originates from the primary user is analyzed in details. The exact closed-form expressions for probability density function, outage probability, and the moments of signal-to-interference and noise ratio (SINR) at the secondary user's receiver are derived. The analytical expressions are verified by using independent Monte Carlo simulation method.

  10. The Spectrum Sensing Algorithm Based AdaBoost in Cognitive Radio

    NASA Astrophysics Data System (ADS)

    Tian, Deyong; Wang, Xin

    To solve the low detection rate of the primary user in the cognitive radio environment, we propose a spectrum sensing method based on AdaBoost in the case of low SNR. In this paper, a set of received signal spectrum features are first calculated and extracted the discriminant feature vector as training samples and testing samples for classification. Finally, we utilize the trained AdaBoost to detect the primary user. Test result shows that the proposed algorithm is not affected by uncertainty factors of noise and has high performance to classification detection compared with ANN, SVM and maximum-minimum eigenvalue (MME).

  11. A Survey on Node Clustering in Cognitive Radio Wireless Sensor Networks

    PubMed Central

    Joshi, Gyanendra Prasad; Kim, Sung Won

    2016-01-01

    Cognitive radio wireless sensor networks (CR-WSNs) have attracted a great deal of attention recently due to the emerging spectrum scarcity issue. This work attempts to provide a detailed analysis of the role of node clustering in CR-WSNs. We outline the objectives, requirements, and advantages of node clustering in CR-WSNs. We describe how a CR-WSN with node clustering differs from conventional wireless sensor networks, and we discuss its characteristics, architecture, and topologies. We survey the existing clustering algorithms and compare their objectives and features. We suggest how clustering issues and challenges can be handled. PMID:27626421

  12. A Survey on Node Clustering in Cognitive Radio Wireless Sensor Networks.

    PubMed

    Joshi, Gyanendra Prasad; Kim, Sung Won

    2016-09-10

    Cognitive radio wireless sensor networks (CR-WSNs) have attracted a great deal of attention recently due to the emerging spectrum scarcity issue. This work attempts to provide a detailed analysis of the role of node clustering in CR-WSNs. We outline the objectives, requirements, and advantages of node clustering in CR-WSNs. We describe how a CR-WSN with node clustering differs from conventional wireless sensor networks, and we discuss its characteristics, architecture, and topologies. We survey the existing clustering algorithms and compare their objectives and features. We suggest how clustering issues and challenges can be handled.

  13. 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.

  14. Spectrum Handoffs Based on Preemptive Repeat Priority Queue in Cognitive Radio Networks.

    PubMed

    Yang, Xiaolong; Tan, Xuezhi; Ye, Liang; Ma, Lin

    2016-07-20

    Cognitive radio can significantly improve the spectrum efficiency, and spectrum handoff is considered as an important functionality to guarantee the quality of service (QoS) of primary users (PUs) and the continuity of data transmission of secondary users (SUs). In this paper, we propose an analytical framework based on a preemptive repeat identical (PRI) M/G/1 queuing network model to characterize spectrum handoff behaviors with general service time distribution of both primary and secondary connections, multiple interruptions and transmission delay resulting from the appearance of primary connections. Then, we derive the close-expression of the extended data delivery and the system sojourn time in both staying and changing scenarios. In addition, based on analysis of spectrum handoff behaviors resulting from multiple interruptions caused by the appearance of the primary connections, we investigate the traffic-adaptive policy, by which the considered SU will optimally adjust its handoff spectrum policy. Moreover, we investigate the admissible region and provide the reference for designing the admission control rule for the arriving secondary connection requests. Finally, simulation results verify that our proposed analytical framework is reasonable and can provide the reference for executing the optimal spectrum handoff strategy and designing the admission control rule for the SU in cognitive radio networks.

  15. A Novel Utility Function for Energy-Efficient Power Control Game in Cognitive Radio Networks

    PubMed Central

    Al-Gumaei, Yousef Ali; Noordin, Kamarul Ariffin; Reza, Ahmed Wasif; Dimyati, Kaharudin

    2015-01-01

    Spectrum scarcity is a major challenge in wireless communications systems requiring efficient usage and utilization. Cognitive radio network (CRN) is found as a promising technique to solve this problem of spectrum scarcity. It allows licensed and unlicensed users to share the same licensed spectrum band. Interference resulting from cognitive radios (CRs) has undesirable effects on quality of service (QoS) of both licensed and unlicensed systems where it causes degradation in received signal-to-noise ratio (SIR) of users. Power control is one of the most important techniques that can be used to mitigate interference and guarantee QoS in both systems. In this paper, we develop a new approach of a distributed power control for CRN based on utility and pricing. QoS of CR user is presented as a utility function via pricing and a distributed power control as a non-cooperative game in which users maximize their net utility (utility-price). We define the price as a real function of transmit power to increase pricing charge of the farthest CR users. We prove that the power control game proposed in this study has Nash Equilibrium as well as it is unique. The obtained results show that the proposed power control algorithm based on a new utility function has a significant reduction in transmit power consumption and high improvement in speed of convergence. PMID:26258522

  16. Joint Subchannel Pairing and Power Control for Cognitive Radio Networks with Amplify-and-Forward Relaying

    PubMed Central

    Shen, Yanyan; Wang, Shuqiang; Wei, Zhiming

    2014-01-01

    Dynamic spectrum sharing has drawn intensive attention in cognitive radio networks. The secondary users are allowed to use the available spectrum to transmit data if the interference to the primary users is maintained at a low level. Cooperative transmission for secondary users can reduce the transmission power and thus improve the performance further. We study the joint subchannel pairing and power allocation problem in relay-based cognitive radio networks. The objective is to maximize the sum rate of the secondary user that is helped by an amplify-and-forward relay. The individual power constraints at the source and the relay, the subchannel pairing constraints, and the interference power constraints are considered. The problem under consideration is formulated as a mixed integer programming problem. By the dual decomposition method, a joint optimal subchannel pairing and power allocation algorithm is proposed. To reduce the computational complexity, two suboptimal algorithms are developed. Simulations have been conducted to verify the performance of the proposed algorithms in terms of sum rate and average running time under different conditions. PMID:25045731

  17. Energy-Efficient Cognitive Radio Sensor Networks: Parametric and Convex Transformations

    PubMed Central

    Naeem, Muhammad; Illanko, Kandasamy; Karmokar, Ashok; Anpalagan, Alagan; Jaseemuddin, Muhammad

    2013-01-01

    Designing energy-efficient cognitive radio sensor networks is important to intelligently use battery energy and to maximize the sensor network life. In this paper, the problem of determining the power allocation that maximizes the energy-efficiency of cognitive radio-based wireless sensor networks is formed as a constrained optimization problem, where the objective function is the ratio of network throughput and the network power. The proposed constrained optimization problem belongs to a class of nonlinear fractional programming problems. Charnes-Cooper Transformation is used to transform the nonlinear fractional problem into an equivalent concave optimization problem. The structure of the power allocation policy for the transformed concave problem is found to be of a water-filling type. The problem is also transformed into a parametric form for which a ε-optimal iterative solution exists. The convergence of the iterative algorithms is proven, and numerical solutions are presented. The iterative solutions are compared with the optimal solution obtained from the transformed concave problem, and the effects of different system parameters (interference threshold level, the number of primary users and secondary sensor nodes) on the performance of the proposed algorithms are investigated. PMID:23966194

  18. Joint optimization of sensing threshold and transmission power in wideband cognitive radio with energy detection

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Bi, Guoan; Jia, Min; Guan, Yong Liang; Zhong, Weizhi; Lin, Rui

    2013-07-01

    this paper, we consider a wideband cognitive radio system that operates over multiple idle subchannels. A joint optimization of sensing threshold and transmission power is proposed, which maximizes the total throughput subject to the constraints on the total interference, the total power, and the probabilities of false alarm and detection of each subchannel. An alternative joint optimization is proposed, which minimizes the total interference under the constraint of the total throughput. The bilevel optimization method is used to solve the proposed optimization problems with a minimized iteration complexity. The mixed-variable optimization problem is divided into two single-variable convex optimization subproblems: the upper level for threshold optimization and the lower level for power optimization. Weighed cooperative sensing is proposed to maximize the detection probability by choosing the optimal weighed factors. The simulations show that the proposed joint optimization algorithm can achieve desirable improvement on the throughput of cognitive radio at the same interference level to primary user, or vice versa within the limits on the probabilities of false alarm and miss detection, and the weighed cooperative sensing can considerably improve sensing performance compared with the unweighed cooperative sensing and single-user sensing.

  19. Estimation of Distribution Algorithm for Resource Allocation in Green Cooperative Cognitive Radio Sensor Networks

    PubMed Central

    Naeem, Muhammad; Pareek, Udit; Lee, Daniel C.; Anpalagan, Alagan

    2013-01-01

    Due to the rapid increase in the usage and demand of wireless sensor networks (WSN), the limited frequency spectrum available for WSN applications will be extremely crowded in the near future. More sensor devices also mean more recharging/replacement of batteries, which will cause significant impact on the global carbon footprint. In this paper, we propose a relay-assisted cognitive radio sensor network (CRSN) that allocates communication resources in an environmentally friendly manner. We use shared band amplify and forward relaying for cooperative communication in the proposed CRSN. We present a multi-objective optimization architecture for resource allocation in a green cooperative cognitive radio sensor network (GC-CRSN). The proposed multi-objective framework jointly performs relay assignment and power allocation in GC-CRSN, while optimizing two conflicting objectives. The first objective is to maximize the total throughput, and the second objective is to minimize the total transmission power of CRSN. The proposed relay assignment and power allocation problem is a non-convex mixed-integer non-linear optimization problem (NC-MINLP), which is generally non-deterministic polynomial-time (NP)-hard. We introduce a hybrid heuristic algorithm for this problem. The hybrid heuristic includes an estimation-of-distribution algorithm (EDA) for performing power allocation and iterative greedy schemes for constraint satisfaction and relay assignment. We analyze the throughput and power consumption tradeoff in GC-CRSN. A detailed analysis of the performance of the proposed algorithm is presented with the simulation results. PMID:23584119

  20. Optimal periodic cooperative spectrum sensing based on weight fusion in cognitive radio networks.

    PubMed

    Liu, Xin; Jia, Min; Gu, Xuemai; Tan, Xuezhi

    2013-04-19

    The performance of cooperative spectrum sensing in cognitive radio (CR) networks depends on the sensing mode, the sensing time and the number of cooperative users. In order to improve the sensing performance and reduce the interference to the primary user (PU), a periodic cooperative spectrum sensing model based on weight fusion is proposed in this paper. Moreover, the sensing period, the sensing time and the searching time are optimized, respectively. Firstly the sensing period is optimized to improve the spectrum utilization and reduce the interference, then the joint optimization algorithm of the local sensing time and the number of cooperative users, is proposed to obtain the optimal sensing time for improving the throughput of the cognitive radio user (CRU) during each period, and finally the water-filling principle is applied to optimize the searching time in order to make the CRU find an idle channel within the shortest time. The simulation results show that compared with the previous algorithms, the optimal sensing period can improve the spectrum utilization of the CRU and decrease the interference to the PU significantly, the optimal sensing time can make the CRU achieve the largest throughput, and the optimal searching time can make the CRU find an idle channel with the least time.

  1. Energy-efficient cognitive radio sensor networks: parametric and convex transformations.

    PubMed

    Naeem, Muhammad; Illanko, Kandasamy; Karmokar, Ashok; Anpalagan, Alagan; Jaseemuddin, Muhammad

    2013-08-21

    Designing energy-efficient cognitive radio sensor networks is important to intelligently use battery energy and to maximize the sensor network life. In this paper, the problem of determining the power allocation that maximizes the energy-efficiency of cognitive radio-based wireless sensor networks is formed as a constrained optimization problem, where the objective function is the ratio of network throughput and the network power. The proposed constrained optimization problem belongs to a class of nonlinear fractional programming problems. Charnes-Cooper Transformation is used to transform the nonlinear fractional problem into an equivalent concave optimization problem. The structure of the power allocation policy for the transformed concave problem is found to be of a water-filling type. The problem is also transformed into a parametric form for which a ε-optimal iterative solution exists. The convergence of the iterative algorithms is proven, and numerical solutions are presented. The iterative solutions are compared with the optimal solution obtained from the transformed concave problem, and the effects of different system parameters (interference threshold level, the number of primary users and secondary sensor nodes) on the performance of the proposed algorithms are investigated.

  2. A novel utility function for energy-efficient power control game in cognitive radio networks.

    PubMed

    Al-Gumaei, Yousef Ali; Noordin, Kamarul Ariffin; Reza, Ahmed Wasif; Dimyati, Kaharudin

    2015-01-01

    Spectrum scarcity is a major challenge in wireless communications systems requiring efficient usage and utilization. Cognitive radio network (CRN) is found as a promising technique to solve this problem of spectrum scarcity. It allows licensed and unlicensed users to share the same licensed spectrum band. Interference resulting from cognitive radios (CRs) has undesirable effects on quality of service (QoS) of both licensed and unlicensed systems where it causes degradation in received signal-to-noise ratio (SIR) of users. Power control is one of the most important techniques that can be used to mitigate interference and guarantee QoS in both systems. In this paper, we develop a new approach of a distributed power control for CRN based on utility and pricing. QoS of CR user is presented as a utility function via pricing and a distributed power control as a non-cooperative game in which users maximize their net utility (utility-price). We define the price as a real function of transmit power to increase pricing charge of the farthest CR users. We prove that the power control game proposed in this study has Nash Equilibrium as well as it is unique. The obtained results show that the proposed power control algorithm based on a new utility function has a significant reduction in transmit power consumption and high improvement in speed of convergence.

  3. Joint subchannel pairing and power control for cognitive radio networks with amplify-and-forward relaying.

    PubMed

    Shen, Yanyan; Wang, Shuqiang; Wei, Zhiming

    2014-01-01

    Dynamic spectrum sharing has drawn intensive attention in cognitive radio networks. The secondary users are allowed to use the available spectrum to transmit data if the interference to the primary users is maintained at a low level. Cooperative transmission for secondary users can reduce the transmission power and thus improve the performance further. We study the joint subchannel pairing and power allocation problem in relay-based cognitive radio networks. The objective is to maximize the sum rate of the secondary user that is helped by an amplify-and-forward relay. The individual power constraints at the source and the relay, the subchannel pairing constraints, and the interference power constraints are considered. The problem under consideration is formulated as a mixed integer programming problem. By the dual decomposition method, a joint optimal subchannel pairing and power allocation algorithm is proposed. To reduce the computational complexity, two suboptimal algorithms are developed. Simulations have been conducted to verify the performance of the proposed algorithms in terms of sum rate and average running time under different conditions.

  4. Spectrum Handoffs Based on Preemptive Repeat Priority Queue in Cognitive Radio Networks

    PubMed Central

    Yang, Xiaolong; Tan, Xuezhi; Ye, Liang; Ma, Lin

    2016-01-01

    Cognitive radio can significantly improve the spectrum efficiency, and spectrum handoff is considered as an important functionality to guarantee the quality of service (QoS) of primary users (PUs) and the continuity of data transmission of secondary users (SUs). In this paper, we propose an analytical framework based on a preemptive repeat identical (PRI) M/G/1 queuing network model to characterize spectrum handoff behaviors with general service time distribution of both primary and secondary connections, multiple interruptions and transmission delay resulting from the appearance of primary connections. Then, we derive the close-expression of the extended data delivery and the system sojourn time in both staying and changing scenarios. In addition, based on analysis of spectrum handoff behaviors resulting from multiple interruptions caused by the appearance of the primary connections, we investigate the traffic-adaptive policy, by which the considered SU will optimally adjust its handoff spectrum policy. Moreover, we investigate the admissible region and provide the reference for designing the admission control rule for the arriving secondary connection requests. Finally, simulation results verify that our proposed analytical framework is reasonable and can provide the reference for executing the optimal spectrum handoff strategy and designing the admission control rule for the SU in cognitive radio networks. PMID:27447644

  5. Leasing-Based Performance Analysis in Energy Harvesting Cognitive Radio Networks.

    PubMed

    Zeng, Fanzi; Xu, Jisheng

    2016-02-27

    In this paper, we consider an energy harvesting cognitive radio network (CRN), where both of primary user (PU) and secondary user (SU) are operating in time slotted mode, and the SU powered exclusively by the energy harvested from the radio signal of the PU. The SU can only perform either energy harvesting or data transmission due to the hardware limitation. In this case, the entire time-slot is segmented into two non-overlapping fractions. During the first sub-timeslot, the SU can harvest energy from the ambient radio signal when the PU is transmitting. In order to obtain more revenue, the PU leases a portion of its time to SU, while the SU can transmit its own data by using the harvested energy. According to convex optimization, we get the optimal leasing time to maximize the SU's throughput while guaranteeing the quality of service (QoS) of PU. To evaluate the performance of our proposed spectrum leasing scheme, we compare the utility of PU and the energy efficiency ratio of the entire networks in our framework with the conventional strategies respectively. The numerical simulation results prove the superiority of our proposed spectrum leasing scheme.

  6. Leasing-Based Performance Analysis in Energy Harvesting Cognitive Radio Networks

    PubMed Central

    Zeng, Fanzi; Xu, Jisheng

    2016-01-01

    In this paper, we consider an energy harvesting cognitive radio network (CRN), where both of primary user (PU) and secondary user (SU) are operating in time slotted mode, and the SU powered exclusively by the energy harvested from the radio signal of the PU. The SU can only perform either energy harvesting or data transmission due to the hardware limitation. In this case, the entire time-slot is segmented into two non-overlapping fractions. During the first sub-timeslot, the SU can harvest energy from the ambient radio signal when the PU is transmitting. In order to obtain more revenue, the PU leases a portion of its time to SU, while the SU can transmit its own data by using the harvested energy. According to convex optimization, we get the optimal leasing time to maximize the SU’s throughput while guaranteeing the quality of service (QoS) of PU. To evaluate the performance of our proposed spectrum leasing scheme, we compare the utility of PU and the energy efficiency ratio of the entire networks in our framework with the conventional strategies respectively. The numerical simulation results prove the superiority of our proposed spectrum leasing scheme. PMID:26927131

  7. A Novel Dynamic Spectrum Access Framework Based on Reinforcement Learning for Cognitive Radio Sensor Networks.

    PubMed

    Lin, Yun; Wang, Chao; Wang, Jiaxing; Dou, Zheng

    2016-10-12

    Cognitive radio sensor networks are one of the kinds of application where cognitive techniques can be adopted and have many potential applications, challenges and future research trends. According to the research surveys, dynamic spectrum access is an important and necessary technology for future cognitive sensor networks. Traditional methods of dynamic spectrum access are based on spectrum holes and they have some drawbacks, such as low accessibility and high interruptibility, which negatively affect the transmission performance of the sensor networks. To address this problem, in this paper a new initialization mechanism is proposed to establish a communication link and set up a sensor network without adopting spectrum holes to convey control information. Specifically, firstly a transmission channel model for analyzing the maximum accessible capacity for three different polices in a fading environment is discussed. Secondly, a hybrid spectrum access algorithm based on a reinforcement learning model is proposed for the power allocation problem of both the transmission channel and the control channel. Finally, extensive simulations have been conducted and simulation results show that this new algorithm provides a significant improvement in terms of the tradeoff between the control channel reliability and the efficiency of the transmission channel.

  8. A Novel Dynamic Spectrum Access Framework Based on Reinforcement Learning for Cognitive Radio Sensor Networks

    PubMed Central

    Lin, Yun; Wang, Chao; Wang, Jiaxing; Dou, Zheng

    2016-01-01

    Cognitive radio sensor networks are one of the kinds of application where cognitive techniques can be adopted and have many potential applications, challenges and future research trends. According to the research surveys, dynamic spectrum access is an important and necessary technology for future cognitive sensor networks. Traditional methods of dynamic spectrum access are based on spectrum holes and they have some drawbacks, such as low accessibility and high interruptibility, which negatively affect the transmission performance of the sensor networks. To address this problem, in this paper a new initialization mechanism is proposed to establish a communication link and set up a sensor network without adopting spectrum holes to convey control information. Specifically, firstly a transmission channel model for analyzing the maximum accessible capacity for three different polices in a fading environment is discussed. Secondly, a hybrid spectrum access algorithm based on a reinforcement learning model is proposed for the power allocation problem of both the transmission channel and the control channel. Finally, extensive simulations have been conducted and simulation results show that this new algorithm provides a significant improvement in terms of the tradeoff between the control channel reliability and the efficiency of the transmission channel. PMID:27754316

  9. Optimal power allocation based on sum-throughput maximization for energy harvesting cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Xie, Zhenwei; Zhu, Qi

    2017-01-01

    In this study, an optimal power allocation algorithm by maximizing the sum-throughput in energy harvesting cognitive radio networks is proposed. Under the causality constraints of the harvested energy by solar radiation, electromagnetic waves and so on in the two secondary users (SUs), and the interference constraint in the primary user (PU), the sum-throughput maximization problem is formulated. The algorithm decomposes the interference threshold constraint to the power upper bounds of the two SUs. Then, the power allocation problems of the two SUs can be solved by a directional water-filling algorithm (DWA) with the power upper bounds, respectively. The paper gives the algorithm steps and simulation results, and the simulation results verify that the proposed algorithm has obvious advantages over the other two algorithms.

  10. Using Trust to Establish a Secure Routing Model in Cognitive Radio Network

    PubMed Central

    Zhang, Guanghua; Chen, Zhenguo; Tian, Liqin; Zhang, Dongwen

    2015-01-01

    Specific to the selective forwarding attack on routing in cognitive radio network, this paper proposes a trust-based secure routing model. Through monitoring nodes’ forwarding behaviors, trusts of nodes are constructed to identify malicious nodes. In consideration of that routing selection-based model must be closely collaborative with spectrum allocation, a route request piggybacking available spectrum opportunities is sent to non-malicious nodes. In the routing decision phase, nodes’ trusts are used to construct available path trusts and delay measurement is combined for making routing decisions. At the same time, according to the trust classification, different responses are made specific to their service requests. By adopting stricter punishment on malicious behaviors from non-trusted nodes, the cooperation of nodes in routing can be stimulated. Simulation results and analysis indicate that this model has good performance in network throughput and end-to-end delay under the selective forwarding attack. PMID:26421843

  11. Spectral Efficiency Comparison of OFDM/FBMC for Uplink Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Le Ruyet, D.; Roviras, D.; Medjahdi, Y.; Sun, H.

    2010-12-01

    Cognitive radio (CR) is proposed to automatically detect and exploit unused spectrum while avoiding harmful interference to the incumbent system. In this paper, we emphasize the channel capacity comparison of a CR network using two types of multicarrier communications: conventional Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) and Filter Bank based MultiCarrier (FBMC) modulations. We use a resource allocation algorithm in which subcarrier assignment and power allocation are carried out sequentially. By taking the impact of Inter-Cell Interference (ICI) resulting from timing offset into account, the maximization of total information rates is formulated under an uplink scenario with pathloss and Rayleigh fading, subject to maximum power constraint as well as mutual interference constraint between primary user (PU) and secondary user (SU). Final simulation results show that FBMC can achieve higher channel capacity than OFDM because of the low spectral leakage of its prototype filter.

  12. Using Trust to Establish a Secure Routing Model in Cognitive Radio Network.

    PubMed

    Zhang, Guanghua; Chen, Zhenguo; Tian, Liqin; Zhang, Dongwen

    2015-01-01

    Specific to the selective forwarding attack on routing in cognitive radio network, this paper proposes a trust-based secure routing model. Through monitoring nodes' forwarding behaviors, trusts of nodes are constructed to identify malicious nodes. In consideration of that routing selection-based model must be closely collaborative with spectrum allocation, a route request piggybacking available spectrum opportunities is sent to non-malicious nodes. In the routing decision phase, nodes' trusts are used to construct available path trusts and delay measurement is combined for making routing decisions. At the same time, according to the trust classification, different responses are made specific to their service requests. By adopting stricter punishment on malicious behaviors from non-trusted nodes, the cooperation of nodes in routing can be stimulated. Simulation results and analysis indicate that this model has good performance in network throughput and end-to-end delay under the selective forwarding attack.

  13. Comparasion of Energy Detection in Cognitive Radio over different fading channels

    NASA Astrophysics Data System (ADS)

    Buttar, Simar

    2012-07-01

    With the advance of wireless communications, the problem of bandwidth scarcity has become more prominent. Cognitive radio technology has come out as a way to solve this problem by allowing the unlicensed users to use the licensed bands opportunistically. To sense the existence of licensed users, many spectrum sensing techniques have been devised. In this paper, energy detection and cyclic prefix is used for spectrum sensing.The comparison of ROC curves has been done for various wireless fading channels using squaring and cubingoperation,the improvement has gone as high as up to 0.6 times for AWGN channel and 0.4 times for Rayleigh channel as we go from squaring to cubing operation in an energy detector. Closed form expressions for Probability of detection for AWGN and Rayleigh channels are described.Nakagami fading channel shows worst results .

  14. Capacity of Cognitive Radio with Partial Channel Distribution Information in Rayleigh Fading Environments

    NASA Astrophysics Data System (ADS)

    Xu, D.; Li, Q.

    2015-11-01

    This paper investigates the capacity of the secondary user (SU) in a cognitive radio (CR) network in Rayleigh fading environments. Different from existing works where perfect channel state information (CSI) or channel distribution information (CDI) of the interference link from the SU to the primary user (PU) is assumed to be available, this paper assumes that only partial CDI is available. Specifically, we assume the distribution parameter is unknown and estimated from a set of channel gain samples. With such partial CDI, closed-form expressions for the ergodic and outage capacities of the SU are obtained under the transmit power and the interference outage constraints. It is shown that the capacity with partial CDI is not degraded compared to that with perfect CDI if the interference outage constraint is loose. It is also shown that the capacity can be significantly improved by increasing the number of channel gain samples.

  15. A DS-UWB Cognitive Radio System Based on Bridge Function Smart Codes

    NASA Astrophysics Data System (ADS)

    Xu, Yafei; Hong, Sheng; Zhao, Guodong; Zhang, Fengyuan; di, Jinshan; Zhang, Qishan

    This paper proposes a direct-sequence UWB Gaussian pulse of cognitive radio systems based on bridge function smart sequence matrix and the Gaussian pulse. As the system uses the spreading sequence code, that is the bridge function smart code sequence, the zero correlation zones (ZCZs) which the bridge function sequences' auto-correlation functions had, could reduce multipath fading of the pulse interference. The Modulated channel signal was sent into the IEEE 802.15.3a UWB channel. We analysis the ZCZs's inhibition to the interference multipath interference (MPI), as one of the main system sources interferences. The simulation in SIMULINK/MATLAB is described in detail. The result shows the system has better performance by comparison with that employing Walsh sequence square matrix, and it was verified by the formula in principle.

  16. SNR Wall Effect Alleviation by Generalized Detector Employed in Cognitive Radio Networks

    PubMed Central

    Shbat, Modar Safir; Tuzlukov, Vyacheslav

    2015-01-01

    The most commonly used spectrum sensing techniques in cognitive radio (CR) networks, such as the energy detector (ED), matched filter (MF), and others, suffer from the noise uncertainty and signal-to-noise ratio (SNR) wall phenomenon. These detectors cannot achieve the required signal detection performance regardless of the sensing time. In this paper, we explore a signal processing scheme, namely, the generalized detector (GD) constructed based on the generalized approach to signal processing (GASP) in noise, in spectrum sensing of CR network based on antenna array with the purpose to alleviate the SNR wall problem and improve the signal detection robustness under the low SNR. The simulation results confirm our theoretical issues and effectiveness of GD implementation in CR networks based on antenna array. PMID:26151216

  17. Energy-Efficient Channel Handoff for Sensor Network-Assisted Cognitive Radio Network

    PubMed Central

    Usman, Muhammad; Sajjad Khan, Muhammad; Vu-Van, Hiep; Insoo, Koo

    2015-01-01

    The visiting and less-privileged status of the secondary users (SUs) in a cognitive radio network obligates them to release the occupied channel instantly when it is reclaimed by the primary user. The SU has a choice to make: either wait for the channel to become free, thus conserving energy at the expense of delayed transmission and delivery, or find and switch to a vacant channel, thereby avoiding delay in transmission at the expense of increased energy consumption. An energy-efficient decision that considers the tradeoff between energy consumption and continuous transmission needs to be taken as to whether to switch the channels. In this work, we consider a sensor network-assisted cognitive radio network and propose a backup channel, which is sensed by the SU in parallel with the operating channel that is being sensed by the sensor nodes. Imperfect channel sensing and residual energy of the SU are considered in order to develop an energy-efficient handoff strategy using the partially observable Markov decision process (POMDP), which considers beliefs about the operating and backup channels and the remaining energy of the SU in order to take an optimal channel handoff decision on the question “Should we switch the channel?” The objective is to dynamically decide in each time slot whether the SU should switch the channel or not in order to maximize throughput by utilizing energy efficiently. Extensive simulations were performed to show the effectiveness of the proposed channel handoff strategy, which was demonstrated in the form of throughput with respect to various parameters, i.e., detection probability, the channel idle probabilities of the operating and backup channels, and the maximum energy of the SU. PMID:26213936

  18. Energy-Efficient Channel Handoff for Sensor Network-Assisted Cognitive Radio Network.

    PubMed

    Usman, Muhammad; Khan, Muhammad Sajjad; Vu-Van, Hiep; Insoo, Koo

    2015-07-23

    The visiting and less-privileged status of the secondary users (SUs) in a cognitive radio network obligates them to release the occupied channel instantly when it is reclaimed by the primary user. The SU has a choice to make: either wait for the channel to become free, thus conserving energy at the expense of delayed transmission and delivery, or find and switch to a vacant channel, thereby avoiding delay in transmission at the expense of increased energy consumption. An energy-efficient decision that considers the tradeoff between energy consumption and continuous transmission needs to be taken as to whether to switch the channels. In this work, we consider a sensor network-assisted cognitive radio network and propose a backup channel, which is sensed by the SU in parallel with the operating channel that is being sensed by the sensor nodes. Imperfect channel sensing and residual energy of the SU are considered in order to develop an energy-efficient handoff strategy using the partially observable Markov decision process (POMDP), which considers beliefs about the operating and backup channels and the remaining energy of the SU in order to take an optimal channel handoff decision on the question "Should we switch the channel?" The objective is to dynamically decide in each time slot whether the SU should switch the channel or not in order to maximize throughput by utilizing energy efficiently. Extensive simulations were performed to show the effectiveness of the proposed channel handoff strategy, which was demonstrated in the form of throughput with respect to various parameters, i.e., detection probability, the channel idle probabilities of the operating and backup channels, and the maximum energy of the SU.

  19. Spectrum sharing in cognitive radio networks--an auction-based approach.

    PubMed

    Wang, Xinbing; Li, Zheng; Xu, Pengchao; Xu, Youyun; Gao, Xinbo; Chen, Hsiao-Hwa

    2010-06-01

    Cognitive radio is emerging as a promising technique to improve the utilization of the radio frequency spectrum. In this paper, we consider the problem of spectrum sharing among primary (or "licensed") users (PUs) and secondary (or "unlicensed") users (SUs). We formulate the problem based on bandwidth auction, in which each SU makes a bid for the amount of spectrum and each PU may assign the spectrum among the SUs by itself according to the information from the SUs without degrading its own performance. We show that the auction is a noncooperative game and that Nash equilibrium (NE) can be its solution. We first consider a single-PU network to investigate the existence and uniqueness of the NE and further discuss the fairness among the SUs under given conditions. Then, we present a dynamic updating algorithm in which each SU achieves NE in a distributed manner. The stability condition of the dynamic behavior for this spectrum-sharing scheme is studied. The discussion is generalized to the case in which there are multiple PUs in the network, where the properties of the NE are shown under appropriate conditions. Simulations were used to evaluate the system performance and verify the effectiveness of the proposed algorithm.

  20. Adaptive threshold determination for efficient channel sensing in cognitive radio network using mobile sensors

    NASA Astrophysics Data System (ADS)

    Morshed, M. N.; Khatun, S.; Kamarudin, L. M.; Aljunid, S. A.; Ahmad, R. B.; Zakaria, A.; Fakir, M. M.

    2017-03-01

    Spectrum saturation problem is a major issue in wireless communication systems all over the world. Huge number of users is joining each day to the existing fixed band frequency but the bandwidth is not increasing. These requirements demand for efficient and intelligent use of spectrum. To solve this issue, the Cognitive Radio (CR) is the best choice. Spectrum sensing of a wireless heterogeneous network is a fundamental issue to detect the presence of primary users' signals in CR networks. In order to protect primary users (PUs) from harmful interference, the spectrum sensing scheme is required to perform well even in low signal-to-noise ratio (SNR) environments. Meanwhile, the sensing period is usually required to be short enough so that secondary (unlicensed) users (SUs) can fully utilize the available spectrum. CR networks can be designed to manage the radio spectrum more efficiently by utilizing the spectrum holes in primary user's licensed frequency bands. In this paper, we have proposed an adaptive threshold detection method to detect presence of PU signal using free space path loss (FSPL) model in 2.4 GHz WLAN network. The model is designed for mobile sensors embedded in smartphones. The mobile sensors acts as SU while the existing WLAN network (channels) works as PU. The theoretical results show that the desired threshold range detection of mobile sensors mainly depends on the noise floor level of the location in consideration.

  1. Non-Orthogonal Random Access in MIMO Cognitive Radio Networks: Beamforming, Power Allocation, and Opportunistic Transmission.

    PubMed

    Lin, Huifa; Shin, Won-Yong

    2017-01-01

    We study secondary random access in multi-input multi-output cognitive radio networks, where a slotted ALOHA-type protocol and successive interference cancellation are used. We first introduce three types of transmit beamforming performed by secondary users, where multiple antennas are used to suppress the interference at the primary base station and/or to increase the received signal power at the secondary base station. Then, we show a simple decentralized power allocation along with the equivalent single-antenna conversion. To exploit the multiuser diversity gain, an opportunistic transmission protocol is proposed, where the secondary users generating less interference are opportunistically selected, resulting in a further reduction of the interference temperature. The proposed methods are validated via computer simulations. Numerical results show that increasing the number of transmit antennas can greatly reduce the interference temperature, while increasing the number of receive antennas leads to a reduction of the total transmit power. Optimal parameter values of the opportunistic transmission protocol are examined according to three types of beamforming and different antenna configurations, in terms of maximizing the cognitive transmission capacity. All the beamforming, decentralized power allocation, and opportunistic transmission protocol are performed by the secondary users in a decentralized manner, thus resulting in an easy implementation in practice.

  2. Channel direction information probing for multi-antenna cognitive radio system

    NASA Astrophysics Data System (ADS)

    Yuan, Fang; Villardi, Gabriel Porto; Kojima, Fumihide; Yano, Hiroyuki

    2015-12-01

    This work studies the problem of channel direction information (CDI) probing for multi-antenna cognitive radio system. The CDI of the channel from the secondary transmitter (ST) to primary receiver (PR) is elementary information in designing the beamforming at the ST for mitigating the interference to the PR. However, lacking the explicit cooperation between primary and secondary systems, the CDI has to be acquired by probing at the ST, which is challenging. To solve this, we consider the line of sight (LoS) channel between the ST and the PR, and propose one CDI probing scheme for the ST. Specifically, the ST sends two types of probing signals by beamforming towards an interested region where both the secondary receiver (SR) and the PR are located and then actively learns the hidden feedback information from the primary system to acquire the CDI. The proposed scheme has a closed-form solution, and avoids the iteration between the probing and acquisition, which is desirable for practical system. Moreover, we show that the proposed probing scheme can be extended for primary systems working under multi-access channel and broadcasting channel. Simulation results demonstrate that the proposed scheme can improve the accuracy of the acquired CDI at the ST in cognitive ratio system remarkably.

  3. Non-Orthogonal Random Access in MIMO Cognitive Radio Networks: Beamforming, Power Allocation, and Opportunistic Transmission

    PubMed Central

    Lin, Huifa; Shin, Won-Yong

    2017-01-01

    We study secondary random access in multi-input multi-output cognitive radio networks, where a slotted ALOHA-type protocol and successive interference cancellation are used. We first introduce three types of transmit beamforming performed by secondary users, where multiple antennas are used to suppress the interference at the primary base station and/or to increase the received signal power at the secondary base station. Then, we show a simple decentralized power allocation along with the equivalent single-antenna conversion. To exploit the multiuser diversity gain, an opportunistic transmission protocol is proposed, where the secondary users generating less interference are opportunistically selected, resulting in a further reduction of the interference temperature. The proposed methods are validated via computer simulations. Numerical results show that increasing the number of transmit antennas can greatly reduce the interference temperature, while increasing the number of receive antennas leads to a reduction of the total transmit power. Optimal parameter values of the opportunistic transmission protocol are examined according to three types of beamforming and different antenna configurations, in terms of maximizing the cognitive transmission capacity. All the beamforming, decentralized power allocation, and opportunistic transmission protocol are performed by the secondary users in a decentralized manner, thus resulting in an easy implementation in practice. PMID:28076402

  4. Q-learning-based cross-layer Learning Engine design for cognitive radio network

    NASA Astrophysics Data System (ADS)

    Liu, Congbin; Jiang, Hong; Yang, Yanchao; Ma, Jinghui

    2013-03-01

    In cognitive radio (CR) networks, Learning Engine has considerable significance on dynamic spectrum access (DSA) and implementation of cognitive function. In this paper, a cross-layer learning engine design scheme is proposed by jointly considering physical-layer dynamic channel selection, modulation and coding scheme, data-link layer frame length in CR networks, with the purpose to maximize system throughput and simultaneously meet heterogeneous Quality of Service (QoS) requirements. The wireless fading channel is modeled as a continuous state space Markov decision process (MDP) and the licensed network activity is abstracted as a finite-state one. We introduce Q-learning algorithm to realize the function of learning from state space and adapt wireless environment. And meanwhile a large scale Qfunction approximator based on support vector machine (SVM) is employed to effectively reduce storage requirement and decrease the operation complexity. A cross-layer learning engine communication platform is realized by using Matlab simulator. the simulation results demonstrate that while lacking system prior knowledge, the learning engine can effectively achieve configuration function by system cross-layer learning approach, and furthermore, it can converge to the best—i.e., realize reconfiguration function in CR networks while meeting users' QoS.

  5. A Software-Based Network Infrastructure for Mobile Ad Hoc Data Networking in Support of Small Tactical Units Using the SINCGARS Radio

    DTIC Science & Technology

    2006-03-01

    RT- 1523C/D/E) is designed to interface with the serial port of Data Terminal Equipment (DTE), such as a laptop computer, via an RS232 protocol...widest impact, the radio used in this research had to provide this well known interface. In RS232 Data Mode, the RT-1523C/D/E is capable of a maximum...have a route to D. Those that do not have a route will prepare to flood the route request. Route Requests are sent with a Time-To-Live ( TTL ) of

  6. The Application of Cognitive Radio to Coordinated Unmanned Aerial Vehicle (UAV) Missions

    DTIC Science & Technology

    2011-06-01

    iii LIST OF FIGURES Figure 1 GNU Radio /USRP-Based UAV Downlink Simulator... radios based on the GNU Radio /Universal Software Radio Peripheral (USRP) open-source platform to meet the needs of the UAVs of interest. Our tests...indicated that the GNU Radio /USRP combination can support data rates of at least 1 Mbps for small UAV platforms using DBPSK, DQPSK, and GMSK modulations

  7. Dynamic Pilot Channel Transmission with Adaptive Receive Filter Configuration for Cognitive Radio System

    NASA Astrophysics Data System (ADS)

    Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro

    When a cognitive radio system dynamically utilizes a frequency band, channel control information must be communicated over the network in order for the currently available carrier frequencies to be shared. In order to keep efficient spectrum utilization, this control information should also be dynamically transmitted through channels such as cognitive pilot channels based on the channel conditions. If transmitters dynamically select carrier frequencies, receivers must receive the control signal without knowledge of its carrier frequencies. A novel scheme called differential code parallel transmission (DCPT) enables receivers to receive low-rate information without any knowledge of the carrier frequency. The transmitter simultaneously transmits two signals whose carrier frequencies are separated by a predefined value. The absolute values of the carrier frequencies can be varied. When the receiver receives the DCPT signal, it multiplies the signal by a frequency-shifted version of itself; this yields a DC component that represents the data signal, which is then demodulated. However, the multiplication process results in the noise power being squared, necessitating high received signal power. In this paper, to realize a bandpass filter that passes only DCPT signals of unknown frequency and that suppresses noise and interference at other frequencies, a DCPT-adaptive bandpass filter (ABF) that employs an adaptive equalizer is proposed. In the training phase, the received signal is the filter input and the frequency-shifted signal is the training input. Then, the filter is trained to pass the higher-frequency signal of the two DCPT signals. The performance of DCPT-ABF is evaluated through computer simulations. We find that DCPT-ABF operates successfully even under strong interference.

  8. A robust power spectrum split cancellation-based spectrum sensing method for cognitive radio systems

    NASA Astrophysics Data System (ADS)

    Qi, Pei-Han; Li, Zan; Si, Jiang-Bo; Gao, Rui

    2014-12-01

    Spectrum sensing is an essential component to realize the cognitive radio, and the requirement for real-time spectrum sensing in the case of lacking prior information, fading channel, and noise uncertainty, indeed poses a major challenge to the classical spectrum sensing algorithms. Based on the stochastic properties of scalar transformation of power spectral density (PSD), a novel spectrum sensing algorithm, referred to as the power spectral density split cancellation method (PSC), is proposed in this paper. The PSC makes use of a scalar value as a test statistic, which is the ratio of each subband power to the full band power. Besides, by exploiting the asymptotic normality and independence of Fourier transform, the distribution of the ratio and the mathematical expressions for the probabilities of false alarm and detection in different channel models are derived. Further, the exact closed-form expression of decision threshold is calculated in accordance with Neyman—Pearson criterion. Analytical and simulation results show that the PSC is invulnerable to noise uncertainty, and can achive excellent detection performance without prior knowledge in additive white Gaussian noise and flat slow fading channels. In addition, the PSC benefits from a low computational cost, which can be completed in microseconds.

  9. Decision-making scenarios for reducing the computational complexity in a green cognitive radio receiver

    NASA Astrophysics Data System (ADS)

    Bourbia, Salma; Guennec, Daniel Le; Grati, Khaled; Ghazel, Adel

    2014-10-01

    The idea that we highlight in this paper is how to reduce the computational complexity by limiting the processing in the receiver chain. For this we seek for limiting the use of the beamforming process and the equalization process according to the conditions. Indeed, with the cognitive features the receiver observes its environment and decides to either keep or turn off these processes without degrading its performances. The decision method that we developed is based on the statistical modeling of the radio environment, and the purpose of this approach is to minimize the percentage of bad decisions by considering the errors of observation. Furthermore, we first address the two decision scenarios separately and we seek to prove that the decisions to turn off the equalizer and the beamforming, when they are not necessary, lead to reduce the computational complexity of the receiver. Then we focus on the behavior of the receiver facing both decision scenarios. Thus, we formulate the decision problem in two different ways: in the first case we consider that the receiver performs joint decisions about the two operations of beamforming and equalization, in the second case we suppose that it handles the two decision scenarios sequentially. We compare then the performance of the receiver in the two cases.

  10. A Real Valued Neural Network Based Autoregressive Energy Detector for Cognitive Radio Application.

    PubMed

    Onumanyi, A J; Onwuka, E N; Aibinu, A M; Ugweje, O C; Salami, M J E

    2014-01-01

    A real valued neural network (RVNN) based energy detector (ED) is proposed and analyzed for cognitive radio (CR) application. This was developed using a known two-layered RVNN model to estimate the model coefficients of an autoregressive (AR) system. By using appropriate modules and a well-designed detector, the power spectral density (PSD) of the AR system transfer function was estimated and subsequent receiver operating characteristic (ROC) curves of the detector generated and analyzed. A high detection performance with low false alarm rate was observed for varying signal to noise ratio (SNR), sample number, and model order conditions. The proposed RVNN based ED was then compared to the simple periodogram (SP), Welch periodogram (WP), multitaper (MT), Yule-Walker (YW), Burg (BG), and covariance (CV) based ED techniques. The proposed detector showed better performance than the SP, WP, and MT while providing better false alarm performance than the YW, BG, and CV. Data provided here support the effectiveness of the proposed RVNN based ED for CR application.

  11. Spectrum Sharing Based on a Bertrand Game in Cognitive Radio Sensor Networks.

    PubMed

    Zeng, Biqing; Zhang, Chi; Hu, Pianpian; Wang, Shengyu

    2017-01-07

    In the study of power control and allocation based on pricing, the utility of secondary users is usually studied from the perspective of the signal to noise ratio. The study of secondary user utility from the perspective of communication demand can not only promote the secondary users to meet the maximum communication needs, but also to maximize the utilization of spectrum resources, however, research in this area is lacking, so from the viewpoint of meeting the demand of network communication, this paper designs a two stage model to solve spectrum leasing and allocation problem in cognitive radio sensor networks (CRSNs). In the first stage, the secondary base station collects the secondary network communication requirements, and rents spectrum resources from several primary base stations using the Bertrand game to model the transaction behavior of the primary base station and secondary base station. The second stage, the subcarriers and power allocation problem of secondary base stations is defined as a nonlinear programming problem to be solved based on Nash bargaining. The simulation results show that the proposed model can satisfy the communication requirements of each user in a fair and efficient way compared to other spectrum sharing schemes.

  12. Throughput Maximization for Sensor-Aided Cognitive Radio Networks with Continuous Energy Arrivals

    PubMed Central

    Nguyen, Thanh-Tung; Koo, Insoo

    2015-01-01

    We consider a Sensor-Aided Cognitive Radio Network (SACRN) in which sensors capable of harvesting energy are distributed throughout the network to support secondary transmitters for sensing licensed channels in order to improve both energy and spectral efficiency. Harvesting ambient energy is one of the most promising solutions to mitigate energy deficiency, prolong device lifetime, and partly reduce the battery size of devices. So far, many works related to SACRN have considered single secondary users capable of harvesting energy in whole slot as well as short-term throughput. In the paper, we consider two types of energy harvesting sensor nodes (EHSN): Type-I sensor nodes will harvest ambient energy in whole slot duration, whereas type-II sensor nodes will only harvest energy after carrying out spectrum sensing. In the paper, we also investigate long-term throughput in the scheduling window, and formulate the throughput maximization problem by considering energy-neutral operation conditions of type-I and -II sensors and the target detection probability. Through simulations, it is shown that the sensing energy consumption of all sensor nodes can be efficiently managed with the proposed scheme to achieve optimal long-term throughput in the window. PMID:26633393

  13. Collision avoidance in TV white spaces: a cross-layer design approach for cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Foukalas, Fotis; Karetsos, George T.

    2015-07-01

    One of the most promising applications of cognitive radio networks (CRNs) is the efficient exploitation of TV white spaces (TVWSs) for enhancing the performance of wireless networks. In this paper, we propose a cross-layer design (CLD) of carrier sense multiple access with collision avoidance (CSMA/CA) mechanism at the medium access control (MAC) layer with spectrum sensing (SpSe) at the physical layer, for identifying the occupancy status of TV bands. The proposed CLD relies on a Markov chain model with a state pair containing both the SpSe and the CSMA/CA from which we derive the collision probability and the achievable throughput. Analytical and simulation results are obtained for different collision avoidance and SpSe implementation scenarios by varying the contention window, back off stage and probability of detection. The obtained results depict the achievable throughput under different collision avoidance and SpSe implementation scenarios indicating thereby the performance of collision avoidance in TVWSs-based CRNs.

  14. Mobility-Enhanced Reliable Geographical Forwarding in Cognitive Radio Sensor Networks

    PubMed Central

    Zubair, Suleiman; Syed Yusoff, Sharifah Kamilah; Fisal, Norsheila

    2016-01-01

    The emergence of the Internet of Things and the proliferation of mobile wireless devices has brought the area of mobile cognitive radio sensor networks (MCRSN) to the research spot light. Notwithstanding the potentials of CRSNs in terms of opportunistic channel usage for bursty traffic, the effect of the mobility of resource-constrained nodes to route stability, mobility-induced spatio-temporal spectral opportunities and primary user (PU) protection still remain open issues that need to be jointly addressed. To this effect, this paper proposes a mobile reliable geographical forwarding routing (MROR) protocol. MROR provides a robust mobile framework for geographical forwarding that is based on a mobility-induced channel availability model. It presents a comprehensive routing strategy that considers PU activity (to take care of routes that have to be built through PU coverage), PU signal protection (by the introduction of a mobility-induced guard (mguard) distance) and the random mobility-induced spatio-temporal spectrum opportunities (for enhancement of throughput). It also addresses the issue of frequent route maintenance that arises when speeds of the mobile nodes are considered as a routing metric. As a result, simulation has shown the ability of MROR to reduce the route failure rate by about 65% as against other schemes. In addition, further results show that MROR can improve both the throughput and goodput at the sink in an energy-efficient manner that is required in CRSNs as against compared works. PMID:26840312

  15. Coalitional Games in Partition Form for Joint Spectrum Sensing and Access in Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Saad, Walid; Han, Zhu; Zheng, Rong; Hjorungnes, Are; Basar, Tamer; Poor, H. Vincent

    2012-04-01

    Unlicensed secondary users (SUs) in cognitive radio networks are subject to an inherent tradeoff between spectrum sensing and spectrum access. Although each SU has an incentive to sense the primary user (PU) channels for locating spectrum holes, this exploration of the spectrum can come at the expense of a shorter transmission time, and, hence, a possibly smaller capacity for data transmission. This paper investigates the impact of this tradeoff on the cooperative strategies of a network of SUs that seek to cooperate in order to improve their view of the spectrum (sensing), reduce the possibility of interference among each other, and improve their transmission capacity (access). The problem is modeled as a coalitional game in partition form and an algorithm for coalition formation is proposed. Using the proposed algorithm, the SUs can make individual distributed decisions to join or leave a coalition while maximizing their utilities which capture the average time spent for sensing as well as the capacity achieved while accessing the spectrum. It is shown that, by using the proposed algorithm, the SUs can self-organize into a network partition composed of disjoint coalitions, with the members of each coalition cooperating to jointly optimize their sensing and access performance. Simulation results show the performance improvement that the proposed algorithm yields with respect to the non-cooperative case. The results also show how the algorithm allows the SUs to self-adapt to changes in the environment such as the change in the traffic of the PUs, or slow mobility.

  16. Joint Sensing and Power Allocation in Nonconvex Cognitive Radio Games: Quasi-Nash Equilibria

    NASA Astrophysics Data System (ADS)

    Pang, Jong-Shi; Scutari, Gesualdo

    2013-05-01

    In this paper, we propose a novel class of Nash problems for Cognitive Radio (CR) networks composed of multiple primary users (PUs) and secondary users (SUs) wherein each SU (player) competes against the others to maximize his own opportunistic throughput by choosing jointly the sensing duration, the detection thresholds, and the vector power allocation over a multichannel link. In addition to power budget constraints, several (deterministic or probabilistic) interference constraints can be accommodated in the proposed general formulation, such as constraints on the maximum individual/aggregate (probabilistic) interference tolerable from the PUs. To keep the optimization as decentralized as possible, global interference constraints, when present, are imposed via pricing; the prices are thus additional variables to be optimized. The resulting players' optimization problems are nonconvex and there are price clearance conditions associated with the nonconvex global interference constraints to be satisfied by the equilibria of the game, which make the analysis of the proposed game a challenging task; none of classical results in the game theory literature can be successfully applied. To deal with the nonconvexity of the game, we introduce a relaxed equilibrium concept, the Quasi-Nash Equilibrium (QNE), and study its main properties, performance, and connection with local Nash equilibria. Quite interestingly, the proposed game theoretical formulations yield a considerable performance improvement with respect to current centralized and decentralized designs of CR systems, which validates the concept of QNE.

  17. Computationally Efficient Power Allocation Algorithm in Multicarrier-Based Cognitive Radio Networks: OFDM and FBMC Systems

    NASA Astrophysics Data System (ADS)

    Shaat, Musbah; Bader, Faouzi

    2010-12-01

    Cognitive Radio (CR) systems have been proposed to increase the spectrum utilization by opportunistically access the unused spectrum. Multicarrier communication systems are promising candidates for CR systems. Due to its high spectral efficiency, filter bank multicarrier (FBMC) can be considered as an alternative to conventional orthogonal frequency division multiplexing (OFDM) for transmission over the CR networks. This paper addresses the problem of resource allocation in multicarrier-based CR networks. The objective is to maximize the downlink capacity of the network under both total power and interference introduced to the primary users (PUs) constraints. The optimal solution has high computational complexity which makes it unsuitable for practical applications and hence a low complexity suboptimal solution is proposed. The proposed algorithm utilizes the spectrum holes in PUs bands as well as active PU bands. The performance of the proposed algorithm is investigated for OFDM and FBMC based CR systems. Simulation results illustrate that the proposed resource allocation algorithm with low computational complexity achieves near optimal performance and proves the efficiency of using FBMC in CR context.

  18. Spectrum Sharing Based on a Bertrand Game in Cognitive Radio Sensor Networks

    PubMed Central

    Zeng, Biqing; Zhang, Chi; Hu, Pianpian; Wang, Shengyu

    2017-01-01

    In the study of power control and allocation based on pricing, the utility of secondary users is usually studied from the perspective of the signal to noise ratio. The study of secondary user utility from the perspective of communication demand can not only promote the secondary users to meet the maximum communication needs, but also to maximize the utilization of spectrum resources, however, research in this area is lacking, so from the viewpoint of meeting the demand of network communication, this paper designs a two stage model to solve spectrum leasing and allocation problem in cognitive radio sensor networks (CRSNs). In the first stage, the secondary base station collects the secondary network communication requirements, and rents spectrum resources from several primary base stations using the Bertrand game to model the transaction behavior of the primary base station and secondary base station. The second stage, the subcarriers and power allocation problem of secondary base stations is defined as a nonlinear programming problem to be solved based on Nash bargaining. The simulation results show that the proposed model can satisfy the communication requirements of each user in a fair and efficient way compared to other spectrum sharing schemes. PMID:28067850

  19. Cooperative spectrum sensing schemes with the interference constraint in cognitive radio networks.

    PubMed

    Do, Tri-Nhu; An, Beongku

    2014-05-05

    In this paper, we propose cooperative spectrum sensing schemes, called decode-and-forward cooperative spectrum sensing (DF-CSS) scheme and amplify-and-forward cooperative spectrum sensing (AF-CSS) scheme, in cognitive radio networks. The main goals and features of the proposed cooperative spectrum sensing schemes are as follows: first, we solve the problem of high demand for bandwidth in a soft decision scheme using in our proposed schemes. Furthermore, the impact of transmission power of relaying users which is determined by the interference constraint on sensing performance of cooperative spectrum sensing schemes is also investigated. Second, we analyze the sensing performance of our proposed cooperative spectrum sensing schemes in terms of detection probability and interference probability, respectively. We take into account the interference caused by secondary user (SU) to primary user (PU) in the case that the transmission power of the relaying users exceeds a predefined interference constraint assigned by the primary user. The simulation results show that in cooperative spectrum sensing schemes the total sensing performance depends not only on the interference tolerance level, but also on the relay protocols used. We also prove that high transmission power of relaying users increases the interference between the secondary networks and the primary network.

  20. Energy Efficiency in MIMO Underlay and Overlay Device-to-Device Communications and Cognitive Radio Systems

    NASA Astrophysics Data System (ADS)

    Zappone, Alessio; Matthiesen, Bho; Jorswieck, Eduard Axel

    2017-02-01

    This paper addresses the problem of resource allocation for systems in which a primary and a secondary link share the available spectrum by an underlay or overlay approach. After observing that such a scenario models both cognitive radio and D2D communications, we formulate the problem as the maximization of the secondary energy efficiency subject to a minimum rate requirement for the primary user. This leads to challenging non-convex, fractional problems. In the underlay scenario, we obtain the global solution by means of a suitable reformulation. In the overlay scenario, two algorithms are proposed. The first one yields a resource allocation fulfilling the first-order optimality conditions of the resource allocation problem, by solving a sequence of easier fractional problems. The second one enjoys a weaker optimality claim, but an even lower computational complexity. Numerical results demonstrate the merits of the proposed algorithms both in terms of energy-efficient performance and complexity, also showing that the two proposed algorithms for the overlay scenario perform very similarly, despite the different complexity.

  1. Performance Analysis of Control Signal Transmission Technique for Cognitive Radios in Dynamic Spectrum Access Networks

    NASA Astrophysics Data System (ADS)

    Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro

    When cognitive radio (CR) systems dynamically use the frequency band, a control signal is necessary to indicate which carrier frequencies are currently available in the network. In order to keep efficient spectrum utilization, this control signal also should be transmitted based on the channel conditions. If transmitters dynamically select carrier frequencies, receivers have to receive control signals without knowledge of their carrier frequencies. To enable such transmission and reception, this paper proposes a novel scheme called DCPT (Differential Code Parallel Transmission). With DCPT, receivers can receive low-rate information with no knowledge of the carrier frequencies. The transmitter transmits two signals whose carrier frequencies are spaced by a predefined value. The absolute values of the carrier frequencies can be varied. When the receiver acquires the DCPT signal, it multiplies the signal by a frequency-shifted version of the signal; this yields a DC component that represents the data signal which is then demodulated. The performance was evaluated by means of numerical analysis and computer simulation. We confirmed that DCPT operates successfully even under severe interference if its parameters are appropriately configured.

  2. Mobility-Enhanced Reliable Geographical Forwarding in Cognitive Radio Sensor Networks.

    PubMed

    Zubair, Suleiman; Syed Yusoff, Sharifah Kamilah; Fisal, Norsheila

    2016-01-29

    The emergence of the Internet of Things and the proliferation of mobile wireless devices has brought the area of mobile cognitive radio sensor networks (MCRSN) to the research spot light. Notwithstanding the potentials of CRSNs in terms of opportunistic channel usage for bursty traffic, the effect of the mobility of resource-constrained nodes to route stability, mobility-induced spatio-temporal spectral opportunities and primary user (PU) protection still remain open issues that need to be jointly addressed. To this effect, this paper proposes a mobile reliable geographical forwarding routing (MROR) protocol. MROR provides a robust mobile framework for geographical forwarding that is based on a mobility-induced channel availability model. It presents a comprehensive routing strategy that considers PU activity (to take care of routes that have to be built through PU coverage), PU signal protection (by the introduction of a mobility-induced guard (mguard) distance) and the random mobility-induced spatio-temporal spectrum opportunities (for enhancement of throughput). It also addresses the issue of frequent route maintenance that arises when speeds of the mobile nodes are considered as a routing metric. As a result, simulation has shown the ability of MROR to reduce the route failure rate by about 65% as against other schemes. In addition, further results show that MROR can improve both the throughput and goodput at the sink in an energy-efficient manner that is required in CRSNs as against compared works.

  3. Application of Reinforcement Learning in Cognitive Radio Networks: Models and Algorithms

    PubMed Central

    Yau, Kok-Lim Alvin; Poh, Geong-Sen; Chien, Su Fong; Al-Rawi, Hasan A. A.

    2014-01-01

    Cognitive radio (CR) enables unlicensed users to exploit the underutilized spectrum in licensed spectrum whilst minimizing interference to licensed users. Reinforcement learning (RL), which is an artificial intelligence approach, has been applied to enable each unlicensed user to observe and carry out optimal actions for performance enhancement in a wide range of schemes in CR, such as dynamic channel selection and channel sensing. This paper presents new discussions of RL in the context of CR networks. It provides an extensive review on how most schemes have been approached using the traditional and enhanced RL algorithms through state, action, and reward representations. Examples of the enhancements on RL, which do not appear in the traditional RL approach, are rules and cooperative learning. This paper also reviews performance enhancements brought about by the RL algorithms and open issues. This paper aims to establish a foundation in order to spark new research interests in this area. Our discussion has been presented in a tutorial manner so that it is comprehensive to readers outside the specialty of RL and CR. PMID:24995352

  4. Secure Cooperative Spectrum Sensing for the Cognitive Radio Network Using Nonuniform Reliability

    PubMed Central

    Usman, Muhammad; Koo, Insoo

    2014-01-01

    Both reliable detection of the primary signal in a noisy and fading environment and nullifying the effect of unauthorized users are important tasks in cognitive radio networks. To address these issues, we consider a cooperative spectrum sensing approach where each user is assigned nonuniform reliability based on the sensing performance. Users with poor channel or faulty sensor are assigned low reliability. The nonuniform reliabilities serve as identification tags and are used to isolate users with malicious behavior. We consider a link layer attack similar to the Byzantine attack, which falsifies the spectrum sensing data. Three different strategies are presented in this paper to ignore unreliable and malicious users in the network. Considering only reliable users for global decision improves sensing time and decreases collisions in the control channel. The fusion center uses the degree of reliability as a weighting factor to determine the global decision in scheme I. Schemes II and III consider the unreliability of users, which makes the computations even simpler. The proposed schemes reduce the number of sensing reports and increase the inference accuracy. The advantages of our proposed schemes over conventional cooperative spectrum sensing and the Chair-Varshney optimum rule are demonstrated through simulations. PMID:25295288

  5. Optimisation of sensing time and transmission time in cognitive radio-based smart grid networks

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Fu, Yuli; Yang, Junjie

    2016-07-01

    Cognitive radio (CR)-based smart grid (SG) networks have been widely recognised as emerging communication paradigms in power grids. However, a sufficient spectrum resource and reliability are two major challenges for real-time applications in CR-based SG networks. In this article, we study the traffic data collection problem. Based on the two-stage power pricing model, the power price is associated with the efficient received traffic data in a metre data management system (MDMS). In order to minimise the system power price, a wideband hybrid access strategy is proposed and analysed, to share the spectrum between the SG nodes and CR networks. The sensing time and transmission time are jointly optimised, while both the interference to primary users and the spectrum opportunity loss of secondary users are considered. Two algorithms are proposed to solve the joint optimisation problem. Simulation results show that the proposed joint optimisation algorithms outperform the fixed parameters (sensing time and transmission time) algorithms, and the power cost is reduced efficiently.

  6. Optimal Power Allocation of Relay Sensor Node Capable of Energy Harvesting in Cooperative Cognitive Radio Network

    PubMed Central

    Son, Pham Ngoc; Har, Dongsoo; Cho, Nam Ik; Kong, Hyung Yun

    2017-01-01

    A cooperative cognitive radio scheme exploiting primary signals for energy harvesting is proposed. The relay sensor node denoted as the secondary transmitter (ST) harvests energy from the primary signal transmitted from the primary transmitter, and then uses it to transmit power superposed codes of the secrecy signal of the secondary network (SN) and of the primary signal of the primary network (PN). The harvested energy is split into two parts according to a power splitting ratio, one for decoding the primary signal and the other for charging the battery. In power superposition coding, the amount of fractional power allocated to the primary signal is determined by another power allocation parameter (e.g., the power sharing coefficient). Our main concern is to investigate the impact of the two power parameters on the performances of the PN and the SN. Analytical or mathematical expressions of the outage probabilities of the PN and the SN are derived in terms of the power parameters, location of the ST, channel gain, and other system related parameters. A jointly optimal power splitting ratio and power sharing coefficient for achieving target outage probabilities of the PN and the SN, are found using these expressions and validated by simulations. PMID:28335561

  7. Optimal Power Allocation of Relay Sensor Node Capable of Energy Harvesting in Cooperative Cognitive Radio Network.

    PubMed

    Son, Pham Ngoc; Har, Dongsoo; Cho, Nam Ik; Kong, Hyung Yun

    2017-03-21

    A cooperative cognitive radio scheme exploiting primary signals for energy harvesting is proposed. The relay sensor node denoted as the secondary transmitter (ST) harvests energy from the primary signal transmitted from the primary transmitter, and then uses it to transmit power superposed codes of the secrecy signal of the secondary network (SN) and of the primary signal of the primary network (PN). The harvested energy is split into two parts according to a power splitting ratio, one for decoding the primary signal and the other for charging the battery. In power superposition coding, the amount of fractional power allocated to the primary signal is determined by another power allocation parameter (e.g., the power sharing coefficient). Our main concern is to investigate the impact of the two power parameters on the performances of the PN and the SN. Analytical or mathematical expressions of the outage probabilities of the PN and the SN are derived in terms of the power parameters, location of the ST, channel gain, and other system related parameters. A jointly optimal power splitting ratio and power sharing coefficient for achieving target outage probabilities of the PN and the SN, are found using these expressions and validated by simulations.

  8. Q-Learning and p-persistent CSMA based rendezvous protocol for cognitive radio networks operating with shared spectrum activity

    NASA Astrophysics Data System (ADS)

    Watson, Clifton L.; Biswas, Subir

    2014-06-01

    With an increasing demand for spectrum, dynamic spectrum access (DSA) has been proposed as viable means for providing the flexibility and greater access to spectrum necessary to meet this demand. Within the DSA concept, unlicensed secondary users temporarily "borrow" or access licensed spectrum, while respecting the licensed primary user's rights to that spectrum. As key enablers for DSA, cognitive radios (CRs) are based on software-defined radios which allow them to sense, learn, and adapt to the spectrum environment. These radios can operate independently and rapidly switch channels. Thus, the initial setup and maintenance of cognitive radio networks are dependent upon the ability of CR nodes to find each other, in a process known as rendezvous, and create a link on a common channel for the exchange of data and control information. In this paper, we propose a novel rendezvous protocol, known as QLP, which is based on Q-learning and the p-persistent CSMA protocol. With the QLP protocol, CR nodes learn which channels are best for rendezvous and thus adapt their behavior to visit those channels more frequently. We demonstrate through simulation that the QLP protocol provides a rendevous capability for DSA environments with different dynamics of PU activity, while attempting to achieve the following performance goals: (1) minimize the average time-to-rendezvous, (2) maximize system throughput, (3) minimize primary user interference, and (4) minimize collisions among CR nodes.

  9. An energy-efficient and compact clustering scheme with temporary support nodes for cognitive radio sensor networks.

    PubMed

    Salim, Shelly; Moh, Sangman; Choi, Dongmin; Chung, Ilyong

    2014-08-11

    A cognitive radio sensor network (CRSN) is a wireless sensor network whose sensor nodes are equipped with cognitive radio capability. Clustering is one of the most challenging issues in CRSNs, as all sensor nodes, including the cluster head, have to use the same frequency band in order to form a cluster. However, due to the nature of heterogeneous channels in cognitive radio, it is difficult for sensor nodes to find a cluster head. This paper proposes a novel energy-efficient and compact clustering scheme named clustering with temporary support nodes (CENTRE). CENTRE efficiently achieves a compact cluster formation by adopting two-phase cluster formation with fixed duration. By introducing a novel concept of temporary support nodes to improve the cluster formation, the proposed scheme enables sensor nodes in a network to find a cluster head efficiently. The performance study shows that not only is the clustering process efficient and compact but it also results in remarkable energy savings that prolong the overall network lifetime. In addition, the proposed scheme decreases both the clustering overhead and the average distance between cluster heads and their members.

  10. Using Pharmacological Manipulation and High-precision Radio Telemetry to Study the Spatial Cognition in Free-ranging Animals.

    PubMed

    Roth, Timothy C; Krochmal, Aaron R; Gerwig, William B; Rush, Sage; Simmons, Nathaniel T; Sullivan, Jeffery D; Wachter, Katrina

    2016-11-06

    An animal's ability to perceive and learn about its environment plays a key role in many behavioral processes, including navigation, migration, dispersal and foraging. However, the understanding of the role of cognition in the development of navigation strategies and the mechanisms underlying these strategies is limited by the methodological difficulties involved in monitoring, manipulating the cognition of, and tracking wild animals. This study describes a protocol for addressing the role of cognition in navigation that combines pharmacological manipulation of behavior with high-precision radio telemetry. The approach uses scopolamine, a muscarinic acetylcholine receptor antagonist, to manipulate cognitive spatial abilities. Treated animals are then monitored with high frequency and high spatial resolution via remote triangulation. This protocol was applied within a population of Eastern painted turtles (Chrysemys picta) that has inhabited seasonally ephemeral water sources for ~100 years, moving between far-off sources using precise (± 3.5 m), complex (i.e., non-linear with high tortuosity that traverse multiple habitats), and predictable routes learned before 4 years of age. This study showed that the processes used by these turtles are consistent with spatial memory formation and recall. Together, these results are consistent with a role of spatial cognition in complex navigation and highlight the integration of ecological and pharmacological techniques in the study of cognition and navigation.

  11. Reciprocally-Benefited Secure Transmission for Spectrum Sensing-Based Cognitive Radio Sensor Networks.

    PubMed

    Wang, Dawei; Ren, Pinyi; Du, Qinghe; Sun, Li; Wang, Yichen

    2016-11-25

    The rapid proliferation of independently-designed and -deployed wireless sensor networks extremely crowds the wireless spectrum and promotes the emergence of cognitive radio sensor networks (CRSN). In CRSN, the sensor node (SN) can make full use of the unutilized licensed spectrum, and the spectrum efficiency is greatly improved. However, inevitable spectrum sensing errors will adversely interfere with the primary transmission, which may result in primary transmission outage. To compensate the adverse effect of spectrum sensing errors, we propose a reciprocally-benefited secure transmission strategy, in which SN's interference to the eavesdropper is employed to protect the primary confidential messages while the CRSN is also rewarded with a loose spectrum sensing error probability constraint. Specifically, according to the spectrum sensing results and primary users' activities, there are four system states in this strategy. For each state, we analyze the primary secrecy rate and the SN's transmission rate by taking into account the spectrum sensing errors. Then, the SN's transmit power is optimally allocated for each state so that the average transmission rate of CRSN is maximized under the constraint of the primary maximum permitted secrecy outage probability. In addition, the performance tradeoff between the transmission rate of CRSN and the primary secrecy outage probability is investigated. Moreover, we analyze the primary secrecy rate for the asymptotic scenarios and derive the closed-form expression of the SN's transmission outage probability. Simulation results show that: (1) the performance of the SN's average throughput in the proposed strategy outperforms the conventional overlay strategy; (2) both the primary network and CRSN benefit from the proposed strategy.

  12. Reciprocally-Benefited Secure Transmission for Spectrum Sensing-Based Cognitive Radio Sensor Networks

    PubMed Central

    Wang, Dawei; Ren, Pinyi; Du, Qinghe; Sun, Li; Wang, Yichen

    2016-01-01

    The rapid proliferation of independently-designed and -deployed wireless sensor networks extremely crowds the wireless spectrum and promotes the emergence of cognitive radio sensor networks (CRSN). In CRSN, the sensor node (SN) can make full use of the unutilized licensed spectrum, and the spectrum efficiency is greatly improved. However, inevitable spectrum sensing errors will adversely interfere with the primary transmission, which may result in primary transmission outage. To compensate the adverse effect of spectrum sensing errors, we propose a reciprocally-benefited secure transmission strategy, in which SN’s interference to the eavesdropper is employed to protect the primary confidential messages while the CRSN is also rewarded with a loose spectrum sensing error probability constraint. Specifically, according to the spectrum sensing results and primary users’ activities, there are four system states in this strategy. For each state, we analyze the primary secrecy rate and the SN’s transmission rate by taking into account the spectrum sensing errors. Then, the SN’s transmit power is optimally allocated for each state so that the average transmission rate of CRSN is maximized under the constraint of the primary maximum permitted secrecy outage probability. In addition, the performance tradeoff between the transmission rate of CRSN and the primary secrecy outage probability is investigated. Moreover, we analyze the primary secrecy rate for the asymptotic scenarios and derive the closed-form expression of the SN’s transmission outage probability. Simulation results show that: (1) the performance of the SN’s average throughput in the proposed strategy outperforms the conventional overlay strategy; (2) both the primary network and CRSN benefit from the proposed strategy. PMID:27897988

  13. Radio vs. Television: Their Cognitive Impact on Children of Different Socioeconomic and Ethnic Groups.

    ERIC Educational Resources Information Center

    Greenfield, Patricia; Beagles-Roos, Jessica

    1988-01-01

    Reports on two studies which compared the impact of radio and television on children from different social classes and ethnic groups. Found that radio was more stimulating than television to the imagination (especially among white children) and that television led to greater overall recall of information. (ARH)

  14. The Cognition of Multiaircraft Control (MAC): Cognitive Ability Predictors, Working Memory, Interference, and Attention Control in Radio Communication

    DTIC Science & Technology

    2015-03-26

    performance as the number of call signs are increased from 5 to 7 in the presence of PI. Additionally, this study seeks to understand if individual...differences in working memory and attention predict performance on the multiaircraft control radio communication task through the application of the... Performance Measures ..................................................................................................17 Results

  15. Optimal Power Allocation for CC-HARQ-based Cognitive Radio with Statistical CSI in Nakagami Slow Fading Channels

    NASA Astrophysics Data System (ADS)

    Xu, Ding; Li, Qun

    2017-01-01

    This paper addresses the power allocation problem for cognitive radio (CR) based on hybrid-automatic-repeat-request (HARQ) with chase combining (CC) in Nakagamimslow fading channels. We assume that, instead of the perfect instantaneous channel state information (CSI), only the statistical CSI is available at the secondary user (SU) transmitter. The aim is to minimize the SU outage probability under the primary user (PU) interference outage constraint. Using the Lagrange multiplier method, an iterative and recursive algorithm is derived to obtain the optimal power allocation for each transmission round. Extensive numerical results are presented to illustrate the performance of the proposed algorithm.

  16. Energy efficiency in cognitive radio network: Study of cooperative sensing using different channel sensing methods

    NASA Astrophysics Data System (ADS)

    Cui, Chenxuan

    When cognitive radio (CR) operates, it starts by sensing spectrum and looking for idle bandwidth. There are several methods for CR to make a decision on either the channel is occupied or idle, for example, energy detection scheme, cyclostationary detection scheme and matching filtering detection scheme [1]. Among them, the most common method is energy detection scheme because of its algorithm and implementation simplicities [2]. There are two major methods for sensing, the first one is to sense single channel slot with varying bandwidth, whereas the second one is to sense multiple channels and each with same bandwidth. After sensing periods, samples are compared with a preset detection threshold and a decision is made on either the primary user (PU) is transmitting or not. Sometimes the sensing and decision results can be erroneous, for example, false alarm error and misdetection error may occur. In order to better control error probabilities and improve CR network performance (i.e. energy efficiency), we introduce cooperative sensing; in which several CR within a certain range detect and make decisions on channel availability together. The decisions are transmitted to and analyzed by a data fusion center (DFC) to make a final decision on channel availability. After the final decision is been made, DFC sends back the decision to the CRs in order to tell them to stay idle or start to transmit data to secondary receiver (SR) within a preset transmission time. After the transmission, a new cycle starts again with sensing. This thesis report is organized as followed: Chapter II review some of the papers on optimizing CR energy efficiency. In Chapter III, we study how to achieve maximal energy efficiency when CR senses single channel with changing bandwidth and with constrain on misdetection threshold in order to protect PU; furthermore, a case study is given and we calculate the energy efficiency. In Chapter IV, we study how to achieve maximal energy efficiency when CR

  17. An Adaptive Cooperative Strategy for Underlay MIMO Cognitive Radio Networks: An Opportunistic and Low-Complexity Approach

    NASA Astrophysics Data System (ADS)

    Mazoochi, M.; Pourmina, M. A.; Bakhshi, H.

    2015-03-01

    The core aim of this work is the maximization of the achievable data rate of the secondary user pairs (SU pairs), while ensuring the QoS of primary users (PUs). All users are assumed to be equipped with multiple antennas. It is assumed that when PUs are present, the direct communications between SU pairs introduces intolerable interference to PUs and thereby SUs transmit signal using the cooperation of other SUs and avoid transmitting in the direct channel. In brief, an adaptive cooperative strategy for multiple-input/multiple-output (MIMO) cognitive radio networks is proposed. At the presence of PUs, the issue of joint relay selection and power allocation in Underlay MIMO Cooperative Cognitive Radio Networks (U-MIMO-CCRN) is addressed. The optimal approach for determining the power allocation and the cooperating SU is proposed. Besides, the outage probability of the proposed communication protocol is further derived. Due to high complexity of the optimal approach, a low-complexity approach is further proposed and its performance is evaluated using simulations. The simulation results reveal that the performance loss due to the low-complexity approach is only about 14%, while the complexity is greatly reduced.

  18. Dynamic fair node spectrum allocation for ad hoc networks using random matrices

    NASA Astrophysics Data System (ADS)

    Rahmes, Mark; Lemieux, George; Chester, Dave; Sonnenberg, Jerry

    2015-05-01

    Dynamic Spectrum Access (DSA) is widely seen as a solution to the problem of limited spectrum, because of its ability to adapt the operating frequency of a radio. Mobile Ad Hoc Networks (MANETs) can extend high-capacity mobile communications over large areas where fixed and tethered-mobile systems are not available. In one use case with high potential impact, cognitive radio employs spectrum sensing to facilitate the identification of allocated frequencies not currently accessed by their primary users. Primary users own the rights to radiate at a specific frequency and geographic location, while secondary users opportunistically attempt to radiate at a specific frequency when the primary user is not using it. We populate a spatial radio environment map (REM) database with known information that can be leveraged in an ad hoc network to facilitate fair path use of the DSA-discovered links. Utilization of high-resolution geospatial data layers in RF propagation analysis is directly applicable. Random matrix theory (RMT) is useful in simulating network layer usage in nodes by a Wishart adjacency matrix. We use the Dijkstra algorithm for discovering ad hoc network node connection patterns. We present a method for analysts to dynamically allocate node-node path and link resources using fair division. User allocation of limited resources as a function of time must be dynamic and based on system fairness policies. The context of fair means that first available request for an asset is not envied as long as it is not yet allocated or tasked in order to prevent cycling of the system. This solution may also save money by offering a Pareto efficient repeatable process. We use a water fill queue algorithm to include Shapley value marginal contributions for allocation.

  19. Outage Capacity of Spectrum Sharing Cognitive Radio with Channel Estimation Errors and Feedback Delay in Rayleigh Fading Environments

    NASA Astrophysics Data System (ADS)

    Xu, D.; Feng, Z.; Zhang, P.

    2013-04-01

    This paper considers a spectrum sharing cognitive radio (CR) network consisting of one secondary user (SU) and one primary user (PU) in Rayleigh fading environments. The channel state information (CSI) between the secondary transmitter (STx) and the primary receiver (PRx) is assumed to be imperfect. Particularly, this CSI is assumed to be not only having channel estimation errors but also outdated due to feedback delay, which is different from existing work. We derive the closed-form expression for the outage capacity of the SU with this imperfect CSI under the average interference power constraint at the PU. Analytical results confirmed by simulations are presented to show the effect of the imperfect CSI. Particularly, it is shown that the outage capacity of the SU is robust to the channel estimation errors and feedback delay for low outage probability and high channel estimation errors and feedback delay.

  20. PAD-MAC: Primary User Activity-Aware Distributed MAC for Multi-Channel Cognitive Radio Networks

    PubMed Central

    Ali, Amjad; Piran, Md. Jalil; Kim, Hansoo; Yun, Jihyeok; Suh, Doug Young

    2015-01-01

    Cognitive radio (CR) has emerged as a promising technology to solve problems related to spectrum scarcity and provides a ubiquitous wireless access environment. CR-enabled secondary users (SUs) exploit spectrum white spaces opportunistically and immediately vacate the acquired licensed channels as primary users (PUs) arrive. Accessing the licensed channels without the prior knowledge of PU traffic patterns causes severe throughput degradation due to excessive channel switching and PU-to-SU collisions. Therefore, it is significantly important to design a PU activity-aware medium access control (MAC) protocol for cognitive radio networks (CRNs). In this paper, we first propose a licensed channel usage pattern identification scheme, based on a two-state Markov model, and then estimate the future idle slots using previous observations of the channels. Furthermore, based on these past observations, we compute the rank of each available licensed channel that gives SU transmission success assessment during the estimated idle slot. Secondly, we propose a PU activity-aware distributed MAC (PAD-MAC) protocol for heterogeneous multi-channel CRNs that selects the best channel for each SU to enhance its throughput. PAD-MAC controls SU activities by allowing them to exploit the licensed channels only for the duration of estimated idle slots and enables predictive and fast channel switching. To evaluate the performance of the proposed PAD-MAC, we compare it with the distributed QoS-aware MAC (QC-MAC) and listen-before-talk MAC schemes. Extensive numerical results show the significant improvements of the PAD-MAC in terms of the SU throughput, SU channel switching rate and PU-to-SU collision rate. PMID:25831084

  1. SACRB-MAC: A High-Capacity MAC Protocol for Cognitive Radio Sensor Networks in Smart Grid.

    PubMed

    Yang, Zhutian; Shi, Zhenguo; Jin, Chunlin

    2016-03-31

    The Cognitive Radio Sensor Network (CRSN) is considered as a viable solution to enhance various aspects of the electric power grid and to realize a smart grid. However, several challenges for CRSNs are generated due to the harsh wireless environment in a smart grid. As a result, throughput and reliability become critical issues. On the other hand, the spectrum aggregation technique is expected to play an important role in CRSNs in a smart grid. By using spectrum aggregation, the throughput of CRSNs can be improved efficiently, so as to address the unique challenges of CRSNs in a smart grid. In this regard, we proposed Spectrum Aggregation Cognitive Receiver-Based MAC (SACRB-MAC), which employs the spectrum aggregation technique to improve the throughput performance of CRSNs in a smart grid. Moreover, SACRB-MAC is a receiver-based MAC protocol, which can provide a good reliability performance. Analytical and simulation results demonstrate that SACRB-MAC is a promising solution for CRSNs in a smart grid.

  2. SACRB-MAC: A High-Capacity MAC Protocol for Cognitive Radio Sensor Networks in Smart Grid

    PubMed Central

    Yang, Zhutian; Shi, Zhenguo; Jin, Chunlin

    2016-01-01

    The Cognitive Radio Sensor Network (CRSN) is considered as a viable solution to enhance various aspects of the electric power grid and to realize a smart grid. However, several challenges for CRSNs are generated due to the harsh wireless environment in a smart grid. As a result, throughput and reliability become critical issues. On the other hand, the spectrum aggregation technique is expected to play an important role in CRSNs in a smart grid. By using spectrum aggregation, the throughput of CRSNs can be improved efficiently, so as to address the unique challenges of CRSNs in a smart grid. In this regard, we proposed Spectrum Aggregation Cognitive Receiver-Based MAC (SACRB-MAC), which employs the spectrum aggregation technique to improve the throughput performance of CRSNs in a smart grid. Moreover, SACRB-MAC is a receiver-based MAC protocol, which can provide a good reliability performance. Analytical and simulation results demonstrate that SACRB-MAC is a promising solution for CRSNs in a smart grid. PMID:27043573

  3. Cognitive Wireless Communications - A paradigm shift in dealing with radio resources as a prerequisite for the wireless network of the future - An overview on the topic of cognitive wireless technologies

    NASA Astrophysics Data System (ADS)

    Haustein, Thomas; Stanczak, Slawomir; Wolisz, Adam; Jondral, Friedrich; Schotten, Hans; Kraemer, Rolf; Mück, Markus; Mennenga, Horst; Bender, Paul

    2016-07-01

    Wireless radio communications systems form the basis for mobile network connections in the digital society. A limited amount of radio spectrum and a spatially densified use of wireless communications systems require a resource-efficient use of the spectrum. Mechanisms of cognitive radio may hold the key to a more efficient use of the available spectrum under consideration of quality of service requirements. These mechanisms take advantage of location-specific knowledge of the wireless channel occupation in the dimensions of frequency, time, location and direction in space and therefore enable co-existent and reliable wireless communication. The authors give an introduction to the status of cognitive wireless communication technology, which represents the starting point of a series of research projects promoted by BMBF during 2012-2014.

  4. Cognitive Radio Low-Energy Signal Analysis Sensor Integrated Circuits (CLASIC): A Broadband Mixed-Signal Iterative Down Conversion Spectrum Analyzer for Signal Recognition Applications

    DTIC Science & Technology

    2015-12-01

    mechanisms described in the previous section, this would result in signal leakage for every band. We propose a 3-way IDC architecture (shown in Fig. 42 (a...AFRL-RY-WP-TR-2015-0144 COGNITIVE RADIO LOW- ENERGY SIGNAL ANALYSIS SENSOR INTEGRATED CIRCUITS (CLASIC) A Broadband Mixed-Signal Iterative Down...See additional restrictions described on inside pages STINFO COPY AIR FORCE RESEARCH LABORATORY SENSORS DIRECTORATE WRIGHT-PATTERSON AIR FORCE

  5. A Subcarrier-Pair Based Resource Allocation Scheme Using Proportional Fairness for Cooperative OFDM-Based Cognitive Radio Networks

    PubMed Central

    Ma, Yongtao; Zhou, Liuji; Liu, Kaihua

    2013-01-01

    The paper presents a joint subcarrier-pair based resource allocation algorithm in order to improve the efficiency and fairness of cooperative multiuser orthogonal frequency division multiplexing (MU-OFDM) cognitive radio (CR) systems. A communication model where one source node communicates with one destination node assisted by one half-duplex decode-and-forward (DF) relay is considered in the paper. An interference-limited environment is considered, with the constraint of transmitted sum-power over all channels and aggregate average interference towards multiple primary users (PUs). The proposed resource allocation algorithm is capable of maximizing both the system transmission efficiency and fairness among secondary users (SUs). Besides, the proposed algorithm can also keep the interference introduced to the PU bands below a threshold. A proportional fairness constraint is used to assure that each SU can achieve a required data rate, with quality of service guarantees. Moreover, we extend the analysis to the scenario where each cooperative SU has no channel state information (CSI) about non-adjacent links. We analyzed the throughput and fairness tradeoff in CR system. A detailed analysis of the performance of the proposed algorithm is presented with the simulation results. PMID:23939586

  6. 50 MHz-10 GHz low-power resistive feedback current-reuse mixer with inductive peaking for cognitive radio receiver.

    PubMed

    Vitee, Nandini; Ramiah, Harikrishnan; Chong, Wei-Keat; Tan, Gim-Heng; Kanesan, Jeevan; Reza, Ahmed Wasif

    2014-01-01

    A low-power wideband mixer is designed and implemented in 0.13 µm standard CMOS technology based on resistive feedback current-reuse (RFCR) configuration for the application of cognitive radio receiver. The proposed RFCR architecture incorporates an inductive peaking technique to compensate for gain roll-off at high frequency while enhancing the bandwidth. A complementary current-reuse technique is used between transconductance and IF stages to boost the conversion gain without additional power consumption by reusing the DC bias current of the LO stage. This downconversion double-balanced mixer exhibits a high and flat conversion gain (CG) of 14.9 ± 1.4 dB and a noise figure (NF) better than 12.8 dB. The maximum input 1-dB compression point (P1dB) and maximum input third-order intercept point (IIP3) are -13.6 dBm and -4.5 dBm, respectively, over the desired frequency ranging from 50 MHz to 10 GHz. The proposed circuit operates down to a supply headroom of 1 V with a low-power consumption of 3.5 mW.

  7. A robust cooperative spectrum sensing scheme based on Dempster-Shafer theory and trustworthiness degree calculation in cognitive radio networks

    NASA Astrophysics Data System (ADS)

    Wang, Jinlong; Feng, Shuo; Wu, Qihui; Zheng, Xueqiang; Xu, Yuhua; Ding, Guoru

    2014-12-01

    Cognitive radio (CR) is a promising technology that brings about remarkable improvement in spectrum utilization. To tackle the hidden terminal problem, cooperative spectrum sensing (CSS) which benefits from the spatial diversity has been studied extensively. Since CSS is vulnerable to the attacks initiated by malicious secondary users (SUs), several secure CSS schemes based on Dempster-Shafer theory have been proposed. However, the existing works only utilize the current difference of SUs, such as the difference in SNR or similarity degree, to evaluate the trustworthiness of each SU. As the current difference is only one-sided and sometimes inaccurate, the statistical information contained in each SU's historical behavior should not be overlooked. In this article, we propose a robust CSS scheme based on Dempster-Shafer theory and trustworthiness degree calculation. It is carried out in four successive steps, which are basic probability assignment (BPA), trustworthiness degree calculation, selection and adjustment of BPA, and combination by Dempster-Shafer rule, respectively. Our proposed scheme evaluates the trustworthiness degree of SUs from both current difference aspect and historical behavior aspect and exploits Dempster-Shafer theory's potential to establish a `soft update' approach for the reputation value maintenance. It can not only differentiate malicious SUs from honest ones based on their historical behaviors but also reserve the current difference for each SU to achieve a better real-time performance. Abundant simulation results have validated that the proposed scheme outperforms the existing ones under the impact of different attack patterns and different number of malicious SUs.

  8. An Energy-Efficient Spectrum-Aware Reinforcement Learning-Based Clustering Algorithm for Cognitive Radio Sensor Networks.

    PubMed

    Mustapha, Ibrahim; Mohd Ali, Borhanuddin; Rasid, Mohd Fadlee A; Sali, Aduwati; Mohamad, Hafizal

    2015-08-13

    It is well-known that clustering partitions network into logical groups of nodes in order to achieve energy efficiency and to enhance dynamic channel access in cognitive radio through cooperative sensing. While the topic of energy efficiency has been well investigated in conventional wireless sensor networks, the latter has not been extensively explored. In this paper, we propose a reinforcement learning-based spectrum-aware clustering algorithm that allows a member node to learn the energy and cooperative sensing costs for neighboring clusters to achieve an optimal solution. Each member node selects an optimal cluster that satisfies pairwise constraints, minimizes network energy consumption and enhances channel sensing performance through an exploration technique. We first model the network energy consumption and then determine the optimal number of clusters for the network. The problem of selecting an optimal cluster is formulated as a Markov Decision Process (MDP) in the algorithm and the obtained simulation results show convergence, learning and adaptability of the algorithm to dynamic environment towards achieving an optimal solution. Performance comparisons of our algorithm with the Groupwise Spectrum Aware (GWSA)-based algorithm in terms of Sum of Square Error (SSE), complexity, network energy consumption and probability of detection indicate improved performance from the proposed approach. The results further reveal that an energy savings of 9% and a significant Primary User (PU) detection improvement can be achieved with the proposed approach.

  9. Opportunistic Capacity-Based Resource Allocation for Chunk-Based Multi-Carrier Cognitive Radio Sensor Networks

    PubMed Central

    Huang, Jie; Zeng, Xiaoping; Jian, Xin; Tan, Xiaoheng; Zhang, Qi

    2017-01-01

    The spectrum allocation for cognitive radio sensor networks (CRSNs) has received considerable research attention under the assumption that the spectrum environment is static. However, in practice, the spectrum environment varies over time due to primary user/secondary user (PU/SU) activity and mobility, resulting in time-varied spectrum resources. This paper studies resource allocation for chunk-based multi-carrier CRSNs with time-varied spectrum resources. We present a novel opportunistic capacity model through a continuous time semi-Markov chain (CTSMC) to describe the time-varied spectrum resources of chunks and, based on this, a joint power and chunk allocation model by considering the opportunistically available capacity of chunks is proposed. To reduce the computational complexity, we split this model into two sub-problems and solve them via the Lagrangian dual method. Simulation results illustrate that the proposed opportunistic capacity-based resource allocation algorithm can achieve better performance compared with traditional algorithms when the spectrum environment is time-varied. PMID:28106803

  10. QoS Differential Scheduling in Cognitive-Radio-Based Smart Grid Networks: An Adaptive Dynamic Programming Approach.

    PubMed

    Yu, Rong; Zhong, Weifeng; Xie, Shengli; Zhang, Yan; Zhang, Yun

    2016-02-01

    As the next-generation power grid, smart grid will be integrated with a variety of novel communication technologies to support the explosive data traffic and the diverse requirements of quality of service (QoS). Cognitive radio (CR), which has the favorable ability to improve the spectrum utilization, provides an efficient and reliable solution for smart grid communications networks. In this paper, we study the QoS differential scheduling problem in the CR-based smart grid communications networks. The scheduler is responsible for managing the spectrum resources and arranging the data transmissions of smart grid users (SGUs). To guarantee the differential QoS, the SGUs are assigned to have different priorities according to their roles and their current situations in the smart grid. Based on the QoS-aware priority policy, the scheduler adjusts the channels allocation to minimize the transmission delay of SGUs. The entire transmission scheduling problem is formulated as a semi-Markov decision process and solved by the methodology of adaptive dynamic programming. A heuristic dynamic programming (HDP) architecture is established for the scheduling problem. By the online network training, the HDP can learn from the activities of primary users and SGUs, and adjust the scheduling decision to achieve the purpose of transmission delay minimization. Simulation results illustrate that the proposed priority policy ensures the low transmission delay of high priority SGUs. In addition, the emergency data transmission delay is also reduced to a significantly low level, guaranteeing the differential QoS in smart grid.

  11. 50 MHz–10 GHz Low-Power Resistive Feedback Current-Reuse Mixer with Inductive Peaking for Cognitive Radio Receiver

    PubMed Central

    Reza, Ahmed Wasif

    2014-01-01

    A low-power wideband mixer is designed and implemented in 0.13 µm standard CMOS technology based on resistive feedback current-reuse (RFCR) configuration for the application of cognitive radio receiver. The proposed RFCR architecture incorporates an inductive peaking technique to compensate for gain roll-off at high frequency while enhancing the bandwidth. A complementary current-reuse technique is used between transconductance and IF stages to boost the conversion gain without additional power consumption by reusing the DC bias current of the LO stage. This downconversion double-balanced mixer exhibits a high and flat conversion gain (CG) of 14.9 ± 1.4 dB and a noise figure (NF) better than 12.8 dB. The maximum input 1-dB compression point (P1dB) and maximum input third-order intercept point (IIP3) are −13.6 dBm and −4.5 dBm, respectively, over the desired frequency ranging from 50 MHz to 10 GHz. The proposed circuit operates down to a supply headroom of 1 V with a low-power consumption of 3.5 mW. PMID:25133252

  12. Weighted sum-rate maximization for multi-user SIMO multiple access channels in cognitive radio networks

    NASA Astrophysics Data System (ADS)

    He, Peter; Zhao, Lian; Lu, Jianhua

    2013-12-01

    In this article, an efficient distributed and parallel algorithm is proposed to maximize the sum-rate and optimize the input distribution policy for the multi-user single input multiple output multiple access channel (MU-SIMO MAC) system with concurrent access within a cognitive radio (CR) network. The single input means that every user has a single antenna and multiple output means that base station(s) has multiple antennas. The main features are: (i) the power distribution for the users is updated by using variable scale factors which effectively and efficiently maximize the objective function at each iteration; (ii) distributed and parallel computation is employed to expedite convergence of the proposed distributed algorithm; and (iii) a novel water-filling with mixed constraints is investigated, and used as a fundamental block of the proposed algorithm. Due to sufficiently exploiting the structure of the proposed model, the proposed algorithm owns fast convergence. Numerical results verify that the proposed algorithm is effective and fast convergent. Using the proposed approach, for the simulated range, the required number of iterations for convergence is two and this number is not sensitive to the increase of the number of users. This feature is quite desirable for large scale systems with dense active users. In addition, it is also worth noting that the proposed algorithm is a monotonic feasible operator to the iteration. Thus, the stop criterion for computation could be easily set up.

  13. An Energy-Efficient Spectrum-Aware Reinforcement Learning-Based Clustering Algorithm for Cognitive Radio Sensor Networks

    PubMed Central

    Mustapha, Ibrahim; Ali, Borhanuddin Mohd; Rasid, Mohd Fadlee A.; Sali, Aduwati; Mohamad, Hafizal

    2015-01-01

    It is well-known that clustering partitions network into logical groups of nodes in order to achieve energy efficiency and to enhance dynamic channel access in cognitive radio through cooperative sensing. While the topic of energy efficiency has been well investigated in conventional wireless sensor networks, the latter has not been extensively explored. In this paper, we propose a reinforcement learning-based spectrum-aware clustering algorithm that allows a member node to learn the energy and cooperative sensing costs for neighboring clusters to achieve an optimal solution. Each member node selects an optimal cluster that satisfies pairwise constraints, minimizes network energy consumption and enhances channel sensing performance through an exploration technique. We first model the network energy consumption and then determine the optimal number of clusters for the network. The problem of selecting an optimal cluster is formulated as a Markov Decision Process (MDP) in the algorithm and the obtained simulation results show convergence, learning and adaptability of the algorithm to dynamic environment towards achieving an optimal solution. Performance comparisons of our algorithm with the Groupwise Spectrum Aware (GWSA)-based algorithm in terms of Sum of Square Error (SSE), complexity, network energy consumption and probability of detection indicate improved performance from the proposed approach. The results further reveal that an energy savings of 9% and a significant Primary User (PU) detection improvement can be achieved with the proposed approach. PMID:26287191

  14. A Game-Theoretic Approach for Opportunistic Spectrum Sharing in Cognitive Radio Networks with Incomplete Information

    NASA Astrophysics Data System (ADS)

    Tan, Xuesong Jonathan; Li, Liang; Guo, Wei

    One important issue in cognitive transmission is for multiple secondary users to dynamically acquire spare spectrum from the single primary user. The existing spectrum sharing scheme adopts a deterministic Cournot game to formulate this problem, of which the solution is the Nash equilibrium. This formulation is based on two implicit assumptions. First, each secondary user is willing to fully exchange transmission parameters with all others and hence knows their complete information. Second, the unused spectrum of the primary user for spectrum sharing is always larger than the total frequency demand of all secondary users at the Nash equilibrium. However, both assumptions may not be true in general. To remedy this, the present paper considers a more realistic assumption of incomplete information, i.e., each secondary user may choose to conceal their private information for achieving higher transmission benefit. Following this assumption and given that the unused bandwidth of the primary user is large enough, we adopt a probabilistic Cournot game to formulate an opportunistic spectrum sharing scheme for maximizing the total benefit of all secondary users. Bayesian equilibrium is considered as the solution of this game. Moreover, we prove that a secondary user can improve their expected benefit by actively hiding its transmission parameters and increasing their variance. On the other hand, when the unused spectrum of the primary user is smaller than the maximal total frequency demand of all secondary users at the Bayesian equilibrium, we formulate a constrained optimization problem for the primary user to maximize its profit in spectrum sharing and revise the proposed spectrum sharing scheme to solve this problem heuristically. This provides a unified approach to overcome the aforementioned two limitations of the existing spectrum sharing scheme.

  15. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  16. Using "HOCS-Centered Learning" as a Pathway to Promote Science Teachers' Metacognitive Development

    ERIC Educational Resources Information Center

    Leou, Mary; Abder, Pamela; Riordan, Megan; Zoller, Uri

    2006-01-01

    An element of current reform in science education worldwide is the shift from the dominant traditional algorithmic lower-order cognitive skills (LOCS) teaching, to the higher-order cognitive skills (HOCS)-promoting learning; that is, the development of students' capabilities including those of question asking (QA), critical/system thinking (CST),…

  17. Ground-based observations and AD HOC models

    NASA Astrophysics Data System (ADS)

    Ground based observations of B stars in the visible, the infrared, and the radio region are described along with the ad hoc models proposed to interpret them. It is shown that these observations refer essentially to the photosphere and to the regions of the outer atmosphere where the gas is cool and at low velocity. The characteristics of the variability of the continuous and line spectrum are examined in general and in the cases of individual stars. Finally, linear polarization in the B stars is discussed.

  18. A Novel Component Carrier Configuration and Switching Scheme for Real-Time Traffic in a Cognitive-Radio-Based Spectrum Aggregation System

    PubMed Central

    Fu, Yunhai; Ma, Lin; Xu, Yubin

    2015-01-01

    In spectrum aggregation (SA), two or more component carriers (CCs) of different bandwidths in different bands can be aggregated to support a wider transmission bandwidth. The scheduling delay is the most important design constraint for the broadband wireless trunking (BWT) system, especially in the cognitive radio (CR) condition. The current resource scheduling schemes for spectrum aggregation become questionable and are not suitable for meeting the challenge of the delay requirement. Consequently, the authors propose a novel component carrier configuration and switching scheme for real-time traffic (RT-CCCS) to satisfy the delay requirement in the CR-based SA system. In this work, the authors consider a sensor-network-assisted CR network. The authors first introduce a resource scheduling structure for SA in the CR condition. Then the proposed scheme is analyzed in detail. Finally, simulations are carried out to verify the analysis on the proposed scheme. Simulation results prove that our proposed scheme can satisfy the delay requirement in the CR-based SA system. PMID:26393594

  19. Algorithmic, LOCS and HOCS (chemistry) exam questions: performance and attitudes of college students

    NASA Astrophysics Data System (ADS)

    Zoller, Uri

    2002-02-01

    The performance of freshmen biology and physics-mathematics majors and chemistry majors as well as pre- and in-service chemistry teachers in two Israeli universities on algorithmic (ALG), lower-order cognitive skills (LOCS), and higher-order cognitive skills (HOCS) chemistry exam questions were studied. The driving force for the study was an interest in moving science and chemistry instruction from an algorithmic and factual recall orientation dominated by LOCS, to a decision-making, problem-solving and critical system thinking approach, dominated by HOCS. College students' responses to the specially designed ALG, LOCS and HOCS chemistry exam questions were scored and analysed for differences and correlation between the performance means within and across universities by the questions' category. This was followed by a combined student interview - 'speaking aloud' problem solving session for assessing the thinking processes involved in solving these types of questions and the students' attitudes towards them. The main findings were: (1) students in both universities performed consistently in each of the three categories in the order of ALG > LOCS > HOCS; their 'ideological' preference, was HOCS > algorithmic/LOCS, - referred to as 'computational questions', but their pragmatic preference was the reverse; (2) success on algorithmic/LOCS does not imply success on HOCS questions; algorithmic questions constitute a category on its own as far as students success in solving them is concerned. Our study and its results support the effort being made, worldwide, to integrate HOCS-fostering teaching and assessment strategies and, to develop HOCS-oriented science-technology-environment-society (STES)-type curricula within science and chemistry education.

  20. EVA Radio DRATS 2011 Report

    NASA Technical Reports Server (NTRS)

    Swank, Aaron J.; Bakula, Casey J.

    2012-01-01

    In the Fall of 2011, National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) participated in the Desert Research and Technology Studies (DRATS) field experiments held near Flagstaff, Arizona. The objective of the DRATS outing is to provide analog mission testing of candidate technologies for space exploration, especially those technologies applicable to human exploration of extra- terrestrial rocky bodies. These activities are performed at locations with similarities to extra-terrestrial conditions. This report describes the Extravehicular Activity (EVA) Dual-Band Radio Communication System which was demonstrated during the 2011 outing. The EVA radio system is designed to transport both voice and telemetry data through a mobile ad hoc wireless network and employs a dual-band radio configuration. Some key characteristics of this system include: 1. Dual-band radio configuration. 2. Intelligent switching between two different capability wireless networks. 3. Self-healing network. 4. Simultaneous data and voice communication.

  1. FROM REQUIREMENTS CAPTURE TO SILICON: A MODEL-DRIVEN SYSTEMS ENGINEERING APPROACH TO RAPID DESIGN, PROTOTYPING AND DEVELOPMENT USED IN THE OAK RIDGE NATIONAL LABORATORY'S COGNITIVE RADIO PROGRAM

    SciTech Connect

    Buckner, Mark A; Kaldenbach, Brian J; Nory, Nakhaee; Moore, Michael Roy; Bouldin, Donald; Mills, Jonathan

    2008-01-01

    The performance and complexity of the signal processing hardware accessible to SDR/CR/RADAR designers has quickly out-paced the available design tools. The advances in Digital Signal Processors (DSP) both fixed- and floating-point, Field Programmable Gate Arrays (FPGA), and multicore processors have enabled rapid prototyping and deployment of platforms that can be dynamically reconfigured in the field to implement a variety of SDR/CR/RADAR waveforms. Until recently the process of creating waveforms meant starting with high-level mathematical models and simulations and then creating production quality code that can operate on this variety of specialized hardware using either hand coding or vendor specific tools, which are typically limited to single processor solutions. This paper discusses an integrated model-driven design process and tool-flow used in ORNL's Cognitive Radio Program. It describes how the process and tool-flow are used on a variety of SDR and CR projects and in the development of a software-defined RADAR environment simulator. It describes how, from a single Simulink model, a single deadlock free real-time multiprocessor application is created and executed on a network of heterogeneous processors. We also describe recent progress on extending the process/tool-flow to design digital ASICs and our plans for future extensions. We close by highlighting the benefits being realized from applying this design flow to SDR/CR/RADAR projects at ORNL: (1) a significant reduction in the time required to develop, prototype, implement and test SDR/CR/RADAR waveforms, (2) increased reusability/retargetabilty of SDR/CR/RADAR designs and signal processing library components, (3) the ability to quickly port SDR/CR/RADAR waveforms to different hardware systems and processor types, (4) improvements in documentation, and (5) traceability of system components back to original requirements.

  2. The effect of galantamine on brain atrophy rate in subjects with mild cognitive impairment is modified by apolipoprotein E genotype: post-hoc analysis of data from a randomized controlled trial

    PubMed Central

    2014-01-01

    Introduction The aim of this investigation was to assess the effect of galantamine, an acetylcholinesterase inhibitor and allosteric modulator of nicotinic receptors, on brain atrophy in individuals with mild cognitive impairment (MCI), and to assess effect modification by apolipoprotein E (APOE) genotype. Methods We used data from the Galantamine-International-11 (Gal-Int-11) trial, a 24-month, randomized, double blind, placebo-controlled, flexible-dose (16 to 24 mg daily) study in patients with MCI. Brain magnetic resonance imaging (MRI), including a 3-dimensional T1-weighted gradient echo volumetric sequence, was performed at screening and at 24 months. We recorded whole brain and hippocampal volumes, and calculated annual atrophy rates. Linear regression analysis was used to calculate adjusted mean differences in the rate of whole brain and hippocampal atrophy, between MCI patients treated with galantamine and with placebo. Additionally, we performed stratified analyses according to APOE genotype. Results Data from 364 MCI patients with 24-month MRI data (galantamine, n = 176; placebo, n = 188) were included in the volumetric analysis. Subjects treated with galantamine demonstrated a lower rate of whole brain atrophy compared to those treated with placebo (adjusted mean difference 0.18% per year (95% confidence interval (CI) 0.04; 0.30)). Stratified analyses according to APOE genotype, showed that this effect was confined to patients who carried an APOE ϵ4 allele (adjusted mean difference 0.28% per year (95% CI 0.07; 0.50)). Rates of hippocampal atrophy did not differ significantly between study groups. Conclusions Patients with MCI who were treated with galantamine demonstrated a lower rate of whole brain atrophy, but not of hippocampal atrophy, over a 24-month treatment period, compared to those treated with placebo. This protective effect of galantamine on whole brain atrophy rate in MCI was only present in APOE ϵ4 carriers. PMID:25478019

  3. Adaptive link-layer intelligence for enhanced ad hoc networking

    NASA Astrophysics Data System (ADS)

    MacLennan, James; Walburg, Bill; Nevins, Larry; Hartup, David

    2005-05-01

    Networked radio systems that utilize self-forming, fault tolerant techniques offer needed communication functions for Homeland Security and Law Enforcement agencies. The use of an ad hoc mesh network architecture solves some of the problems inherent to the wireless physical layer such as interferers, multi-path fading, shadowing, and loss of line-of-site. These effects severely limit the performance of current 802.11 wireless network implementations. This paper describes the use of Adaptive Link-layer Intelligence for Enhanced ad hoc Networking. This technology enhances recognition and characterization of sources of wireless channel perturbations and predicts their effects on wireless link quality. Identifying and predicting channel problems at the link level improves dynamic route discovery, circumvents channel disruptions before they cause a link failure, and increases communications reliability and data rate. First Responders, Homeland Security, and Law Enforcement agencies operating in locations lacking infrastructure, such as Urban Search and Rescue (USAR) operations, can benefit from increased communications reliability in highly impaired channels that are typical in disaster response scenarios.

  4. Collaborative Beamfocusing Radio (COBRA)

    NASA Astrophysics Data System (ADS)

    Rode, Jeremy P.; Hsu, Mark J.; Smith, David; Husain, Anis

    2013-05-01

    A Ziva team has recently demonstrated a novel technique called Collaborative Beamfocusing Radios (COBRA) which enables an ad-hoc collection of distributed commercial off-the-shelf software defined radios to coherently align and beamform to a remote radio. COBRA promises to operate even in high multipath and non-line-of-sight environments as well as mobile applications without resorting to computationally expensive closed loop techniques that are currently unable to operate with significant movement. COBRA exploits two key technologies to achieve coherent beamforming. The first is Time Reversal (TR) which compensates for multipath and automatically discovers the optimal spatio-temporal matched filter to enable peak signal gains (up to 20 dB) and diffraction-limited focusing at the intended receiver in NLOS and severe multipath environments. The second is time-aligned buffering which enables TR to synchronize distributed transmitters into a collaborative array. This time alignment algorithm avoids causality violations through the use of reciprocal buffering. Preserving spatio-temporal reciprocity through the TR capture and retransmission process achieves coherent alignment across multiple radios at ~GHz carriers using only standard quartz-oscillators. COBRA has been demonstrated in the lab, aligning two off-the-shelf software defined radios over-the-air to an accuracy of better than 2 degrees of carrier alignment at 450 MHz. The COBRA algorithms are lightweight, with computation in 5 ms on a smartphone class microprocessor. COBRA also has low start-up latency, achieving high accuracy from a cold-start in 30 ms. The COBRA technique opens up a large number of new capabilities in communications, and electronic warfare including selective spatial jamming, geolocation and anti-geolocation.

  5. Radio Days.

    ERIC Educational Resources Information Center

    Sanderson, Neil

    1998-01-01

    Thousands of today's high school students run FM radio stations at school, carrying on a tradition that began 50 years ago. Radio helps students learn to work with others and develop a strong sense of responsibility. A sidebar gives advice on starting a high school radio station. (MLF)

  6. Firefighters' Radios

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Public Technology Inc. asked for NASA assistance to devise the original firefighter's radio. Good short-range radio communications are essential during a fire to coordinate hose lines, rescue victims, and otherwise increase efficiency. Useful firefighting tool is lower cost, more rugged short range two-way radio. Inductorless electronic circuit replaced inductances and coils in radio circuits with combination of transistors and other low-cost components. Substitution promises reduced circuit size and cost. Enhanced electrical performance made radio more durable and improved maintainability by incorporating modular construction.

  7. Nanotube Radio

    NASA Astrophysics Data System (ADS)

    Jensen, Kenneth; Weldon, Jeff; Garcia, Henry; Zettl, Alex

    2008-03-01

    We have constructed a fully functional, fully integrated radio receiver from a single carbon nanotube. The nanotube serves simultaneously as all essential components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A direct current voltage source, as supplied by a battery, powers the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, we demonstrate successful music and voice reception.

  8. Radio Science

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Radio science experiments use electromagnetic waves to probe or study the solar system. Three major research areas were identified within this discipline: radio astronomy, radar astronomy, and celestial mechanics. Radio astronomy (or radiometry) is the detection and measurement of naturally produced radio frequency emissions. Sources include surfaces, atmospheres, rings, and plasmas. Radar astronomy is the observation of man-made signals after their interaction with a target. Both imaging and non-imaging results. Celestial mechanics includes all studies related to the motions of (and gravity fields of) bodies within the solar system. These should not be considered rigid separations, but aid in the discussion of the data sets.

  9. Distribution of Information in Ad Hoc Networks

    DTIC Science & Technology

    2007-09-01

    INTENTIONALLY LEFT BLANK v ABSTRACT Ad-hoc networks are distributed, self-organized networks which do not need a fixed infrastructure. Entities in...73 V . CONCLUSIONS AND FUTURE WORK ............................75 A. OVERVIEW ..........................................75 B. CONCLUSIONS...statistical analysis on the results. Finally, Chapter V concludes the research and provides suggestions for further research. 7 II. BACKGROUND A

  10. Anomaly Detection Techniques for Ad Hoc Networks

    ERIC Educational Resources Information Center

    Cai, Chaoli

    2009-01-01

    Anomaly detection is an important and indispensable aspect of any computer security mechanism. Ad hoc and mobile networks consist of a number of peer mobile nodes that are capable of communicating with each other absent a fixed infrastructure. Arbitrary node movements and lack of centralized control make them vulnerable to a wide variety of…

  11. Space-Time Processing for Tactical Mobile Ad Hoc Networks

    DTIC Science & Technology

    2008-08-01

    Maximization in Multi-User, MIMO Channels with Linear Processing...58 2.9 Using Feedback in Ad Hoc Networks....................................................................65 2.10 Feedback MIMO ...in MIMO Ad Hoc Interference Networks.......................................................................................................75 2.12

  12. College Radio.

    ERIC Educational Resources Information Center

    Sauls, Samuel J.

    As with commercial stations, the underlying premise of the college radio station is to serve the community, whether it be the campus community or the community at large, but in unique ways often geared to underserved niches of the population. Much of college radio's charm lies in its unpredictable nature and constant mutations. The stations give…

  13. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Taylor, R. M.; Manchester, R. N.

    1980-01-01

    The activities of the Deep Space Network in support of radio and radar astronomy operations during July and August 1980 are reported. A brief update on the OSS-sponsored planetary radio astronomy experiment is provided. Also included are two updates, one each from Spain and Australia on current host country activities.

  14. Radio stars.

    PubMed

    Hjellming, R M; Wade, C M

    1971-09-17

    Up to the present time six classes of radio stars have been established. The signals are almost always very faint and drastically variable. Hence their discovery has owed as much to serendipity as to the highly sophisticated equipment and techniques that have been used. When the variations are regular, as with the pulsars, this characteristic can be exploited very successfully in the search for new objects as well as in the detailed study of those that are already known. The detection of the most erratically variable radio stars, the flare stars and the x-ray stars, is primarily a matter of luck and patience. In the case of the novas, one at least knows where and oughly when to look for radio emission. A very sensitive interferometer is clearly the best instrument to use in the initial detection of a radio star. The fact that weak background sources are frequently present makes it essential to prove that the position of a radio source agrees with that of a star to within a few arc seconds. The potential of radio astronomy for the study of radio stars will not be realized until more powerful instruments than those that are available today can be utilized. So far, we have been able to see only the most luminous of the radio stars.

  15. AD Hoc Study on Human Robot Interface Issues

    DTIC Science & Technology

    2002-09-01

    ARMY SCIENCE BOARD AD HOC STUDY ON HUMAN ROBOT INTERFACE ISSUES FINAL REPORT SEPTEMBER 2002 Distribution: Approved for...conclusions contained in this report are those of the 2002 Ad Hoc Study Panel on “Human- Robot Interface Issues” and do not necessarily reflect the official...DATES COVERED Army Science Board – 2002 Ad Hoc Study 4. TITLE AND SUBTITLE AD HOC STUDY ON HUMAN ROBOT INTERFACE ISSUES 6. AUTHOR(S) Study

  16. 14 CFR 1203.903 - Ad hoc committees.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Ad hoc committees. 1203.903 Section 1203... NASA Information Security Program Committee § 1203.903 Ad hoc committees. The Chairperson is authorized to establish such ad hoc panels or subcommittees as may be necessary in the conduct of the...

  17. 14 CFR 1203.903 - Ad hoc committees.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Ad hoc committees. 1203.903 Section 1203.903... Information Security Program Committee § 1203.903 Ad hoc committees. The Chairperson is authorized to establish such ad hoc panels or subcommittees as may be necessary in the conduct of the Committee's work....

  18. 21 CFR 14.90 - Ad hoc advisory committee members.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Ad hoc advisory committee members. 14.90 Section... PUBLIC HEARING BEFORE A PUBLIC ADVISORY COMMITTEE Members of Advisory Committees § 14.90 Ad hoc advisory committee members. In selecting members of an ad hoc advisory committee, the Commissioner may use...

  19. 21 CFR 14.90 - Ad hoc advisory committee members.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Ad hoc advisory committee members. 14.90 Section... PUBLIC HEARING BEFORE A PUBLIC ADVISORY COMMITTEE Members of Advisory Committees § 14.90 Ad hoc advisory committee members. In selecting members of an ad hoc advisory committee, the Commissioner may use...

  20. Supporting Dynamic Ad hoc Collaboration Capabilities

    SciTech Connect

    Agarwal, Deborah A.; Berket, Karlo

    2003-07-14

    Modern HENP experiments such as CMS and Atlas involve as many as 2000 collaborators around the world. Collaborations this large will be unable to meet often enough to support working closely together. Many of the tools currently available for collaboration focus on heavy-weight applications such as videoconferencing tools. While these are important, there is a more basic need for tools that support connecting physicists to work together on an ad hoc or continuous basis. Tools that support the day-to-day connectivity and underlying needs of a group of collaborators are important for providing light-weight, non-intrusive, and flexible ways to work collaboratively. Some example tools include messaging, file-sharing, and shared plot viewers. An important component of the environment is a scalable underlying communication framework. In this paper we will describe our current progress on building a dynamic and ad hoc collaboration environment and our vision for its evolution into a HENP collaboration environment.

  1. Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Beskin, V. S.; Chernov, S. V.; Gwinn, C. R.; Tchekhovskoy, A. A.

    2015-10-01

    Almost 50 years after radio pulsars were discovered in 1967, our understanding of these objects remains incomplete. On the one hand, within a few years it became clear that neutron star rotation gives rise to the extremely stable sequence of radio pulses, that the kinetic energy of rotation provides the reservoir of energy, and that electromagnetic fields are the braking mechanism. On the other hand, no consensus regarding the mechanism of coherent radio emission or the conversion of electromagnetic energy to particle energy yet exists. In this review, we report on three aspects of pulsar structure that have seen recent progress: the self-consistent theory of the magnetosphere of an oblique magnetic rotator; the location, geometry, and optics of radio emission; and evolution of the angle between spin and magnetic axes. These allow us to take the next step in understanding the physical nature of the pulsar activity.

  2. Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Wolken, P. R.; Shaffer, R. D.

    1983-01-01

    Deep Space Network (DSN) 26- and 64-meter antenna stations were utilized in support of Radio Astronomy Experiment Selection Panel experiments. Within a time span of 10 days, in May 1983 (267.75 hours total), nine RAES experiments were supported. Most of these experiments involved multifacility interferometry using Mark 3 data recording terminals and as many as six non-DSN observatories. Investigations of black holes, quasars, galaxies, and radio sources are discussed.

  3. Airborne and Maritime/Fixed Station Joint Tactical Radio System (AMF JTRS)

    DTIC Science & Technology

    2015-12-01

    multi- band, multi-mode, mobile ad hoc networking radios, providing simultaneous voice and data communications for Army aviation platforms. The radios...services to the platform, and connecting Army aviation platforms to Army ground and Joint air network domains. AMF will procure the Small Airborne...requirements as validated by the Army aviation community. SANR will provide increased data throughput to Army aviation platforms via the Soldier Radio Waveform

  4. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Kellermann, Kenneth I.; Heeschen, David; Backer, Donald C.; Cohen, Marshall H.; Davis, Michael; Depater, Imke; Deyoung, David; Dulk, George A.; Fisher, J. R.; Goss, W. Miller

    1991-01-01

    The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations.

  5. Cooperative Multi-Agent Systems in Mobile Ad Hoc Networks

    DTIC Science & Technology

    2006-01-01

    COOPERATIVE MULTI - AGENT SYSTEMS IN MOBILE AD HOC NETWORKS Joseph P. Macker William Chao Myriam Abramson Ian Downard Information Technology Division...are, mobile ad hoc networking (MANET) and Multi - Agent Systems (MAS). Despite their value in enabling more autonomous network system operation...2006 to 00-00-2006 4. TITLE AND SUBTITLE Cooperative Multi - Agent Systems in Mobile Ad Hoc Networks 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  6. Assured Resource Sharing in Ad-Hoc Collaboration

    SciTech Connect

    Ahn, Gail-Joon

    2015-12-19

    The project seeks an innovative framework to enable users to access and selectively share resources in distributed environments, enhancing the scalability of information sharing. We have investigated secure sharing & assurance approaches for ad-hoc collaboration, focused on Grids, Clouds, and ad-hoc network environments.

  7. 14 CFR 1203.903 - Ad hoc committees.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Ad hoc committees. 1203.903 Section 1203.903 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION INFORMATION SECURITY PROGRAM NASA Information Security Program Committee § 1203.903 Ad hoc committees. The Chairperson is...

  8. 14 CFR § 1203.903 - Ad hoc committees.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 5 2014-01-01 2014-01-01 false Ad hoc committees. § 1203.903 Section § 1203.903 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION INFORMATION SECURITY PROGRAM NASA Information Security Program Committee § 1203.903 Ad hoc committees. The Chairperson...

  9. 14 CFR 1203.903 - Ad hoc committees.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Ad hoc committees. 1203.903 Section 1203.903 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION INFORMATION SECURITY PROGRAM NASA Information Security Program Committee § 1203.903 Ad hoc committees. The Chairperson is...

  10. Space-Time Processing for Tactical Mobile Ad Hoc Networks

    DTIC Science & Technology

    2010-05-01

    Sagnik Ghosh, Bhaskar D. Rao, and James R. Zeidler; "Outage-Efficient Strategies for Multiuser MIMO Networks with Channel Distribution Information... Distributed cooperative routing and hybrid ARQ in MIMO -BLAST ad hoc networks”, submitted to IEEE Transactions on Communications, 2009. Davide...mobile ad hoc networks using polling techniques for MIMO nodes. Centralized and distributed topology control algorithms have been develop to

  11. Assured Information Sharing for Ad-Hoc Collaboration

    ERIC Educational Resources Information Center

    Jin, Jing

    2009-01-01

    Collaborative information sharing tends to be highly dynamic and often ad hoc among organizations. The dynamic natures and sharing patterns in ad-hoc collaboration impose a need for a comprehensive and flexible approach to reflecting and coping with the unique access control requirements associated with the environment. This dissertation…

  12. The Radio JOVE Project - Shoestring Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

    2010-01-01

    Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

  13. Enhanced Weight based DSR for Mobile Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Verma, Samant; Jain, Sweta

    2011-12-01

    Routing in ad hoc network is a great problematic, since a good routing protocol must ensure fast and efficient packet forwarding, which isn't evident in ad hoc networks. In literature there exists lot of routing protocols however they don't include all the aspects of ad hoc networks as mobility, device and medium constraints which make these protocols not efficient for some configuration and categories of ad hoc networks. Thus in this paper we propose an improvement of Weight Based DSR in order to include some of the aspects of ad hoc networks as stability, remaining battery power, load and trust factor and proposing a new approach Enhanced Weight Based DSR.

  14. Receiver-Based Ad Hoc On Demand Multipath Routing Protocol for Mobile Ad Hoc Networks

    PubMed Central

    Al-Nahari, Abdulaziz; Mohamad, Mohd Murtadha

    2016-01-01

    Decreasing the route rediscovery time process in reactive routing protocols is challenging in mobile ad hoc networks. Links between nodes are continuously established and broken because of the characteristics of the network. Finding multiple routes to increase the reliability is also important but requires a fast update, especially in high traffic load and high mobility where paths can be broken as well. The sender node keeps re-establishing path discovery to find new paths, which makes for long time delay. In this paper we propose an improved multipath routing protocol, called Receiver-based ad hoc on demand multipath routing protocol (RB-AOMDV), which takes advantage of the reliability of the state of the art ad hoc on demand multipath distance vector (AOMDV) protocol with less re-established discovery time. The receiver node assumes the role of discovering paths when finding data packets that have not been received after a period of time. Simulation results show the delay and delivery ratio performances are improved compared with AOMDV. PMID:27258013

  15. RADIO ALTIMETERS

    DOEpatents

    Bogle, R.W.

    1960-11-22

    A radio ranging device is described which utilizes a superregenerative oscillator having alternate sending and receiving phases with an intervening ranging interval between said phases, means for varying said ranging interval, means responsive to an on-range noise reduction condition for stopping said means for varying the ranging interval and indicating means coupled to the ranging interval varying means and calibrated in accordance with one-half the product of the ranging interval times the velocity of light whereby the range is indicated.

  16. Spontaneous Ad Hoc Mobile Cloud Computing Network

    PubMed Central

    Lacuesta, Raquel; Sendra, Sandra; Peñalver, Lourdes

    2014-01-01

    Cloud computing helps users and companies to share computing resources instead of having local servers or personal devices to handle the applications. Smart devices are becoming one of the main information processing devices. Their computing features are reaching levels that let them create a mobile cloud computing network. But sometimes they are not able to create it and collaborate actively in the cloud because it is difficult for them to build easily a spontaneous network and configure its parameters. For this reason, in this paper, we are going to present the design and deployment of a spontaneous ad hoc mobile cloud computing network. In order to perform it, we have developed a trusted algorithm that is able to manage the activity of the nodes when they join and leave the network. The paper shows the network procedures and classes that have been designed. Our simulation results using Castalia show that our proposal presents a good efficiency and network performance even by using high number of nodes. PMID:25202715

  17. Spontaneous ad hoc mobile cloud computing network.

    PubMed

    Lacuesta, Raquel; Lloret, Jaime; Sendra, Sandra; Peñalver, Lourdes

    2014-01-01

    Cloud computing helps users and companies to share computing resources instead of having local servers or personal devices to handle the applications. Smart devices are becoming one of the main information processing devices. Their computing features are reaching levels that let them create a mobile cloud computing network. But sometimes they are not able to create it and collaborate actively in the cloud because it is difficult for them to build easily a spontaneous network and configure its parameters. For this reason, in this paper, we are going to present the design and deployment of a spontaneous ad hoc mobile cloud computing network. In order to perform it, we have developed a trusted algorithm that is able to manage the activity of the nodes when they join and leave the network. The paper shows the network procedures and classes that have been designed. Our simulation results using Castalia show that our proposal presents a good efficiency and network performance even by using high number of nodes.

  18. Radio Jove: Jupiter Radio Astronomy for Citizens

    NASA Astrophysics Data System (ADS)

    Higgins, Charles; Thieman, J. R.; Flagg, R.; Reyes, F. J.; Sky, J.; Greenman, W.; Brown, J.; Typinski, D.; Ashcraft, T.; Mount, A.

    2014-01-01

    Radio JOVE is a hands-on educational activity that brings the radio sounds of the Sun, Jupiter, the Milky Way Galaxy, and terrestrial radio noise to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with professional radio observatories in real-time over the Internet. Our website (http://radiojove.gsfc.nasa.gov) includes science information, construction manuals, observing guides, and education resources for teachers and students. Radio Jove is continually expanding its participants with over 1800 kits sold to more than 70 countries worldwide. Recently some of our most dedicated observers have upgraded their Radio Jove antennas to semi-professional observatories. We have spectrographs and wide band antennas, some with 8 MHz bandwidth and some with dual polarization capabilities. In an effort to add to the science literature, these observers are coordinating their efforts to pursue some basic questions about Jupiter’s radio emissions (radio source locations, spectral structure, long term changes, etc.). We can compare signal and ionosphere variations using the many Radio Jove observers at different locations. Observers are also working with members of the Long Wavelength Array Station 1 (LWA1) radio telescope to coordinate observations of Jupiter; Radio Jove is planning to make coordinated observations while the Juno Mission is active beginning in 2015. The Radio Jove program is overviewed, its hardware and software are highlighted, recent sample observations are shown, and we demonstrate that we are capable of real citizen science.

  19. Learning radio astronomy by doing radio astronomy

    NASA Astrophysics Data System (ADS)

    Vaquerizo Gallego, J. A.

    2011-11-01

    PARTNeR (Proyecto Académico con el Radio Telescopio de NASA en Robledo, Academic Project with the NASA Radio Telescope at Robledo) is an educational program that allows high school and undergraduate students to control a 34 meter radio telescope and conduct radio astronomical observations via the internet. High-school teachers who join the project take a course to learn about the science of radio astronomy and how to use the antenna as an educational resource. Also, teachers are provided with learning activities they can do with their students and focused on the classroom implementation of the project within an interdisciplinary framework. PARTNeR provides students with firsthand experience in radio astronomy science. Thus, remote radio astronomical observations allow students to learn with a first rate scientific equipment the basics of radio astronomy research, aiming to arouse scientific careers and positive attitudes toward science. In this contribution we show the current observational programs and some recent results.

  20. Robust message routing for mobile (wireless) ad hoc networks.

    SciTech Connect

    Goldsby, Michael E.; Johnson, Michael M.; Kilman, Dominique Marie; Bierbaum, Neal Robert; Chen, Helen Y.; Ammerlahn, Heidi R.; Tsang, Rose P.; Nicol, David M.

    2004-01-01

    This report describes the results of research targeting improvements in the robustness of message transport in wireless ad hoc networks. The first section of the report provides an analysis of throughput and latency in the wireless medium access control (MAC) layer and relates the analysis to the commonly used 802.11 protocol. The second section describes enhancements made to several existing models of wireless MAC and ad hoc routing protocols; the models were used in support of the work described in the following section. The third section of the report presents a lightweight transport layer protocol that is superior to TCP for use in wireless networks. In addition, it introduces techniques that improve the performance of any ad hoc source routing protocol. The fourth section presents a novel, highly scalable ad hoc routing protocol that is based on geographic principles but requires no localization hardware.

  1. 78 FR 66288 - An Inquiry Into the Commission's Policies and Rules Regarding AM Radio Service Directional...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-05

    ...-800-378-3160. This document is available in alternative formats (computer diskette, large print, audio... ad hoc technical group of radio broadcasters, equipment manufacturers, and broadcast consulting... multiple towers, which may be several hundred meters apart. The relatively large spacing...

  2. The Radio Amateur's Handbook.

    ERIC Educational Resources Information Center

    Blakeslee, Douglas, Ed.

    The objectives of this basic reference work for the radio amateur are to present radio theory and practice in terms of application and to reflect both the fundamentals and the rapidly-advancing technology of radio communications so that the radio amateur will have a guide to what is practical, meaningful, proven, and useful. Twenty-three chapters…

  3. The Frequency Spectrum Radio.

    ERIC Educational Resources Information Center

    Howkins, John, Ed.

    1979-01-01

    This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

  4. Cognitive Radio for Tactical Wireless Communication Networks

    DTIC Science & Technology

    2011-10-09

    ary modulation that can be derived from biorthogonal signals. Military applications require the use of error-control coding, which is not permitted in...bandwidth. Another valuable modulation format for a CM library is a modulation method that is commonly referred to as quadrature amplitude modulation ( QAM ... modulation , and it is also less robust than standard QPSK. Among other problems with QAM is the requirement for accurate estimates of the phase and

  5. Ultra-Wideband Impulse Radio for Tactical Ad-Hoc Military Communications

    DTIC Science & Technology

    2010-09-02

    21], [23]. Rather than using simulations to show the bit-error- probability ( BEP ) performance with MAI as found in [14] and [15], we incorporate...the power 4 delay profile (PDP) of the channel, inspired by the work in [13], to derive the variance of the MAI, enabling theoretical BEP analysis. Our...an upper bound on the BEP , the number of equal-power users that the system can support is evaluated for different modulation order M. The network

  6. Radio frequency detection assembly and method for detecting radio frequencies

    SciTech Connect

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  7. Auto-configuration protocols in mobile ad hoc networks.

    PubMed

    Villalba, Luis Javier García; Matesanz, Julián García; Orozco, Ana Lucila Sandoval; Díaz, José Duván Márquez

    2011-01-01

    The TCP/IP protocol allows the different nodes in a network to communicate by associating a different IP address to each node. In wired or wireless networks with infrastructure, we have a server or node acting as such which correctly assigns IP addresses, but in mobile ad hoc networks there is no such centralized entity capable of carrying out this function. Therefore, a protocol is needed to perform the network configuration automatically and in a dynamic way, which will use all nodes in the network (or part thereof) as if they were servers that manage IP addresses. This article reviews the major proposed auto-configuration protocols for mobile ad hoc networks, with particular emphasis on one of the most recent: D2HCP. This work also includes a comparison of auto-configuration protocols for mobile ad hoc networks by specifying the most relevant metrics, such as a guarantee of uniqueness, overhead, latency, dependency on the routing protocol and uniformity.

  8. Routing Protocol of Sparse Urban Vehicular Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Li, Huxiong

    Vehicular ad hoc network (VANET) is an application of mobile ad hoc technology in transportation systems, it has become an important part of ITS. Since multi-hop link is hard to set up in sparse VANET, a traffic-aware routing (TAR) protocol is proposed which estimates vehicle average neighbors (VAN) of roads by exchanging beacon messages between encounter vehicles. Road with high VAN is preferred to be selected as part of forwarding path at intersection. Packets are forwarded to the next intersection in road in a greedy manner. Simulations show that TAR outperforms the compared protocols in terms of both packet delivery ratio and average end-to-end delay.

  9. Global Coverage from Ad-Hoc Constellations in Rideshare Orbits

    NASA Technical Reports Server (NTRS)

    Ellis, Armin; Mercury, Michael; Brown, Shannon

    2012-01-01

    A promising area of small satellite development is in providing higher temporal resolution than larger satellites. Traditional constellations have required specific orbits and dedicated launch vehicles. In this paper we discuss an alternative architecture in which the individual elements of the constellation are launched as rideshare opportunities. We compare the coverage of such an ad-hoc constellation with more traditional constellations. Coverage analysis is based on actual historical data from rideshare opportunities. Our analysis includes ground coverage and temporal revisits for Polar, Tropics, Temperate, and Global regions, comparing ad-hoc and Walker constellation.

  10. How to Bootstrap Security for Ad-Hoc Network: Revisited

    NASA Astrophysics Data System (ADS)

    Shin, Wook; Gunter, Carl A.; Kiyomoto, Shinsaku; Fukushima, Kazuhide; Tanaka, Toshiaki

    There are various network-enabled and embedded computers deployed around us. Although we can get enormous conveniences by connecting them together, it is difficult to securely associate them in an ad-hoc manner. The difficulties originate from authentication and key distribution problems among devices that are strangers to each other. In this paper, we review the existing ways of initiating secure communication for ad-hoc network devices, and propose another solution. Exploiting Pairing-based cryptography and the notion of location-limited channel, the proposed solution bootstraps security conveniently and efficiently. Further, it supports ownership enforcement and key-escrow.

  11. Evolution of a radio communication relay system

    NASA Astrophysics Data System (ADS)

    Nguyen, Hoa G.; Pezeshkian, Narek; Hart, Abraham; Burmeister, Aaron; Holz, Kevin; Neff, Joseph; Roth, Leif

    2013-05-01

    Providing long-distance non-line-of-sight control for unmanned ground robots has long been recognized as a problem, considering the nature of the required high-bandwidth radio links. In the early 2000s, the DARPA Mobile Autonomous Robot Software (MARS) program funded the Space and Naval Warfare Systems Center (SSC) Pacific to demonstrate a capability for autonomous mobile communication relaying on a number of Pioneer laboratory robots. This effort also resulted in the development of ad hoc networking radios and software that were later leveraged in the development of a more practical and logistically simpler system, the Automatically Deployed Communication Relays (ADCR). Funded by the Joint Ground Robotics Enterprise and internally by SSC Pacific, several generations of ADCR systems introduced increasingly more capable hardware and software for automatic maintenance of communication links through deployment of static relay nodes from mobile robots. This capability was finally tapped in 2010 to fulfill an urgent need from theater. 243 kits of ruggedized, robot-deployable communication relays were produced and sent to Afghanistan to extend the range of EOD and tactical ground robots in 2012. This paper provides a summary of the evolution of the radio relay technology at SSC Pacific, and then focuses on the latest two stages, the Manually-Deployed Communication Relays and the latest effort to automate the deployment of these ruggedized and fielded relay nodes.

  12. Resonance and Radio

    ERIC Educational Resources Information Center

    Starrett, Malin J.

    2008-01-01

    The science and technology of radio receives little attention in contemporary education. This article discusses ways to explore the basic operating principles of radio. (Contains 4 figures, 3 footnotes, and 2 notes.)

  13. Ad Hoc Technical Committee for Vocational Agriculture. Final Report.

    ERIC Educational Resources Information Center

    Indiana State Commission on Vocational and Technical Education, Indianapolis.

    The goal of the Ad Hoc Technical Committee for Vocational Agriculture in Indiana was to develop a model and recommendations that would result in improved student knowledge and skills for the present and future, address labor market needs, and promote program excellence at all levels of education. The committee developed recommendations for…

  14. 14 CFR § 1203.1002 - Ad hoc committees.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 5 2014-01-01 2014-01-01 false Ad hoc committees. § 1203.1002 Section § 1203.1002 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION INFORMATION SECURITY PROGRAM Special Access Programs (SAP) and Sensitive Compartmented Information (SCI) Programs...

  15. Providing Location Security in Vehicular Ad Hoc Networks

    ERIC Educational Resources Information Center

    Yan, Gongjun

    2010-01-01

    Location is fundamental information in Vehicular Ad-hoc Networks (VANETs). Almost all VANET applications rely on location information. Therefore it is of importance to ensure location information integrity, meaning that location information is original (from the generator), correct (not bogus or fabricated) and unmodified (value not changed). We…

  16. Commercial Radio as Communication.

    ERIC Educational Resources Information Center

    Rothenbuhler, Eric W.

    1996-01-01

    Compares the day-to-day work routines of commercial radio with the principles of a theoretical communication model. Illuminates peculiarities of the conduct of communication by commercial radio. Discusses the application of theoretical models to the evaluation of practicing institutions. Offers assessments of commercial radio deriving from…

  17. Extragalactic Radio Sources

    ERIC Educational Resources Information Center

    Kellerman, Kenneth I.

    1973-01-01

    Discusses new problems arising from the growing observational data through radio telescope arrays, involving the origin of radio sources, apparent superluminal velocities, conversion of radio sources to relativistic particles, and the nature of compact opaque and extended transparent sources. New physics may be needed to answer these cosmological…

  18. Effusion of hydrophobic organic compounds (HOCs) from fog droplets

    SciTech Connect

    Lee, W.M.; Tsay, C.

    1998-12-31

    In this study, the effects of surface-active substances, pH and salt on the effusion of HOCs from droplets were investigated. An HOCs-effusion reactor was established for experiments. N-octane was used for the HOCs and Sodium Dodecyl Sulfate (SDS) was selected as the surface-active substance. A correction factor to mass exchange constant, defined as the deviation of exchange constant of n-octane in fog phase from that in planar aqueous phase was used to quantify the effects of surface-active substance, pH, and salt concentration on the effusion rate of HOCs from fog droplets by a modified double-layer diffusion model. The results showed that surface-active substances, SDS cab decrease the effusion rate of n-octane from fog droplets by about 40%--62% and the values of were in the range of 0.382 to 0.609. The salt, sodium chloride, at the concentration of 1.00 {times} 10{sup {minus}3} [M] can further decrease the mass transfer rate of n-octane from fog droplets because the values changed from 0.590 to 0.368, so that the effusion rate was further decrease by salt. When pH values were between 5.60 and 2.00, values varied from 0.609 to 0.367 at SDS concentration of 1.00 x 10{sup 3}[M]. This indicated that the effusion rate of HOCs from fog droplets decreased with decreasing pH value.

  19. Cognitive Structures in BBC Financial Reports.

    ERIC Educational Resources Information Center

    Marmaridou, A. Sophia S.

    Extracts from financial reports broadcast on two British Broadcasting Corporation (BBC) radio channels are analyzed for cognitive structures that affect the conceptual organization of this discourse type. The approach used for the analysis is based on two assumptions in the relationship of communication and cognition. These are: (1) financial…

  20. Developing a Conceptual Unmanned Aerial Vehicle Communications Mobile AD Hoc Network Simulation Model

    DTIC Science & Technology

    2002-06-01

    Elizabeth Royer described the Ad Hoc On-Demand Distance Vector (AODV) routing protocol as “providing quick and efficient route establishment between...Network.” Thesis, Naval Postgraduate School, December 2000. 8. Das, Samir R., Perkins, Charles E., and Royer, Elizabeth M. “ The Ad-hoc On-Demand...Lidong. “Securing Ad Hoc Networks.” Paper Cornell University, Itaca, New York, NY. 16. Corson , Scott S., and Macker, J. “Mobile Ad Hoc

  1. 75 FR 15742 - NASA Advisory Council; Ad-Hoc Task Force on Planetary Defense; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-30

    ... SPACE ADMINISTRATION NASA Advisory Council; Ad-Hoc Task Force on Planetary Defense; Meeting AGENCY... Administration announces a meeting of the Ad-Hoc Task Force on Planetary Defense of the NASA Advisory Council... include: Ad-Hoc Task Force on Planetary Defense Terms of Reference. NASA Near Earth Object (NEO)...

  2. 29 CFR 1912.11 - Terms of ad hoc committee members.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 7 2011-07-01 2011-07-01 false Terms of ad hoc committee members. 1912.11 Section 1912.11..., DEPARTMENT OF LABOR (CONTINUED) ADVISORY COMMITTEES ON STANDARDS Organizational Matters § 1912.11 Terms of ad hoc committee members. Each member of an ad hoc advisory committee shall serve for such period as...

  3. 75 FR 43565 - NASA Advisory Council; Ad-Hoc Task Force on Planetary Defense; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-26

    ... SPACE ADMINISTRATION NASA Advisory Council; Ad-Hoc Task Force on Planetary Defense; Meeting AGENCY... Administration announces a two-part meeting of the Ad-Hoc Task Force on Planetary Defense of the NASA Advisory...@nasa.gov . SUPPLEMENTARY INFORMATION: The agenda topic is: Drafting of the Ad-Hoc Task Force...

  4. 29 CFR 1912.11 - Terms of ad hoc committee members.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false Terms of ad hoc committee members. 1912.11 Section 1912.11..., DEPARTMENT OF LABOR (CONTINUED) ADVISORY COMMITTEES ON STANDARDS Organizational Matters § 1912.11 Terms of ad hoc committee members. Each member of an ad hoc advisory committee shall serve for such period as...

  5. Smart radio: spectrum access for first responders

    NASA Astrophysics Data System (ADS)

    Silvius, Mark D.; Ge, Feng; Young, Alex; MacKenzie, Allen B.; Bostian, Charles W.

    2008-04-01

    This paper details the Wireless at Virginia Tech Center for Wireless Telecommunications' (CWT) design and implementation of its Smart Radio (SR) communication platform. The CWT SR can identify available spectrum within a pre-defined band, rendezvous with an intended receiver, and transmit voice and data using a selected quality of service (QoS). This system builds upon previous cognitive technologies developed by CWT for the public safety community, with the goal of providing a prototype mobile communications package for military and public safety First Responders. A master control (MC) enables spectrum awareness by characterizing the radio environment with a power spectrum sensor and an innovative signal detection and classification module. The MC also enables spectrum and signal memory by storing sensor results in a knowledge database. By utilizing a family radio service (FRS) waveform database, the CWT SR can create a new communication link on any designated FRS channel frequency using FM, BPSK, QPSK, or 8PSK modulations. With FM, it supports analog voice communications with legacy hand-held FRS radios. With digital modulations, it supports IP data services, including a CWT developed CVSD-based VoIP protocol. The CWT SR coordinates spectrum sharing between analog primary users and digital secondary users by applying a simple but effective channel-change protocol. It also demonstrates a novel rendezvous protocol to facilitate the detection and initialization of communications links with neighboring SR nodes through the transmission of frequency-hopped rendezvous beacons. By leveraging the GNU Radio toolkit, writing key modules entirely in Python, and utilizing the USRP hardware front-end, the CWT SR provides a dynamic spectrum test bed for future smart and cognitive radio research.

  6. Credible Mobile and Ad Hoc Network Simulation-Based Studies

    DTIC Science & Technology

    2006-10-26

    packet radio. In Proceed- ings of the 9th ARRL /CRRL Amateur Radio Computer Networking Conference, pages 134-140, 1990. [45] H. Kee. NAM support for...Selected Areas in Communications (JSAC), pages 1335-1346, 2004. [102] P. Welch. The Computer Performance Modeling Handbook , chapter The Statis- tical

  7. Shuttle-run synchronization in mobile ad hoc networks

    NASA Astrophysics Data System (ADS)

    Ma, Sheng-Fei; Bi, Hong-Jie; Zou, Yong; Liu, Zong-Hua; Guan, Shu-Guang

    2015-06-01

    In this work, we study the collective dynamics of phase oscillators in a mobile ad hoc network whose topology changes dynamically. As the network size or the communication radius of individual oscillators increases, the topology of the ad hoc network first undergoes percolation, forming a giant cluster, and then gradually achieves global connectivity. It is shown that oscillator mobility generally enhances the coherence in such networks. Interestingly, we find a new type of phase synchronization/clustering, in which the phases of the oscillators are distributed in a certain narrow range, while the instantaneous frequencies change signs frequently, leading to shuttle-run-like motion of the oscillators in phase space. We conduct a theoretical analysis to explain the mechanism of this synchronization and obtain the critical transition point.

  8. Distributed Reinforcement Learning Approach for Vehicular Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Wu, Celimuge; Kumekawa, Kazuya; Kato, Toshihiko

    In Vehicular Ad hoc Networks (VANETs), general purpose ad hoc routing protocols such as AODV cannot work efficiently due to the frequent changes in network topology caused by vehicle movement. This paper proposes a VANET routing protocol QLAODV (Q-Learning AODV) which suits unicast applications in high mobility scenarios. QLAODV is a distributed reinforcement learning routing protocol, which uses a Q-Learning algorithm to infer network state information and uses unicast control packets to check the path availability in a real time manner in order to allow Q-Learning to work efficiently in a highly dynamic network environment. QLAODV is favored by its dynamic route change mechanism, which makes it capable of reacting quickly to network topology changes. We present an analysis of the performance of QLAODV by simulation using different mobility models. The simulation results show that QLAODV can efficiently handle unicast applications in VANETs.

  9. Decentralized session initiation protocol solution in ad hoc networks

    NASA Astrophysics Data System (ADS)

    Han, Lu; Jin, Zhigang; Shu, Yantai; Dong, Linfang

    2006-10-01

    With the fast development of ad hoc networks, SIP has attracted more and more attention in multimedia service. This paper proposes a new architecture to provide SIP service for ad hoc users, although there is no centralized SIP server deployed. In this solution, we provide the SIP service by the introduction of two nodes: Designated SIP Server (DS) and its Backup Server (BDS). The nodes of ad hoc network designate DS and BDS when they join the session nodes set and when some pre-defined events occur. A new sip message type called REGISTRAR is presented so nodes can send others REGISTRAR message to declare they want to be DS. According to the IP information taken in the message, an algorithm works like the election of DR and BDR in OSPF protocol is used to vote DS and BDS SIP servers. Naturally, the DS will be replaced by BDS when the DS is down for predicable or unpredictable reasons. To facilitate this, the DS should register to the BDS and transfer a backup of the SIP users' database. Considering the possibility DS or BDS may abruptly go down, a special policy is given. When there is no DS and BDS, a new election procedure is triggered just like the startup phase. The paper also describes how SIP works normally in the decentralized model as well as the evaluation of its performance. All sessions based on SIP in ad hoc such as DS voting have been tested in the real experiments within a 500m*500m square area where about 30 random nodes are placed.

  10. MWAHCA: A Multimedia Wireless Ad Hoc Cluster Architecture

    PubMed Central

    Diaz, Juan R.; Jimenez, Jose M.; Sendra, Sandra

    2014-01-01

    Wireless Ad hoc networks provide a flexible and adaptable infrastructure to transport data over a great variety of environments. Recently, real-time audio and video data transmission has been increased due to the appearance of many multimedia applications. One of the major challenges is to ensure the quality of multimedia streams when they have passed through a wireless ad hoc network. It requires adapting the network architecture to the multimedia QoS requirements. In this paper we propose a new architecture to organize and manage cluster-based ad hoc networks in order to provide multimedia streams. Proposed architecture adapts the network wireless topology in order to improve the quality of audio and video transmissions. In order to achieve this goal, the architecture uses some information such as each node's capacity and the QoS parameters (bandwidth, delay, jitter, and packet loss). The architecture splits the network into clusters which are specialized in specific multimedia traffic. The real system performance study provided at the end of the paper will demonstrate the feasibility of the proposal. PMID:24737996

  11. MAC Protocol for Ad Hoc Networks Using a Genetic Algorithm

    PubMed Central

    Elizarraras, Omar; Panduro, Marco; Méndez, Aldo L.

    2014-01-01

    The problem of obtaining the transmission rate in an ad hoc network consists in adjusting the power of each node to ensure the signal to interference ratio (SIR) and the energy required to transmit from one node to another is obtained at the same time. Therefore, an optimal transmission rate for each node in a medium access control (MAC) protocol based on CSMA-CDMA (carrier sense multiple access-code division multiple access) for ad hoc networks can be obtained using evolutionary optimization. This work proposes a genetic algorithm for the transmission rate election considering a perfect power control, and our proposition achieves improvement of 10% compared with the scheme that handles the handshaking phase to adjust the transmission rate. Furthermore, this paper proposes a genetic algorithm that solves the problem of power combining, interference, data rate, and energy ensuring the signal to interference ratio in an ad hoc network. The result of the proposed genetic algorithm has a better performance (15%) compared to the CSMA-CDMA protocol without optimizing. Therefore, we show by simulation the effectiveness of the proposed protocol in terms of the throughput. PMID:25140339

  12. MWAHCA: a multimedia wireless ad hoc cluster architecture.

    PubMed

    Diaz, Juan R; Lloret, Jaime; Jimenez, Jose M; Sendra, Sandra

    2014-01-01

    Wireless Ad hoc networks provide a flexible and adaptable infrastructure to transport data over a great variety of environments. Recently, real-time audio and video data transmission has been increased due to the appearance of many multimedia applications. One of the major challenges is to ensure the quality of multimedia streams when they have passed through a wireless ad hoc network. It requires adapting the network architecture to the multimedia QoS requirements. In this paper we propose a new architecture to organize and manage cluster-based ad hoc networks in order to provide multimedia streams. Proposed architecture adapts the network wireless topology in order to improve the quality of audio and video transmissions. In order to achieve this goal, the architecture uses some information such as each node's capacity and the QoS parameters (bandwidth, delay, jitter, and packet loss). The architecture splits the network into clusters which are specialized in specific multimedia traffic. The real system performance study provided at the end of the paper will demonstrate the feasibility of the proposal.

  13. Auto-Configuration Protocols in Mobile Ad Hoc Networks

    PubMed Central

    Villalba, Luis Javier García; Matesanz, Julián García; Orozco, Ana Lucila Sandoval; Díaz, José Duván Márquez

    2011-01-01

    The TCP/IP protocol allows the different nodes in a network to communicate by associating a different IP address to each node. In wired or wireless networks with infrastructure, we have a server or node acting as such which correctly assigns IP addresses, but in mobile ad hoc networks there is no such centralized entity capable of carrying out this function. Therefore, a protocol is needed to perform the network configuration automatically and in a dynamic way, which will use all nodes in the network (or part thereof) as if they were servers that manage IP addresses. This article reviews the major proposed auto-configuration protocols for mobile ad hoc networks, with particular emphasis on one of the most recent: D2HCP. This work also includes a comparison of auto-configuration protocols for mobile ad hoc networks by specifying the most relevant metrics, such as a guarantee of uniqueness, overhead, latency, dependency on the routing protocol and uniformity. PMID:22163814

  14. Dominion Radio Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The Dominion Radio Astrophysical Observatory began operating in 1959, and joined the NATIONAL RESEARCH COUNCIL in 1970. It became part of the Herzberg Institute of Astrophysics in 1975. The site near Penticton, BC has a 26 m radio telescope, a seven-antenna synthesis telescope on a 600 m baseline and two telescopes dedicated to monitoring the solar radio flux at 10.7 cm. This part of the Institu...

  15. Radio determination satellite service

    NASA Astrophysics Data System (ADS)

    Briskman, Robert D.

    1990-07-01

    The capabilities and measured performance of a geosynchronous satellite-based service called the radio determination satellite service (RDSS), which operates at radio frequencies allocated by the International Telecommunications Union (ITU) and is licensed in the United States by the Federal Communications Commission (FCC), are discussed. Plans for both improvement in capability and expansion to nearly global coverage are described. Since RDSS can also provide radio navigation, some comparisons of this service with the Global Positioning System (GPS) are made.

  16. Radio data transmission for SCADA

    SciTech Connect

    Frasier, W.E. )

    1989-09-01

    Enron has used such wireless systems as meteor burst radio, 952 MHz multiple address radio, VSAT and L-band satellite, cellular radio and ACSB radio. The company's experience with meteor burst radio communications is discussed in this paper. It indicates good system reliability and consequently all back-up telephone lines have been removed from sites using this system.

  17. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, Henry D.; Fugitt, Jock A.; Howard, Donald R.

    1984-01-01

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  18. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1984-12-25

    Disclosed is a long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator. 5 figs.

  19. Amateur Radio Satellite Communications.

    ERIC Educational Resources Information Center

    Koch, David P.

    The Amateur Radio Satellite Communications project had, as its goal, the assembly of an amateur radio satellite station in a high school physics classroom. Specific objectives were to provide: (1) a special source of interest as a motivator for attracting students and building public relations; (2) a center of interest as a motivator for the study…

  20. Planetary foreshock radio emissions

    NASA Astrophysics Data System (ADS)

    Kuncic, Zdenka; Cairns, Iver H.

    2005-07-01

    The electron foreshock regions upstream of Earth's bow shock and upstream of traveling interplanetary shocks are known to be propitious sites for a variety of energetic particle and plasma wave phenomena, including radio emissions. A quantitative theoretical model has been developed for radio emissions associated with the terrestrial foreshock and for type II radio bursts associated with interplanetary shocks. Here, we generalize this model and apply it to other planetary foreshocks. We present predictions for the levels of planetary foreshock radio emissions and compare these with observations by past and present space missions. One key result is that Mercury can be a strong source of foreshock radio emissions, and this prediction may be testable with the anticipated BepiColombo space mission. Although the terrestrial foreshock radio emissions are the most detectable with existing instruments, our results predict that they are the second strongest in absolute terms, following the Jovian foreshock emissions. Indeed, we predict that the radio instrument on board Ulysses should have detected Jovian foreshock radio emissions, and we suggest that there is some evidence in the data to support this. We also suggest that Cassini was potentially capable of detecting foreshock emissions from Venus during its gravity-assist flybys and may possibly be capable of detecting foreshock emissions from Saturn under favorable solar wind conditions.

  1. Radio Astronomy for Amateurs

    NASA Astrophysics Data System (ADS)

    Quinn, N.; Murdin, P.

    2003-04-01

    Karl Jansky is considered the father of RADIOASTRONOMY. During the 1930s, Jansky worked for the Bell Telephone Laboratories studying the origin of static noise from thunderstorms. During the course of this work he discovered that some signals had an extraterrestrial origin. However, it was Grote Reber, a professional radio engineer and radio amateur, who carried out further investigations. In 1937...

  2. The Radio Jove Project

    NASA Technical Reports Server (NTRS)

    Thieman, J. R.

    2010-01-01

    The Radio love Project is a hands-on education and outreach project in which students, or any other interested individuals or groups build a radio telescope from a kit, operate the radio telescope, transmit the resulting signals through the internet if desired, analyze the results, and share the results with others through archives or general discussions among the observers. Radio love is intended to provide an introduction to radio astronomy for the observer. The equipment allows the user to observe radio signals from Jupiter, the Sun, the galaxy, and Earth-based radiation both natural and man-made. The project was started through a NASA Director's Discretionary Fund grant more than ten years ago. it has continued to be carried out through the dedicated efforts of a group of mainly volunteers. Dearly 1500 kits have been distributed throughout the world. Participation can also be done without building a kit. Pre-built kits are available. Users can also monitor remote radio telescopes through the internet using free downloadable software available through the radiosky.com website. There have been many stories of prize-winning projects, inspirational results, collaborative efforts, etc. We continue to build the community of observers and are always open to new thoughts about how to inspire the observers to still greater involvement in the science and technology associated with Radio Jove.

  3. Writing for Radio.

    ERIC Educational Resources Information Center

    Tupper, Marianna S.

    1995-01-01

    Describes a 24-hour commercial radio station simulation class project for eighth-grade language arts. Students wrote their own scripts, chose music and were disc jockeys on their own music and talk shows, and prepared news and traffic reports. Guest speakers from actual commercial radio came in to discuss issues such as advertising, censorship,…

  4. Film, Radio, and Television.

    ERIC Educational Resources Information Center

    Hardesty, Carolyn, Ed.

    1990-01-01

    This journal issue covers the history of film, radio, and television in Iowa. The first article, "When Pictures and Sound Came to Iowa," summarizes the origin of movies and radio and their early beginnings in Iowa. Using old photographs and measurement charts, the viewing, reading, and listening habits of young people in 1950 and 1958…

  5. Radio efficiency of pulsars

    SciTech Connect

    Szary, Andrzej; Melikidze, George I.; Gil, Janusz; Zhang, Bing; Xu, Ren-Xin E-mail: zhang@physics.unlv.edu

    2014-03-20

    We investigate radio emission efficiency, ξ, of pulsars and report a near-linear inverse correlation between ξ and the spin-down power, E-dot , as well as a near-linear correlation between ξ and pulsar age, τ. This is a consequence of very weak, if any, dependences of radio luminosity, L, on pulsar period, P, and the period derivative, P-dot , in contrast to X-ray or γ-ray emission luminosities. The analysis of radio fluxes suggests that these correlations are not due to a selection effect, but are intrinsic to the pulsar radio emission physics. We have found that, although with a large variance, the radio luminosity of pulsars is ≈10{sup 29} erg s{sup –1}, regardless of the position in the P-- P-dot diagram. Within such a picture, a model-independent statement can be made that the death line of radio pulsars corresponds to an upper limit in the efficiency of radio emission. If we introduce the maximum value for radio efficiency into the Monte Carlo-based population syntheses we can reproduce the observed sample using the random luminosity model. Using the Kolmogorov-Smirnov test on a synthetic flux distribution reveals a high probability of reproducing the observed distribution. Our results suggest that the plasma responsible for generating radio emission is produced under similar conditions regardless of pulsar age, dipolar magnetic field strength, and spin-down rate. The magnetic fields near the pulsar surface are likely dominated by crust-anchored, magnetic anomalies, which do not significantly differ among pulsars, leading to similar conditions for generating electron-positron pairs necessary to power radio emission.

  6. Ubiquitous and Secure Certificate Service for Wireless Ad Hoc Network

    NASA Astrophysics Data System (ADS)

    Ge, Meng; Lam, Kwok-Yan; Li, Jianbin; Chung, Siu-Leung

    Wireless ad hoc network is one of the most suitable platforms for providing communication services to support mobile applications in public areas where no fixed communication infrastructure exists. However, due to the open nature of wireless links and lack of security infrastructure in an ad hoc network environment, applications operating on ad hoc network platforms are subjected to non-trivial security challenges. Asymmetric key management, which is widely adopted to be an effective basis for security services in an open network environment, typically plays a crucial role in meeting the security requirements of such applications. In this paper, we propose a secure asymmetric key management scheme, the Ubiquitous and Secure Certificate Service (USCS), which is based on a variant of the Distributed Certificate Authority (DCA) - the Fully Distributed Certificate Authority (FDCA). Similar to FDCA, USCS introduces the presence of 1-hop neighbors which hold shares of DCA's private signature key, and can collaborate to issue certificates, thereby providing asymmetric key management service. Both USCS and FDCA aim to achieve higher availability than the basic DCA scheme; however, USCS is more secure than FDCA in that the former achieves high availability by distributing existing shares to new members, rather than generating new shares as the FDCA scheme does. In order to realise the high availability potential of USCS, a share selection algorithm is also proposed. Experimental results demonstrated that USCS is a more secure approach of the DCA scheme in that it can achieve stronger security than FDCA while attaining high availability similar to that of FDCA. Experiments also showed that USCS incurs only moderate communication overheads.

  7. Scalable Architecture for Multihop Wireless ad Hoc Networks

    NASA Technical Reports Server (NTRS)

    Arabshahi, Payman; Gray, Andrew; Okino, Clayton; Yan, Tsun-Yee

    2004-01-01

    A scalable architecture for wireless digital data and voice communications via ad hoc networks has been proposed. Although the details of the architecture and of its implementation in hardware and software have yet to be developed, the broad outlines of the architecture are fairly clear: This architecture departs from current commercial wireless communication architectures, which are characterized by low effective bandwidth per user and are not well suited to low-cost, rapid scaling in large metropolitan areas. This architecture is inspired by a vision more akin to that of more than two dozen noncommercial community wireless networking organizations established by volunteers in North America and several European countries.

  8. A Survey on Trust Management for Mobile Ad Hoc Networks

    DTIC Science & Technology

    2011-11-01

    accumulate between these entities.” Capra [34] proposes to use a human trust model based on human interactions in a trust model for fully distributed...network environments such as MANETs. Capra defines trust as the degree of a belief about the behavior of other entities (or agents). Li and Singhal [35...2004. [34] L. Capra , “Toward a Human Trust Model for Mobile Ad-hoc Net- works,” Proc. 2nd UK-UbiNet Workshop, 5-7 May 2004, Cambridge University

  9. Ad Hoc Selection of Voice over Internet Streams

    NASA Technical Reports Server (NTRS)

    Macha, Mitchell G. (Inventor); Bullock, John T. (Inventor)

    2008-01-01

    A method and apparatus for a communication system technique involving ad hoc selection of at least two audio streams is provided. Each of the at least two audio streams is a packetized version of an audio source. A data connection exists between a server and a client where a transport protocol actively propagates the at least two audio streams from the server to the client. Furthermore, software instructions executable on the client indicate a presence of the at least two audio streams, allow selection of at least one of the at least two audio streams, and direct the selected at least one of the at least two audio streams for audio playback.

  10. Approximate ad-hoc query engine for simulation data

    SciTech Connect

    Abdulla, G; Baldwin, C; Critchlow, T; Kamimura, R; Lozares, I; Musick, R; Tang, N; Lee, B S; Snapp, R

    2001-02-01

    In this paper, we describe AQSim, an ongoing effort to design and implement a system to manage terabytes of scientific simulation data. The goal of this project is to reduce data storage requirements and access times while permitting ad-hoc queries using statistical and mathematical models of the data. In order to facilitate data exchange between models based on different representations, we are evaluating using the ASCI common data model which is comprised of several layers of increasing semantic complexity. To support queries over the spatial-temporal mesh structured data we are in the process of defining and implementing a grammar for MeshSQL.

  11. Ad Hoc Selection of Voice over Internet Streams

    NASA Technical Reports Server (NTRS)

    Macha, Mitchell G. (Inventor); Bullock, John T. (Inventor)

    2014-01-01

    A method and apparatus for a communication system technique involving ad hoc selection of at least two audio streams is provided. Each of the at least two audio streams is a packetized version of an audio source. A data connection exists between a server and a client where a transport protocol actively propagates the at least two audio streams from the server to the client. Furthermore, software instructions executable on the client indicate a presence of the at least two audio streams, allow selection of at least one of the at least two audio streams, and direct the selected at least one of the at least two audio streams for audio playback.

  12. Radio broadcasting via satellite

    NASA Astrophysics Data System (ADS)

    Helm, Neil R.; Pritchard, Wilbur L.

    1990-10-01

    Market areas offering potential for future narrowband broadcast satellites are examined, including international public diplomacy, government- and advertising-supported, and business-application usages. Technical issues such as frequency allocation, spacecraft types, transmission parameters, and radio receiver characteristics are outlined. Service and system requirements, advertising revenue, and business communications services are among the economic issues discussed. The institutional framework required to provide an operational radio broadcast service is studied, and new initiatives in direct broadcast audio radio systems, encompassing studies, tests, in-orbit demonstrations of, and proposals for national and international commercial broadcast services are considered.

  13. Effects of Data Replication on Data Exfiltration in Mobile Ad Hoc Networks Utilizing Reactive Protocols

    DTIC Science & Technology

    2015-03-01

    IN MOBILE AD HOC NETWORKS UTILIZING REACTIVE PROTOCOLS THESIS Presented to the Faculty Department of Electrical and Computer Engineering Graduate...EFFECTS OF DATA REPLICATION ON DATA EXFILTRATION IN MOBILE AD HOC NETWORKS UTILIZING REACTIVE PROTOCOLS THESIS Corey T. Willinger, Captain, USAF AFIT...APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT-ENG-MS-15-M-035 EFFECTS OF DATA REPLICATION ON DATA EXFILTRATION IN MOBILE AD HOC NETWORKS

  14. Energy Efficient Probabilistic Broadcasting for Mobile Ad-Hoc Network

    NASA Astrophysics Data System (ADS)

    Kumar, Sumit; Mehfuz, Shabana

    2016-08-01

    In mobile ad-hoc network (MANETs) flooding method is used for broadcasting route request (RREQ) packet from one node to another node for route discovery. This is the simplest method of broadcasting of RREQ packets but it often results in broadcast storm problem, originating collisions and congestion of packets in the network. A probabilistic broadcasting is one of the widely used broadcasting scheme for route discovery in MANETs and provides solution for broadcasting storm problem. But it does not consider limited energy of the battery of the nodes. In this paper, a new energy efficient probabilistic broadcasting (EEPB) is proposed in which probability of broadcasting RREQs is calculated with respect to remaining energy of nodes. The analysis of simulation results clearly indicate that an EEPB route discovery scheme in ad-hoc on demand distance vector (AODV) can increase the network lifetime with a decrease in the average power consumption and RREQ packet overhead. It also decreases the number of dropped packets in the network, in comparison to other EEPB schemes like energy constraint gossip (ECG), energy aware gossip (EAG), energy based gossip (EBG) and network lifetime through energy efficient broadcast gossip (NEBG).

  15. Towards Trust-based Cognitive Networks: A Survey of Trust Management for Mobile Ad Hoc Networks

    DTIC Science & Technology

    2009-06-01

    destination.  Wormhole attack: A group of cooperating malicious nodes can pretend to connect two distant points in the network with a low-latency...communication link called wormhole link, causing disruptions in normal traffic load and flow.  Black hole attack: A malicious node, the so called

  16. Eratosthenes via Ham Radio

    ERIC Educational Resources Information Center

    Koser, John F.

    1975-01-01

    A secondary geology class used Eratosthenes' method for measuring the circumference of the earth by comparing their measurements of the shadow of a vertical rod to the measurements made by another person contacted by ham radio. (MLH)

  17. Unveiling the radio cosmos

    NASA Astrophysics Data System (ADS)

    Vanderlinde, Keith

    2017-02-01

    Using a radio telescope with no moving parts, the dark energy speeding up the expansion of the Universe can be probed in unprecedented detail, says Keith Vanderlinde, on behalf of the CHIME collaboration.

  18. Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Kaspi, Victoria M.

    2017-01-01

    Fast Radio Bursts (FRBs) are a recently discovered phenomenon consisting of short (few ms) bursts of radio waves that have dispersion measures that strongly suggest an extragalactic and possibly cosmological origin. Current best estimates for the rate of FRBs is several thousand per sky per day at radio frequencies near 1.4 GHz. Even with so high a rate, to date, fewer than 20 FRBs have been reported, with one source showing repeated bursts. In this talk I will describe known FRB properties including what is known about the lone repeating source, as well as models for the origin of these mysterious events. I will also describe the CHIME radio telescope, currently under construction in Canada. Thanks to its great sensitivity and unprecedented field-of-view, CHIME promises major progress on FRBs.

  19. Packet Radio for Library Automation.

    ERIC Educational Resources Information Center

    Brownrigg, Edwin B.; And Others

    1984-01-01

    This tutorial on packet radio (communication system using radio and digital packet-switching technology) highlights radio transmission of data, brief history, special considerations in applying packet radio to library online catalogs, technology, defining protocol at physical and network levels, security, geographic coverage, and components. (A…

  20. Soldier’s Radio

    DTIC Science & Technology

    1992-02-14

    individual soldier. "t’s primary use is by individuals in squads or small units, but may also be used to interconnect into local and wide area...Velopilnq the concept for the Soldier’s Radio. The operation of the SR can be partitioned into two areas. The architecture required to provide intra- squad ... SQUAD CONMECTrVITY The basic radio ccmmunications architectures suitable for :cnsideration for the SR intra- squad operations include the Net, .tar

  1. The Radio JOVE Project

    NASA Astrophysics Data System (ADS)

    Garcia, L.; Thieman, J.; Higgins, C.

    1999-09-01

    Radio JOVE is an interactive educational activity which brings the radio sounds of Jupiter and the Sun to students, teachers, and the general public. This is accomplished through the construction of a simple radio telescope kit and the use of a real-time radio observatory on the Internet. Our website (http://radiojove.gsfc.nasa.gov/) will contain science information, instruction manuals, observing guides, and education resources for students and teachers. Our target audience is high school science classes, but subjects can be tailored to college undergraduate physics and astronomy courses or even to middle school science classes. The goals of the project are: 1) Educate people about planetary and solar radio astronomy, space physics, and the scientific method 2) Provide teachers and students with a hands-on radio astronomy exercise as a science curriculum support activity by building and using a simple radio telescope receiver/antenna kit 3) Create the first ever online radio observatory which provides real-time data for those with internet access 4) Allow interactions among participating schools by facilitating exchanges of ideas, data, and observing experiences. Our current funding will allow us to impact 100 schools by partially subsidizing their participation in the program. We expect to expand well beyond this number as publicity and general interest increase. Additional schools are welcome to fully participate, but we will not be able to subsidize their kit purchases. We hope to make a wide impact among the schools by advertising through appropriate newsletters, space grant consortia, the INSPIRE project (http://image.gsfc.nasa.gov/poetry/inspire/), electronic links, and science and education meetings. We would like to acknoledge support from the NASA/GSFC Director's Discretionary Fund, the STScI IDEAS grant program and the NASA/GSFC Space Science Data Operations Office.

  2. Radio spectrum surveillance station

    NASA Technical Reports Server (NTRS)

    Hersey, D. R.

    1979-01-01

    The paper presents a general and functional description of a low-cost surveillance station designed as the first phase of NASA's program to develop a radio spectrum surveillance capability for deep space stations for identifying radio frequency interference sources. The station described has identified several particular interferences and is yielding spectral signature data which, after cataloging, will serve as a library for rapid identification of frequently observed interference. Findings from the use of the station are discussed.

  3. Radio observations of solar eclipse.

    NASA Astrophysics Data System (ADS)

    Liu, Yuying; Fu, Qijun

    1998-09-01

    For radio astronomy, a solar eclipse provides an opportunity for making solar radio observations with high one-dimension spatial resolution. The radio observation of a solar eclipse has played an important role in solar radio physics. Some important factors for radio observation of a solar eclipse are introduced and analysed. Solar eclipse radio observation has also played an important role in the progress of solar radio atronomy in China. The solar eclipses of 1958, 1968, 1980 and 1987, which were observed in China, are introduced, and the main results of these observations are briefly shown.

  4. Astrometry of southern radio sources.

    PubMed

    White, G L; Jauncey, D L; Harvey, B R; Savage, A; Gulkis, S; Preston, R A; Peterson, B A; Reynolds, J E; Nicolson, G D; Malin, D F

    1991-01-01

    An overview is presented of a number of astrometry and astrophysics programs based on radio sources from the Parkes 2.7 GHz catalogues. The programs cover the optical identification and spectroscopy of flat-spectrum Parkes sources and the determination of their milliarc-second radio structures and positions. Work is also in progress to tie together the radio and Hipparcos positional reference frames. A parallel program of radio and optical astrometry of southern radio stars is also under way.

  5. Cognitive ecology.

    PubMed

    Hutchins, Edwin

    2010-10-01

    Cognitive ecology is the study of cognitive phenomena in context. In particular, it points to the web of mutual dependence among the elements of a cognitive ecosystem. At least three fields were taking a deeply ecological approach to cognition 30 years ago: Gibson's ecological psychology, Bateson's ecology of mind, and Soviet cultural-historical activity theory. The ideas developed in those projects have now found a place in modern views of embodied, situated, distributed cognition. As cognitive theory continues to shift from units of analysis defined by inherent properties of the elements to units defined in terms of dynamic patterns of correlation across elements, the study of cognitive ecosystems will become an increasingly important part of cognitive science.

  6. Intelligent routing protocol for ad hoc wireless network

    NASA Astrophysics Data System (ADS)

    Peng, Chaorong; Chen, Chang Wen

    2006-05-01

    A novel routing scheme for mobile ad hoc networks (MANETs), which combines hybrid and multi-inter-routing path properties with a distributed topology discovery route mechanism using control agents is proposed in this paper. In recent years, a variety of hybrid routing protocols for Mobile Ad hoc wireless networks (MANETs) have been developed. Which is proactively maintains routing information for a local neighborhood, while reactively acquiring routes to destinations beyond the global. The hybrid protocol reduces routing discovery latency and the end-to-end delay by providing high connectivity without requiring much of the scarce network capacity. On the other side the hybrid routing protocols in MANETs likes Zone Routing Protocol still need route "re-discover" time when a route between zones link break. Sine the topology update information needs to be broadcast routing request on local zone. Due to this delay, the routing protocol may not be applicable for real-time data and multimedia communication. We utilize the advantages of a clustering organization and multi-routing path in routing protocol to achieve several goals at the same time. Firstly, IRP efficiently saves network bandwidth and reduces route reconstruction time when a routing path fails. The IRP protocol does not require global periodic routing advertisements, local control agents will automatically monitor and repair broke links. Secondly, it efficiently reduces congestion and traffic "bottlenecks" for ClusterHeads in clustering network. Thirdly, it reduces significant overheads associated with maintaining clusters. Fourthly, it improves clusters stability due to dynamic topology changing frequently. In this paper, we present the Intelligent Routing Protocol. First, we discuss the problem of routing in ad hoc networks and the motivation of IRP. We describe the hierarchical architecture of IRP. We describe the routing process and illustrate it with an example. Further, we describe the control manage

  7. Device Discovery in Frequency Hopping Wireless Ad Hoc Networks

    DTIC Science & Technology

    2004-09-01

    Thesis, Blekinge Institute of Technology, Available: http://www.inst-informatica.pt/v20/cid/ biblioteca digital /telecomunicacoes...Single-Channel Ground And Airborne Radio System,” Available: http://www.fas.org/man/dod-101/sys/land/docs/sincgars.pdf, 1996. Skl01. B. Sklar, Digital

  8. Infrared spectra of two isomers of protonated carbonyl sulfide (HOCS+ and HSCO+) and t-HOCS in solid para-hydrogen

    NASA Astrophysics Data System (ADS)

    Tsuge, Masashi; Lee, Yuan-Pern

    2016-10-01

    We report infrared (IR) spectra of HOCS+, HSCO+, t-HOCS, and other species produced on electron bombardment of a mixture of carbonyl sulfide (OCS) and para-hydrogen (p-H2) during deposition at 3.2 K. After maintenance of the matrix in darkness for 15 h, the intensities of absorption features of HOCS+ at 2945.9 (ν1), 1875.3 (ν2), and 1041.9 (ν3) cm-1 and those of HSCO+ at 2506.9 (ν1) and 2074.2 (ν2) cm-1 decreased through neutralization with trapped electrons. Lines observed at 3563.4, 1394.8, and 1199.0 cm-1, which decreased slightly in intensity after maintenance in darkness and were nearly depleted after irradiation at 373 nm, are assigned to a t-HOCS radical. The corresponding spectra of their 13C- and D-isotopologues were observed. The IR spectra of HSCO+ and t-HOCS and those of modes ν2 and ν3 of HOCS+ are new. The assignments were made according to the expected chemical behavior and a comparison of experimental and calculated wavenumbers and 13C- and D-isotopic shifts. The wavenumber of the OH stretching mode (2945.9 cm-1) of HOCS+ in solid p-H2 is significantly red-shifted from that (3435.16 cm-1) reported for gaseous HOCS+; this shift is attributed to partial sharing of a proton between OCS and H2. The corresponding p-H2 induced shift is small in HSCO+ because of a much weaker interaction between HSCO+ and H2.

  9. Topology for efficient information dissemination in ad-hoc networking

    NASA Technical Reports Server (NTRS)

    Jennings, E.; Okino, C. M.

    2002-01-01

    In this paper, we explore the information dissemination problem in ad-hoc wirless networks. First, we analyze the probability of successful broadcast, assuming: the nodes are uniformly distributed, the available area has a lower bould relative to the total number of nodes, and there is zero knowledge of the overall topology of the network. By showing that the probability of such events is small, we are motivated to extract good graph topologies to minimize the overall transmissions. Three algorithms are used to generate topologies of the network with guaranteed connectivity. These are the minimum radius graph, the relative neighborhood graph and the minimum spanning tree. Our simulation shows that the relative neighborhood graph has certain good graph properties, which makes it suitable for efficient information dissemination.

  10. Remote Upload of Evidence over Mobile Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Ray, Indrajit

    In this work, we report on one aspect of an autonomous robot-based digital evidence acquisition system that we are developing. When forensic investigators operate within a hostile environment they may use remotely operated unmanned devices to gather digital evidence. These systems periodically upload the evidence to a remote central server using a mobile ad hoc network. In such cases, large pieces of information need to be fragmented and transmitted in an appropriate manner. To support proper forensic analysis, certain properties must ensured for each fragment of evidence — confidentiality during communication, authenticity and integrity of the data, and, most importantly, strong evidence of membership for fragments. This paper describes a framework to provide these properties for the robot-based evidence acquisition system under development.

  11. Realistic Mobility Modeling for Vehicular Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Akay, Hilal; Tugcu, Tuna

    2009-08-01

    Simulations used for evaluating the performance of routing protocols for Vehicular Ad Hoc Networks (VANET) are mostly based on random mobility and fail to consider individual behaviors of the vehicles. Unrealistic assumptions about mobility produce misleading results about the behavior of routing protocols in real deployments. In this paper, a realistic mobility modeling tool, Mobility for Vehicles (MOVE), which considers the basic mobility behaviors of vehicles, is proposed for a more accurate evaluation. The proposed model is tested against the Random Waypoint (RWP) model using AODV and OLSR protocols. The results show that the mobility model significantly affects the number of nodes within the transmission range of a node, the volume of control traffic, and the number of collisions. It is shown that number of intersections, grid size, and node density are important parameters when dealing with VANET performance.

  12. Ad hoc committee on global climate issues: Annual report

    USGS Publications Warehouse

    Gerhard, L.C.; Hanson, B.M.B.

    2000-01-01

    The AAPG Ad Hoc Committee on Global Climate Issues has studied the supposition of human-induced climate change since the committee's inception in January 1998. This paper details the progress and findings of the committee through June 1999. At that time there had been essentially no geologic input into the global climate change debate. The following statements reflect the current state of climate knowledge from the geologic perspective as interpreted by the majority of the committee membership. The committee recognizes that new data could change its conclusions. The earth's climate is constantly changing owing to natural variability in earth processes. Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time.

  13. Opportunistic Channel Scheduling for Ad Hoc Networks with Queue Stability

    NASA Astrophysics Data System (ADS)

    Dong, Lei; Wang, Yongchao

    2015-03-01

    In this paper, a distributed opportunistic channel access strategy in ad hoc network is proposed. We consider the multiple sources contend for the transmission opportunity, the winner source decides to transmit or restart contention based on the current channel condition. Owing to real data assumption at all links, the decision still needs to consider the stability of the queues. We formulate the channel opportunistic scheduling as a constrained optimization problem which maximizes the system average throughput with the constraints that the queues of all links are stable. The proposed optimization model is solved by Lyapunov stability in queueing theory. The successive channel access problem is decoupled into single optimal stopping problem at every frame and solved with Lyapunov algorithm. The threshold for every frame is different, and it is derived based on the instantaneous queue information. Finally, computer simulations are conducted to demonstrate the validity of the proposed strategy.

  14. Undilatable Stent Neoatherosclerosis Treated with Ad Hoc Rotational Atherectomy

    PubMed Central

    Koutouzis, Michael; Maniotis, Christos; Tsiafoutis, Ioannis; Argyriou, Mihalis

    2017-01-01

    A middle age woman with known ischemic heart disease and old stents in proximal left anterior descending coronary artery (LAD) was admitted to Coronary Care Unit with acute coronary syndrome. The coronary angiography showed one vessel disease with significant restenosis within the previously implanted stents. The lesion was tough and remained undilatable despite high pressure balloon inflation. Eventually, the balloon ruptured creating a massive dissection of the LAD beginning immediately after the distal part of the undilatable lesion. We proceeded with a challenging ad hoc rotational atherectomy of the lesion and finally stenting of the lesion. In-stent restenosis many years after stent implantation is considered to be mainly due to neoatheromatosis compared to intimal hyperplasia, making lesion treatment more difficult and unpredictable. PMID:28168062

  15. A Token Ring Protocol for Dynamic Ad-hoc Wireless Environments

    SciTech Connect

    Top, P; Kohlhepp, V; Dowla, F

    2005-09-30

    A wireless ad-hoc networking protocol is presented. The protocol is designed to be flexible, easy to use and adaptable to a wide variety of potential applications. The primary considerations in design are small code size, guaranteed bandwidth access, limited delay, and error resilience in a highly dynamic ad-hoc environment. These considerations are achieved through the use of token ring protocol.

  16. 32 CFR 2800.7 - Designation of chairperson for Ad Hoc Committees.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Designation of chairperson for Ad Hoc Committees... VICE PRESIDENT OF THE UNITED STATES SECURITY PROCEDURES § 2800.7 Designation of chairperson for Ad Hoc Committees. The Counsel to the Vice President is designated as the responsible official to chair Ad...

  17. 32 CFR 2800.7 - Designation of chairperson for Ad Hoc Committees.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 6 2011-07-01 2011-07-01 false Designation of chairperson for Ad Hoc Committees... VICE PRESIDENT OF THE UNITED STATES SECURITY PROCEDURES § 2800.7 Designation of chairperson for Ad Hoc Committees. The Counsel to the Vice President is designated as the responsible official to chair Ad...

  18. Typicality Mediates Performance during Category Verification in Both Ad-Hoc and Well-Defined Categories

    ERIC Educational Resources Information Center

    Sandberg, Chaleece; Sebastian, Rajani; Kiran, Swathi

    2012-01-01

    Background: The typicality effect is present in neurologically intact populations for natural, ad-hoc, and well-defined categories. Although sparse, there is evidence of typicality effects in persons with chronic stroke aphasia for natural and ad-hoc categories. However, it is unknown exactly what influences the typicality effect in this…

  19. Saccharomyces Cerevisiae Hoc1, a Suppressor of Pkc1, Encodes a Putative Glycosyltransferase

    PubMed Central

    Neiman, A. M.; Mhaiskar, V.; Manus, V.; Galibert, F.; Dean, N.

    1997-01-01

    The Saccharomyces cerevisiae gene PKC1 encodes a protein kinase C isozyme that regulates cell wall synthesis. Here we describe the characterization of HOC1, a gene identified by its ability to suppress the cell lysis phenotype of pkc1-371 cells. The HOC1 gene (Homologous to OCH1) is predicted to encode a type II integral membrane protein that strongly resembles Och1p, an α-1,6-mannosyltransferase. Immunofluorescence studies localized Hoc1p to the Golgi apparatus. While overexpression of HOC1 rescued the pkc1-371 temperature-sensitive cell lysis phenotype, disruption of HOC1 lowered the restrictive temperature of the pkc1-371 allele. Disruption of HOC1 also resulted in hypersensitivity to Calcofluor White and hygromycin B, phenotypes characteristic of defects in cell wall integrity and protein glycosylation, respectively. The function of HOC1 appears to be distinct from that of OCH1. Taken together, these results suggest that HOC1 encodes a Golgi-localized putative mannosyltransferase required for the proper construction of the cell wall. PMID:9055074

  20. Radio data archiving system

    NASA Astrophysics Data System (ADS)

    Knapic, C.; Zanichelli, A.; Dovgan, E.; Nanni, M.; Stagni, M.; Righini, S.; Sponza, M.; Bedosti, F.; Orlati, A.; Smareglia, R.

    2016-07-01

    Radio Astronomical Data models are becoming very complex since the huge possible range of instrumental configurations available with the modern Radio Telescopes. What in the past was the last frontiers of data formats in terms of efficiency and flexibility is now evolving with new strategies and methodologies enabling the persistence of a very complex, hierarchical and multi-purpose information. Such an evolution of data models and data formats require new data archiving techniques in order to guarantee data preservation following the directives of Open Archival Information System and the International Virtual Observatory Alliance for data sharing and publication. Currently, various formats (FITS, MBFITS, VLBI's XML description files and ancillary files) of data acquired with the Medicina and Noto Radio Telescopes can be stored and handled by a common Radio Archive, that is planned to be released to the (inter)national community by the end of 2016. This state-of-the-art archiving system for radio astronomical data aims at delegating as much as possible to the software setting how and where the descriptors (metadata) are saved, while the users perform user-friendly queries translated by the web interface into complex interrogations on the database to retrieve data. In such a way, the Archive is ready to be Virtual Observatory compliant and as much as possible user-friendly.

  1. Cognitive problems following hematopoietic stem cell transplant: relationships with sleep, depression and fatigue.

    PubMed

    Ghazikhanian, S E; Dorfman, C S; Somers, T J; O'Sullivan, M L; Fisher, H M; Edmond, S N; Wren, A A; Kelleher, S A; Rowe Nichols, K A; Chao, N; Shelby, R A

    2017-02-01

    Cognitive problems are a significant, persistent concern for patients undergoing hematopoietic stem cell transplant (HSCT). Sleep is important for many cognitive tasks; however, the relationship between sleep and cognitive problems for HSCT patients is unknown. This study examined the relationship between sleep and cognitive problems for HSCT patients from pre to post transplant. Patients undergoing HSCT (N=138) completed questionnaires at pre-transplant and during the 12 months following transplant. Questionnaires assessed sleep and cognitive problems as well as commonly co-occurring symptoms: depressive symptoms, fatigue and pain. Post hoc analyses examined the relationship of specific sleep problems with cognitive problems. Sleep problems covaried with cognitive problems even after controlling for depressive symptoms, fatigue and pain. Depressive symptoms and fatigue were also uniquely related to cognitive problems. Post hoc analyses suggest that sleep somnolence, shortness of breath, snoring and perceptions of inadequate sleep may contribute to the association found between sleep and cognitive problems. Findings suggest that sleep problems are associated with and may contribute to cognitive problems for HSCT patients. However, sleep problems are rarely screened for or discussed during clinic visits. Assessing and treating specific sleep problems in addition to depressive symptoms and fatigue may have implications for improving cognitive problems for HSCT patients.

  2. Comets at radio wavelengths

    NASA Astrophysics Data System (ADS)

    Crovisier, Jacques; Bockelée-Morvan, Dominique; Colom, Pierre; Biver, Nicolas

    2016-11-01

    Comets are considered as the most primitive objects in the Solar System. Their composition provides information on the composition of the primitive solar nebula, 4.6 Gyr ago. The radio domain is a privileged tool to study the composition of cometary ices. Observations of the OH radical at 18 cm wavelength allow us to measure the water production rate. A wealth of molecules (and some of their isotopologues) coming from the sublimation of ices in the nucleus have been identified by observations in the millimetre and submillimetre domains. We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nançay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe.

  3. High redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.

    1993-01-01

    High redshift galaxies that host powerful radio sources are examined. An overview is presented of the content of radio surveys: 3CR and 3CRR, 4C and 4C/USS, B2/1 Jy, MG, MRC/1Jy, Parkes/PSR, B3, and ESO Key-Project. Narrow-line radio galaxies in the visible and UV, the source of ionization and excitation of the emission lines, emission-line luminosities, morphology of the line-emitting gas, physical properties and energetics, kinematics of the line-emitting gas, and implications from the emission lines are discussed. The morphologies and environments of the host galaxies, the alignment effect, and spectral energy distributions and ages are also examined.

  4. Radio coverage statistics.

    PubMed

    Lynn, W

    1984-01-01

    The Clearinghouse on Development Communication surveyed 135 countries in Asia, Africa, Europe, North and South America, for U.S.A.I.D., to determine the number of radio and television broadcast stations and receivers. Some of the data were obtained from the World Factbook, the World Radio and TV Handbook, and the World Radio and T.V. Facts and Figures, from 1979 to 1981. In those countries where stations are privately owned, audience surveys are often available. In 2 out of 3 developing countries, however, stations are government owned, and no such information is available. Numbers of receivers can sometimes be ascertained from receiver license applications. There is a need for more complete information on broadcast demographics, listening and viewing patterns by the community of world development program personnel.

  5. Radio frequency spectrum management

    NASA Astrophysics Data System (ADS)

    Sujdak, E. J., Jr.

    1980-03-01

    This thesis is a study of radio frequency spectrum management as practiced by agencies and departments of the Federal Government. After a brief introduction to the international agency involved in radio frequency spectrum management, the author concentrates on Federal agencies engaged in frequency management. These agencies include the National Telecommunications and Information Administration (NTIA), the Interdepartment Radio Advisory Committee (IRAC), and the Department of Defense (DoD). Based on an analysis of Department of Defense frequency assignment procedures, recommendations are given concerning decentralizing military frequency assignment by delegating broader authority to unified commanders. This proposal includes a recommendation to colocate the individual Service frequency management offices at the Washington level. This would result in reduced travel costs, lower manpower requirements, and a common tri-Service frequency management data base.

  6. Planetary radio waves

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.

    1986-01-01

    Three planets, the earth, Jupiter and Saturn are known to emit nonthermal radio waves which require coherent radiation processes. The characteristic features (frequency spectrum, polarization, occurrence probability, radiation pattern) are discussed. Radiation which is externally controlled by the solar wind is distinguished from internally controlled radiation which only originates from Jupiter. The efficiency of the externally controlled radiation is roughly the same at all three planets (5 x 10 to the -6th) suggesting that similar processes are active there. The maser radiation mechanism for the generation of the radio waves and general requirements for the mechanism which couples the power generator to the region where the radio waves are generated are briefly discussed.

  7. Radio Emission from Supernovae

    SciTech Connect

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; Van Dyk, Schuyler D.; Stockdale, Christopher J.; Kelley, Matthew T.

    2009-05-03

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect dumpiness of the circumstellar material.

  8. Radio Observations of Meteors.

    PubMed

    Millman, P M

    1954-08-27

    To summarize, we find that the radio technique of meteor observation enables us to extend the systematic recording of meteor rates down to the 9th or 10th magnitude; to determine satisfactory heights and velocities on a scale previously impossible; to calculate the orbits of meteor showers and individual meteors, in particular those that appear only in the daytime; and to study wind drift and fine structure in the ionosphere. The radio observations have quite definitely indicated that down to the 9th magnitude, corresponding to particles approximately 1 mm in diameter, meteors are members of the solar system and do not come from interstellar space.

  9. Sensors Locate Radio Interference

    NASA Technical Reports Server (NTRS)

    2009-01-01

    After receiving a NASA Small Business Innovation Research (SBIR) contract from Kennedy Space Center, Soneticom Inc., based in West Melbourne, Florida, created algorithms for time difference of arrival and radio interferometry, which it used in its Lynx Location System (LLS) to locate electromagnetic interference that can disrupt radio communications. Soneticom is collaborating with the Federal Aviation Administration (FAA) to install and test the LLS at its field test center in New Jersey in preparation for deploying the LLS at commercial airports. The software collects data from each sensor in order to compute the location of the interfering emitter.

  10. Radio astronomy with microspacecraft

    NASA Technical Reports Server (NTRS)

    Collins, D.

    2001-01-01

    A dynamic constellation of microspacecraft in lunar orbit can carry out valuable radio astronomy investigations in the frequency range of 30kHz--30MHz, a range that is difficult to explore from Earth. In contrast to the radio astronomy ivestigations that have flown on individual spacecraft, the four microspacecraft together with a carrier spacecraft, which transported them to lunar orbit, form an interferometer with far superior angular resolution. Use of microspacecraft allows the entire constellation to be launched with a Taurus-class vehicle. Also distinguishing this approach is that the Moon is used as needed to shield the constellation from RF interference from the Earth and Sun.

  11. e-POP Radio Science Using Amateur Radio Transmissions

    NASA Astrophysics Data System (ADS)

    Frissell, N. A.; Perry, G. W.; Miller, E. S.; Shovkoplyas, A.; Moses, M. L.; James, H. G.; Yau, A. W.

    2015-12-01

    A major component of the enhanced Polar Outflow Probe (e-POP) Radio Receiver Instrument (RRI) mission is to utilize artificially generated radio emissions to study High Frequency (HF) radio wave propagation in the ionosphere. In the North American and European sectors, communications between amateur radio operators are a persistent and abundant source source of HF transmissions. We present the results of HF radio wave propagation experiments using amateur radio transmissions as an HF source for e-POP RRI. We detail how a distributed and autonomously operated amateur radio network can be leveraged to study HF radio wave propagation as well as the structuring and dynamics of the ionosphere over a large geographic region. In one case, the sudden disappearance of nearly two-dozen amateur radio HF sources located in the midwestern United States was used to detect a enhancement in foF2 in that same region. We compare our results to those from other more conventional radio instruments and models of the ionosphere to demonstrate the scientific merit of incorporating amateur radio networks for radio science at HF.

  12. Prism beamswitch for radio telescopes.

    PubMed

    Payne, J M; Ulich, B L

    1978-12-01

    A dielectric prism and switching mechanism have been constructed for beamswitching a Cassegrain radio telescope. Spatially extended radio sources may be mapped without significant confusion utilizing the sensitivity and stability inherent in the conventional Dicke radiometer.

  13. Svetloe Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Rahimov, Ismail

    2013-01-01

    This report summarizes information about the Svetloe Radio Astronomical Observatory activities in 2012. Last year, a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to their required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  14. Zelenchukskaya Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Dyakov, Andrei

    2013-01-01

    This report summarizes information about Zelenchukskaya Radio Astronomical Observatory activities in 2012. Last year a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to the required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  15. RADIO RANGING DEVICE

    DOEpatents

    Nieset, R.T.

    1961-05-16

    A radio ranging device is described. It utilizes a super regenerative detector-oscillator in which echoes of transmitted pulses are received in proper phase to reduce noise energy at a selected range and also at multiples of the selected range.

  16. Community Radio in Canada.

    ERIC Educational Resources Information Center

    Canadian Broadcasting Corp., Ottawa (Ontario).

    Results are presented of a survey of 20 community radio organizations operating in Canada. For each of the 20 agencies, information is provided relating to: (1) the name and address of the organization; (2) the name and population of the community served; (3) the station's call letters, frequency, and power; (4) the date of the station's license;…

  17. Radio Channel Simulator (RCSM)

    SciTech Connect

    2007-01-31

    This is a simulation package for making site specific predictions of radio signal strength. The software computes received power at discrete grid points as a function of the transmitter location and propagation environment. It is intended for use with wireless network simulation packages and to support wireless network deployments.

  18. Albanian: Basic Radio Communications.

    ERIC Educational Resources Information Center

    Defense Language Inst., Washington, DC.

    This volume has been designed as a supplement to a course in Albanian developed by the Defense Language Institute. The emphasis in this text is placed on radio communications instruction. The volume is divided into five exercises, each of which contains a vocabulary, dictation, and an air-to-ground communications procedure conducted in Albanian…

  19. Torun Radio Astronomy Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Torun Center for Astronomy is located at Piwnice, 15 km north of Torun, Poland. A part of the Faculty of Physics and Astronomy of the Nicolaus Copernicus University, it was created by the union of Torun Radio Astronomy Observatory (TRAO) and the Institute of Astronomy on 1 January 1997....

  20. Educational Broadcasting--Radio.

    ERIC Educational Resources Information Center

    Ahamed, Uvais; Grimmett, George

    This manual is intended for those who must conduct educational radio broadcasting training courses in Asia-Pacific countries without the resources of experienced personnel, as well as for individuals to use in self-learning situations. The selection of material has been influenced by the need to use broadcasting resources effectively in programs…

  1. Visual cognition

    SciTech Connect

    Pinker, S.

    1985-01-01

    This book consists of essays covering issues in visual cognition presenting experimental techniques from cognitive psychology, methods of modeling cognitive processes on computers from artificial intelligence, and methods of studying brain organization from neuropsychology. Topics considered include: parts of recognition; visual routines; upward direction; mental rotation, and discrimination of left and right turns in maps; individual differences in mental imagery, computational analysis and the neurological basis of mental imagery: componental analysis.

  2. Does Ad Hoc Coronary Intervention Reduce Radiation Exposure? – Analysis of 568 Patients

    PubMed Central

    Truffa, Márcio A. M.; Alves, Gustavo M.P.; Bernardi, Fernando; Esteves Filho, Antonio; Ribeiro, Expedito; Galon, Micheli Z.; Spadaro, André; Kajita, Luiz J.; Arrieta, Raul; Lemos, Pedro A.

    2015-01-01

    Background Advantages and disadvantages of ad hoc percutaneous coronary intervention have been described. However little is known about the radiation exposure of that procedure as compared with the staged intervention. Objective To compare the radiation dose of the ad hoc percutaneous coronary intervention with that of the staged procedure Methods The dose-area product and total Kerma were measured, and the doses of the diagnostic and therapeutic procedures were added. In addition, total fluoroscopic time and number of acquisitions were evaluated. Results A total of 568 consecutive patients were treated with ad hoc percutaneous coronary intervention (n = 320) or staged percutaneous coronary intervention (n = 248). On admission, the ad hoc group had less hypertension (74.1% vs 81.9%; p = 0.035), dyslipidemia (57.8% vs. 67.7%; p = 0.02) and three-vessel disease (38.8% vs. 50.4%; p = 0.015). The ad hoc group was exposed to significantly lower radiation doses, even after baseline characteristic adjustment between both groups. The ad hoc group was exposed to a total dose-area product of 119.7 ± 70.7 Gycm2, while the staged group, to 139.2 ± 75.3 Gycm2 (p < 0.001). Conclusion Ad hoc percutaneous coronary intervention reduced radiation exposure as compared with diagnostic and therapeutic procedures performed at two separate times. PMID:26351982

  3. COGNITIVE ECONOMICS.

    PubMed

    Kimball, Miles

    2015-06-01

    Cognitive economics is the economics of what is in people's minds. It is a vibrant area of research (much of it within behavioural economics, labour economics and the economics of education) that brings into play novel types of data, especially novel types of survey data. Such data highlight the importance of heterogeneity across individuals and highlight thorny issues for welfare economics. A key theme of cognitive economics is finite cognition (often misleadingly called "bounded rationality"), which poses theoretical challenges that call for versatile approaches. Cognitive economics brings a rich toolbox to the task of understanding a complex world.

  4. COGNITIVE ECONOMICS

    PubMed Central

    KIMBALL, MILES

    2017-01-01

    Cognitive economics is the economics of what is in people’s minds. It is a vibrant area of research (much of it within behavioural economics, labour economics and the economics of education) that brings into play novel types of data, especially novel types of survey data. Such data highlight the importance of heterogeneity across individuals and highlight thorny issues for welfare economics. A key theme of cognitive economics is finite cognition (often misleadingly called “bounded rationality”), which poses theoretical challenges that call for versatile approaches. Cognitive economics brings a rich toolbox to the task of understanding a complex world. PMID:28149186

  5. Community Control of Local Radio.

    ERIC Educational Resources Information Center

    Lewis, Peter M.

    This study was designed to determine to what extent local communities control the local radio which serves them, by what formal mechanisms their control is secured, and the underlying assumptions and goals which govern the practice of the professionals who have charge of the facilities. Two British radio stations, BBC Radio Bristol and the…

  6. Ham Radio is Mir Magic.

    ERIC Educational Resources Information Center

    Evans, Gary

    1997-01-01

    Presents a classroom activity in which students communicated with U.S. and Russian astronauts via ham radio while they were in orbit on the space station Mir. Gives suggestions for other ham radio classroom activities as well as names of organizations, publications, and grant programs that teachers can access to help in bring ham radio into their…

  7. Radio: Your Publics Are Listening!

    ERIC Educational Resources Information Center

    Marx, Gary

    The purpose of this booklet is to provide school board members, administrators, teachers, and others interested in education with an understanding of radio, how it works, and how school systems can take advantage of the communications possibilities offered by radio. After providing background information on radio as a mass communications medium…

  8. The importance of Radio Quiet Zone (RQZ) for radio astronomy

    NASA Astrophysics Data System (ADS)

    Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

    2013-05-01

    Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

  9. Ad-Hoc Queries over Document Collections - A Case Study

    NASA Astrophysics Data System (ADS)

    Löser, Alexander; Lutter, Steffen; Düssel, Patrick; Markl, Volker

    We discuss the novel problem of supporting analytical business intelligence queries over web-based textual content, e.g., BI-style reports based on 100.000's of documents from an ad-hoc web search result. Neither conventional search engines nor conventional Business Intelligence and ETL tools address this problem, which lies at the intersection of their capabilities. "Google Squared" or our system GOOLAP.info, are examples of these kinds of systems. They execute information extraction methods over one or several document collections at query time and integrate extracted records into a common view or tabular structure. Frequent extraction and object resolution failures cause incomplete records which could not be joined into a record answering the query. Our focus is the identification of join-reordering heuristics maximizing the size of complete records answering a structured query. With respect to given costs for document extraction we propose two novel join-operations: The multi-way CJ-operator joins records from multiple relationships extracted from a single document. The two-way join-operator DJ ensures data density by removing incomplete records from results. In a preliminary case study we observe that our join-reordering heuristics positively impact result size, record density and lower execution costs.

  10. Z306 molecular contamination ad hoc committee results

    NASA Technical Reports Server (NTRS)

    Golden, Johnny L.

    1992-01-01

    LDEF external surfaces which did not receive significant amounts of atomic oxygen were observed to be coated with a brown contamination, apparently the result of a condensed organic residue darkened due to UV radiation exposure. During the initial Materials Special Investigation Group (MSIG) Meeting after LDEF deintegration, held in Seattle - July 1990, this organic contamination was the subject of much discussion. The amount of contamination was thought to be significant and its source was immediately believed to be the Z306 black thermal control coating used to coat the entire inner surface of LDEF. Due to the size of the structure, it was not feasible to bake-out the coating. However, initial data on the contamination film was confusing in that significant amounts of silicon was observed by several different researchers. Silicon (from silicone) was not expected to be a potential outgassing product of the Z306 polyurethane coating. To investigate the connection between external contamination and the interior paint, a MSIG ad hoc committee was formed.

  11. Performance Improvement in Geographic Routing for Vehicular Ad Hoc Networks

    PubMed Central

    Kaiwartya, Omprakash; Kumar, Sushil; Lobiyal, D. K.; Abdullah, Abdul Hanan; Hassan, Ahmed Nazar

    2014-01-01

    Geographic routing is one of the most investigated themes by researchers for reliable and efficient dissemination of information in Vehicular Ad Hoc Networks (VANETs). Recently, different Geographic Distance Routing (GEDIR) protocols have been suggested in the literature. These protocols focus on reducing the forwarding region towards destination to select the Next Hop Vehicles (NHV). Most of these protocols suffer from the problem of elevated one-hop link disconnection, high end-to-end delay and low throughput even at normal vehicle speed in high vehicle density environment. This paper proposes a Geographic Distance Routing protocol based on Segment vehicle, Link quality and Degree of connectivity (SLD-GEDIR). The protocol selects a reliable NHV using the criteria segment vehicles, one-hop link quality and degree of connectivity. The proposed protocol has been simulated in NS-2 and its performance has been compared with the state-of-the-art protocols: P-GEDIR, J-GEDIR and V-GEDIR. The empirical results clearly reveal that SLD-GEDIR has lower link disconnection and end-to-end delay, and higher throughput as compared to the state-of-the-art protocols. It should be noted that the performance of the proposed protocol is preserved irrespective of vehicle density and speed. PMID:25429415

  12. Resistivity tomography of Pointe du Hoc cliffs for stability assessment

    NASA Astrophysics Data System (ADS)

    Udphuay, S.; Everett, M. E.; Warden, R.

    2008-12-01

    Pointe du Hoc WWII battlefield overlooking the English Channel in western Normandy, France, is an important cultural resource, being an integral component of the June 6 1944 D-Day invasion. Two major buildings, the forward observation post (OP) and Col. Rudder's command post (RCP), are now perched perilously close to the cliff's edge owing to six decades of cliff retreat. Geophysical surveys were carried out in March 2008 to investigate the risk of cliff failure and to inform possible geotechnical remediation strategies with a final goal toward re-opening the observation post that is now closed to visitors. The geophysical surveying is accomplished by high-resolution resistivity tomography, conducted in extreme topography and in the midst of dense cultural clutter. The results of the OP tomography indicate that the highest mass movement hazard is associated with the marine caverns at the base of the cliff at the point of strongest wave attack. These caverns occupy the future site of a sea arch which will threaten the OP building. There is a high probability of a soil wedge failure on the east facing cliff edge close to the OP building. Such a failure could damage or destroy the building. The possibility of a sudden catastrophic failure along any one of these fractures cannot be ruled out. The greatest risk at the RCP site, which is under less immediate threat, is associated with soil wedge failures at the top of the cliffs.

  13. Performance improvement in geographic routing for Vehicular Ad Hoc Networks.

    PubMed

    Kaiwartya, Omprakash; Kumar, Sushil; Lobiyal, D K; Abdullah, Abdul Hanan; Hassan, Ahmed Nazar

    2014-11-25

    Geographic routing is one of the most investigated themes by researchers for reliable and efficient dissemination of information in Vehicular Ad Hoc Networks (VANETs). Recently, different Geographic Distance Routing (GEDIR) protocols have been suggested in the literature. These protocols focus on reducing the forwarding region towards destination to select the Next Hop Vehicles (NHV). Most of these protocols suffer from the problem of elevated one-hop link disconnection, high end-to-end delay and low throughput even at normal vehicle speed in high vehicle density environment. This paper proposes a Geographic Distance Routing protocol based on Segment vehicle, Link quality and Degree of connectivity (SLD-GEDIR). The protocol selects a reliable NHV using the criteria segment vehicles, one-hop link quality and degree of connectivity. The proposed protocol has been simulated in NS-2 and its performance has been compared with the state-of-the-art protocols: P-GEDIR, J-GEDIR and V-GEDIR. The empirical results clearly reveal that SLD-GEDIR has lower link disconnection and end-to-end delay, and higher throughput as compared to the state-of-the-art protocols. It should be noted that the performance of the proposed protocol is preserved irrespective of vehicle density and speed.

  14. Objectivity in confirmation: post hoc monsters and novel predictions.

    PubMed

    Votsis, Ioannis

    2014-03-01

    The aim of this paper is to put in place some cornerstones in the foundations for an objective theory of confirmation by considering lessons from the failures of predictivism. Discussion begins with a widely accepted challenge, to find out what is needed in addition to the right kind of inferential-semantical relations between hypothesis and evidence to have a complete account of confirmation, one that gives a definitive answer to the question whether hypotheses branded as "post hoc monsters" can be confirmed. The predictivist view is then presented as a way to meet this challenge. Particular attention is paid to Worrall's version of predictivism, as it appears to be the most sophisticated of the lot. It is argued that, despite its faults, his view turns our heads in the right direction by attempting to remove contingent considerations from confirmational matters. The demand to remove such considerations becomes the first of four cornerstones. Each cornerstone is put in place with the aim to steer clear of the sort of failures that plague various kinds of predictivism. In the process, it becomes obvious that the original challenge is wrongheaded and in need of revision. The paper ends with just such a revision.

  15. Detecting and isolating malicious nodes in wireless ad hoc networks

    NASA Astrophysics Data System (ADS)

    Li, Fanzhi; Jassim, Sabah

    2007-04-01

    Malicious nodes can seriously impair the performance of wireless ad hoc networks as a result of different actions such as packet dropping. Secure routes are shortest paths on which every node on the route is trusted even if unknown. Secure route discovery requires the adoption of mechanisms of associating trust to nodes. Most existing secure route discovery mechanisms rely on shared keys and digital signature. In the absence of central nodes that act as certification authority, such protocols suffer from heavy computational burden and are vulnerable to malicious attacks. In this paper we shall review existing techniques for secure routing and propose to complement route finding with creditability scores. Each node would have a credit list for its neighbors. Each node monitors its neighbors' pattern of delivering packets and regularly credits are reviewed and updated accordingly. Unlike most existing schemes the focus of our work is based on post route discovery stage, i.e. when packets are transmitted on discovered routes. The level of trust in any route will be based on the credits associated with the neighbors belonging to the discovered route. We shall evaluate the performance of the proposed scheme by modifying our simulation system so that each node has a dynamic changing "credit list" for its neighbors' behavior. We shall conduct a series of simulations with and without the proposed scheme and compare the results. We will demonstrate that the proposed mechanism is capable of isolating malicious nodes and thereby counteracting black hole attacks.

  16. Random Time Identity Based Firewall In Mobile Ad hoc Networks

    NASA Astrophysics Data System (ADS)

    Suman, Patel, R. B.; Singh, Parvinder

    2010-11-01

    A mobile ad hoc network (MANET) is a self-organizing network of mobile routers and associated hosts connected by wireless links. MANETs are highly flexible and adaptable but at the same time are highly prone to security risks due to the open medium, dynamically changing network topology, cooperative algorithms, and lack of centralized control. Firewall is an effective means of protecting a local network from network-based security threats and forms a key component in MANET security architecture. This paper presents a review of firewall implementation techniques in MANETs and their relative merits and demerits. A new approach is proposed to select MANET nodes at random for firewall implementation. This approach randomly select a new node as firewall after fixed time and based on critical value of certain parameters like power backup. This approach effectively balances power and resource utilization of entire MANET because responsibility of implementing firewall is equally shared among all the nodes. At the same time it ensures improved security for MANETs from outside attacks as intruder will not be able to find out the entry point in MANET due to the random selection of nodes for firewall implementation.

  17. Accurate radio and optical positions for southern radio sources

    NASA Technical Reports Server (NTRS)

    Harvey, Bruce R.; Jauncey, David L.; White, Graeme L.; Nothnagel, Axel; Nicolson, George D.; Reynolds, John E.; Morabito, David D.; Bartel, Norbert

    1992-01-01

    Accurate radio positions with a precision of about 0.01 arcsec are reported for eight compact extragalactic radio sources south of -45-deg declination. The radio positions were determined using VLBI at 8.4 GHz on the 9589 km Tidbinbilla (Australia) to Hartebeesthoek (South Africa) baseline. The sources were selected from the Parkes Catalogue to be strong, flat-spectrum radio sources with bright optical QSO counterparts. Optical positions of the QSOs were also measured from the ESO B Sky Survey plates with respect to stars from the Perth 70 Catalogue, to an accuracy of about 0.19 arcsec rms. These radio and optical positions are as precise as any presently available in the far southern sky. A comparison of the radio and optical positions confirms the estimated optical position errors and shows that there is overall agreement at the 0.1-arcsec level between the radio and Perth 70 optical reference frames in the far south.

  18. A Prototype System for Using Multiple Radios in Directional MANET (Mobile Ad Hoc Network): A NISE Funded Applied Research Project

    DTIC Science & Technology

    2013-09-01

    Reception Algorithms in WLANs with Directional Antennas for QoS Support,” IEEE Networks (May/June), vol. 19, no. 3, pp. 27–32. [11] C. Cirullo, R. Olsen...ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: a. REPORT b. ABSTRACT c. THIS PAGE 17. LIMITATION OF ABSTRACT 18. NUMBER OF

  19. Reasoning, cognitive control, and moral intuition

    PubMed Central

    Patterson, Richard; Rothstein, Jared; Barbey, Aron K.

    2012-01-01

    Recent Social Intuitionist work suggests that moral judgments are intuitive (not based on conscious deliberation or any significant chain of inference), and that the reasons we produce to explain or justify our judgments and actions are for the most part post hoc rationalizations rather than the actual source of those judgments. This is consistent with work on judgment and explanation in other domains, and it correctly challenges one-sidedly rationalistic accounts. We suggest that in fact reasoning has a great deal of influence on moral judgments and on intuitive judgments in general. This influence is not apparent from study of judgments simply in their immediate context, but it is crucial for the question of how cognition can help us avoid deleterious effects and enhance potentially beneficial effects of affect on judgment, action, and cognition itself. We begin with established work on several reactive strategies for cognitive control of affect (e.g., suppression, reappraisal), then give special attention to more complex sorts of conflict (“extended deliberation”) involving multiple interacting factors, both affective and reflective. These situations are especially difficult to study in a controlled way, but we propose some possible experimental approaches. We then review proactive strategies for control, including avoidance of temptation and mindfulness meditation (Froeliger et al., 2012, this issue). We give special attention to the role of slow or “cool” cognitive processes (e.g., deliberation, planning, and executive control) in the inculcation of long-term dispositions, traits, intuitions, skills, or habits. The latter are critical because they in turn give rise to a great many of our fast, intuitive judgments. The reasoning processes involved here are distinct from post hoc rationalizations and have a very real impact on countless intuitive judgments in concrete situations. This calls for a substantial enlargement of research on cognitive control

  20. Reasoning, cognitive control, and moral intuition.

    PubMed

    Patterson, Richard; Rothstein, Jared; Barbey, Aron K

    2012-01-01

    Recent Social Intuitionist work suggests that moral judgments are intuitive (not based on conscious deliberation or any significant chain of inference), and that the reasons we produce to explain or justify our judgments and actions are for the most part post hoc rationalizations rather than the actual source of those judgments. This is consistent with work on judgment and explanation in other domains, and it correctly challenges one-sidedly rationalistic accounts. We suggest that in fact reasoning has a great deal of influence on moral judgments and on intuitive judgments in general. This influence is not apparent from study of judgments simply in their immediate context, but it is crucial for the question of how cognition can help us avoid deleterious effects and enhance potentially beneficial effects of affect on judgment, action, and cognition itself. We begin with established work on several reactive strategies for cognitive control of affect (e.g., suppression, reappraisal), then give special attention to more complex sorts of conflict ("extended deliberation") involving multiple interacting factors, both affective and reflective. These situations are especially difficult to study in a controlled way, but we propose some possible experimental approaches. We then review proactive strategies for control, including avoidance of temptation and mindfulness meditation (Froeliger et al., 2012, this issue). We give special attention to the role of slow or "cool" cognitive processes (e.g., deliberation, planning, and executive control) in the inculcation of long-term dispositions, traits, intuitions, skills, or habits. The latter are critical because they in turn give rise to a great many of our fast, intuitive judgments. The reasoning processes involved here are distinct from post hoc rationalizations and have a very real impact on countless intuitive judgments in concrete situations. This calls for a substantial enlargement of research on cognitive control, drawing

  1. Cognitive Readiness

    DTIC Science & Technology

    2002-10-01

    II-4 C. Metacognition ...which requires cognitive mediation. • Metacognition . Metacognition refers to the executive functions of thought, particularly those pertaining to...knowledge and regulation of one’s cognitive processes and progress toward accepted goals. Metacognitive skills can be enhanced by exercises designed to

  2. Visual cognition

    SciTech Connect

    Pinker, S.

    1985-01-01

    This collection of research papers on visual cognition first appeared as a special issue of Cognition: International Journal of Cognitive Science. The study of visual cognition has seen enormous progress in the past decade, bringing important advances in our understanding of shape perception, visual imagery, and mental maps. Many of these discoveries are the result of converging investigations in different areas, such as cognitive and perceptual psychology, artificial intelligence, and neuropsychology. This volume is intended to highlight a sample of work at the cutting edge of this research area for the benefit of students and researchers in a variety of disciplines. The tutorial introduction that begins the volume is designed to help the nonspecialist reader bridge the gap between the contemporary research reported here and earlier textbook introductions or literature reviews.

  3. Primate cognition.

    PubMed

    Seed, Amanda; Tomasello, Michael

    2010-07-01

    As the cognitive revolution was slow to come to the study of animal behavior, the vast majority of what we know about primate cognition has been discovered in the last 30 years. Building on the recognition that the physical and social worlds of humans and their living primate relatives pose many of the same evolutionary challenges, programs of research have established that the most basic cognitive skills and mental representations that humans use to navigate those worlds are already possessed by other primates. There may be differences between humans and other primates, however, in more complex cognitive skills, such as reasoning about relations, causality, time, and other minds. Of special importance, the human primate seems to possess a species-unique set of adaptations for "cultural intelligence," which are broad reaching in their effects on human cognition.

  4. Students' Self-Assessment in Chemistry Examinations Requiring Higher- and Lower-Order Cognitive Skills

    NASA Astrophysics Data System (ADS)

    Zoller*, Uri; Fastow, Michal; Lubezky, Aviva; Tsaparlis, Georgios

    1999-01-01

    The development of students' higher-order cognitive skills (HOCS) in the context of both chemistry and the complex interrelationships of science, technology, environment, and society is widely accepted as one of the most important goals of chemical education. Consequently, the translation of this goal into teaching, assessment, and learning strategies is a central issue in chemistry teaching. Students' self-assessment in chemistry examinations is a HOCS-promoting strategy. We evaluated the differences between students' self-assessment and their professors' assessment on midterm exams in introductory college courses in Israel and Greece, together with the students' appraisal of their capability for self- and peer-assessment. We found that (i) there were small (not significant) and large (significant) differences between students' self-grading and their professors' grading on LOCS and HOCS exam questions, respectively; (ii) students' estimates of their grades were higher than those of their professors, particularly for HOCS questions; and (iii) students believed that they were capable of self- and peer-assessment and were confident in making these assessments. Our results suggest that (i) students' self-assessment of LOCS-type exams can be successfully implemented immediately, whereas (ii) implementation of self-assessment for HOCS-type exam questions should be gradual, following appropriate preparation to close the gap between the future HOCS and contemporary dominant LOCS orientations in chemistry teaching and learning.

  5. Abnormal salience network in normal aging and in amnestic mild cognitive impairment and Alzheimer's disease.

    PubMed

    He, Xiaoxi; Qin, Wen; Liu, Yong; Zhang, Xinqing; Duan, Yunyun; Song, Jinyu; Li, Kuncheng; Jiang, Tianzi; Yu, Chunshui

    2014-07-01

    The salience network (SN) serves to identify salient stimuli and to switch between the central executive network (CEN) and the default-mode network (DMN), both of which are impaired in Alzheimer's disease (AD)/amnestic mild cognitive impairment (aMCI). We hypothesized that both the structural and functional organization of the SN and functional interactions between the SN and CEN/DMN are altered in normal aging and in AD/aMCI. Gray matter volume (GMV) and resting-state functional connectivity (FC) were analyzed from healthy younger (HYC) to older controls (HOC) and from HOC to aMCI and AD patients. All the SN components showed significant differences in the GMV, intranetwork FC, and internetwork FC between the HYC and HOC. Most of the SN components showed differences in the GMV between the HOC and AD and between the aMCI and AD. Compared with the HOC, AD patients exhibited significant differences in intra- and internetwork FCs of the SN, whereas aMCI patients demonstrated differences in internetwork FC of the SN. Most of the GMVs and internetwork FCs of the SN and part of the intranetwork FC of the SN were correlated with cognitive differences in older subjects. Our findings suggested that structural and functional impairments of the SN may occur as early as in normal aging and that functional disconnection between the SN and CEN/ DMN may also be associated with both normal aging and disease progression.

  6. 32 CFR 2800.7 - Designation of chairperson for Ad Hoc Committees.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... VICE PRESIDENT OF THE UNITED STATES SECURITY PROCEDURES § 2800.7 Designation of chairperson for Ad Hoc Committees. The Counsel to the Vice President is designated as the responsible official to chair Ad...

  7. 32 CFR 2800.7 - Designation of chairperson for Ad Hoc Committees.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... VICE PRESIDENT OF THE UNITED STATES SECURITY PROCEDURES § 2800.7 Designation of chairperson for Ad Hoc Committees. The Counsel to the Vice President is designated as the responsible official to chair Ad...

  8. 32 CFR 2800.7 - Designation of chairperson for Ad Hoc Committees.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... VICE PRESIDENT OF THE UNITED STATES SECURITY PROCEDURES § 2800.7 Designation of chairperson for Ad Hoc Committees. The Counsel to the Vice President is designated as the responsible official to chair Ad...

  9. Voice Communications over 802.11 Ad Hoc Networks: Modeling, Optimization and Call Admission Control

    NASA Astrophysics Data System (ADS)

    Xu, Changchun; Xu, Yanyi; Liu, Gan; Liu, Kezhong

    Supporting quality-of-service (QoS) of multimedia communications over IEEE 802.11 based ad hoc networks is a challenging task. This paper develops a simple 3-D Markov chain model for queuing analysis of IEEE 802.11 MAC layer. The model is applied for performance analysis of voice communications over IEEE 802.11 single-hop ad hoc networks. By using the model, we finish the performance optimization of IEEE MAC layer and obtain the maximum number of voice calls in IEEE 802.11 ad hoc networks as well as the statistical performance bounds. Furthermore, we design a fully distributed call admission control (CAC) algorithm which can provide strict statistical QoS guarantee for voice communications over IEEE 802.11 ad hoc networks. Extensive simulations indicate the accuracy of the analytical model and the CAC scheme.

  10. A Group Based Key Sharing and Management Algorithm for Vehicular Ad Hoc Networks

    PubMed Central

    Moharram, Mohammed Morsi; Azam, Farzana

    2014-01-01

    Vehicular ad hoc networks (VANETs) are one special type of ad hoc networks that involves vehicles on roads. Typically like ad hoc networks, broadcast approach is used for data dissemination. Blind broadcast to each and every node results in exchange of useless and irrelevant messages and hence creates an overhead. Unicasting is not preferred in ad-hoc networks due to the dynamic topology and the resource requirements as compared to broadcasting. Simple broadcasting techniques create several problems on privacy, disturbance, and resource utilization. In this paper, we propose media mixing algorithm to decide what information should be provided to each user and how to provide such information. Results obtained through simulation show that fewer number of keys are needed to share compared to simple broadcasting. Privacy is also enhanced through this approach. PMID:24587749

  11. A group based key sharing and management algorithm for vehicular ad hoc networks.

    PubMed

    Khan, Zeeshan Shafi; Moharram, Mohammed Morsi; Alaraj, Abdullah; Azam, Farzana

    2014-01-01

    Vehicular ad hoc networks (VANETs) are one special type of ad hoc networks that involves vehicles on roads. Typically like ad hoc networks, broadcast approach is used for data dissemination. Blind broadcast to each and every node results in exchange of useless and irrelevant messages and hence creates an overhead. Unicasting is not preferred in ad-hoc networks due to the dynamic topology and the resource requirements as compared to broadcasting. Simple broadcasting techniques create several problems on privacy, disturbance, and resource utilization. In this paper, we propose media mixing algorithm to decide what information should be provided to each user and how to provide such information. Results obtained through simulation show that fewer number of keys are needed to share compared to simple broadcasting. Privacy is also enhanced through this approach.

  12. Design and Analysis of A Beacon-Less Routing Protocol for Large Volume Content Dissemination in Vehicular Ad Hoc Networks.

    PubMed

    Hu, Miao; Zhong, Zhangdui; Ni, Minming; Baiocchi, Andrea

    2016-11-01

    Large volume content dissemination is pursued by the growing number of high quality applications for Vehicular Ad hoc NETworks(VANETs), e.g., the live road surveillance service and the video-based overtaking assistant service. For the highly dynamical vehicular network topology, beacon-less routing protocols have been proven to be efficient in achieving a balance between the system performance and the control overhead. However, to the authors' best knowledge, the routing design for large volume content has not been well considered in the previous work, which will introduce new challenges, e.g., the enhanced connectivity requirement for a radio link. In this paper, a link Lifetime-aware Beacon-less Routing Protocol (LBRP) is designed for large volume content delivery in VANETs. Each vehicle makes the forwarding decision based on the message header information and its current state, including the speed and position information. A semi-Markov process analytical model is proposed to evaluate the expected delay in constructing one routing path for LBRP. Simulations show that the proposed LBRP scheme outperforms the traditional dissemination protocols in providing a low end-to-end delay. The analytical model is shown to exhibit a good match on the delay estimation with Monte Carlo simulations, as well.

  13. Design and Analysis of A Beacon-Less Routing Protocol for Large Volume Content Dissemination in Vehicular Ad Hoc Networks

    PubMed Central

    Hu, Miao; Zhong, Zhangdui; Ni, Minming; Baiocchi, Andrea

    2016-01-01

    Large volume content dissemination is pursued by the growing number of high quality applications for Vehicular Ad hoc NETworks(VANETs), e.g., the live road surveillance service and the video-based overtaking assistant service. For the highly dynamical vehicular network topology, beacon-less routing protocols have been proven to be efficient in achieving a balance between the system performance and the control overhead. However, to the authors’ best knowledge, the routing design for large volume content has not been well considered in the previous work, which will introduce new challenges, e.g., the enhanced connectivity requirement for a radio link. In this paper, a link Lifetime-aware Beacon-less Routing Protocol (LBRP) is designed for large volume content delivery in VANETs. Each vehicle makes the forwarding decision based on the message header information and its current state, including the speed and position information. A semi-Markov process analytical model is proposed to evaluate the expected delay in constructing one routing path for LBRP. Simulations show that the proposed LBRP scheme outperforms the traditional dissemination protocols in providing a low end-to-end delay. The analytical model is shown to exhibit a good match on the delay estimation with Monte Carlo simulations, as well. PMID:27809285

  14. AIDS radio triggers.

    PubMed

    Elias, A M

    1991-07-01

    In April 1991, the Ethnic Communities' Council of NSW was granted funding under the Community AIDS Prevention and Education Program through the Department of Community Services and Health, to produce a series of 6x50 second AIDS radio triggers with a 10-second tag line for further information. The triggers are designed to disseminate culturally-sensitive information about HIV/AIDS in English, Italian, Greek, Spanish, Khmer, Turkish, Macedonian, Serbo-Croatian, Arabic, Cantonese, and Vietnamese, with the goal of increasing awareness and decreasing the degree of misinformation about HIV/AIDS among people of non-English-speaking backgrounds through radio and sound. The 6 triggers cover the denial that AIDS exists in the community, beliefs that words and feelings do not protect one from catching HIV, encouraging friends to be compassionate, compassion within the family, AIDS information for a young audience, and the provision of accurate and honest information on HIV/AIDS. The triggers are slated to be completed by the end of July 1991 and will be broadcast on all possible community, ethnic, and commercial radio networks across Australia. They will be available upon request in composite form with an information kit for use by health care professionals and community workers.

  15. MULTIMOMENT RADIO TRANSIENT DETECTION

    SciTech Connect

    Spitler, L. G.; Cordes, J. M.; Chatterjee, S.; Stone, J.

    2012-04-01

    We present a multimoment technique for signal classification and apply it to the detection of fast radio transients in incoherently dedispersed data. Specifically, we define a spectral modulation index in terms of the fractional variation in intensity across a spectrum. A signal whose intensity is distributed evenly across the entire band has a lower modulation index than a spectrum whose intensity is localized in a single channel. We are interested in broadband pulses and use the modulation index to excise narrowband radio frequency interference by applying a modulation index threshold above which candidate events are removed. The technique is tested both with simulations and using data from known sources of radio pulses (RRAT J1928+15 and giant pulses from the Crab pulsar). The method is generalized to coherent dedispersion, image cubes, and astrophysical narrowband signals that are steady in time. We suggest that the modulation index, along with other statistics using higher order moments, should be incorporated into signal detection pipelines to characterize and classify signals.

  16. The Askaryan Radio Array

    NASA Astrophysics Data System (ADS)

    Hoffman, Kara D.

    2013-01-01

    Ultra high energy cosmogenic neutrinos could be most efficiently detected in dense, radio frequency (RF) transparent media via the Askaryan effect. Building on the expertise gained by RICE, ANITA and IceCube's radio extension in the use of the Askaryan effect in cold Antarctic ice, we are currently developing an antenna array known as ARA (The Askaryan Radio Array) to be installed in boreholes extending 200 m below the surface of the ice near the geographic South Pole. The unprecedented scale of ARA, which will cover a fiducial area of ~ 100 square kilometers, was chosen to ensure the detection of the flux of neutrinos suggested by the observation of a drop in high energy cosmic ray flux consistent with the GZK cutoff by HiRes and the Pierre Auger Observatory. Funding to develop the instrumentation and install the first prototypes has been granted, and the first components of ARA were installed during the austral summer of 2010-2011. Within 3 years of commencing operation, the full ARA will exceed the sensitivity of any other instrument in the 0.1-10 EeV energy range by an order of magnitude. The primary goal of the ARA array is to establish the absolute cosmogenic neutrino flux through a modest number of events. This information would frame the performance requirements needed to expand the array in the future to measure a larger number of neutrinos with greater angular precision in order to study their spectrum and origins.

  17. Scalable Mobile Ad Hoc Network (MANET) to Enhance Situational Awareness in Distributed Small Unit Operations

    DTIC Science & Technology

    2015-06-01

    saying that he has called for “a network that would allow soldiers to tap their laptop or smart phone keyboards and obtain the information they need, as...AD HOC NETWORK (MANET) TO ENHANCE SITUATIONAL AWARENESS IN DISTRIBUTED SMALL UNIT OPERATIONS by Jonathan Clarke Driesslein June 2015...REPORT DATE June 2015 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE SCALABLE MOBILE AD HOC NETWORK (MANET) TO

  18. Improving English and Chinese Ad-hoc Retrieval: Tipster Text Phase 3

    DTIC Science & Technology

    1998-10-01

    IMPROVING ENGLISH AND CHINESE AD-HOC RETRIEVAL: TIPSTER TEXT PHASE 3 FINAL REPORT Kui-Lam Kwok Computer Science Department, Queens College, CUNY...all past TREC experiments with consistently superior results. Since 1996, we have also participated in the TIPSTER Text Phase 3 program. This...COVERED 00-00-1998 to 00-00-1998 4. TITLE AND SUBTITLE Improving English and Chinese Ad-hoc Retrieval: TIPSTER Text Phase 3 Final Report 5a

  19. Preferential survival in models of complex ad hoc networks

    NASA Astrophysics Data System (ADS)

    Kong, Joseph S.; Roychowdhury, Vwani P.

    2008-05-01

    There has been a rich interplay in recent years between (i) empirical investigations of real-world dynamic networks, (ii) analytical modeling of the microscopic mechanisms that drive the emergence of such networks, and (iii) harnessing of these mechanisms to either manipulate existing networks, or engineer new networks for specific tasks. We continue in this vein, and study the deletion phenomenon in the web by the following two different sets of websites (each comprising more than 150,000 pages) over a one-year period. Empirical data show that there is a significant deletion component in the underlying web networks, but the deletion process is not uniform. This motivates us to introduce a new mechanism of preferential survival (PS), where nodes are removed according to the degree-dependent deletion kernel, D(k)∝k, with α≥0. We use the mean-field rate equation approach to study a general dynamic model driven by Preferential Attachment (PA), Double PA (DPA), and a tunable PS (i.e., with any α>0), where c nodes ( c<1) are deleted per node added to the network, and verify our predictions via large-scale simulations. One of our results shows that, unlike in the case of uniform deletion (i.e., where α=0), the PS kernel when coupled with the standard PA mechanism, can lead to heavy-tailed power-law networks even in the presence of extreme turnover in the network. Moreover, a weak DPA mechanism, coupled with PS, can help to make the network even more heavy-tailed, especially in the limit when deletion and insertion rates are almost equal, and the overall network growth is minimal. The dynamics reported in this work can be used to design and engineer stable ad hoc networks and explain the stability of the power-law exponents observed in real-world networks.

  20. Studying synaptic efficiency by post-hoc immunolabelling

    PubMed Central

    2013-01-01

    Background In terms of vesicular recycling, synaptic efficiency is a key determinant of the fidelity of synaptic transmission. The ability of a presynaptic terminal to reuse its vesicular content is thought to be a signature of synaptic maturity and this process depends on the activity of several proteins that govern exo/endocytosis. Upon stimulation, individual terminals in networks of cultured cerebellar granule neurons exhibit heterogeneous exocytic responses, which reflect the distinct states of maturity and plasticity intrinsic to individual synaptic terminals. This dynamic scenario serves as the substrate for processes such as scaling, plasticity and synaptic weight redistribution. Presynaptic strength has been associated with the activity of several types of proteins, including the scaffolding proteins that form the active zone cytomatrix and the proteins involved in presynaptic exocytosis. Methods We have combined fluorescence imaging techniques using the styryl dye FM1-43 in primary cultures of cerebellar granule cells with subsequent post-hoc immunocytochemistry in order to study synaptic efficiency in terms of vesicular release. We describe a protocol to easily quantify these results with minimal user intervention. Results In this study we describe a technique that specifically correlates presynaptic activity with the levels of presynaptic markers. This method involves the use of the styryl dye FM1-43 to estimate the release capacity of a synaptic terminal, and the subsequent post-hoc immunolabelling of thousands of individual nerve terminals. We observed a strong correlation between the release capacity of the nerve terminal and the levels of the RIM1α but not the Munc13-1 protein in the active zone. Conclusions Our findings support those of previous studies and point out to RIM1α as a crucial factor in determining synaptic efficiency. These results also demonstrate that this technique is a useful tool to analyse the molecular differences

  1. Cognitive Performance and Cognitive Style.

    ERIC Educational Resources Information Center

    International Journal of Behavioral Development, 1985

    1985-01-01

    Investigates (1) the relationships between cognitive performance and cognitive styles and predictive possibilities and (2) performance differences by sex, school, grade, and income in 92 Indian adolescents. Assessment measures included Liquid Conservation, Islands, Goat-Lion, Hanoi-Tower, Rabbits (Piagetian); Block Design (WISC-R); Paper Cutting…

  2. Cognitive anthropology is a cognitive science.

    PubMed

    Boster, James S

    2012-07-01

    Cognitive anthropology contributes to cognitive science as a complement to cognitive psychology. The chief threat to its survival has not been rejection by other cognitive scientists but by other cultural anthropologists. It will remain a part of cognitive science as long as cognitive anthropologists research, teach, and publish.

  3. Workshop on Radio Transients

    NASA Astrophysics Data System (ADS)

    Croft, Steve; Gaensler, Bryan

    2012-04-01

    abstract-type="normal">SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted. The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop. 1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys. 2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified. 3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes

  4. Reconfigurable cognitive transceiver for opportunistic networks

    NASA Astrophysics Data System (ADS)

    Maso, Marco; Baştuğ, Ejder; Cardoso, Leonardo S.; Debbah, Mérouane; Özdemir, Özgür

    2014-12-01

    In this work, we provide the implementation and analysis of a cognitive transceiver for opportunistic networks. We focus on a previously introduced dynamic spectrum access (DSA) - cognitive radio (CR) solution for primary-secondary coexistence in opportunistic orthogonal frequency division multiplexing (OFDM) networks, called cognitive interference alignment (CIA). The implementation is based on software-defined radio (SDR) and uses GNU Radio and the universal software radio peripheral (USRP) as the implementation toolkit. The proposed flexible transceiver architecture allows efficient on-the-fly reconfigurations of the physical layer into OFDM, CIA or a combination of both. Remarkably, its responsiveness is such that the uplink and downlink channel reciprocity from the medium perspective, inherent to time division duplex (TDD) communications, can be effectively verified and exploited. We show that CIA provides approximately 10 dB of interference isolation towards the OFDM receiver with respect to a fully random precoder. This result is obtained under suboptimal conditions, which indicates that further gains are possible with a better optimization of the system. Our findings point towards the usefulness of a practical CIA implementation, as it yields a non-negligible performance for the secondary system, while providing interference shielding to the primary receiver.

  5. Radio quiet, please! - protecting radio astronomy from interference

    NASA Astrophysics Data System (ADS)

    van Driel, W.

    2011-06-01

    The radio spectrum is a finite and increasingly precious resource for astronomical research, as well as for other spectrum users. Keeping the frequency bands used for radio astronomy as free as possible of unwanted Radio Frequency Interference (RFI) is crucial. The aim of spectrum management, one of the tools used towards achieving this goal, includes setting regulatory limits on RFI levels emitted by other spectrum users into the radio astronomy frequency bands. This involves discussions with regulatory bodies and other spectrum users at several levels - national, regional and worldwide. The global framework for spectrum management is set by the Radio Regulations of the International Telecommunication Union, which has defined that interference is detrimental to radio astronomy if it increases the uncertainty of a measurement by 10%. The Radio Regulations are revised every three to four years, a process in which four organisations representing the interests of the radio astronomical community in matters of spectrum management (IUCAF, CORF, CRAF and RAFCAP) participate actively. The current interests and activities of these four organisations range from preserving what has been achieved through regulatory measures, to looking far into the future of high frequency use and giant radio telescope use.

  6. Cognitive Function

    EPA Science Inventory

    Because chemicals can adversely affect cognitive function in humans, considerable effort has been made to characterize their effects using animal models. Information from such models will be necessary to: evaluate whether chemicals identified as potentially neurotoxic by screenin...

  7. Cognitive Changes

    MedlinePlus

    ... Are the Alternative Treatments for Cognitive Problems? Anxiety Hallucinations/Delusions Speech and Swallowing Problems Vision Changes You ... and the Hope for a Better Drug for Hallucinations and Psychosis in Parkinson’s Disease What's Hot in ...

  8. 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.

  9. Radio emision from supernova remnants

    NASA Astrophysics Data System (ADS)

    Dubner, G.

    2016-06-01

    The vast majority of supernova remnants (SNRs) in our Galaxy and nearby galaxies have been discovered through radio observations, and only a very small number of the SNRs catalogued in the Milky Way have not been detected in the radio band, or are poorly defined by current radio observations. The study of the radio emission from SNRs is an excellent tool to investigate morphological characteristics, marking the location of shock fronts and contact discontinuities; the presence, orientation and intensity of the magnetic field; the energy spectrum of the emitting particles; and the dynamical consequences of the interaction with the circumstellar and interstellar medium. I will review the present knowledge of different important aspects of radio remnants and their impact on the interstellar gas. Also, new radio studies of the Crab Nebula carried out with the Karl Jansky Very Large Array (JVLA) at 3 GHz and with ALMA at 100 GHz, will be presented.

  10. Disembodying cognition

    PubMed Central

    Chatterjee, Anjan

    2010-01-01

    The idea that concepts are embodied by our motor and sensory systems is popular in current theorizing about cognition. Embodied cognition accounts come in different versions and are often contrasted with a purely symbolic amodal view of cognition. Simulation, or the hypothesis that concepts simulate the sensory and motor experience of real world encounters with instances of those concepts, has been prominent in psychology and cognitive neuroscience. Here, with a focus on spatial thought and language, I review some of the evidence cited in support of simulation versions of embodied cognition accounts. While these data are extremely interesting and many of the experiments are elegant, knowing how to best interpret the results is often far from clear. I point out that a quick acceptance of embodied accounts runs the danger of ignoring alternate hypotheses and not scrutinizing neuroscience data critically. I also review recent work from my lab that raises questions about the nature of sensory motor grounding in spatial thought and language. In my view, the question of whether or not cognition is grounded is more fruitfully replaced by questions about gradations in this grounding. A focus on disembodying cognition, or on graded grounding, opens the way to think about how humans abstract. Within neuroscience, I propose that three functional anatomic axes help frame questions about the graded nature of grounded cognition. First, are questions of laterality differences. Do association cortices in both hemispheres instantiate the same kind of sensory or motor information? Second, are questions about ventral dorsal axes. Do neuronal ensembles along this axis shift from conceptual representations of objects to the relationships between objects? Third, are questions about gradients centripetally from sensory and motor cortices towards and within perisylvian cortices. How does sensory and perceptual information become more language-like and then get transformed into language

  11. Cognitive Code-Division Links with Blind Primary-System Identification

    DTIC Science & Technology

    2011-11-01

    cognitive radio, covert communications, steganography and steganalysis. Dr. Li is a member of the IEEE Communications and Signal Processing Societies...covert communications, steganography , compressive sam- pling, adaptive multiuser detection, robust spread-spectrum communications, supervised and

  12. Uzaybimer Radio Telescope Control System

    NASA Astrophysics Data System (ADS)

    Balbay, R.; Öz, G. K.; Arslan, Ö.; Özeren, F. F.; Küçük, İ.

    2016-12-01

    A 13 meters former NATO radar is being converted into a radio telescope. The radio telescope is controlled by a system which has been developed at UZAYBİMER. The Telescope Control System(TCS) has been designed using modern industrial systems. TCS has been developed in LabView platform in which works Windows embedded OS. The position feedback used on radio telescopes is an industrial EtherCAT standard. ASCOM library is used for astronomical calculations.

  13. Radio Emission from Binary Stars

    NASA Astrophysics Data System (ADS)

    Hjellming, R.; Murdin, P.

    2000-11-01

    Stellar radio emission is most common in double star systems where each star provides something essential in producing the large amounts of radio radiation needed for it to be detectable by RADIO TELESCOPES. They transfer mass, supply energy or, when one of the stars is a NEUTRON STAR or BLACK HOLE, have the strong gravitational fields needed for the energetic particles and magnetic fields needed...

  14. The properties of radio ellipticals

    NASA Astrophysics Data System (ADS)

    Sparks, W. B.; Disney, M. J.; Wall, J. V.; Rodgers, A. W.

    1984-03-01

    The authors present optical and additional radio data for the bright galaxies of the Disney & Wall survey. These data form the basis of a statistical comparison of the properties of radio elliptical galaxies to radio-quiet ellipticals. The correlations may be explained by the depth of the gravitational potential well in which the galaxy resides governing the circumstances under which an elliptical galaxy rids itself of internally produced gas.

  15. Radio-loud and Radio-quiet QSOs

    NASA Astrophysics Data System (ADS)

    Kellermann, K. I.; Condon, J. J.; Kimball, A. E.; Perley, R. A.; Ivezić, Željko

    2016-11-01

    We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low-redshift (0.2< z< 0.3) optically selected quasi-stellar objects (QSOs). Our 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities of {L}6≳ {10}23.2 {{W}} {{Hz}}-1 that are primarily generated in the active galactic nucleus (AGN) responsible for the excess optical luminosity that defines a bona fide QSO; and (2) the remaining 80% that are radio-quiet QSOs (RQQs) that have {10}21≲ {L}6≲ {10}23.2 {{W}} {{Hz}}-1 and radio sizes ≲ 10 {kpc}, and we suggest that the bulk of their radio emission is powered by star formation in their host galaxies. “Radio-silent” QSOs ({L}6≲ {10}21 {{W}} {{Hz}}-1) are rare, so most RQQ host galaxies form stars faster than the Milky Way; they are not “red and dead” ellipticals. Earlier radio observations did not have the luminosity sensitivity of {L}6≲ {10}21 {{W}} {{Hz}}-1 that is needed to distinguish between such RLQs and RQQs. Strong, generally double-sided radio emission spanning \\gg 10 {kpc} was found to be associated with 13 of the 18 RLQ cores with peak flux densities of {S}{{p}}> 5 {mJy} {{beam}}-1 ({log}(L)≳ 24). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple “unified” models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGNs or their host galaxies must also determine whether or not a QSO appears radio-loud.

  16. RADIO FREQUENCY ATTENUATOR

    DOEpatents

    Giordano, S.

    1963-11-12

    A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

  17. Packet Radio Communications Project

    DTIC Science & Technology

    1974-12-01

    init.ate any pending DMA channel I/O now possible as a result of the completed DMA I/O operation. For example, if the packet transmision has been...keyboard and printer b. Binary data record I/O fo/from the tape media c. Scan for unsolicited keyboard input 2-12 Software description of experimental...the station and transmit to the station packets input on the radio receivers. The goal is to provide a transparent packet transfer media to

  18. Radio frequency strain monitor

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S. (Inventor); Rogowski, Robert S. (Inventor); Holben, Jr., Milford S. (Inventor)

    1989-01-01

    A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.

  19. Lunar Farside Radio Lab

    NASA Astrophysics Data System (ADS)

    Maccone, Claudio

    2005-03-01

    It is proposed that the Farside of the Moon should be protected legally against man-made radio pollution and uncontrolled exploitation. In fact, only by establishing a radiotelescope on the Farside of the Moon it will finally be possible to cope with the Radio Frequency Interference (RFI) that is now increasingly plaguing all of Radioastronomy, Bioastronomy and Search for Extraterrestrial Intelligence (SETI) Searches done from the surface of the Earth. It is suggested to partition the Farside into 3 sectors, each 60°wide, to ensurethe creation of a future “Lunar Farside Radio Lab” inside crater Daedalus (at 180°E) with our planned Radiotelescope (in practice a Phased Array),complete freedom to exploit the Nearside as well as the four Lagrangian points L1, L3, L4 and L5 of the Earth Moon system by allowing even some International Space Stations to be located there. It is also claimed, however, thatthe “opposite” Lagrangian point L2 should possibly be kept free of spacecrafts that would flood the Farside by the RFI they produce. Realistically, it might be difficult to comply with the latter request in view of the far-future development of a Space Base located there in order to depart towards the Asteroids and the Outer Planets at very reduced fuel consumption. A more reasonable request about any future space station located at the Earth Moon L2 point is thus that this future space station should be shielded to prevent its RFI from reaching the Farside of the Moon.A number of further astrophysical, astronautical and technical issues could just be highlighted in this study and deserve much more elaboration. To mention a few:the precise size of the “Quiet Cone” extending into space above the Farside of the Moon. Also, the experimental measurement of how quiet this Cone actually is by letting a radiometer orbit the Moon (see the web site www.rli.it);the mathematical modelling of the weak ionosphere of the Moon and its possible diffraction effects at very

  20. Solar radio emission

    NASA Technical Reports Server (NTRS)

    Goldman, M. V.; Smith, D. F.

    1981-01-01

    Active areas of both observational and theoretical research in which rapid progress is being made are discussed. These include: (1) the dynamic spectrum or frequency versus time plot; (2) physical mechanisms in the development of various types of bursts; (3) microwave type 1, 2, 3, and moving type 4 bursts; (4) bursts caused by trapped electrons; (5) physics of type 3bursts; (6) the physics of type 2 bursts and their related shocks; (7) the physics of both stationary and moving traps and associated type 1 and moving type 4 bursts; and (8) the status of the field of solar radio emission.

  1. Observations of Solar Radio Transients

    NASA Astrophysics Data System (ADS)

    Paige, Giorla

    2011-05-01

    A low frequency radio telescope has been recently been constructed on the campus of the The College of New Jersey (TCNJ) and has begun conducting observations at 20MHz as part of NASA'a Radio Jove program. This instrument is capable of observations of solar radio emission including strong prompt radio emission associated with solar burst events. We will discuss solar observations conducted with this instrument as well as an effort to conduct coincident observations with the Eight-meter-wavelength Transient Array (ETA) and the Long Wavelength Array (LWA).

  2. Internet Resources for Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Andernach, H.

    A subjective overview of Internet resources for radio-astronomical information is presented. Basic observing techniques and their implications for the interpretation of publicly available radio data are described, followed by a discussion of existing radio surveys, their level of optical identification, and nomenclature of radio sources. Various collections of source catalogues and databases for integrated radio source parameters are reviewed and compared, as well as the web interfaces to interrogate the current and ongoing large-area surveys. Links to radio observatories with archives of raw (uv-) data are presented, as well as services providing images, both of individual objects or extracts (``cutouts'') from large-scale surveys. While the emphasis is on radio continuum data, a brief list of sites providing spectral line data, and atomic or molecular information is included. The major radio telescopes and surveys under construction or planning are outlined. A summary is given of a search for previously unknown optically bright radio sources, as performed by the students as an exercise, using Internet resources only. Over 200 different links are mentioned and were verified, but despite the attempt to make this report up-to-date, it can only provide a snapshot of the situation as of mid-1998.

  3. Typicality Mediates Performance during Category Verification in Both Ad-hoc and Well-defined Categories

    PubMed Central

    Sandberg, Chaleece; Sebastian, Rajani; Kiran, Swathi

    2012-01-01

    Background The typicality effect is present in neurologically intact populations for natural, ad-hoc, and well-defined categories. Although sparse, there is evidence of typicality effects in persons with chronic stroke aphasia for natural and ad-hoc categories. However, it is unknown exactly what influences the typicality effect in this population. Aims The present study explores the possible contributors to the typicality effect in persons with aphasia by analyzing and comparing data from both normal and language-disordered populations, from persons with aphasia with more semantic impairment versus those with less semantic impairment, and from two types of categories with very different boundary structure (ad-hoc vs. well-defined). Methods and procedures A total of 40 neurologically healthy adults (20 older, 20 younger) and 35 persons with aphasia (20 LSI (less-semantically impaired) patients, 15 MSI (more-semantically impaired) patients) participated in the study. Participants completed one of two tasks: either category verification for ad-hoc categories or category verification for well-defined categories. Outcomes and Results Neurologically healthy participants showed typicality effects for both ad-hoc and well-defined categories. MSI patients showed a typicality effect for well-defined categories, but not for ad-hoc categories, whereas LSI patients showed a typicality effect for ad-hoc categories, but not for well-defined categories. Conclusions These results suggest that the degree of semantic impairment mediates the typicality effect in persons with aphasia depending on the structure of the category. PMID:22261305

  4. Optical emission in the radio lobes of radio galaxies. II - New observations of 21 radio lobes

    NASA Astrophysics Data System (ADS)

    Crane, P.; Tyson, J. A.; Saslaw, W. C.

    1983-02-01

    The authors report new identifications of optical emission associated with the radio lobes of double radio galaxies. Optical emission is present in the outer radio structure of the sources 3C 219, 3C 244.1, 3C 247, 3C 252, 3C 268.2, 3C 321, 3C 319, 3C 337, and possibly in 3C 330. The authors have not found emission to the detection limit of V ≡ 24 in the sources 3C 79, 3C 173.1, 3C 223, 3C 325, and 3C 381. Of the 21 separate sources in optical studies of extended lobes of radio galaxies reported to date, 16 radio sources observed so far show significant optical emission within one or both lobes, while in 11 of these the optical object is within 2arcsec of the radio peak.

  5. Radio frequency identification enabled wireless sensing for intelligent food logistics.

    PubMed

    Zou, Zhuo; Chen, Qiang; Chen, Qing; Uysal, Ismail; Zheng, Lirong

    2014-06-13

    Future technologies and applications for the Internet of Things (IoT) will evolve the process of the food supply chain and create added value of business. Radio frequency identifications (RFIDs) and wireless sensor networks (WSNs) have been considered as the key technological enablers. Intelligent tags, powered by autonomous energy, are attached on objects, networked by short-range wireless links, allowing the physical parameters such as temperatures and humidities as well as the location information to seamlessly integrate with the enterprise information system over the Internet. In this paper, challenges, considerations and design examples are reviewed from system, implementation and application perspectives, particularly with focus on intelligent packaging and logistics for the fresh food tracking and monitoring service. An IoT platform with a two-layer network architecture is introduced consisting of an asymmetric tag-reader link (RFID layer) and an ad-hoc link between readers (WSN layer), which are further connected to the Internet via cellular or Wi-Fi. Then, we provide insights into the enabling technology of RFID with sensing capabilities. Passive, semi-passive and active RFID solutions are discussed. In particular, we describe ultra-wideband radio RFID which has been considered as one of the most promising techniques for ultra-low-power and low-cost wireless sensing. Finally, an example is provided in the form of an application in fresh food tracking services and corresponding field testing results.

  6. Comparative responses to radio and television anti-smoking advertisements to encourage smoking cessation.

    PubMed

    Durkin, Sarah; Wakefield, Melanie

    2010-03-01

    While mass media campaigns have been shown to contribute to reductions in smoking prevalence, little research has been undertaken on the effectiveness of radio advertising as a communication medium. This is despite radio being less expensive and having greater reach than television in some low and middle income countries. We aimed to explore the potential of radio as an adjunct or alternative to televised campaigns by comparing reactions to a radio anti-smoking ad with three televised anti-smoking ads, all of which communicated the serious health consequences of smoking in an emotionally evocative way. In pre-exposure interviews, 18-59-year-old daily smokers (n = 306) were asked to listen to a particular radio time slot/watch a particular television program that they usually listened to/watched, in which the ad was broadcast. Post-exposure interviews were conducted within 3 days of exposure and measured recall, recognition, emotional and cognitive responses, and intentions to quit smoking. Findings indicate that the radio ad showed similar or slightly higher levels than a concurrently aired television ad on understanding (radio: 96%; television: 95%), believability (radio: 89%; television: 90%), concern about smoking (both 77%) and motivation to quit (radio: 51%; television: 45%), and significantly higher levels of unprompted recall (radio: 20%; television: 6%). It also compared well against two subsequent anti-smoking television ads. Emotionally evocative radio advertising may be an effective adjunct or alternative to television advertising in jurisdictions where there are substantial limits on funds available for airing these campaigns, or where the reach of radio outstrips television.

  7. The Extragalactic Radio Background

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2011-01-01

    The existence of an isotropic component of the high-latitude radio sky has been recognized for nearly fifty years, but has typically been assumed to be Galactic in origin. We use recent radio observations to test whether the observed high-latitude component could originate within either an extended Galactic halo or a more local "bubble" structure. The lack of significant polarization from the isotropic component, combined with the lack of significant correlation with the Galactic far-infrared emission, rule out an origin within the Galaxy. We conclude that an extragalactic origin is the only viable alternative for the bulk of the isotropic high-latitude emission. The extragalactic component is 2-3 times brighter than local (Galactic) emission towards the Galactic poles and is consistent with a power law in frequency with amplitude T(sub r) = 24.1 plus or minus 2.1 K and spectral index beta = -2.599 plus or minus 0.036 evaluated at reference frequency 310 MHz.

  8. Visual cognition

    PubMed Central

    Cavanagh, Patrick

    2011-01-01

    Visual cognition, high-level vision, mid-level vision and top-down processing all refer to decision-based scene analyses that combine prior knowledge with retinal input to generate representations. The label “visual cognition” is little used at present, but research and experiments on mid- and high-level, inference-based vision have flourished, becoming in the 21st century a significant, if often understated part, of current vision research. How does visual cognition work? What are its moving parts? This paper reviews the origins and architecture of visual cognition and briefly describes some work in the areas of routines, attention, surfaces, objects, and events (motion, causality, and agency). Most vision scientists avoid being too explicit when presenting concepts about visual cognition, having learned that explicit models invite easy criticism. What we see in the literature is ample evidence for visual cognition, but few or only cautious attempts to detail how it might work. This is the great unfinished business of vision research: at some point we will be done with characterizing how the visual system measures the world and we will have to return to the question of how vision constructs models of objects, surfaces, scenes, and events. PMID:21329719

  9. From Malicious Eyes: A Method for Concise Representation of Ad-Hoc Networks and Efficient Attack Survivability Analysis

    DTIC Science & Technology

    2012-07-01

    a modification of OSPF that is optimized for mobile ad-hoc networks . OSPFv3MDR uses IPv6 addressing. Topology. In attempts to achieve a suitable...From Malicious Eyes: A Method for Concise Representation of Ad-Hoc Networks and Efficient Attack Survivability Analysis by Jaime C. Acosta...White Sands Missile Range, NM 88002-5501 ARL-TR-6035 July 2012 From Malicious Eyes: A Method for Concise Representation of Ad-Hoc Networks

  10. Analysis of the Robustness Dynamics of Wireless Mobile Ad Hoc Networks via Time Varying Dual Basis Representation

    DTIC Science & Technology

    2015-01-08

    Analysis of the Robustness Dynamics of Wireless Mobile Ad Hoc Networks via Time Varying Dual Basis Representation Thomas Parker, Jamie Johnson...between nodes to analyze the robustness of a wireless mobile ad hoc network (MANET) with a time-varying wireless channel. This spectral analysis and...a single eigenvalue is evaluated. 1. Introduction Mobile ad hoc networks (MANETs) are complex systems that can be foreseen supporting

  11. Space Telecommunications Radio Architecture (STRS)

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.

    2006-01-01

    A software defined radio (SDR) architecture used in space-based platforms proposes to standardize certain aspects of radio development such as interface definitions, functional control and execution, and application software and firmware development. NASA has charted a team to develop an open software defined radio hardware and software architecture to support NASA missions and determine the viability of an Agency-wide Standard. A draft concept of the proposed standard has been released and discussed among organizations in the SDR community. Appropriate leveraging of the JTRS SCA, OMG's SWRadio Architecture and other aspects are considered. A standard radio architecture offers potential value by employing common waveform software instantiation, operation, testing and software maintenance. While software defined radios offer greater flexibility, they also poses challenges to the radio development for the space environment in terms of size, mass and power consumption and available technology. An SDR architecture for space must recognize and address the constraints of space flight hardware, and systems along with flight heritage and culture. NASA is actively participating in the development of technology and standards related to software defined radios. As NASA considers a standard radio architecture for space communications, input and coordination from government agencies, the industry, academia, and standards bodies is key to a successful architecture. The unique aspects of space require thorough investigation of relevant terrestrial technologies properly adapted to space. The talk will describe NASA s current effort to investigate SDR applications to space missions and a brief overview of a candidate architecture under consideration for space based platforms.

  12. Safety and Special Radio Services.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    Numerous radio stations across the nation perform nonbroadcast services in areas ranging from aviation, forestry protection, and telephone maintenance to amateur and citizen radio. These services can be grouped in four general categories: (1) safety, (2) industry, (3) land transportation, and (4) miscellaneous purposes. This bulletin briefly…

  13. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

  14. Stabilized radio-frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1982-09-29

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  15. The future for radio astronomy

    NASA Astrophysics Data System (ADS)

    Breton, Rene P.; Hassall, Tom

    2013-12-01

    THE TRANSIENT UNIVERSE Rene P Breton and Tom Hassall argue that, while radio astronomy has always involved transient phenomena, exploration of this part of the electromagnetic spectrum has been falling behind because of the lack of data. But the advent of a new generation of radio telescopes such as LOFAR, could change that.

  16. Audiences for Contemporary Radio Formats.

    ERIC Educational Resources Information Center

    Lull, James T.; And Others

    A radio audience survey of 110 sample geographic clusters in the Santa Barbara, California, area served a twofold purpose: the construction of a demographic profile of audience types according to radio format choices, and the identification and analysis of various audience subgroups. A skip interval technique of these geographic clusters resulted…

  17. The Radio Phenomenon in Italy.

    ERIC Educational Resources Information Center

    Faenza, Roberto

    One in a series of studies of experiments in new audiovisual techniques in Europe and the situations in some member countries, this paper traces the development of radio in Italy. Opposing views about radio broadcasting (public monopoly vs. freedom of broadcasting) are examined, and the various political and legal aspects of communications in…

  18. 78 FR 32165 - Commercial Radio Operators; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-29

    ... COMMISSION 47 CFR Part 0 Commercial Radio Operators; Correction AGENCY: Federal Communication Commission... rules concerning radio operator licenses for maritime and aviation in order to reduce administrative...) Administers the Commission's commercial radio operator program (part 13 of this chapter); the...

  19. Galaxy clusters: Radio relics from fossil electrons

    NASA Astrophysics Data System (ADS)

    Johnston-Hollitt, Melanie

    2017-01-01

    The detection of a tailed radio galaxy in a galaxy cluster conjoined to a region of diffuse radio emission confirms that radio galaxies provide the energetic electrons needed to explain the origin of this enigmatic emission.

  20. Autocorrelation-Based Spectrum Sensing Algorithms for Cognitive Radios (POSTPRINT)

    DTIC Science & Technology

    2010-06-01

    Toeplitz matrix and a Hankel matrix. Q1 = T (qr,0,L,qr,0,L) +H(qr,0,L,qr,L,2L), (37) Q2 = T (qi,−1,L−1,qi,−1,−L) +H(qi,1,L+1,qi,L+1,2L), (38) and Q3 = T...qr,0,L−1,qr,0,L−1) −H(qr,2,L+1,qr,L+1,2L), (39) where T (c, r) represents a Toeplitz matrix with the first column c and the first row r, H(c, r

  1. Opportunistic Access in Frequency Hopping Cognitive Radio Networks

    DTIC Science & Technology

    2014-03-27

    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...42 4.16 Adaptive BER performance as the spectrum sensing rate increases relative to the environment change rate with OFDM interference

  2. Reconfigurable Front-end Antennas for Cognitive Radio Applications

    DTIC Science & Technology

    2011-01-01

    narrowband antenna is a microstrip patch printed on the reverse side of the substrate, connected to the wideband antenna via a shorting pin and designed to...operate from 5.15 to 5.35 GHz. A reconfigurable C-slot microstrip patch antenna is proposed in [20]. Reconfigurability is achieved by switching on and...off two patches using PIN diodes. The antenna can operate in dual- band or in a very wideband mode. In [21], a quad- antenna with a directional

  3. Cognitive linguistics.

    PubMed

    Evans, Vyvyan

    2012-03-01

    Cognitive linguistics is one of the fastest growing and influential perspectives on the nature of language, the mind, and their relationship with sociophysical (embodied) experience. It is a broad theoretical and methodological enterprise, rather than a single, closely articulated theory. Its primary commitments are outlined. These are the Cognitive Commitment-a commitment to providing a characterization of language that accords with what is known about the mind and brain from other disciplines-and the Generalization Commitment-which represents a dedication to characterizing general principles that apply to all aspects of human language. The article also outlines the assumptions and worldview which arises from these commitments, as represented in the work of leading cognitive linguists. WIREs Cogn Sci 2012, 3:129-141. doi: 10.1002/wcs.1163 For further resources related to this article, please visit the WIREs website.

  4. Cognitive fitness.

    PubMed

    Gilkey, Roderick; Kilts, Clint

    2007-11-01

    Recent neuroscientific research shows that the health of your brain isn't, as experts once thought, just the product of childhood experiences and genetics; it reflects your adult choices and experiences as well. Professors Gilkey and Kilts of Emory University's medical and business schools explain how you can strengthen your brain's anatomy, neural networks, and cognitive abilities, and prevent functions such as memory from deteriorating as you age. The brain's alertness is the result of what the authors call cognitive fitness -a state of optimized ability to reason, remember, learn, plan, and adapt. Certain attitudes, lifestyle choices, and exercises enhance cognitive fitness. Mental workouts are the key. Brain-imaging studies indicate that acquiring expertise in areas as diverse as playing a cello, juggling, speaking a foreign language, and driving a taxicab expands your neural systems and makes them more communicative. In other words, you can alter the physical makeup of your brain by learning new skills. The more cognitively fit you are, the better equipped you are to make decisions, solve problems, and deal with stress and change. Cognitive fitness will help you be more open to new ideas and alternative perspectives. It will give you the capacity to change your behavior and realize your goals. You can delay senescence for years and even enjoy a second career. Drawing from the rapidly expanding body of neuroscience research as well as from well-established research in psychology and other mental health fields, the authors have identified four steps you can take to become cognitively fit: understand how experience makes the brain grow, work hard at play, search for patterns, and seek novelty and innovation. Together these steps capture some of the key opportunities for maintaining an engaged, creative brain.

  5. Radio characteristics of galactic nuclei

    NASA Astrophysics Data System (ADS)

    Condon, J. J.

    1986-02-01

    Radio characteristics of galactic nuclei, providing such unique information as spectral data on source variability, and the long-term history of the central engine and its duration of activity and total energy, are reviewed. The compact radio source characteristics are complicated by orientation-dependent relativistic beaming and by refractive focusing in the interstellar medium. Incoherent synchrotron radiation is thought to be the emission mechanism, with the result that synchrotron self-absorption in compact sources hides the central engine from direct radio observation. However, the history revealed by the extended jets and lobes of radio galaxies and quasars favors a single massive object not supported by radiation pressure, either a spinar or a black hole, as the energy source in radio-galaxy nuclei.

  6. Radio outburst of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Buemi, C. S.; Leto, P.; Trigilio, C.; Umana, G.; Giroletti, M.; Orienti, M.; Raiteri, C. M.; Villata, M.; Bach, U.

    2013-04-01

    We report on extremely high radio flux of BL Lacertae at 43 and 8 GHz. Observations at 43 GHz with the 32 m radio telescope in Noto (Italy) revealed a flux density of 10.5 +/- 0.2 Jy on 2013 April 10.65, while observations at 8 GHz with the 32 m radio telescope in Medicina (Italy) detected a flux density of 8.2 +/- 0.7 Jy on April 12.22. These extremely high radio fluxes show that the radio activity likely correlated to the strong optical, near-infrared, and gamma-ray activity of 2011-2012 (see ATels #4028, #4031, #4155, #4271, #4277, #4349, #4565, #4600), and X-ray activity of late 2012 (ATels #4557, #4627), is far to be exhausted.

  7. Exploring the Dynamic Radio Sky

    NASA Astrophysics Data System (ADS)

    Mooley, Kunal P.; Hallinan, Gregg; Frail, Dale A.; Myers, Steven T.; Kulkarni, Shrinivas R.; Bourke, Stephen; Horesh, Assaf

    2015-01-01

    Most of what is currently known about slow radio transients (supernovae, gamma-ray bursts, tidal disruption events, stellar flares, etc.) has come via radio follow-up of objects identified by synoptic telescopes at optical, X-ray or gamma-ray wavelengths. However, with the ability to capture obscured, unbeamed and magnetically-driven phenomena, radio surveys offer unique discovery strong diagnostic for cosmic transients. For the first time, we are systematically exploring the dynamic radio sky on timescales between one day to several years using multi-epoch large surveys with the Karl G. Jansky Array (VLA). We have carried out surveys in the COSMOS deep field as well as wide fields like Stripe 82. I have developed a unique infrastructure for near-real-time calibration, imaging, transient search, transient vetting, rapid multiwavelength follow-up, and contemporaneous optical surveys to better characterize radio transient phenomena. A large part of my thesis includes the commissioning of a new observing mode at the VLA: On-The-Fly Mosaicking. This mode has significantly improved the survey efficiency of the VLA, and it is a driver for VLASS, the future all-sky survey planned with this telescope. Through our radio surveys we have discovered several fascinating transients that are unique to the radio. These surveys have established the VLA as an efficient transient discovery machine. My thesis has enormous implications for how to design efficient transient surveys for the next generation of radio interferometer facilities like ASKAP, MeerKAT, WSRT/Apertif and LOFAR. My work has also provided answers to key problems such as the rates of transients, demographics of variability of radio sources including AGN, and false-positive foreground for future searches for the radio counterparts of gravitational-wave (GW) sources.

  8. The Radio Language Arts Project: adapting the radio mathematics model.

    PubMed

    Christensen, P R

    1985-01-01

    Kenya's Radio Language Arts Project, directed by the Academy for Educational Development in cooperation with the Kenya Institute of Education in 1980-85, sought to teach English to rural school children in grades 1-3 through use of an intensive, radio-based instructional system. Daily 1/2 hour lessons are broadcast throughout the school year and supported by teachers and print materials. The project further was aimed at testing the feasibility of adaptation of the successful Nicaraguan Radio Math Project to a new subject area. Difficulties were encountered in articulating a language curriculum with the precision required for a media-based instructional system. Also a challenge was defining the acceptable regional standard for pronunciation and grammar; British English was finally selected. An important modification of the Radio Math model concerned the role of the teacher. While Radio Math sought to reduce the teacher's responsibilities during the broadcast, Radio Language Arts teachers played an important instructional role during the English lesson broadcasts by providing translation and checks on work. Evaluations of the Radio language Arts Project suggest significant gains in speaking, listening, and reading skills as well as high levels of satisfaction on the part of parents and teachers.

  9. Radio frequency coaxial feedthrough

    DOEpatents

    Owens, Thomas L.

    1989-01-17

    An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

  10. Radio Seeing Monitor Interferometer

    NASA Astrophysics Data System (ADS)

    Hiriart, David; Valdez, Jorge; Zaca, Placido; Medina, José L.

    2002-10-01

    A two-element interferometer for monitoring atmospheric phase fluctuations (radio seeing) is presented; this uses the unmodulated beacon signal at 11.715 GHz from a geostationary satellite. The system measures phase differences on the signal received by two small antennas separated by 50 m. The system incorporates the best features from previous designs: a heterodyne phase-lock receiver and an IQ demodulator system. Phase fluctuations measured at this frequency may be extrapolated to millimetric and submillimetric wavelengths since the atmosphere is not dispersive at these frequencies. The instrument has been tested at the Observatory San Pedro Martir (Mexico) at 2800 m above sea level. The final destination of the instrument is Cerro la Negra (Mexico), where the Large Millimeter Telescope is under construction, at an altitude of 4600 m.

  11. Radio pulsar disk electrodynamics

    NASA Technical Reports Server (NTRS)

    Michel, F. C.

    1983-01-01

    Macroscopic physics are discussed for the case of a disk close to an isolated, magnetized, rotating neutron star that acts as a Faraday disk dynamo, while the disk acts as both a load and a neutral sheet. This sheet allows the polar cap current to return to the neutron star, splitting a dipolar field into two monopolar halves. The dominant energy loss is from the stellar wind torque, and the next contribution is dissipation in the auroral zones, where the current returns to the star in a 5 cm-thick sheet. The disk itself may be a source of visible radiation comparable to that in pulsed radio frequency emission. As the pulsar ages, the disk expands and narrows into a ring which, it is suggested, may lead to a cessation of pulsed emission at periods of a few sec.

  12. A Decentralized VPN Service over Generalized Mobile Ad-Hoc Networks

    NASA Astrophysics Data System (ADS)

    Fujita, Sho; Shima, Keiichi; Uo, Yojiro; Esaki, Hiroshi

    We present a decentralized VPN service that can be built over generalized mobile ad-hoc networks (Generalized MANETs), in which topologies can be represented as a time-varying directed multigraph. We address wireless ad-hoc networks and overlay ad-hoc networks as instances of Generalized MANETs. We first propose an architecture to operate on various kinds of networks through a single set of operations. Then, we design and implement a decentralized VPN service on the proposed architecture. Through the development and operation of a prototype system we implemented, we found that the proposed architecture makes the VPN service applicable to each instance of Generalized MANETs, and that the VPN service makes it possible for unmodified applications to operate on the networks.

  13. Fuzzy Multiple Metrics Link Assessment for Routing in Mobile Ad-Hoc Network

    NASA Astrophysics Data System (ADS)

    Soo, Ai Luang; Tan, Chong Eng; Tay, Kai Meng

    2011-06-01

    In this work, we investigate on the use of Sugeno fuzzy inference system (FIS) in route selection for mobile Ad-Hoc networks (MANETs). Sugeno FIS is introduced into Ad-Hoc On Demand Multipath Distance Vector (AOMDV) routing protocol, which is derived from its predecessor, Ad-Hoc On Demand Distance Vector (AODV). Instead of using the conventional way that considering only a single metric to choose the best route, our proposed fuzzy decision making model considers up to three metrics. In the model, the crisp inputs of the three parameters are fed into an FIS and being processed in stages, i.e., fuzzification, inference, and defuzzification. Finally, after experiencing all the stages, a single value score is generated from the combination metrics, which will be used to measure all the discovered routes credibility. Results obtained from simulations show a promising improvement as compared to AOMDV and AODV.

  14. Radio Astronomy Explorer /RAE/. I - Observations of terrestrial radio noise.

    NASA Technical Reports Server (NTRS)

    Herman, J. R.; Caruso, J. A.; Stone, R. G.

    1973-01-01

    Radio Astronomy Explorer (RAE) I data are analyzed to establish characteristics of HF terrestrial radio noise at an altitude of about 6000 km. Time and frequency variations in amplitude of the observed noise well above cosmic noise background are explained on the basis of temporal and spatial variations in ionospheric critical frequency coupled with those in noise source distributions. It is shown that terrestrial radio noise regularly breaks through the ionosphere and reaches RAE with magnitudes 15 dB and more above cosmic noise background, on frequencies above the F-layer critical frequency.

  15. Cognitive Science.

    ERIC Educational Resources Information Center

    Soni, P. Sarita, Ed.; Carmichael, Ann G., Ed.

    1993-01-01

    This theme issue features five articles profiling Indiana University faculty whose work on various campuses continues to broaden and advance knowledge about cognitive science. The articles in the journal are: "A Matter of Time" (Karen Grooms) which discusses the work of Robert F. Port; "Perceiving as a Complex System" (Tom…

  16. Cognitive Science.

    ERIC Educational Resources Information Center

    Cocking, Rodney R.; Mestre, Jose P.

    The focus of this paper is on cognitive science as a model for understanding the application of human skills toward effective problem-solving. Sections include: (1) "Introduction" (discussing information processing framework, expert-novice distinctions, schema theory, and learning process); (2) "Application: The Expert-Novice…

  17. Cognitive Challenges

    MedlinePlus

    ... Custom Post Type Home En Español International Request Information DONATE About TSC New treatments today. A cure tomorrow. What is TSC? How is ... questions on intellectual disability. Disabled World — Cognitive disability: information on intellectual disabilities. Healthy ... Also in this Section What is TSC? How ...

  18. A high-precision ab initio determination of the equilibrium geometry and force field of HOC(+)

    NASA Technical Reports Server (NTRS)

    Defrees, D. J.; Bunker, P. R.; Binkley, J. S.; Mclean, A. D.

    1987-01-01

    The results of an ab initio molecular orbital investigation of the isoformyl cation, HOC(+), shape are reported. The effects of expanding the basis set to near the Hartree-Fock limit and of electron correlation were examined, and the results indicate that near the Hartree-Fock limit the HOC(+) is linear. An analytic potential function is presented, from which the calculated rotational energies are only 0.03 percent different from the experimental values. This represents a nearly two orders of magnitude reduction in error from earlier work.

  19. Reliable on-demand multicast routing with congestion control in wireless ad hoc networks

    NASA Astrophysics Data System (ADS)

    Tang, Ken; Gerla, Mario

    2001-07-01

    In this paper, we address the congestion control multicast routing problem in wireless ad hoc networks through the medium access control (MAC) layer. We first introduce the Broadcast Medium Window (BMW) MAC protocol, which provides reliable delivery to broadcast packets at the MAC layer. We then extend the wireless On-Demand Multicast Routing Protocol (ODMRP) to facilitate congestion control in ad hoc networks using BMW. Through simulation, we show that ODMRP with congestion control adapts well to multicast sources that are aggressive in data transmissions.

  20. Performance Evaluation of Ad Hoc Routing Protocols in a Swarm of Autonomous Unmanned Aerial Vehicles

    DTIC Science & Technology

    2007-03-01

    research in mobile, ad hoc routing protocols. Broch , et al. performed a simulation comparison of the DSDV, DSR, AODV and Temporally-Ordered...July 6, 2005. [Bel58] R. Bellman, “On a Routing Problem,” in Quarterly of Applied Mathematics, 16(1), pp.87-90, 1958. [BJM04] J. Broch , D. B...vol. AD- A404703, 2002. [BMJ98] J. Broch , D. A. Maltz, D. B. Johnson, Y. Hu and J. Jetcheva, “A performance comparison of multi-hop wireless ad hoc

  1. Routing Protocols to Minimize the Number of Route Disconnections for Communication in Mobile Ad Hoc Networks

    DTIC Science & Technology

    2009-09-01

    Broch , "DSR: The Dynamic Source Routing Protocol for Multi-hop Wireless Ad hoc Networks," in Ad hoc Networking, Chapter 5, C. E. Perkins, Eds. Addison...Project Report: 09/23/2008 to 09/22/2009 W911NF-08-2-0061 References [I] J. Broch , D. A. Maltz, D. B. Johnson, Y. C. Hu and J. Jetcheva, "A...and Mobile Computing, Vol. 2, pp. 723 - 726, Sept. 2005. [4] D. B. Johnson, D. A. Maltz and J. Broch , "DSR: The Dynamic Source Routing Protocol for

  2. Space-Based Reconfigurable Software Defined Radio Test Bed Aboard International Space Station

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.; Lux, James P.

    2014-01-01

    The National Aeronautical and Space Administration (NASA) recently launched a new software defined radio research test bed to the International Space Station. The test bed, sponsored by the Space Communications and Navigation (SCaN) Office within NASA is referred to as the SCaN Testbed. The SCaN Testbed is a highly capable communications system, composed of three software defined radios, integrated into a flight system, and mounted to the truss of the International Space Station. Software defined radios offer the future promise of in-flight reconfigurability, autonomy, and eventually cognitive operation. The adoption of software defined radios offers space missions a new way to develop and operate space transceivers for communications and navigation. Reconfigurable or software defined radios with communications and navigation functions implemented in software or VHDL (Very High Speed Hardware Description Language) provide the capability to change the functionality of the radio during development or after launch. The ability to change the operating characteristics of a radio through software once deployed to space offers the flexibility to adapt to new science opportunities, recover from anomalies within the science payload or communication system, and potentially reduce development cost and risk by adapting generic space platforms to meet specific mission requirements. The software defined radios on the SCaN Testbed are each compliant to NASA's Space Telecommunications Radio System (STRS) Architecture. The STRS Architecture is an open, non-proprietary architecture that defines interfaces for the connections between radio components. It provides an operating environment to abstract the communication waveform application from the underlying platform specific hardware such as digital-to-analog converters, analog-to-digital converters, oscillators, RF attenuators, automatic gain control circuits, FPGAs, general-purpose processors, etc. and the interconnections among

  3. Radio studies of extragalactic supernovae.

    PubMed

    Weiler, K W; Sramek, R A; Panagia, N

    1986-03-14

    Some exploding stars (supernovae) are powerful emitters of centimeter radio radiation. Detailed observations have shown that these supernovae quickly become detectable in the radio range, first at shorter wavelengths (higher frequencies) and later at progressively longer and longer wavelengths (lower frequencies). This part of the phenomenon appears to be well explained by a monotonic decrease in the amount of ionized material surrounding the radio-emitting regions as the shock from the explosion travels outward. The radio emission itself is of a nonthermal, synchrotron origin, as is the case in most bright cosmic radio sources. Once the absorption effects become negligible, the radio intensity declines with time until reaching the detection limit of the telescope. Models suggest that the absorbing material originates in a dense wind of matter lost by the supernova progenitor star, or by its companion if it is in a binary system, in the last stages of evolution before the explosion. The synchrotron radio emission can be generated either externally by the shock wave from the explosion propagating through this same high density stellar wind or internally by a rapidly rotating neutron star, which is the collapsed core of the exploded star. Present results appear to favor the former model for at least the first several years after the supernova explosion, although the latter model remains viable.

  4. Radio emission in Mercury magnetosphere

    NASA Astrophysics Data System (ADS)

    Varela, J.; Reville, V.; Brun, A. S.; Pantellini, F.; Zarka, P.

    2016-10-01

    Context. Active stars possess magnetized wind that has a direct impact on planets that can lead to radio emission. Mercury is a good test case to study the effect of the solar wind and interplanetary magnetic field (IMF) on radio emission driven in the planet magnetosphere. Such studies could be used as proxies to characterize the magnetic field topology and intensity of exoplanets. Aims: The aim of this study is to quantify the radio emission in the Hermean magnetosphere. Methods: We use the magnetohydrodynamic code PLUTO in spherical coordinates with an axisymmetric multipolar expansion for the Hermean magnetic field, to analyze the effect of the IMF orientation and intensity, as well as the hydrodynamic parameters of the solar wind (velocity, density and temperature), on the net power dissipated on the Hermean day and night side. We apply the formalism derived by Zarka et al. (2001, Astrophys. Space Sci., 277, 293), Zarka (2007, Planet. Space Sci., 55, 598) to infer the radio emission level from the net dissipated power. We perform a set of simulations with different hydrodynamic parameters of the solar wind, IMF orientations and intensities, that allow us to calculate the dissipated power distribution and infer the existence of radio emission hot spots on the planet day side, and to calculate the integrated radio emission of the Hermean magnetosphere. Results: The obtained radio emission distribution of dissipated power is determined by the IMF orientation (associated with the reconnection regions in the magnetosphere), although the radio emission strength is dependent on the IMF intensity and solar wind hydro parameters. The calculated total radio emission level is in agreement with the one estimated in Zarka et al. (2001, Astrophys. Space Sci., 277, 293) , between 5 × 105 and 2 × 106 W.

  5. Radio protection zone evaluation at the Dominion Radio Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Tapping, Ken

    Increasing use of the radio spectrum by licensed and unlicensed devices, together with the encroachment of housing developments are an issue facing many radio observatories, including the Dominion Radio Astrophysical Observatory (DRAO), located near Penticton in Southern British Columbia. A joint study by Industry Canada (Canada's national spectrum manager), and the National Research Council (Operator of DRAO) is currently in progress to examine protection zone needs and the reliability of the definitions of the zone, and the general level of background noise from growing local communities. The objectives are to produce a definition of a protection zone that is useful in spectrum management to protect the observatory, and to establish how much local community development is acceptable if the observatory is to remain a viable location for radio astronomical observations. This presentation will summarize the results so far in this ongoing study.

  6. Radio Search For Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Zarka, P.

    Theoretical justification and ongoing observational efforts in view of detecting radio emissions from extrasolar planets will be presented. On the "prediction" side, a heuris- tic scaling law has been established relating the radio output of any magnetized flow- obstacle system to the incident magnetic energy flux on the obstacle. Its confirmation by the observation of radio emission from extrasolar planets would help to understand the energy budget of such a system. On the "detection" side, specific procedures have been developed for interference mitigation and weak burst detection.

  7. Recurrent Activity in Radio Galaxies

    SciTech Connect

    Jamrozy, Marek; Konar, Chiranjib; Machalski, Jerzy; Mack, Karl-Heinz; Saikia, Dhruba; Siemiginowska, Aneta; Stawarz, Lukasz; /KIPAC, Menlo Park /Jagiellonian U.

    2007-10-15

    One of the outstanding issues concerning extragalactic radio sources is the total duration of their active phase and the possible existence of duty cycles of their nuclear activity. A duty cycle can be recognized if there is a mechanism which preserves the information of past activity for a sufficiently long time after a new activity has started up. If a new cycle starts before the radio lobes created during a former activity period have faded, we can recognize this by the observations of a young radio source embedded in an old relic structure.

  8. Searches for Fast Radio Transients

    NASA Astrophysics Data System (ADS)

    Cordes, J. M.; McLaughlin, M. A.

    2003-10-01

    We discuss optimal detection of fast radio transients from astrophysical objects while taking into account the effects of propagation through intervening ionized media, including dispersion, scattering, and scintillation. Our analysis applies to the giant-pulse phenomenon exhibited by some pulsars, for which we show examples, and to radio pulses from other astrophysical sources, such as prompt radio emission from gamma-ray burst sources and modulated signals from extraterrestrial civilizations. We estimate scintillation parameters for extragalactic sources that take into account scattering both in the host galaxy and in foreground Galactic plasma.

  9. The Helios radio astronomy experiment

    NASA Technical Reports Server (NTRS)

    Kayser, S.; Stone, R.

    1984-01-01

    Radio bursts traveling between the Sun and the Earth were tracked by radio astronomy experiments on Helios 1 and 2. A relatively short dipole antenna with a well-defined toroidal reception pattern was flown. The antenna spins in the ecliptic at 60.3 rpm and 2 frequencies are measured in each revolution. The signal analysis determines the strength of the signal, the direction of the source in the ecliptic, and the degree of modulation, and estimates source size. The experiments provide three-dimensional direction finding in space. They extend the radio frequency window beyond what is observable on Earth, and offer a long triangulation baseline.

  10. Potential of Cognitive Computing and Cognitive Systems

    NASA Astrophysics Data System (ADS)

    Noor, Ahmed K.

    2014-11-01

    Cognitive computing and cognitive technologies are game changers for future engineering systems, as well as for engineering practice and training. They are major drivers for knowledge automation work, and the creation of cognitive products with higher levels of intelligence than current smart products. This paper gives a brief review of cognitive computing and some of the cognitive engineering systems activities. The potential of cognitive technologies is outlined, along with a brief description of future cognitive environments, incorporating cognitive assistants - specialized proactive intelligent software agents designed to follow and interact with humans and other cognitive assistants across the environments. The cognitive assistants engage, individually or collectively, with humans through a combination of adaptive multimodal interfaces, and advanced visualization and navigation techniques. The realization of future cognitive environments requires the development of a cognitive innovation ecosystem for the engineering workforce. The continuously expanding major components of the ecosystem include integrated knowledge discovery and exploitation facilities (incorporating predictive and prescriptive big data analytics); novel cognitive modeling and visual simulation facilities; cognitive multimodal interfaces; and cognitive mobile and wearable devices. The ecosystem will provide timely, engaging, personalized / collaborative, learning and effective decision making. It will stimulate creativity and innovation, and prepare the participants to work in future cognitive enterprises and develop new cognitive products of increasing complexity. http://www.aee.odu.edu/cognitivecomp

  11. The excess radio background and fast radio transients

    SciTech Connect

    Kehayias, John; Kephart, Thomas W.; Weiler, Thomas J. E-mail: thomas.w.kephart@vanderbilt.edu

    2015-10-01

    In the last few years ARCADE 2, combined with older experiments, has detected an additional radio background, measured as a temperature and ranging in frequency from 22 MHz to 10 GHz, not accounted for by known radio sources and the cosmic microwave background. One type of source which has not been considered in the radio background is that of fast transients (those with event times much less than the observing time). We present a simple estimate, and a more detailed calculation, for the contribution of radio transients to the diffuse background. As a timely example, we estimate the contribution from the recently-discovered fast radio bursts (FRBs). Although their contribution is likely 6 or 7 orders of magnitude too small (though there are large uncertainties in FRB parameters) to account for the ARCADE 2 excess, our development is general and so can be applied to any fast transient sources, discovered or yet to be discovered. We estimate parameter values necessary for transient sources to noticeably contribute to the radio background.

  12. Ad Hoc Supervision of General Practice Registrars as a "Community of Practice": Analysis, Interpretation and Re-Presentation

    ERIC Educational Resources Information Center

    Clement, T.; Brown, J.; Morrison, J.; Nestel, D.

    2016-01-01

    General practice registrars in Australia undertake most of their vocational training in accredited general practices. They typically see patients alone from the start of their community-based training and are expected to seek timely ad hoc support from their supervisor. Such ad hoc encounters are a mechanism for ensuring patient safety, but also…

  13. 76 FR 71308 - Codex Alimentarius Commission: Meeting of the Ad Hoc Intergovernmental Codex Task Force on Animal...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-17

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Food Safety and Inspection Service Codex Alimentarius Commission: Meeting of the Ad Hoc... United States (U.S.) positions that will be discussed at the 6th Session of the Ad Hoc...

  14. Protocols for Detection and Removal of Wormholes for Secure Routing and Neighborhood Creation in Wireless Ad Hoc Networks

    ERIC Educational Resources Information Center

    Hayajneh, Thaier Saleh

    2009-01-01

    Wireless ad hoc networks are suitable and sometimes the only solution for several applications. Many applications, particularly those in military and critical civilian domains (such as battlefield surveillance and emergency rescue) require that ad hoc networks be secure and stable. In fact, security is one of the main barriers to the extensive use…

  15. Cognitive Astrophysics

    NASA Astrophysics Data System (ADS)

    Madore, Barry F.

    2012-09-01

    Cognitive Astrophysics works at the cusp between Cognitive Science and Astrophysics, drawing upon lessons learned in the Philosophy of Science, Linguistics and Artificial Intelligence. We will introduce and illustrate the concept of ``Downward Causation,'' common in philosophical discussions, but either unknown to or disdained by most physicists. A clear example operating on cosmological scales involving the origin of large-scale structure will be given. We will also make the case that on scales exceeding most laboratory experiments, self-gravitating matter can be considered to be in a ``fifth state'', characterized primarily by its negative specific heat, as first recognized by Lynden-Bell and Lynden-Bell (1977, MNRAS, 181, 405). Such systems increase their temperature as they lose energy. Numerous examples will be given and discussed.

  16. The Business of Radio Promotion.

    ERIC Educational Resources Information Center

    Hall, Jonathan

    This speech suggests that public radio stations should examine and use the techniques employed by commercial stations to increase their listening audience--creative promotion based on community involvement and participation. Some examples are included. (SC)

  17. Radio astronomy - The next decade

    NASA Astrophysics Data System (ADS)

    Kellermann, Kenneth I.

    1991-09-01

    Discoveries made over the past several decades by radio astronomers include radio galaxies, quasars, pulsars, gravitational lenses, energetic bursts from the sun and Jupiter, the greenhouse effect on Venus, the rotation of Mercury, giant molecular clouds, violent activity in galactic nuclei, and cosmic background radiation. This paper discusses the development of ever more powerful radio telescopes, which include the VLA operated by NRAO near Socorro (New Mexico); the new NRAO's 100-m Green Bank Telescope being constructed in Green Bank (West Virginia); and the proposed Millimeter Array, which will consist of 40 antennas, each 8-m across, arranged in any of four different ways depending on the size of the region under study. Consideration is also given to methods for increasing the resolving power and image quality of radio telescopes, with special attention given to very-long-baseline interferometry.

  18. Facilities for radio-iodination.

    PubMed

    Ramsey, N W; Bhattacharyya, A K; Dunn, M J

    1980-02-01

    A fume cabinet with a sloping front, fitted with a chemical absorbing filter and extractor fan, but without exhaust ducting, appears to possess considerable advantages for radio-iodination work compared with standard fume cupboards.

  19. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 1 2011-10-01 2011-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  20. 75 FR 66709 - Commercial Radio Operators Rules

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-29

    ... COMMISSION 47 CFR Parts 0, 1, 13, 80, and 87 Commercial Radio Operators Rules AGENCY: Federal Communications... radio operator licenses for maritime and aviation radio stations who perform certain functions performed within the commercial radio operators service, to determine which rules can be clarified, streamlined,...

  1. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 1 2014-10-01 2014-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  2. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 1 2012-10-01 2012-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  3. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  4. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 1 2013-10-01 2013-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  5. PARTNeR: Radio astromony for students

    NASA Astrophysics Data System (ADS)

    Blasco, C.; Vaquerizo, J. A.

    2008-06-01

    PARTNeR stands for Proyecto Academico con el Radiotelescopio de NASA en Robledo (the Academic Project with NASA's radio telescope at Robledo), and allows students to perform radio astronomy observations. High school and university students can access the PARTNeR radio telescope via the internet. The students can operate the antenna from their own school or university and perform radio astronomy observations.

  6. Innovativeness and the Public Radio Audience.

    ERIC Educational Resources Information Center

    Williams, Wenmouth, Jr.; Krugman, Dean M.

    1981-01-01

    A public radio audience was surveyed to test the hypothesis that a relationship exists between innovativeness and public radio listening. Rather than supporting the hypothesis, findings indicate that the entertainment and information elements of public radio are the primary attractions for the public radio audience. (MER)

  7. Report of the Ad Hoc Committee on Religious and Cultural Celebrations in the Library.

    ERIC Educational Resources Information Center

    Rathemacher, Andree; Grubman, Sheila Black; Lahiri, Amar; Gilton, Donna; Sharif, Mohammed

    The charge of the University of Rhode Island's Ad Hoc Committee on Religious and Cultural Celebrations in the Library was to: investigate all opportunities for the library to educate the campus community about religious and cultural holidays; consider all the major religions of the world and the possibility of having displays for the symbols of…

  8. The 5th Meeting of the Ad Hoc Panel on Terminal Configured Vehicles

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A report of the fifth meeting of the NASA Research and Technology Advisory Council, Ad Hoc panel on Terminal Configured Vehicles is presented. Some of the following topics were discussed; (1) microwave landing systems; (2) whole word computer system status; (3) flight path angle control: (4) VTOL approaches and landing technology; and (5) simulation study in wind shear.

  9. A Comprehensive Performance Comparison of On-Demand Routing Protocols in Mobile Ad-Hoc Networks

    NASA Astrophysics Data System (ADS)

    Khan, Jahangir; Hayder, Syed Irfan

    Mobile ad hoc network is an autonomous system of mobile nodes connected by wireless links. Each node operates not only as an end system, but also as a router to forward packets. The nodes are free to move about and organize themselves on a fly. In this paper we focus on the performance of the on-demand routing protocols such as DSR and AODV in ad-hoc networks. We have observed the performance change of each protocol through simulation with varying the data in intermediate nodes and to compare data throughput in each mobile modes of each protocol to analyze the packet fraction for application data. The objective of this work is to evaluate two routing protocols such as On-demand behavior, namely, Ad hoc Demand Distance vector (AODV) and Dynamic Source Routing (DSR), for wireless ad hoc networks based on performance of intermediate nodes for the delivery of data form source to destination and vice versa in order to compare the efficiency of throughput in the neighbors nodes. To overcome we have proposed OPNET simulator for performance comparison of hop to hop delivery of data packet in autonomous system.

  10. Using Dominating Sets to Improve the Performance of Mobile Ad Hoc Networks

    DTIC Science & Technology

    2005-09-01

    Communications Research Group (CCRG) directed by J.J., and students (Cintia, Nacho, Kumar and Venkatesh ) in Katia’s lab for their fellowship. I cannot...wireless conference, pages 156–162, 2002. [41] Katia Obraczka, Kumar Viswanath , and Gene Tsudik. Flooding for reliable multicast in multi-hop ad hoc

  11. Post-Hoc IRT Equating of Previously Administered English Tests for Comparison of Test Scores

    ERIC Educational Resources Information Center

    Saida, Chisato; Hattori, Tamaki

    2008-01-01

    Despite growing concerns about declining scholastic abilities of Japanese students throughout Japan prior to the implementation of the revised Courses of Study in 2002, little empirical evidence was available at that time to support this perceived decline in academic performance. This research describes post-hoc IRT equating of previously…

  12. Moving beyond Univariate Post-Hoc Testing in Exercise Science: A Primer on Descriptive Discriminate Analysis

    ERIC Educational Resources Information Center

    Barton, Mitch; Yeatts, Paul E.; Henson, Robin K.; Martin, Scott B.

    2016-01-01

    There has been a recent call to improve data reporting in kinesiology journals, including the appropriate use of univariate and multivariate analysis techniques. For example, a multivariate analysis of variance (MANOVA) with univariate post hocs and a Bonferroni correction is frequently used to investigate group differences on multiple dependent…

  13. Combining Infrastructure and Ad Hoc Collaboration for Data Management in Mobile Wireless Networks

    DTIC Science & Technology

    2005-01-01

    Elizabeth M. Royer. "Ad hoc On-Demand Distance Vector Routing." Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and Applications...Charles Perkins, ACM SIGCOMM󈨢 Conference on Communications Architectures, Protocols and Applications 22. Vincent D. Park and M. Scott Corson , A

  14. Work, Family, and Community: Summary Proceedings of an Ad Hoc Committee.

    ERIC Educational Resources Information Center

    Hayes, Cheryl D., Ed.

    These proceedings contain summaries of five working group discussions and a discussion of suggestions for future research from an ad hoc meeting on Work, Family, and Community (Fedruary 21-22, 1980) in Washington, D.C. The meeting had these objectives: (1) to identify salient policy and research issues associated with changing patterns of labor…

  15. Can cognitive science create a cognitive economics?

    PubMed

    Chater, Nick

    2015-02-01

    Cognitive science can intersect with economics in at least three productive ways: by providing richer models of individual behaviour for use in economic analysis; by drawing from economic theory in order to model distributed cognition; and jointly to create more powerful 'rational' models of cognitive processes and social interaction. There is the prospect of moving from behavioural economics to a genuinely cognitive economics.

  16. Ondvrejov solar radio WWW page

    NASA Astrophysics Data System (ADS)

    Jivrivcka, Karel; Meszarosova, Hana

    Since mid 1997 the Solar Radio Astronomy Group of the Astronomical Institute in Ondvrejov has been running a new WWW page. You can find us at the address --- http://sunkl.asu.cas.cz/radio/ --- where information about our instruments, observed frequencies, as well as about our data archive is available. The home page includes four main topics: 1. Observation & Instrumentation --- here you can find information about which instruments are currently in use, observed frequencies, time resolutions etc. Presently we use for solar radio observations three dedicated instruments: RT3 -- single frequency 3 GHz receiver with 10 ms time resolution RT4 -- radio spectrograph 2.0--4.5 GHz with 100 ms time resolution RT5 -- radio spectrograph 0.8--2.0 GHz with 100 ms time resolution The observations are run daily, while the Sun is higher then 5 degrees above the horizon. Because of the tremendous amount of data, only chosen time intervals with radio events are archived. Event Archive Info: --- here you can find information about archived data (date, time interval) as well as overall images of individual events in GIF format (the image names are at the same time hyperlinks for direct loading) sorted by date and time of observation. Gallery: --- here you can find some representative examples of spectra of solar radio events, recorded by our instruments. Anonymous FTP Server: --- enables direct FTP access to our image archive. This WWW page should give you an insight, what data are available and what the events look roughly like. The uncalibrated rough data from our archive can be processed only by special programs and are not generally free. But if you are interested in a particular event from our archive, you can contact us via e-mail address: radio@asu.cas.cz This work has been supported by the Czech Academy of Sciences through grant no.A3003707.

  17. Populations of extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Wall, J. V.

    In the late 1950s and early 1960s, radio sky surveys were the center of an intense and public debate -- Big-Bang versus Steady-State cosmology -- the arguments revolving about source counts and statistical interpretations in the face of instrumental complications. The 1965 discovery of the microwave background took the fire from the debate, but left the momentum in place for large-area radio surveys at different frequencies, and for extensive identification/redshift-measurement programs. By the 1970s the data enabled us to start disentangling the different populations of extragalactic radio sources. We could refine our taxonomy, and we could view the possibility of delineating individual cosmic histories and evolutions. We could at least describe a goal to elucidate the birth-life-death cycles of the objects involved 1quasi-stellar objects (QSOs) and radio galaxies: together the 'active galactic nuclei' (AGNs)1 whose unaccountably prodigious energies somehow produce the beautifully aligned radio structures with which we are now familiar. One part of John Bolton's vision was to see how distorted a view of the AGN universe the original long-wavelength surveys provided. One legacy is thus the 'short-wavelength survey' for extragalactic radio sources, which has done so much to balance our picture of the radio sky. And indeed the legacy continues in the form of the immense sky surveys at present under way, complete with their sub-industries of radio-positioning and identification. From these, yet further results are emerging on spatial distribution and the skeleton structure of the universe. It is the purpose of this paper to outline something of this current view of the populations, their differences, similarities and unifying concepts.

  18. National Centre for Radio Astrophysics

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    India's National Centre for Radio Astrophysics (NCRA), located on the Pune University Campus, is part of the TATA INSTITUTE OF FUNDAMENTAL RESEARCH. At Khodad, 80 km from Pune, NCRA has set up the Giant Metrewave Radio Telescope (GMRT), the world's largest telescope operating at meter wavelengths. GMRT consists of 30 fully steerable dishes of 45 m diameter, spread over a 25 km area. Another meter...

  19. Historic Radio Astronomy Working Group

    NASA Astrophysics Data System (ADS)

    2007-06-01

    This special issue of Astronomische Nachrichten contains the proceedings of a session of the Historic Radio Astronomy Working Group of the International Astronomical Union that took place during the 26th General Assembly of the IAU in Prague on 17th August 2006. In addition to the talks presented in Prague some contributions were solicited to give a more complete overview of `The Early History of European Radio Astronomy'.

  20. Radio emission from supernova remnants

    NASA Astrophysics Data System (ADS)

    Dubner, Gloria; Giacani, Elsa

    2015-09-01

    The explosion of a supernova releases almost instantaneously about 10^{51} ergs of mechanic energy, changing irreversibly the physical and chemical properties of large regions in the galaxies. The stellar ejecta, the nebula resulting from the powerful shock waves, and sometimes a compact stellar remnant, constitute a supernova remnant (SNR). They can radiate their energy across the whole electromagnetic spectrum, but the great majority are radio sources. Almost 70 years after the first detection of radio emission coming from an SNR, great progress has been achieved in the comprehension of their physical characteristics and evolution. We review the present knowledge of different aspects of radio remnants, focusing on sources of the Milky Way and the Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief overview of theoretical background, analyze morphology and polarization properties, and review and critically discuss different methods applied to determine the radio spectrum and distances. The consequences of the interaction between the SNR shocks and the surrounding medium are examined, including the question of whether SNRs can trigger the formation of new stars. Cases of multispectral comparison are presented. A section is devoted to reviewing recent results of radio SNRs in the Magellanic Clouds, with particular emphasis on the radio properties of SN 1987A, an ideal laboratory to investigate dynamical evolution of an SNR in near real time. The review concludes with a summary of issues on radio SNRs that deserve further study, and analysis of the prospects for future research with the latest-generation radio telescopes.

  1. A zero-power radio receiver.

    SciTech Connect

    Brocato, Robert Wesley

    2004-09-01

    This report describes both a general methodology and some specific examples of passive radio receivers. A passive radio receiver uses no direct electrical power but makes sole use of the power available in the radio spectrum. These radio receivers are suitable as low data-rate receivers or passive alerting devices for standard, high power radio receivers. Some zero-power radio architectures exhibit significant improvements in range with the addition of very low power amplifiers or signal processing electronics. These ultra-low power radios are also discussed and compared to the purely zero-power approaches.

  2. Natural radio lasing at Jupiter

    NASA Technical Reports Server (NTRS)

    Calvert, W.; Leblanc, Y.; Ellis, G. R. A.

    1988-01-01

    Like the comparable AKR radio emissions from earth's magnetosphere, the well-known decametric radio S-bursts from Jupiter, observed in France and Australia at frequencies from 10 to 26 MHz, have been found to exhibit equally spaced discrete spectral components which can be attributed to the adjacent longitudinal oscillation modes of natural radio lasers. Implying sizes of only a few kilometers for the individual radio lasers producing the S-bursts, the frequency spacing of these modes was roughly constant with frequency and about 30 to 50 kHz. Their corresponding temporal spacings, however, varied inversely proportional to the observing frequency, suggesting that the radio lasers producing the S-bursts were expanding uniformly at a rate of about 4 km/s. Presumably caused by the projected motion of Io with respect to the planet, this expansion of the S-burst radio lasers would account for the downward frequency drifts of the S-bursts without the energetic electron bunches which have heretofore always been assumed necessary to account for such behavior.

  3. Radio galaxies and their environment

    SciTech Connect

    van Breugel, W.

    1993-02-24

    The relationships between radio galaxies and their environment are varied, complex, and evolve with cosmic epoch. Basic questions are what role the environment plays in triggering and fuelling (radio) galaxy activity what the effects of this activity are on its environment, and how radio galaxies and environment evolve. Clearly, this could be the topic of a workshop all in itself and the scope of this review will necessarily be limited. A review of the connections between environment and galaxy activity in general has been given by Heckman. First, I will briefly summarize the relationships between parent galaxy and cluster environments, and radio galaxies. A more detailed discussion of various aspects of this will be given elsewhere by F. Owen, J.0. Burns and R. Perley. I will then discuss the current status of investigations of extended emission-line regions in radio galaxies, again referring elsewhere in this volume for more detailed discussions of some particular aspects (kinematics and ionization mechanisms by K. Meisenheimer; polarization and spectral index lobe asymmetries by G. Pooley). I will conclude with a brief discussion of the current status of observations of high redshift radio galaxies.

  4. Flare stars at radio wavelengths

    NASA Technical Reports Server (NTRS)

    Lang, Kenneth R.

    1990-01-01

    The radio emission from dMe flare stars is discussed using Very Large Array and Arecibo observations as examples. Active flare stars emit weak, unpolarized, quiescent radio radiation that may be always present. Although thermal bremsstrahlung and/or thermal gyroresonance radiation account for the slowly-varying, quiescent radio radiation of solar active regions, these processes cannot account for the long-wavelength quiescent radiation observed from nearby dMe flare stars. It has been attributed to nonthermal gyrosynchrotron radiation, but some as yet unexplained mechanism must be continually producing the energetic electrons. Long duration, narrow-band radiation is also emitted from some nearby dMe stars at 20 cm wavelength. Such radiation may be attributed to coherent plasma radiation or to coherent electron-cyclotron masers. Impulsive stellar flares exhibit rapid variations that require radio sources that are smaller than the star in size, and high brightness temperatures greater than 10(exp 15) K that are also explained by coherent radiation processes. Quasi-periodic temporal fluctuations suggest pulsations during some radio flares. Evidence for frequency structure and positive or negative frequency drifts during radio flares from dMe stars is also presented.

  5. Flare stars at radio wavelengths

    NASA Technical Reports Server (NTRS)

    Lang, Kenneth R.

    1989-01-01

    The radio emission from dMe flare stars is discussed using Very Large Array and Arecibo observations as examples. Active flare stars emit weak, unpolarized, quiescent radio radiation that may be always present. Although thermal bremsstrahlung and/or thermal gyroresonance radiation account for the slowly-varying, quiescent radio radiation of solar active regions, these processes cannot account for the long-wavelength quiescent radiation observed from nearby dMe flare stars. It has been attributed to nonthermal gyrosynchrotron radiation, but some as yet unexplained mechanism must be continually producing the energetic electrons. Long duration, narrow-band radiation is also emitted from some nearby dMe stars at 20 cm wavelength. Such radiation may be attributed to coherent plasma radiation or to coherent electron-cyclotron masers. Impulsive stellar flares exhibit rapid variations that require radio sources that are smaller than the star in size, and high brightness temperatures greater than 10(exp 15) K that are also explained by coherent radiation processes. Quasi-periodic temporal fluctuations suggest pulsations during some radio flares. Evidence for frequency structure and positive or negative frequency drifts during radio flares from dMe stars is also presented.

  6. Applications of software-defined radio (SDR) technology in hospital environments.

    PubMed

    Chávez-Santiago, Raúl; Mateska, Aleksandra; Chomu, Konstantin; Gavrilovska, Liljana; Balasingham, Ilangko

    2013-01-01

    A software-defined radio (SDR) is a radio communication system where the major part of its functionality is implemented by means of software in a personal computer or embedded system. Such a design paradigm has the major advantage of producing devices that can receive and transmit widely different radio protocols based solely on the software used. This flexibility opens several application opportunities in hospital environments, where a large number of wired and wireless electronic devices must coexist in confined areas like operating rooms and intensive care units. This paper outlines some possible applications in the 2360-2500 MHz frequency band. These applications include the integration of wireless medical devices in a common communication platform for seamless interoperability, and cognitive radio (CR) for body area networks (BANs) and wireless sensor networks (WSNs) for medical environmental surveillance. The description of a proof-of-concept CR prototype is also presented.

  7. The radio properties of infrared-faint radio sources

    NASA Astrophysics Data System (ADS)

    Middelberg, E.; Norris, R. P.; Hales, C. A.; Seymour, N.; Johnston-Hollitt, M.; Huynh, M. T.; Lenc, E.; Mao, M. Y.

    2011-02-01

    Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 μm when using sensitive Spitzer observations with μJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims: High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods: We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results: We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 μm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions: The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

  8. Brown University Radio Student Telescope (BURST)

    NASA Astrophysics Data System (ADS)

    Miller, Michelle

    2017-01-01

    The Brown University Radio Student Telescope (BURST) is a rooftop low frequency radio interferometer that we hope to potentially use to observe radio transients, non-thermal radio emission from Galactic synchrotron and supernova remnants, and extragalactic radio sources. It was built by a group of Brown undergraduates this past summer. An overview of the design, ultimate installation, challenges in implementation and data acquisition will be covered in the poster.

  9. Cognitive Enhancement and Education

    ERIC Educational Resources Information Center

    Buchanan, Allen

    2011-01-01

    Cognitive enhancement--augmenting normal cognitive capacities--is not new. Literacy, numeracy, computers, and the practices of science are all cognitive enhancements. Science is now making new cognitive enhancements possible. Biomedical cognitive enhancements (BCEs) include the administration of drugs, implants of genetically engineered or…

  10. 78 FR 8145 - Sequence 24 Findings of the EISA 436(h) Ad-Hoc Review Group on Green Building Certification Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-05

    ... ADMINISTRATION Sequence 24 Findings of the EISA 436(h) Ad-Hoc Review Group on Green Building Certification... partners in the EISA 436(h) Ad-Hoc Discussion Group are seeking public input regarding possible approaches... certification of green Federal buildings. GSA is using the deliberations from the EISA 436(h) Ad-hoc...

  11. IA-Regional-Radio - Social Network for Radio Recommendation

    NASA Astrophysics Data System (ADS)

    Dziczkowski, Grzegorz; Bougueroua, Lamine; Wegrzyn-Wolska, Katarzyna

    This chapter describes the functions of a system proposed for the music hit recommendation from social network data base. This system carries out the automatic collection, evaluation and rating of music reviewers and the possibility for listeners to rate musical hits and recommendations deduced from auditor's profiles in the form of regional Internet radio. First, the system searches and retrieves probable music reviews from the Internet. Subsequently, the system carries out an evaluation and rating of those reviews. From this list of music hits, the system directly allows notation from our application. Finally, the system automatically creates the record list diffused each day depending on the region, the year season, the day hours and the age of listeners. Our system uses linguistics and statistic methods for classifying music opinions and data mining techniques for recommendation part needed for recorded list creation. The principal task is the creation of popular intelligent radio adaptive on auditor's age and region - IA-Regional-Radio.

  12. a Radio-Frequency

    NASA Astrophysics Data System (ADS)

    Foo, Thomas Kwok-Fah

    Radio-frequency (RF) inhomogeneity encountered in magnetic resonance (MR) imaging poses a significant impediment to obtaining images of the highest diagnostic quality. This inhomogeneity arises from the conductivity effect, which attenuates the RF field with increasing depth, and the permittivity effect. The latter is the dominant effect at 1.5 Tesla (64 MHz), and contributes to standing waves within the body. A theoretical model has been developed which describes these effects for an infinitely long right circularly cylindrical object inside a concentric RF coil and RF shield. This model assumes that the RF field propagates as a travelling wave in the z direction, along the long axis of the cylinder. The resulting solutions adequately predict the field distribution for RF coils which have both a finite wavelength and an infinite wavelength in z. This corresponds to high-pass and low-pass birdcage resonators, respectively, that are in general used in MR imaging. Standing wave models are easily obtained from the superposition of solutions of two travelling waves in opposite directions. The results of this model indicate that the axial propagation constant k_{z} is a strong function of the dielectric present in the coil -to-shield space. The field distribution in the axial plane can be represented by the Bessel function J_1(k _{rho}r), where k _sp{rho}{2} = k^2-k_sp{z}{2} . By varying the dielectric material occupying the coil-to-shield space, an optimum value of k _{z} can be obtained for a particular coil and shield configuration which minimizes the amplitude variations in the axial plane. Experimental verification of the theoretical model has been obtained. These measurements were performed on a non-resonant, travelling wave test coil with a saline phantom as a load simulating the body. The measured field profiles in the axial plane agree with the predicted values, establishing the validity of the theoretical model. As expected, optimal RF homogeneity was obtained

  13. Video via radio testbed

    NASA Astrophysics Data System (ADS)

    Szu, Harold H.; Hsu, Charles C.

    2002-03-01

    to enable us to transmit live video via the SINGARS radio at a narrow bandwidth of 16 K bps.

  14. Jovian type III radio bursts

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

    1989-01-01

    Radio bursts have been observed in the Voyager plasma wave data from Jupiter that bear a striking resemblance to solar type III radio bursts. The emissions lie in the frequency range near 10 kHz, have durations of a minute or so, and occur in a set of periodically spaced bursts. The spacing between primary bursts is typically 15 min, but the bursts may have additional components which recur on time scales of about 3 min. The similarity with solar type III radio bursts suggests a source mechanism involving the movement of energetic electrons through a density gradient in the plasma surrounding Jupiter. The periodicity of bursts suggests Io may be involved in the generation of waves, since the timing is similar to the Alfven wave travel time from one hemisphere to the other through the Io torus.

  15. The development of radio astronomy

    NASA Astrophysics Data System (ADS)

    Reich, W.; Wielebinski, R.

    2002-07-01

    Following the detection of extraterrestrial radio waves in 1932 by Karl Jansky, radio astronomy developed quickly after World War II. It established itself soon as a new branch of astronomy with today's outstanding record in the detection of new phenomena in space. These have been honoured by a number of Nobel prizes. Radio astronomy largely depends on technical developments in receiver technology, antenna systems, electronics and computing power. Ever shorter wavelengths down to the submm-wavelength range became accessible, resulting in new exciting discoveries. However, now and in future care must be taken, in particular for the lower frequency range, of harmful man-made interferences, which might mask the weak signals from space. New international facilities with orders-of-magnitude higher sensitivity like ALMA and SKA are planned or under construction. Space-borne observatories like PLANCK will detect weak fluctuations of the cosmic microwave background, which will constrain cosmological models with an unprecedented accuracy.

  16. Miniature EVA Software Defined Radio

    NASA Technical Reports Server (NTRS)

    Pozhidaev, Aleksey

    2012-01-01

    As NASA embarks upon developing the Next-Generation Extra Vehicular Activity (EVA) Radio for deep space exploration, the demands on EVA battery life will substantially increase. The number of modes and frequency bands required will continue to grow in order to enable efficient and complex multi-mode operations including communications, navigation, and tracking applications. Whether conducting astronaut excursions, communicating to soldiers, or first responders responding to emergency hazards, NASA has developed an innovative, affordable, miniaturized, power-efficient software defined radio that offers unprecedented power-efficient flexibility. This lightweight, programmable, S-band, multi-service, frequency- agile EVA software defined radio (SDR) supports data, telemetry, voice, and both standard and high-definition video. Features include a modular design, an easily scalable architecture, and the EVA SDR allows for both stationary and mobile battery powered handheld operations. Currently, the radio is equipped with an S-band RF section. However, its scalable architecture can accommodate multiple RF sections simultaneously to cover multiple frequency bands. The EVA SDR also supports multiple network protocols. It currently implements a Hybrid Mesh Network based on the 802.11s open standard protocol. The radio targets RF channel data rates up to 20 Mbps and can be equipped with a real-time operating system (RTOS) that can be switched off for power-aware applications. The EVA SDR's modular design permits implementation of the same hardware at all Network Nodes concept. This approach assures the portability of the same software into any radio in the system. It also brings several benefits to the entire system including reducing system maintenance, system complexity, and development cost.

  17. Enhancements for distributed certificate authority approaches for mobile wireless ad hoc networks.

    SciTech Connect

    Van Leeuwen, Brian P.; Michalski, John T.; Anderson, William Erik

    2003-12-01

    Mobile wireless ad hoc networks that are resistant to adversarial manipulation are necessary for distributed systems used in military and security applications. Critical to the successful operation of these networks, which operate in the presence of adversarial stressors, are robust and efficient information assurance methods. In this report we describe necessary enhancements for a distributed certificate authority (CA) used in secure wireless network architectures. Necessary cryptographic algorithms used in distributed CAs are described and implementation enhancements of these algorithms in mobile wireless ad hoc networks are developed. The enhancements support a network's ability to detect compromised nodes and facilitate distributed CA services. We provide insights to the impacts the enhancements will have on network performance with timing diagrams and preliminary network simulation studies.

  18. PNNI routing support for ad hoc mobile networking: A flat architecture

    SciTech Connect

    Martinez, L.; Sholander, P.; Tolendino, L.

    1997-12-01

    This contribution extends the Outside Nodal Hierarchy List (ONHL) procedures described in ATM Form Contribution 97-0766. These extensions allow multiple mobile networks to form either an ad hoc network or an extension of a fixed PNNI infrastructure. This contribution covers the simplest case where the top-most Logical Group Nodes (LGNs), in those mobile networks, all reside at the same level in a PNNI hierarchy. Future contributions will cover the general case where those top-most LGNs reside at different hierarchy levels. This contribution considers a flat ad hoc network architecture--in the sense that each mobile network always participates in the PNNI hierarchy at the preconfigured level of its top-most LGN.

  19. Design of free patterns of nanocrystals with ad hoc features via templated dewetting

    NASA Astrophysics Data System (ADS)

    Aouassa, M.; Berbezier, I.; Favre, L.; Ronda, A.; Bollani, M.; Sordan, R.; Delobbe, A.; Sudraud, P.

    2012-07-01

    Design of monodisperse ultra-small nanocrystals (NCs) into large scale patterns with ad hoc features is demonstrated. The process makes use of solid state dewetting of a thin film templated through alloy liquid metal ion source focused ion beam (LMIS-FIB) nanopatterning. The solid state dewetting initiated at the edges of the patterns controllably creates the ordering of NCs with ad hoc placement and periodicity. The NC size is tuned by varying the nominal thickness of the film while their position results from the association of film retraction from the edges of the lay out and Rayleigh-like instability. The use of ultra-high resolution LMIS-FIB enables to produce monocrystalline NCs with size, periodicity, and placement tunable as well. It provides routes for the free design of nanostructures for generic applications in nanoelectronics.

  20. Forming an ad-hoc nearby storage, based on IKAROS and social networking services

    NASA Astrophysics Data System (ADS)

    Filippidis, Christos; Cotronis, Yiannis; Markou, Christos

    2014-06-01

    We present an ad-hoc "nearby" storage, based on IKAROS and social networking services, such as Facebook. By design, IKAROS is capable to increase or decrease the number of nodes of the I/O system instance on the fly, without bringing everything down or losing data. IKAROS is capable to decide the file partition distribution schema, by taking on account requests from the user or an application, as well as a domain or a Virtual Organization policy. In this way, it is possible to form multiple instances of smaller capacity higher bandwidth storage utilities capable to respond in an ad-hoc manner. This approach, focusing on flexibility, can scale both up and down and so can provide more cost effective infrastructures for both large scale and smaller size systems. A set of experiments is performed comparing IKAROS with PVFS2 by using multiple clients requests under HPC IOR benchmark and MPICH2.

  1. The Ad Hoc process to strengthen the framework convention on climate change

    SciTech Connect

    Ramakrishna, K.; Deutz, A.M.; Jacobsen, L.A.

    1995-11-01

    The Woods Hole Research Center convened an International Conference on The Ad Hoc Process to Strengthen the Framework Convention on Climate Change in Woods Hole, MA, on October 7-9, 1995. The conference was conducted to examine the prospects for successful adoption of a protocol to the Framework Convention on Climate Change by 1997. In preparation for the Second session of the Ad Hoc Group on the Berlin Mandate, several governmental and nongovernmental representatives met in Woods Hole to discuss the process and possible outcome of the Berlin Mandate negotiations for a protocol or other legal instrument to strengthen the Convention. The conference was by invitation and all participants attended in their personal capacities.

  2. PNNI routing support for ad hoc mobile networking: The multilevel case

    SciTech Connect

    Martinez, L.; Sholander, P.; Tolendino, L.

    1998-01-01

    This contribution extends the Outside Nodal Hierarchy List (ONHL) procedures described in ATM Forum Contributions 97-0766 and 97-0933. These extensions allow multiple mobile networks to form either an ad hoc network or an extension of a fixed PNNI infrastructure. A previous contribution (97-1073) covered the simplest case where the top-most Logical Group Nodes (LGNs), in those mobile networks, all resided at the same level in a PNNI hierarchy. This contribution covers the more general case wherein those top-most LGNs may reside at different PNNI hierarchy levels. Both of the SNL contributions consider flat ad hoc network architectures in the sense that each mobile network always participates in the PNNI hierarchy at the pre-configured level of its top-most LGN.

  3. Analysis and Proposal of Position-Based Routing Protocols for Vehicular Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Okada, Hiraku; Takano, Akira; Mase, Kenichi

    One of the most promising applications of a mobile ad hoc network is a vehicular ad hoc network (VANET). Each vehicle is aware of its position information by GPS or other methods, so position-based routing is a useful approach in VANET. The position-based routing protocol can be classified roughly into a next-hop forwarding method and a directed flooding method. We evaluate performance of both methods by analytic approach and compare them in this paper. From the evaluation results, we conclude that it is effective for the position-based routing to choose either the next-hop forwarding method or the directed flooding method according to the environment. Then we propose the hybrid transmission method which can select one of them according to the environment, and clarify that the proposed method can keep the packet delivery ratio at a high level and reduce the delay time.

  4. Vehicular ad hoc network for a surveillance system using multifrequency band enhancement

    NASA Astrophysics Data System (ADS)

    Bunruangses, Montree; Sunat, Khamron; Mitatha, Somsak; Yupapin, Preecha P.

    2010-09-01

    We present a new design of a surveillance system via a vehicular ad hoc network (VANET) integrated by a 3-G or 4-G cellular wireless network. We propose dense wavelength division multiplexing wavelength enhancement for increasing the channel capacity and signal security. Increase in the number of channels can be obtained by increasing the wavelength density. Signal security is introduced by a specific wavelength filter controlled by the central operator. Optical communication wavelength enhancement is reviewed. The advantage of this proposed system is that it can easily be implemented and incorporated into the existing communication link in either a cellular or ad hoc wireless system, where signal security and hence privacy can be provided.

  5. An Ad-Hoc Adaptive Pilot Model for Pitch Axis Gross Acquisition Tasks

    NASA Technical Reports Server (NTRS)

    Hanson, Curtis E.

    2012-01-01

    An ad-hoc algorithm is presented for real-time adaptation of the well-known crossover pilot model and applied to pitch axis gross acquisition tasks in a generic fighter aircraft. Off-line tuning of the crossover model to human pilot data gathered in a fixed-based high fidelity simulation is first accomplished for a series of changes in aircraft dynamics to provide expected values for model parameters. It is shown that in most cases, for this application, the traditional crossover model can be reduced to a gain and a time delay. The ad-hoc adaptive pilot gain algorithm is shown to have desirable convergence properties for most types of changes in aircraft dynamics.

  6. An Optimal CDS Construction Algorithm with Activity Scheduling in Ad Hoc Networks.

    PubMed

    Penumalli, Chakradhar; Palanichamy, Yogesh

    2015-01-01

    A new energy efficient optimal Connected Dominating Set (CDS) algorithm with activity scheduling for mobile ad hoc networks (MANETs) is proposed. This algorithm achieves energy efficiency by minimizing the Broadcast Storm Problem [BSP] and at the same time considering the node's remaining energy. The Connected Dominating Set is widely used as a virtual backbone or spine in mobile ad hoc networks [MANETs] or Wireless Sensor Networks [WSN]. The CDS of a graph representing a network has a significant impact on an efficient design of routing protocol in wireless networks. Here the CDS is a distributed algorithm with activity scheduling based on unit disk graph [UDG]. The node's mobility and residual energy (RE) are considered as parameters in the construction of stable optimal energy efficient CDS. The performance is evaluated at various node densities, various transmission ranges, and mobility rates. The theoretical analysis and simulation results of this algorithm are also presented which yield better results.

  7. Valid randomization-based p-values for partially post hoc subgroup analyses

    PubMed Central

    Lee, Joseph J.; Rubin, Donald B.

    2015-01-01

    By ‘partially post-hoc’ subgroup analyses, we mean analyses that compare existing data from a randomized experiment—from which a subgroup specification is derived—to new, subgroup-only experimental data. We describe a motivating example in which partially post hoc subgroup analyses instigated statistical debate about a medical device’s efficacy. We clarify the source of such analyses’ invalidity and then propose a randomization-based approach for generating valid posterior predictive p-values for such partially post hoc subgroups. Lastly, we investigate the approach’s operating characteristics in a simple illustrative setting through a series of simulations, showing that it can have desirable properties under both null and alternative hypotheses. PMID:25959735

  8. Ad-hoc and context-dependent adjustments of selective attention in conflict control: an ERP study with visual probes.

    PubMed

    Nigbur, R; Schneider, J; Sommer, W; Dimigen, O; Stürmer, B

    2015-02-15

    Cognitive conflict control in flanker tasks has often been described using the zoom-lens metaphor of selective attention. However, whether and how selective attention - in terms of suppression and enhancement - operates in this context has remained unclear. To examine the dynamic interplay of selective attention and cognitive control we used electrophysiological measures and presented task-irrelevant visual probe stimuli at foveal, parafoveal, and peripheral display positions. Target-flanker congruency varied either randomly from trial to trial (mixed-block) or block-wise (fixed-block) in order to induce reactive versus proactive control modes, respectively. Three EEG measures were used to capture ad-hoc adjustments within trials as well as effects of context-based predictions: the N1 component of the visual evoked potential (VEP) to probes, the VEP to targets, and the conflict-related midfrontal N2 component. Results from probe-VEPs indicate that enhanced processing of the foveal target rather than suppression of the peripheral flankers supports interference control. In incongruent mixed-block trials VEPs were larger to probes near the targets. In the fixed-blocks probe-VEPs were not modulated, but contrary to the mixed-block the preceding target-related VEP was affected by congruency. Results of the control-related N2 reveal largest amplitudes in the unpredictable context, which did not differentiate for stimulus and response incongruency. In contrast, in the predictable context, N2 amplitudes were reduced overall and differentiated between stimulus and response incongruency. Taken together these results imply that predictability alters interference control by a reconfiguration of stimulus processing. During unpredictable sequences participants adjust their attentional focus dynamically on a trial-by-trial basis as reflected in congruency-dependent probe-VEP-modulation. This reactive control mode also elicits larger N2 amplitudes. In contrast, when task demands

  9. Mobile radio interferometric geodetic systems

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.; Niell, A. E.; Ong, K. M.; Resch, G. M.; Morabito, D. D.; Claflin, E. S.; Lockhart, T. G.

    1978-01-01

    Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed.

  10. Radio Relays Improve Wireless Products

    NASA Technical Reports Server (NTRS)

    2009-01-01

    Signal Hill, California-based XCOM Wireless Inc. developed radio frequency micromachine (RF MEMS) relays with a Phase II Small Business Innovation Research (SBIR) contract through NASA?s Jet Propulsion Laboratory. In order to improve satellite communication systems, XCOM produced wireless RF MEMS relays and tunable capacitors that use metal-to-metal contact and have the potential to outperform most semiconductor technologies while using less power. These relays are used in high-frequency test equipment and instrumentation, where increased speed can mean significant cost savings. Applications now also include mainstream wireless applications and greatly improved tactical radios.

  11. EGPS: An Efficient Privacy Preserving Scheme for Vehicular ad hoc Networks

    NASA Astrophysics Data System (ADS)

    Zhao, Baokang; Su, Xiangyu; Su, Jinshu; Song, Ziming; Sun, Yipin; Tao, Jing; Tang, Yong; Chen, Shuhui; Zhao, Guohong; Chen, Yijiao

    2010-09-01

    In this paper, we propose EGPS, an efficient privacy preserving scheme for vehicular ad hoc networks. The EGPS scheme is based on a very efficient group signature and Identity Based Cryptography(IBC) techniques. Several security properties of EGPS, including the correctness and unforgeability have been proved. Furthermore, EGPS is also proved to be more efficient than GSIS, which is currently one of the best state-of-the-art VANET privacy preserving schemes.

  12. Modelling of Medium Access Control (MAC) Protocols for Mobile Ad-Hoc Networks

    DTIC Science & Technology

    2005-06-01

    Slot IP Internet Protocol LAN Local Area Network MAC Medium Access Control MACAW Medium Access Protocol for Wireless LANs MANET Mobile Ad-hoc...Unforced state – It waits after entering the state until it is invoked by another process or an interrupt. It is in dark grey on this report, and red ... green in OPNET. A MAC process model is built for general initialisations of the MAC module, and to invoke the selected MAC protocol process model

  13. Adaptive Demand-Driven Multicast Routing in Multi-Hop Wireless Ad Hoc Networks

    DTIC Science & Technology

    2004-05-06

    16] L. Ji and M. S. Corson . A Lightweight Adaptive Multicast Algorithm. In Proceedings of IEEE GLOBECOM ’98, pages 1036–1042, December 1998. [17] L...Ji and M. S. Corson . Differential Destination Multicast (DDM) Specification. Internet- Draft, draft-ietf-manet-ddm-00.txt, July 2000. Work in...3 [30] Charles E. Perkins, Elizabeth M. Royer, and Samir R. Das. Ad Hoc On Demand Distance Vector (AODV) Routing. Internet-Draft, draft-ietf-manet

  14. A Performance Comparison of On-Demand Multicast Routing Protocols for Ad Hoc Networks

    DTIC Science & Technology

    2004-12-15

    33–44, October 2001. [10] L. Ji and M. S. Corson . A Lightweight Adaptive Multicast Algorithm. In Proceedings of IEEE GLOBECOM ’98, pages 1036–1042...December 1998. [11] L. Ji and M. S. Corson . Differential Destination Multicast (DDM) Specification. Internet- Draft, draft-ietf-manet-ddm-00.txt, July... Elizabeth M. Royer and Charles E. Perkins. Multicast Operation of the Ad-hoc On- Demand Distance Vector Routing Protocol. In Proceedings of the Fifth

  15. Cognitive Tactical Radios: Cognition Through Learning and Strategy (CLearStrategy)

    DTIC Science & Technology

    2012-12-08

    Sahand H. A. Ahmad . Atomic Congestion Games on Graphs and Their Applications in Networking, IEEE/ACM Transactions on Networking, (10 2012): 1541...Information Theory (12 2011) 12/27/2011 3.00 Cem Tekin, Mingyan Liu, Richard Southwell , Jianwei Huang , Sahand H. A. Ahmad. Atomic Congestion Games on

  16. Ad Hoc Categories and False Memories: Memory Illusions for Categories Created On-the-Spot.

    PubMed

    Soro, Jerônimo C; Ferreira, Mário B; Semin, Gün R; Mata, André; Carneiro, Paula

    2017-04-06

    Three experiments were designed to test whether experimentally created ad hoc associative networks evoke false memories. We used the DRM (Deese, Roediger, McDermott) paradigm with lists of ad hoc categories composed of exemplars aggregated toward specific goals (e.g., going for a picnic) that do not share any consistent set of features. Experiment 1 revealed considerable levels of false recognitions of critical words from ad hoc categories. False recognitions occurred even when the lists were presented without an organizing theme (i.e., the category's label). Experiments 1 and 2 tested whether (a) the ease of identifying the categories' themes, and (b) the lists' backward associative strength could be driving the effect. List identifiability did not correlate with false recognition, and the effect remained even when backward associative strength was controlled for. Experiment 3 manipulated the distractor items in the recognition task to address the hypothesis that the salience of unrelated items could be facilitating the occurrence of the phenomenon. The effect remained when controlling for this source of facilitation. These results have implications for assumptions made by theories of false memories, namely the preexistence of associations in the activation-monitoring framework and the central role of gist extraction in fuzzy-trace theory, while providing evidence of the occurrence of false memories for more dynamic and context-dependent knowledge structures. (PsycINFO Database Record

  17. Real Time Semantic Interoperability in AD HOC Networks of Geospatial Data Sources: Challenges, Achievements and Perspectives

    NASA Astrophysics Data System (ADS)

    Mostafavi, M. A.; Bakillah, M.

    2012-07-01

    Recent advances in geospatial technologies have made available large amount of geospatial data. Meanwhile, new developments in Internet and communication technologies created a shift from isolated geospatial databases to ad hoc networks of geospatial data sources, where data sources can join or leave the network, and form groups to share data and services. However, effective integration and sharing of geospatial data among these data sources and their users are hampered by semantic heterogeneities. These heterogeneities affect the spatial, temporal and thematic aspects of geospatial concepts. There have been many efforts to address semantic interoperability issues in the geospatial domain. These efforts were mainly focused on resolving heterogeneities caused by different and implicit representations of the concepts. However, many approaches have focused on the thematic aspects, leaving aside the explicit representation of spatial and temporal aspects. Also, most semantic interoperability approaches for networks have focused on automating the semantic mapping process. However, the ad hoc network structure is continuously modified by source addition or removal, formation of groups, etc. This dynamic aspect is often neglected in those approaches. This paper proposes a conceptual framework for real time semantic interoperability in ad hoc networks of geospatial data sources. The conceptual framework presents the fundamental elements of real time semantic interoperability through a hierarchy of interrelated semantic states and processes. Then, we use the conceptual framework to set the discussion on the achievements that have already been made, the challenges that remain to be addressed and perspectives with respect to these challenges.

  18. A Dirichlet reputation system in reliable routing of wireless ad hoc network

    SciTech Connect

    Yang, Dr. Li; Cui, Xiaohui; Cemerlic, Alma

    2010-01-01

    Ad hoc networks are very helpful in situations when no fixed network infrastructure is available, such as natural disasters and military conflicts. In such a network, all wireless nodes are equal peers simultaneously serving as both senders and routers for other nodes. Therefore, how to route packets through reliable paths becomes a fundamental problems when behaviors of certain nodes deviate from wireless ad hoc routing protocols. We proposed a novel Dirichlet reputation model based on Bayesian inference theory which evaluates reliability of each node in terms of packet delivery. Our system offers a way to predict and select a reliable path through combination of first-hand observation and second-hand reputation reports. We also proposed moving window mechanism which helps to adjust ours responsiveness of our system to changes of node behaviors. We integrated the Dirichlet reputation into routing protocol of wireless ad hoc networks. Our extensive simulation indicates that our proposed reputation system can improve good throughput of the network and reduce negative impacts caused by misbehaving nodes.

  19. Cross-Layer Service Discovery Mechanism for OLSRv2 Mobile Ad Hoc Networks

    PubMed Central

    Vara, M. Isabel; Campo, Celeste

    2015-01-01

    Service discovery plays an important role in mobile ad hoc networks (MANETs). The lack of central infrastructure, limited resources and high mobility make service discovery a challenging issue for this kind of network. This article proposes a new service discovery mechanism for discovering and advertising services integrated into the Optimized Link State Routing Protocol Version 2 (OLSRv2). In previous studies, we demonstrated the validity of a similar service discovery mechanism integrated into the previous version of OLSR (OLSRv1). In order to advertise services, we have added a new type-length-value structure (TLV) to the OLSRv2 protocol, called service discovery message (SDM), according to the Generalized MANET Packet/Message Format defined in Request For Comments (RFC) 5444. Each node in the ad hoc network only advertises its own services. The advertisement frequency is a user-configurable parameter, so that it can be modified depending on the user requirements. Each node maintains two service tables, one to store information about its own services and another one to store information about the services it discovers in the network. We present simulation results, that compare our service discovery integrated into OLSRv2 with the one defined for OLSRv1 and with the integration of service discovery in Ad hoc On-demand Distance Vector (AODV) protocol, in terms of service discovery ratio, service latency and network overhead. PMID:26205272

  20. Capacity-Delay Trade-Off in Collaborative Hybrid Ad-Hoc Networks with Coverage Sensing

    PubMed Central

    Chen, Lingyu; Luo, Wenbin; Liu, Chen; Hong, Xuemin; Shi, Jianghong

    2017-01-01

    The integration of ad hoc device-to-device (D2D) communications and open-access small cells can result in a networking paradigm called hybrid the ad hoc network, which is particularly promising in delivering delay-tolerant data. The capacity-delay performance of hybrid ad hoc networks has been studied extensively under a popular framework called scaling law analysis. These studies, however, do not take into account aspects of interference accumulation and queueing delay and, therefore, may lead to over-optimistic results. Moreover, focusing on the average measures, existing works fail to give finer-grained insights into the distribution of delays. This paper proposes an alternative analytical framework based on queueing theoretic models and physical interference models. We apply this framework to study the capacity-delay performance of a collaborative cellular D2D network with coverage sensing and two-hop relay. The new framework allows us to fully characterize the delay distribution in the transform domain and pinpoint the impacts of coverage sensing, user and base station densities, transmit power, user mobility and packet size on the capacity-delay trade-off. We show that under the condition of queueing equilibrium, the maximum throughput capacity per device saturates to an upper bound of 0.7239 λb/λu bits/s/Hz, where λb and λu are the densities of base stations and mobile users, respectively. PMID:28134769

  1. Cross-Layer Service Discovery Mechanism for OLSRv2 Mobile Ad Hoc Networks.

    PubMed

    Vara, M Isabel; Campo, Celeste

    2015-07-20

    Service discovery plays an important role in mobile ad hoc networks (MANETs). The lack of central infrastructure, limited resources and high mobility make service discovery a challenging issue for this kind of network. This article proposes a new service discovery mechanism for discovering and advertising services integrated into the Optimized Link State Routing Protocol Version 2 (OLSRv2). In previous studies, we demonstrated the validity of a similar service discovery mechanism integrated into the previous version of OLSR (OLSRv1). In order to advertise services, we have added a new type-length-value structure (TLV) to the OLSRv2 protocol, called service discovery message (SDM), according to the Generalized MANET Packet/Message Format defined in Request For Comments (RFC) 5444. Each node in the ad hoc network only advertises its own services. The advertisement frequency is a user-configurable parameter, so that it can be modified depending on the user requirements. Each node maintains two service tables, one to store information about its own services and another one to store information about the services it discovers in the network. We present simulation results, that compare our service discovery integrated into OLSRv2 with the one defined for OLSRv1 and with the integration of service discovery in Ad hoc On-demand Distance Vector (AODV) protocol, in terms of service discovery ratio, service latency and network overhead.

  2. Systematic lossy error protection for video transmission over wireless ad hoc networks

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoqing; Rane, Shantanu; Girod, Bernd

    2005-07-01

    Wireless ad hoc networks present a challenge for error-resilient video transmission, since node mobility and multipath fading result in time-varying link qualities in terms of packet loss ratio and available bandwidth. In this paper, we propose to use a systematic lossy error protection (SLEP) scheme for video transmission over wireless ad hoc networks. The transmitted video signal has two parts-a systematic portion consisting of a video sequence transmitted without channel coding over an error-prone channel, and error protection information consisting of a bitstream generated by Wyner-Ziv encoding of the video sequence. Using an end-to-end video distortion model in conjunction with online estimates of packet loss ratio and available bandwidth, the optimal Wyner-Ziv description can be selected dynamically according to current channel conditions. The scheme can also be applied to choose one path for transmission from amongst multiple candidate routes with varying available bandwidths and packet loss ratios, so that the expected end-to-end video distortion is maximized. Experimental results of video transmission over a simulated ad hoc wireless network shows that the proposed SLEP scheme outperforms the conventional application layer FEC approach in that it provides graceful degradation of received video quality over a wider range of packet loss ratios and is less susceptible to inaccuracy in the packet loss ratio estimation.

  3. A Lightweight Radio Propagation Model for Vehicular Communication in Road Tunnels.

    PubMed

    Qureshi, Muhammad Ahsan; Noor, Rafidah Md; Shamim, Azra; Shamshirband, Shahaboddin; Raymond Choo, Kim-Kwang

    2016-01-01

    Radio propagation models (RPMs) are generally employed in Vehicular Ad Hoc Networks (VANETs) to predict path loss in multiple operating environments (e.g. modern road infrastructure such as flyovers, underpasses and road tunnels). For example, different RPMs have been developed to predict propagation behaviour in road tunnels. However, most existing RPMs for road tunnels are computationally complex and are based on field measurements in frequency band not suitable for VANET deployment. Furthermore, in tunnel applications, consequences of moving radio obstacles, such as large buses and delivery trucks, are generally not considered in existing RPMs. This paper proposes a computationally inexpensive RPM with minimal set of parameters to predict path loss in an acceptable range for road tunnels. The proposed RPM utilizes geometric properties of the tunnel, such as height and width along with the distance between sender and receiver, to predict the path loss. The proposed RPM also considers the additional attenuation caused by the moving radio obstacles in road tunnels, while requiring a negligible overhead in terms of computational complexity. To demonstrate the utility of our proposed RPM, we conduct a comparative summary and evaluate its performance. Specifically, an extensive data gathering campaign is carried out in order to evaluate the proposed RPM. The field measurements use the 5 GHz frequency band, which is suitable for vehicular communication. The results demonstrate that a close match exists between the predicted values and measured values of path loss. In particular, an average accuracy of 94% is found with R2 = 0.86.

  4. 802.11s based multi-radio multi-channel mesh networking for fractionated spacecraft

    NASA Astrophysics Data System (ADS)

    Michel, Tony; Thapa, Bishal; Taylor, Steve

    802.11s is a new IEEE standard for mesh networking. It defines the protocols needed to build mobile ad hoc networks that operate over 802.11a, b, g and n waveforms running on inexpensive, and high performance commercial WiFi stations. We have developed a new capability to add to the 802.11s that uses multiple directional radio links that can operate simultaneously within a single mesh node. This is the basis of our multi-channel multi-radio mesh network used in the DARPA F6 program called F6Net. We have developed an analysis and emulation facility that lets us model the F6Net and evaluate the performance in a real world experimentation setup. This paper presents an “ Over-the-Air” experimentation testbed that uses standard Commercial Off-The-Shelf (COTS) 2.4GHz WiFi dongles in an indoor environment, and a shared-code simulation testbed that uses hardware simulated drivers within NS3's channel simulation facility to test 80211s network. To the best of our knowledge, this is the first work that provides a comprehensive evaluation platform with a full-fledged COTS hardware/software prototype to evaluate 802.11s network. Furthermore, we explain the design and development of multi-radio mesh extension for 802.11s that yields a robust and scalable mesh network suitable for clusters of LEO satellites.

  5. A Lightweight Radio Propagation Model for Vehicular Communication in Road Tunnels

    PubMed Central

    Shamim, Azra; Shamshirband, Shahaboddin; Raymond Choo, Kim-Kwang

    2016-01-01

    Radio propagation models (RPMs) are generally employed in Vehicular Ad Hoc Networks (VANETs) to predict path loss in multiple operating environments (e.g. modern road infrastructure such as flyovers, underpasses and road tunnels). For example, different RPMs have been developed to predict propagation behaviour in road tunnels. However, most existing RPMs for road tunnels are computationally complex and are based on field measurements in frequency band not suitable for VANET deployment. Furthermore, in tunnel applications, consequences of moving radio obstacles, such as large buses and delivery trucks, are generally not considered in existing RPMs. This paper proposes a computationally inexpensive RPM with minimal set of parameters to predict path loss in an acceptable range for road tunnels. The proposed RPM utilizes geometric properties of the tunnel, such as height and width along with the distance between sender and receiver, to predict the path loss. The proposed RPM also considers the additional attenuation caused by the moving radio obstacles in road tunnels, while requiring a negligible overhead in terms of computational complexity. To demonstrate the utility of our proposed RPM, we conduct a comparative summary and evaluate its performance. Specifically, an extensive data gathering campaign is carried out in order to evaluate the proposed RPM. The field measurements use the 5 GHz frequency band, which is suitable for vehicular communication. The results demonstrate that a close match exists between the predicted values and measured values of path loss. In particular, an average accuracy of 94% is found with R2 = 0.86. PMID:27031989

  6. Cosmology: Home of a fast radio burst

    NASA Astrophysics Data System (ADS)

    Lorimer, Duncan

    2016-02-01

    Our understanding of fast radio bursts -- intense pulses of radio waves -- and their use as cosmic probes promises to be transformed now that one burst has been associated with a galaxy of known distance from Earth. See Letter p.453

  7. Educational Radio: Directions in the Pacific.

    ERIC Educational Resources Information Center

    Reddy, Sachida

    1986-01-01

    This personal perspective on developments in educational radio broadcasting in some small island nations of the South Pacific discusses radio as a powerful teaching aid, curriculum development, educational communicators, printed support materials, costs, facilities duplication, and future trends. (MBR)

  8. Radio frequency power load and associated method

    NASA Technical Reports Server (NTRS)

    Sims, III, William Herbert (Inventor); Chavers, Donald Gregory (Inventor); Richeson, James J. (Inventor)

    2010-01-01

    A radio frequency power load and associated method. A radio frequency power load apparatus includes a container and a fluid having an ion source therein, the fluid being contained in the container. Two conductors are immersed in the fluid. A radio frequency transmission system includes a radio frequency transmitter, a radio frequency amplifier connected to the transmitter and a radio frequency power load apparatus connected to the amplifier. The apparatus includes a fluid having an ion source therein, and two conductors immersed in the fluid. A method of dissipating power generated by a radio frequency transmission system includes the steps of: immersing two conductors of a radio frequency power load apparatus in a fluid having an ion source therein; and connecting the apparatus to an amplifier of the transmission system.

  9. Kashima 34-m Radio Telescope

    NASA Technical Reports Server (NTRS)

    Sekido, Mamoru; Kawai, Eiji

    2013-01-01

    The Kashima 34-m radio telescope has been continuously operated and maintained by the National Institute of Information and Communications Technology (NICT) as a facility of the Kashima Space Technology Center (KSTC) in Japan. This brief report summarizes the status of this telescope, the staff, and activities during 2012.

  10. RadioActive101 Practices

    ERIC Educational Resources Information Center

    Brites, Maria José; Ravenscroft, Andrew; Dellow, James; Rainey, Colin; Jorge, Ana; Santos, Sílvio Correia; Rees, Angela; Auwärter, Andreas; Catalão, Daniel; Balica, Magda; Camilleri, Anthony F.

    2014-01-01

    In keeping with the overarching RadioActive101 (RA101) spirit and ethos, this report is the product of collaborative and joined-up thinking from within the European consortium spread across five countries. As such, it is not simply a single voice reporting on the experiences and knowledge gained during the project. Rather it is a range of…

  11. Hybrid spread spectrum radio system

    DOEpatents

    Smith, Stephen F [London, TN; Dress, William B [Camas, WA

    2010-02-09

    Systems and methods are described for hybrid spread spectrum radio systems. A method, includes receiving a hybrid spread spectrum signal including: fast frequency hopping demodulating and direct sequence demodulating a direct sequence spread spectrum signal, wherein multiple frequency hops occur within a single data-bit time and each bit is represented by chip transmissions at multiple frequencies.

  12. Radio Days in the Classroom

    ERIC Educational Resources Information Center

    Schuchat, Dan

    2005-01-01

    What social studies project challenges students with interdisciplinary learning, engages their various abilities and learning styles, offers them the opportunity for collaborative work-and encourages them to speak in strange voices? The answer is an eighth grade radio drama project. For most of the month of March 2004, the entire eighth grade at…

  13. Exploring the Dynamic Radio Sky

    NASA Astrophysics Data System (ADS)

    Mooley, Kunal; Horesh, A.; Hallinan, G.; Bourke, S.; Kulkarni, S. R.; Frail, D. A.; Ofek, E.

    2013-01-01

    The dynamic radio sky remains a rich area for discovery. Taking advantage of the new capabilities of the Jansky-VLA, we have carried out a near-real-time survey for radio transients in the SDSS Stripe 82 region. We observed 50 sq. deg. at 3 GHz at 3 epochs separated by 1 week and 1 month with 75uJy rms. In contrast to previous surveys, our survey is coupled with contemporaneous optical monitoring (with the Palomar Transient Factory) and rapid follow-up (at X-ray through radio frequencies), enabling physical interpretation of the detected transients. Supernovae, non-thermal tidal disruption events (TDEs), stellar flares, orphan long-duration Gamma Ray Bursts (GRBs) and NS-NS coalescence events are among those which we expect to see. Such detections will have large impact on several key questions such as the rate of TDEs, obscured supernovae, the beaming factor of GRBs and the rate of NS-NS mergers. This systematic search for transient and variable radio sources is meant to be a fore-runner of next-generation surveys planned for WSRT/Apertif, ASKAP, LOFAR and MeerKAT.

  14. Radio Monitoring of Protoplanetary Discs

    NASA Astrophysics Data System (ADS)

    Ubach, C.; Maddison, S. T.; Wright, C. M.; Wilner, D. J.; Lommen, D. J. P.; Koribalski, B.

    2017-01-01

    Protoplanetary disc systems observed at radio wavelengths often show excess emission above that expected from a simple extrapolation of thermal dust emission observed at short millimetre wavelengths. Monitoring the emission at radio wavelengths can be used to help disentangle the physical mechanisms responsible for this excess, including free-free emission from a wind or jet, and chromospheric emission associated with stellar activity. We present new results from a radio monitoring survey conducted with Australia Telescope Compact Array over the course of several years with observation intervals spanning days, months and years, where the flux variability of 11 T Tauri stars in the Chamaeleon and Lupus star forming regions was measured at 7 and 15 mm and 3 and 6 cm. Results show that for most sources are variable to some degree at 7 mm, indicating the presence of emission mechanisms other than thermal dust in some sources. Additionally, evidence of grain growth to cm-sized pebbles was found for some sources that also have signs of variable flux at 7 mm. We conclude that multiple processes contributing to the emission are common in T Tauri stars at 7 mm and beyond, and that a detection at a single epoch at radio wavelengths should not be used to determine all processes contributing to the emission.

  15. Low Frequency Radio Experiment (LORE)

    NASA Astrophysics Data System (ADS)

    Manoharan, P. K.; Naidu, Arun; Joshi, B. C.; Roy, Jayashree; Kate, G.; Pethe, Kaiwalya; Galande, Shridhar; Jamadar, Sachin; Mahajan, S. P.; Patil, R. A.

    2016-03-01

    In this paper, we present a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii, i.e., at frequencies below 30 MHz. The LORE can be complimentary to the planned Indian solar mission, “Aditya-L1” and its other payloads as well as synergistic to ground-based interplanetary scintillation (IPS) observations, which are routinely carried out by the Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and its particular suitability for providing measurements on the detailed time and frequency structure of fast drifting type-III and slow drifting type-II radio bursts with unprecedented time and frequency resolutions. We also brief the gonio-polarimetry, which is possible with better-designed antennas and state-of-the-art electronics, employing FPGAs and an intelligent data management system. These would enable us to make a wide range of studies, such as nonlinear plasma processes in the Sun-Earth distance, in-situ radio emission from coronal mass ejections (CMEs), interplanetary CME driven shocks, nature of ICMEs driving decelerating IP shocks and space weather effects of solar wind interaction regions.

  16. A Medley of Radio Winners.

    ERIC Educational Resources Information Center

    Raley, Nancy

    1984-01-01

    The potential for college use and development of radio stations is explored, and innovative and effective ideas from colleges' current efforts are presented. Topics covered include news services, phone-in features, student staff, college program highlights, foreign language programs, paid advertising, and public service announcements. (MSE)

  17. A repeating fast radio burst

    NASA Astrophysics Data System (ADS)

    Spitler, L. G.; Scholz, P.; Hessels, J. W. T.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J.; Ferdman, R. D.; Freire, P. C. C.; Kaspi, V. M.; Lazarus, P.; Lynch, R.; Madsen, E. C.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Seymour, A.; Stairs, I. H.; Stappers, B. W.; van Leeuwen, J.; Zhu, W. W.

    2016-03-01

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

  18. Workplace Training at SBS Radio.

    ERIC Educational Resources Information Center

    Simons, Lynette

    2001-01-01

    Notes that at Australia's Special Broadcasting Services Radio, workplace training is an essential requirement for on-air staff but a degree in journalism or communications is an enormous advantage. Describes several in-house accredited competency-based modules in journalism and broadcasting. (RS)

  19. Counselor Effectiveness Through Radio Communication.

    ERIC Educational Resources Information Center

    Tentoni, Stuart C.

    This study determined the effectiveness of the use of radio as a means of providing immediate feedback on student counselors in a practicum setting. Using a non-equivalent group experimental design, 10 experimental subjects were compared to 10 control subjects with respect to counselor effectiveness. The experimental subjects were given immediate…

  20. Digital Audio Radio Field Tests

    NASA Technical Reports Server (NTRS)

    Hollansworth, James E.

    1997-01-01

    Radio history continues to be made at the NASA Lewis Research Center with the beginning of phase two of Digital Audio Radio testing conducted by the Consumer Electronic Manufacturers Association (a sector of the Electronic Industries Association and the National Radio Systems Committee) and cosponsored by the Electronic Industries Association and the National Association of Broadcasters. The bulk of the field testing of the four systems should be complete by the end of October 1996, with results available soon thereafter. Lewis hosted phase one of the testing process, which included laboratory testing of seven proposed digital audio radio systems and modes (see the following table). Two of the proposed systems operate in two modes, thus making a total of nine systems for testing. These nine systems are divided into the following types of transmission: in-band on channel (IBOC), in-band adjacent channel (IBAC), and new bands - the L-band (1452 to 1492 MHz) and the S-band (2310 to 2360 MHz).