Science.gov

Sample records for downlink packet access

  1. Computer Accessibility Technology Packet.

    ERIC Educational Resources Information Center

    Department of Education, Washington, DC.

    This technology information packet includes information about the technical aspects of access to technology, legal obligations concerning technology and individuals with disabilities, and a list of resources for further information and assistance. A question and answer section addresses: barriers to educational technology for students with…

  2. Control with a random access protocol and packet dropouts

    NASA Astrophysics Data System (ADS)

    Wang, Liyuan; Guo, Ge

    2016-08-01

    This paper investigates networked control systems whose actuators communicate with the controller via a limited number of unreliable channels. The access to the channels is decided by a so-called group random access protocol, which is modelled as a binary Markov sequence. Data packet dropouts in the channels are modelled as independent Bernoulli processes. For such systems, a systematic characterisation for controller synthesis is established and stated in terms of the transition probabilities of the Markov protocol and the packet dropout probabilities. The results are illustrated via a numerical example.

  3. Random access with adaptive packet aggregation in LTE/LTE-A.

    PubMed

    Zhou, Kaijie; Nikaein, Navid

    While random access presents a promising solution for efficient uplink channel access, the preamble collision rate can significantly increase when massive number of devices simultaneously access the channel. To address this issue and improve the reliability of the random access, an adaptive packet aggregation method is proposed. With the proposed method, a device does not trigger a random access for every single packet. Instead, it starts a random access when the number of aggregated packets reaches a given threshold. This method reduces the packet collision rate at the expense of an extra latency, which is used to accumulate multiple packets into a single transmission unit. Therefore, the tradeoff between packet loss rate and channel access latency has to be carefully selected. We use semi-Markov model to derive the packet loss rate and channel access latency as functions of packet aggregation number. Hence, the optimal amount of aggregated packets can be found, which keeps the loss rate below the desired value while minimizing the access latency. We also apply for the idea of packet aggregation for power saving, where a device aggregates as many packets as possible until the latency constraint is reached. Simulations are carried out to evaluate our methods. We find that the packet loss rate and/or power consumption are significantly reduced with the proposed method.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  5. Cross-Layer Design for Downlink Multihop Cloud Radio Access Networks With Network Coding

    NASA Astrophysics Data System (ADS)

    Liu, Liang; Yu, Wei

    2017-04-01

    There are two fundamentally different fronthaul techniques in the downlink communication of cloud radio access network (C-RAN): the data-sharing strategy and the compression-based strategy. Under the former strategy, each user's message is multicast from the central processor (CP) to all the serving remote radio heads (RRHs) over the fronthaul network, which then cooperatively serve the users through joint beamforming; while under the latter strategy, the user messages are first beamformed then quantized at the CP, and the compressed signal is unicast to the corresponding RRH, which then decompresses its received signal for wireless transmission. Previous works show that in general the compression-based strategy outperforms the data-sharing strategy. This paper, on the other hand, point s out that in a C-RAN model where the RRHs are connected to the CP via multi-hop routers, data-sharing can be superior to compression if the network coding technique is adopted for multicasting user messages to the cooperating RRHs, and the RRH's beamforming vectors, the user-RRH association, and the network coding design over the fronthaul network are jointly optimized based on the techniques of sparse optimization an d successive convex approximation. This is in comparison to the compression-based strategy, where information is unicast over the fronthaul network by simple routing, and the RRH's compression noise covariance and beamforming vectors, as well as the routing strategy over the fronthaul network are jointly optimized based on the successive convex approximation technique. The observed gain in overall network throughput is due to that information multicast is more efficient than information unicast over the multi-hop fronthaul of a C-RAN.

  6. Description and Simulation of a Fast Packet Switch Architecture for Communication Satellites

    NASA Technical Reports Server (NTRS)

    Quintana, Jorge A.; Lizanich, Paul J.

    1995-01-01

    The NASA Lewis Research Center has been developing the architecture for a multichannel communications signal processing satellite (MCSPS) as part of a flexible, low-cost meshed-VSAT (very small aperture terminal) network. The MCSPS architecture is based on a multifrequency, time-division-multiple-access (MF-TDMA) uplink and a time-division multiplex (TDM) downlink. There are eight uplink MF-TDMA beams, and eight downlink TDM beams, with eight downlink dwells per beam. The information-switching processor, which decodes, stores, and transmits each packet of user data to the appropriate downlink dwell onboard the satellite, has been fully described by using VHSIC (Very High Speed Integrated-Circuit) Hardware Description Language (VHDL). This VHDL code, which was developed in-house to simulate the information switching processor, showed that the architecture is both feasible and viable. This paper describes a shared-memory-per-beam architecture, its VHDL implementation, and the simulation efforts.

  7. Resource allocation for downlink multiuser video transmission over wireless lossy networks.

    PubMed

    Maani, Ehsan; Pahalawatta, Peshala V; Berry, Randall; Pappas, Thrasyvoulos N; Katsaggelos, Aggelos K

    2008-09-01

    Demand for multimedia services, such as video streaming over wireless networks, has grown dramatically in recent years. The downlink transmission of multiple video sequences to multiple users over a shared resource-limited wireless channel, however, is a daunting task. Among the many challenges in this area are the time-varying channel conditions, limited available resources, such as bandwidth and power, and the different transmission requirements of different video content. This work takes into account the time-varying nature of the wireless channels, as well as the importance of individual video packets, to develop a cross-layer resource allocation and packet scheduling scheme for multiuser video streaming over lossy wireless packet access networks. Assuming that accurate channel feedback is not available at the scheduler, random channel losses combined with complex error concealment at the receiver make it impossible for the scheduler to determine the actual distortion of the sequence at the receiver. Therefore, the objective of the optimization is to minimize the expected distortion of the received sequence, where the expectation is calculated at the scheduler with respect to the packet loss probability in the channel. The expected distortion is used to order the packets in the transmission queue of each user, and then gradients of the expected distortion are used to efficiently allocate resources across users. Simulations show that the proposed scheme performs significantly better than a conventional content-independent scheme for video transmission.

  8. Downlink Data Multiplexer

    NASA Technical Reports Server (NTRS)

    Holland, Douglas; Steele, Glen F.; Romero, Denise M.; Koudelka, Robert David

    2004-01-01

    A multiplexer/demultiplexer system has been developed to enable the transmission, over a single channel, of four data streams generated by a variety of sources at different (including variable) bit rates. In the original intended application, replicas of this multiplexer/demultiplexer system would be incorporated into the spacecraft-to-ground communication systems of the space shuttles. The multiplexer of each system would be installed in the spacecraft, where it would acquire and process data from such sources as commercial digital camcorders, video tape recorders, and the spacecraft telemetry system. The demultiplexer of each system would be installed in a ground station. Purely terrestrial systems of similar design could be attractive for use in situations in which there are requirements to transmit multiple streams of high-quality video data and possibly other data over single channels. The figure is a block diagram of the multiplexer as configured to process data received via three fiber-optic channels like those of the International Space Station and one electrical-cable channel that conforms to the Institute of Electrical and Electronic Engineers (IEEE) 1394 standard. (This standard consists of specifications of a high-speed serial data interface, the physical layer of which includes a cable known in the art as "FireWire." An IEEE 1394 interface can also transfer power between the components to which it is connected.) The fiber-optic channels carry packet and/or bit-stream signals that conform to the standards of the Consultative Committee for Space Data Systems (CCSDS). The IEEE 1394 interface accepts an isochronous signal like that from a digital camcorder or a video tape recorder. The processing of the four input data streams to combine them into one output stream is governed by a statistical multiplexing algorithm that features a flow-control capability and makes it possible to utilize the transmission channel with nearly 100-percent efficiency. This

  9. Two-Level Scheduling for Video Transmission over Downlink OFDMA Networks

    PubMed Central

    Tham, Mau-Luen

    2016-01-01

    This paper presents a two-level scheduling scheme for video transmission over downlink orthogonal frequency-division multiple access (OFDMA) networks. It aims to maximize the aggregate quality of the video users subject to the playback delay and resource constraints, by exploiting the multiuser diversity and the video characteristics. The upper level schedules the transmission of video packets among multiple users based on an overall target bit-error-rate (BER), the importance level of packet and resource consumption efficiency factor. Instead, the lower level renders unequal error protection (UEP) in terms of target BER among the scheduled packets by solving a weighted sum distortion minimization problem, where each user weight reflects the total importance level of the packets that has been scheduled for that user. Frequency-selective power is then water-filled over all the assigned subcarriers in order to leverage the potential channel coding gain. Realistic simulation results demonstrate that the proposed scheme significantly outperforms the state-of-the-art scheduling scheme by up to 6.8 dB in terms of peak-signal-to-noise-ratio (PSNR). Further test evaluates the suitability of equal power allocation which is the common assumption in the literature. PMID:26906398

  10. Enhanced Handoff Scheme for Downlink-Uplink Asymmetric Channels in Cellular Systems

    PubMed Central

    2013-01-01

    In the latest cellular networks, data services like SNS and UCC can create asymmetric packet generation rates over the downlink and uplink channels. This asymmetry can lead to a downlink-uplink asymmetric channel condition being experienced by cell edge users. This paper proposes a handoff scheme to cope effectively with downlink-uplink asymmetric channels. The proposed handoff scheme exploits the uplink channel quality as well as the downlink channel quality to determine the appropriate timing and direction of handoff. We first introduce downlink and uplink channel models that consider the intercell interference, to verify the downlink-uplink channel asymmetry. Based on these results, we propose an enhanced handoff scheme that exploits both the uplink and downlink channel qualities to reduce the handoff-call dropping probability and the service interruption time. The simulation results show that the proposed handoff scheme reduces the handoff-call dropping probability about 30% and increases the satisfaction of the service interruption time requirement about 7% under high-offered load, compared to conventional mobile-assisted handoff. Especially, the proposed handoff scheme is more efficient when the uplink QoS requirement is much stricter than the downlink QoS requirement or uplink channel quality is worse than downlink channel quality. PMID:24501576

  11. A Wideband Satcom Based Avionics Network with CDMA Uplink and TDM Downlink

    NASA Technical Reports Server (NTRS)

    Agrawal, D.; Johnson, B. S.; Madhow, U.; Ramchandran, K.; Chun, K. S.

    2000-01-01

    The purpose of this paper is to describe some key technical ideas behind our vision of a future satcom based digital communication network for avionics applications The key features of our design are as follows: (a) Packetized transmission to permit efficient use of system resources for multimedia traffic; (b) A time division multiplexed (TDM) satellite downlink whose physical layer is designed to operate the satellite link at maximum power efficiency. We show how powerful turbo codes (invented originally for linear modulation) can be used with nonlinear constant envelope modulation, thus permitting the satellite amplifier to operate in a power efficient nonlinear regime; (c) A code division multiple access (CDMA) satellite uplink, which permits efficient access to the satellite from multiple asynchronous users. Closed loop power control is difficult for bursty packetized traffic, especially given the large round trip delay to the satellite. We show how adaptive interference suppression techniques can be used to deal with the ensuing near-far problem; (d) Joint source-channel coding techniques are required both at the physical and the data transport layer to optimize the end-to-end performance. We describe a novel approach to multiple description image encoding at the data transport layer in this paper.

  12. Downlink data multiplexer

    NASA Technical Reports Server (NTRS)

    Holland, S. Douglas (Inventor); Steele, Glen F. (Inventor); Romero, Denise M. (Inventor); Koudelka, Robert David (Inventor)

    2008-01-01

    A data multiplexer that accommodates both industry standard CCSDS data packets and bits streams and standard IEEE 1394 data is described. The multiplexer provides a statistical allotment of bandwidth to the channels in turn, preferably four, but expandable in increments of four up to sixteen. A microcontroller determines bandwidth requested by the plurality of channels, as well as the bandwidth available, and meters out the available bandwidth on a statistical basis employing flow control to the input channels.

  13. Performance of a random access packet network with time-capture capability

    NASA Astrophysics Data System (ADS)

    Lin, Y. H.

    The Joint Tactical Information Distribution System (JTIDS) is applied to a digital network supporting the command, control and communication requirements of 105 highly mobile users. User data traffic is bursty and the slotted ALOHA channel access scheme is therefore employed. This paper focuses on the determination of JTIDS system performance in this particular application. Emphasis is directed at the specific time-capture capability of JTIDS. Significant system performance parameters are quantified with analysis and simulation.

  14. Performance of a random access packet network with time-capture capability

    NASA Technical Reports Server (NTRS)

    Lin, Y. H.

    1983-01-01

    The Joint Tactical Information Distribution System (JTIDS) is applied to a digital network supporting the command, control and communication requirements of 105 highly mobile users. User data traffic is bursty and the slotted ALOHA channel access scheme is therefore employed. This paper focuses on the determination of JTIDS system performance in this particular application. Emphasis is directed at the specific time-capture capability of JTIDS. Significant system performance parameters are quantified with analysis and simulation.

  15. Improved MLWDF scheduler for LTE downlink transmission

    NASA Astrophysics Data System (ADS)

    Obinna Nnamani, Christantus; Anioke, Chidera Linda; Ikechukwu Ani, Cosmas

    2016-11-01

    In long-term evolution (LTE) downlink transmission, modified least weighted delay first (MLWDF) scheduler is a quality of service (QoS) aware scheduling scheme for real-time (RT) services. Nevertheless, MLWDF performs below optimal among the trade-off between strict delay and loss restraints of RT and non-RT traffic flows, respectively. This is further worsened with the implementation of hybrid automatic retransmission request (HARQ). As these restraints grow unabated with increasing number of user demands, the performance of MLWDF further reduces. In order to ameliorate this situation, there is a need to directly incorporate the variations in user demands and HARQ implementation as parameters to the MLWDF scheduler. In this work, an improvement to the MLWDF scheduler is proposed. The improvement entails adding two novel parameters that characterise user demand and HARQ implementation. The scheduler was tested using varying three classes of service in QoS class identifiers (QCIs) table standardised by Third Generation Partnership Project for LTE network to characterise different services. It was also tested on the basis of packet prioritisation. The proposed scheduler was simulated with LTE-SIM simulator and compared with the MLWDF and proportional fairness schedulers. In terms of delay, throughput and packet loss ratio; the proposed scheduler increased overall system performance.

  16. Selecting Pixels for Kepler Downlink

    NASA Technical Reports Server (NTRS)

    Bryson, Stephen T.; Jenkins, Jon M.; Klaus, Todd C.; Cote, Miles T.; Quintana, Elisa V.; Hall, Jennifer R.; Ibrahim, Khadeejah; Chandrasekaran, Hema; Caldwell, Douglas A.; Van Cleve, Jeffrey E.; Haas, Michael R.

    2010-01-01

    The Kepler mission monitors > 100,000 stellar targets using 42 2200 1024 pixel CCDs. Bandwidth constraints prevent the downlink of all 96 million pixels per 30-minute cadence, so the Kepler spacecraft downlinks a specified collection of pixels for each target. These pixels are selected by considering the object brightness, background and the signal-to-noise of each pixel, and are optimized to maximize the signal-to-noise ratio of the target. This paper describes pixel selection, creation of spacecraft apertures that efficiently capture selected pixels, and aperture assignment to a target. Diagnostic apertures, short-cadence targets and custom specified shapes are discussed.

  17. Spatial Reuse through Dynamic Power and Routing Control in Common-Channel Random-Access Packet Radio Networks

    DTIC Science & Technology

    1988-08-01

    environment and the thoughtful discussions about packet radio networks. In addition, many thoughtful comments were provided by Mel Bebee , Dr. Ray Bittel, and...the AT&T Network IEEE International Conference on Communications (ICC), June 1987, pages 19B.5.1-19B.5.7 Bebee88 Mel Bebee Personal Communications

  18. Packet Radio: An Alternative Way to Connect.

    ERIC Educational Resources Information Center

    Lucas, Larry W.

    1995-01-01

    Explains packet radio as a form of telecomputing in which digital data is transported via radio waves instead of telephone lines or other cabling, and describes how it can be used by students to access the Internet. Highlights include packet bulletin board systems and equipment needed for a packet radio station. (LRW)

  19. Spacecraft Reed-Solomon downlink module

    NASA Technical Reports Server (NTRS)

    Luong, Huy H. (Inventor); Donaldson, James A. (Inventor); Wood, Steven H. (Inventor)

    1998-01-01

    Apparatus and method for providing downlink frames to be transmitted from a spacecraft to a ground station. Each downlink frame includes a synchronization pattern and a transfer frame. The apparatus may comprise a monolithic Reed-Solomon downlink (RSDL) encoding chip coupled to data buffers for storing transfer frames. The RSKL chip includes a timing device, a bus interface, a timing and control unit, a synchronization pattern unit, and a Reed-Solomon encoding unit, and a bus arbiter.

  20. GUIDANCE PACKET.

    ERIC Educational Resources Information Center

    Modern Language Association of America, New York, NY.

    THIS PACKET PROVIDES VOCATIONAL AND ACADEMIC ADVICE TO THE LANGUAGE LEARNER AND USEFUL INFORMATION ABOUT LANGUAGE LEARNING TO TEACHERS, COUNSELORS, AND ADMINISTRATORS. THE DOCUMENTS, PUBLISHED FROM 1963 TO 1967, ARE--(1) "VOCATIONAL OPPORTUNITIES FOR FOREIGN LANGUAGE STUDENTS" BY GILBERT C. KETTELKAMP, (2) "ADVICE TO THE LANGUAGE LEARNER" BY…

  1. Information Packet.

    ERIC Educational Resources Information Center

    Cable Television Information Center, Washington, DC.

    Documents included in the packet are Federal Communications Commission (FCC) releases dealing with cable television and similar notices from other organizations. Among these are an interpretation of the FCC local origination decision of Dec. 9, 1974, explaining the repeal of the requirement that small cable systems originate programing while…

  2. Extensible packet processing architecture

    DOEpatents

    Robertson, Perry J.; Hamlet, Jason R.; Pierson, Lyndon G.; Olsberg, Ronald R.; Chun, Guy D.

    2013-08-20

    A technique for distributed packet processing includes sequentially passing packets associated with packet flows between a plurality of processing engines along a flow through data bus linking the plurality of processing engines in series. At least one packet within a given packet flow is marked by a given processing engine to signify by the given processing engine to the other processing engines that the given processing engine has claimed the given packet flow for processing. A processing function is applied to each of the packet flows within the processing engines and the processed packets are output on a time-shared, arbitered data bus coupled to the plurality of processing engines.

  3. Program and Product Evaluation: An Information Packet.

    ERIC Educational Resources Information Center

    Ewy, Robert W.; Chase, Cheryl

    This is one of a series of information packets developed as part of Project ACCESS to aid Colorado teachers, educational administrators, and school board members in implementing local educational improvement plans as mandated by Colorado's Educational Accountability Act of 1971. This particular information packet provides a framework for…

  4. Relating Downlink Data Products to Uplink Commands

    NASA Technical Reports Server (NTRS)

    Backes, Paul; Norris, Jeffrey; Powell, Mark

    2003-01-01

    An improved data-labeling system provides for automatic association of data products of an exploratory robot (downlink information) with previously transmitted commands (uplink information) that caused the robot to gather the data. Such association is essential to correct and timely analysis of the data products -- including, for example, association of the data with the correct targets. The system was developed for use on Mars Rover missions during the next few years. The system could also be adapted to terrestrial exploratory telerobots for which delays between commands and data returns are long enough to give rise to questions as to which commands resulted in which data returns. The main advantage of this system over prior data-labeling systems is that given a downlink data product, the uplink command and sequence hierarchy that produced it are automatically provided, and given an uplink sequence and command, the downlink data products that it produced are automatically provided.

  5. Simplifying operations with an uplink/downlink integration toolkit

    NASA Technical Reports Server (NTRS)

    Murphy, Susan C.; Miller, Kevin J.; Guerrero, Ana Maria; Joe, Chester; Louie, John J.; Aguilera, Christine

    1994-01-01

    The Operations Engineering Lab (OEL) at JPL has developed a simple, generic toolkit to integrate the uplink/downlink processes, (often called closing the loop), in JPL's Multimission Ground Data System. This toolkit provides capabilities for integrating telemetry verification points with predicted spacecraft commands and ground events in the Mission Sequence Of Events (SOE) document. In the JPL ground data system, the uplink processing functions and the downlink processing functions are separate subsystems that are not well integrated because of the nature of planetary missions with large one-way light times for spacecraft-to-ground communication. Our new closed-loop monitoring tool allows an analyst or mission controller to view and save uplink commands and ground events with their corresponding downlinked telemetry values regardless of the delay in downlink telemetry and without requiring real-time intervention by the user. An SOE document is a time-ordered list of all the planned ground and spacecraft events, including all commands, sequence loads, ground events, significant mission activities, spacecraft status, and resource allocations. The SOE document is generated by expansion and integration of spacecraft sequence files, ground station allocations, navigation files, and other ground event files. This SOE generation process has been automated within the OEL and includes a graphical, object-oriented SOE editor and real-time viewing tool running under X/Motif. The SOE toolkit was used as the framework for the integrated implementation. The SOE is used by flight engineers to coordinate their operations tasks, serving as a predict data set in ground operations and mission control. The closed-loop SOE toolkit allows simple, automated integration of predicted uplink events with correlated telemetry points in a single SOE document for on-screen viewing and archiving. It automatically interfaces with existing real-time or non real-time sources of information, to

  6. Throughput and packet delay analysis for the H-network - CSMA/CD with adaptive and nonadaptive backoff protocols. [Carrier Sense Multiple-Access

    NASA Technical Reports Server (NTRS)

    Dimopoulos, Nikitas J.

    1987-01-01

    The structure of a high-data-rate (about 7 Mbytes/sec) local area network named the H-Network is described which is used to provide point to point analysis and broadcast communication in a multiprocessor environment, the Homogeneous Multiprocessor (Dimopoulos, 1983). The throughput and packet delay characteristics for the H-Network operating under CSMA/CD are presented, using adaptive and nonadaptive backoff protocols. The network is found to perform quite well, with an average utilization factor of over 60 percent and a maximum packet delay of less than 500 microsec for the case of 10 competing stations.

  7. B-ISBN Onboard Processing Fast Packet Switch Developed

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Future satellite communications applications will require a packet-switched onboard satellite processing system to route packets at very high speeds from uplink beams to different downlink beams. The rapid emergence of point-to-multipoint services, and the important role of satellites in a national and global information infrastructure, makes the multicast function essential to a fast packet switch (FPS). NASA Lewis Research Center's Digital System Technology Branch has been studying possible architectures for high-speed onboard-processing satellite systems. As part of this research, COMSAT Laboratories developed a broadband integrated services digital network (B-ISDN) fast packet switch for Lewis that was delivered on December 1994. The fast packet switch consists of eight inputs and eight outputs that can receive and transmit data, respectively, at a rate of 155 Mbps. The switch features multiple priorities (three) and multiple-size (three) satellite virtual cells that are similar to ATM cells in length (52 bytes). In addition, the fast packet switch features a congestion-control algorithm that allows users to set different thresholds for individual destination ports, thus throttling back the traffic from the transmitting port.

  8. Performance Improvement of Proportional Fairness-Based Resource Allocation in OFDMA Downlink Systems

    NASA Astrophysics Data System (ADS)

    Ruangchaijatupon, Nararat; Ji, Yusheng

    We have developed a novel downlink packet scheduling scheme for a multiuser OFDMA system in which a subchannel can be time-multiplexed among multiple users. This scheme which is called Matrixed-based Proportional Fairness can provide a high system throughput while ensuring fairness. The scheme is based on a Proportional Fairness (PF) utility function and can be applied to any of the PF-based schedulers. Our scheduler explores multichannel multiuser diversity by using a two-dimensional matrix combining user selection, subchannel assignment, and time slot allocation. Furthermore, unlike other PF-based schemes, our scheme considers finitely backlogged queues during the time slot allocation. By doing so, it can exploit multichannel multiuser diversity to utilize bandwidth efficiently and with throughput fairness. Additionally, fairness in the time domain is enhanced by limiting the number of allocated time slots. Intensive simulations considering finitely backlogged queues and user mobility prove the scheme's effectiveness.

  9. Downlinks for DBS - Design and engineering considerations

    NASA Astrophysics Data System (ADS)

    Blecker, M.; Martin, E. R.

    1985-01-01

    The subsystem interrelationships and design parameters choice procedures for a DBS downlink design are discussed from a business decisions point of view. The image quality is determined by customer satisfaction, which is translated to a required carrier/noise (C/N) ratio. The C/N ratio defines acceptable levels of signal fading, a subjective value which is modified by the demographics of the service area. Increasing the satellite on-board transmitting power to meet acceptable broadcast reliability places burdens on the start-up capitalization of the business. Larger receiving antennas in rural areas ameliorates some of the power requirements. The dish size, however, affects the labor costs of installation, but must be kept small enough to be used in heavily populated areas. The satellites must be built, as far as is possible, from off-the-shelf components to keep costs down. Design selections for a sample complete system are listed.

  10. 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

  11. On-board B-ISDN fast packet switching architectures. Phase 2: Development. Proof-of-concept architecture definition report

    NASA Technical Reports Server (NTRS)

    Shyy, Dong-Jye; Redman, Wayne

    1993-01-01

    For the next-generation packet switched communications satellite system with onboard processing and spot-beam operation, a reliable onboard fast packet switch is essential to route packets from different uplink beams to different downlink beams. The rapid emergence of point-to-point services such as video distribution, and the large demand for video conference, distributed data processing, and network management makes the multicast function essential to a fast packet switch (FPS). The satellite's inherent broadcast features gives the satellite network an advantage over the terrestrial network in providing multicast services. This report evaluates alternate multicast FPS architectures for onboard baseband switching applications and selects a candidate for subsequent breadboard development. Architecture evaluation and selection will be based on the study performed in phase 1, 'Onboard B-ISDN Fast Packet Switching Architectures', and other switch architectures which have become commercially available as large scale integration (LSI) devices.

  12. A connectorized fiber downlink for FMOS

    NASA Astrophysics Data System (ADS)

    Murray, Graham J.; Luke, Peter; Robertson, David J.; Tamura, Naoyuki

    2003-04-01

    A consortium of UK, Australian and Japanese groups is designing a fibre-fed near IR (J & H band) multi-object spectrograph (FMOS) for the Subaru telescope. The prime focus of the telescope will support a 400-fibre multi-object positioning system, ECHIDNA. However, the IR spectrographs (of which there are two) are to be located close to the Nasmyth platform, so an interconnecting optical feed is required to deliver light from ECHIDNA. The Astronomical Instrumentation Group at the University of Durham is undertaking the design and construction of a suitable fibre-optic downlink. To allow the prime focus unit that houses ECHIDNA to be removed, the fibre cable is to include a connectorized break, located at the telescope top-end ring. The optical design also calls for a change in focal ratio from that delivered by ECHIDNA in order to couple light to the spectrograph with the greatest efficiency. This will be achieved in the connector coupling by means of an array of high-efficiency GRIN microlenses. The connector will additionally incorporate an integral back-illumination system for on-telescope testing and calibration. This paper describes the preliminary design of the fibre system that is to be constructed in Durham.

  13. Intrinsic interference mitigating coordinated beamforming for the FBMC/OQAM based downlink

    NASA Astrophysics Data System (ADS)

    Cheng, Yao; Li, Peng; Haardt, Martin

    2014-12-01

    In this work, we propose intrinsic interference mitigating coordinated beamforming (IIM-CBF)-based transmission strategies for the downlink of multi-user multiple-input-multiple-out (MIMO) systems and coordinated multi-point (CoMP) systems where filter bank based multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM) is employed. Our goal is to alleviate the dimensionality constraint imposed on the state-of-the-art solutions for FBMC/OQAM-based space division multiple access that the total number of receive antennas of the users must not exceed the number of transmit antennas at the base station. First, two IIM-CBF algorithms are developed for a single-cell multi-user MIMO downlink system. The central idea is to jointly and iteratively calculate the precoding matrix and decoding matrix for each subcarrier to mitigate the multi-user interference as well as the intrinsic interference inherent in FBMC/OQAM-based systems. Second, for a CoMP downlink scenario where partial coordination among the base stations is considered, the application of coordinated beamforming-based transmission schemes is further investigated. An appropriate IIM-CBF technique is proposed. Simulation results show that when the number of transmit antennas at the base station is equal to the total number of receive antennas of the users, the proposed IIM-CBF algorithm outperforms the existing transmission strategies for FBMC/OQAM-based multi-user MIMO downlink systems. Moreover, we evaluate the performances of the IIM-CBF schemes in the downlink of multi-user MIMO systems and CoMP systems where the total number of receive antennas of users exceeds the number of transmit antennas at the base station. It is observed that by employing the IIM-CBF techniques, FBMC/OQAM systems achieve a similar bit error rate (BER) performance as its orthogonal frequency division multiplexing with the cyclic prefix insertion (CP-OFDM)-based counterpart while exhibiting superiority in terms of a higher

  14. PROGRAMMED LEARNING PACKET.

    ERIC Educational Resources Information Center

    Modern Language Association of America, New York, NY.

    MATERIALS CONCERNING PROGRAMED INSTRUCTION IN FOREIGN LANGUAGES, PUBLISHED FROM 1960 TO 1967, ARE COLLECTED IN THIS PACKET FOR LANGUAGE TEACHERS AND PERSONS INTERESTED IN THE FUTURE USES OF THE LANGUAGE LABORATORY. INCLUDED ARE--(1) "PROGRAMED LEARNING OF A SECOND LANGUAGE" BY HARLAN LANE, (2) "A PRIMER OF PROGRAMED INSTRUCTION IN FOREIGN LANGUAGE…

  15. Amelia Earhart Learning Packet.

    ERIC Educational Resources Information Center

    Civil Air Patrol, Maxwell AFB, AL.

    The feats of individuals who have made history in the aerospace world are often misunderstood and soon ignored or forgotten after the first notoriety has been achieved. Amelia Earhart was selected as the subject for this learning packet because of her brilliant accomplishments on the world of flight, a persistent desire to determine what really…

  16. Hoover Dam Learning Packet.

    ERIC Educational Resources Information Center

    Bureau of Reclamation (Dept. of Interior), Washington, DC.

    This learning packet provides background information about Hoover Dam (Nevada) and the surrounding area. Since the dam was built at the height of the Depression in 1931, people came from all over the country to work on it. Because of Hoover Dam, the Colorado River was controlled for the first time in history and farmers in Nevada, California, and…

  17. 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…

  18. Optimized Scheduling Technique of Null Subcarriers for Peak Power Control in 3GPP LTE Downlink

    PubMed Central

    Park, Sang Kyu

    2014-01-01

    Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system. PMID:24883376

  19. Optimized scheduling technique of null subcarriers for peak power control in 3GPP LTE downlink.

    PubMed

    Cho, Soobum; Park, Sang Kyu

    2014-01-01

    Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system.

  20. Novel method of channel estimation for WCDMA downlink

    NASA Astrophysics Data System (ADS)

    Sheng, Bin; You, XiaoHu

    2001-10-01

    A novel scheme for channel estimation is proposed in this paper for WCDMA Downlink where a pilot channel is simultaneously transmitted with a dada traffic channel. The proposed scheme exploits channel information in both pilot and data traffic channels by combining channel estimates from these two channels. It is demonstrated by computer simulations that the performance of the Rake receiver is improved obviously.

  1. Optical packet switching

    NASA Astrophysics Data System (ADS)

    Shekel, Eyal; Ruschin, Shlomo; Majer, Daniel; Levy, Jeff; Matmon, Guy; Koenigsberg, Lisa; Vecht, Jacob; Geron, Amir; Harlavan, Rotem; Shfaram, Harel; Arbel, Arnon; McDermott, Tom; Brewer, Tony

    2005-02-01

    We report here a scalable, multichassis, 6.3 terabit core router, which utilizes our proprietary optical switch. The router is commercially available and deployed in several customer sites. Our solution combines optical switching with electronic routing. An internal optical packet switching network interconnects the router"s electronic line cards, where routing and buffering functions take place electronically. The system architecture and performance will be described. The optical switch is based on Optical Phased Array (OPA) technology. It is a 64 x 64, fully non-blocking, optical crossbar switch, capable of switching in a fraction of a nanosecond. The basic principles of operation will be explained. Loss and crosstalk results will be presented, as well as the results of BER measurements of a 160 Gbps transmission through one channel. Basic principles of operation and measured results will be presented for the burst-mode-receivers, arbitration algorithm and synchronization. Finally, we will present some of our current research work on a next-generation optical switch. The technological issues we have solved in our internal optical packet network can have broad applicability to any global optical packet network.

  2. A novel downlink scheduling strategy for traffic communication system based on TD-LTE technology.

    PubMed

    Chen, Ting; Zhao, Xiangmo; Gao, Tao; Zhang, Licheng

    2016-01-01

    There are many existing classical scheduling algorithms which can obtain better system throughput and user equality, however, they are not designed for traffic transportation environment, which cannot consider whether the transmission performance of various information flows could meet comprehensive requirements of traffic safety and delay tolerance. This paper proposes a novel downlink scheduling strategy for traffic communication system based on TD-LTE technology, which can perform two classification mappings for various information flows in the eNodeB: firstly, associate every information flow packet with traffic safety importance weight according to its relevance to the traffic safety; secondly, associate every traffic information flow with service type importance weight according to its quality of service (QoS) requirements. Once the connection is established, at every scheduling moment, scheduler would decide the scheduling order of all buffers' head of line packets periodically according to the instant value of scheduling importance weight function, which calculated by the proposed algorithm. From different scenario simulations, it can be verified that the proposed algorithm can provide superior differentiated transmission service and reliable QoS guarantee to information flows with different traffic safety levels and service types, which is more suitable for traffic transportation environment compared with the existing popularity PF algorithm. With the limited wireless resource, information flow closed related to traffic safety will always obtain priority scheduling right timely, which can help the passengers' journey more safe. Moreover, the proposed algorithm cannot only obtain good flow throughput and user fairness which are almost equal to those of the PF algorithm without significant differences, but also provide better realtime transmission guarantee to realtime information flow.

  3. A downlink and uplink alignment scheme for power saving in IEEE 802.16 protocol.

    PubMed

    Chen, Jenhui; Tarn, Woei-Hwa; Lee, Jiann-Der

    2014-01-01

    This study shows the problem of power saving mechanism (PSM) that sleep intervals of uplink (UL) connections do not synchronize with sleep intervals of downlink (DL) connections. That is, the energy of a mobile station (MS) is not really saved if the DL connections are in the sleep mode while the UL connections are in normal mode, and vice versa. To avoid the asynchronism of power saving (PS) between UL and DL connections, we invent a mechanism of DL connections regulating UL connections, called DL and UL Alignment (DUAL) scheme, to improve the energy efficiency for PS. Considering that the buffer size of MS is limited, DUAL uses the mean packet arrival rate of UL λ u and a relatively safe threshold of buffer size Q T as the parameters to estimate the maximum allowable waiting time to align the UL with the DL connections. To analyze the performance of DUAL, a system model of PS is proposed to evaluate the performance of DUAL under different conditions. The correctness of performance analysis of DUAL is validated by using simulation with realistic parameters. Numerical experiments show that DUAL improves the energy conservation significantly when UL traffic is greater than DL traffic.

  4. A Downlink and Uplink Alignment Scheme for Power Saving in IEEE 802.16 Protocol

    PubMed Central

    2014-01-01

    This study shows the problem of power saving mechanism (PSM) that sleep intervals of uplink (UL) connections do not synchronize with sleep intervals of downlink (DL) connections. That is, the energy of a mobile station (MS) is not really saved if the DL connections are in the sleep mode while the UL connections are in normal mode, and vice versa. To avoid the asynchronism of power saving (PS) between UL and DL connections, we invent a mechanism of DL connections regulating UL connections, called DL and UL Alignment (DUAL) scheme, to improve the energy efficiency for PS. Considering that the buffer size of MS is limited, DUAL uses the mean packet arrival rate of UL λu and a relatively safe threshold of buffer size QT as the parameters to estimate the maximum allowable waiting time to align the UL with the DL connections. To analyze the performance of DUAL, a system model of PS is proposed to evaluate the performance of DUAL under different conditions. The correctness of performance analysis of DUAL is validated by using simulation with realistic parameters. Numerical experiments show that DUAL improves the energy conservation significantly when UL traffic is greater than DL traffic. PMID:24526884

  5. Particlelike wave packets in complex scattering systems

    NASA Astrophysics Data System (ADS)

    Gérardin, Benoît; Laurent, Jérôme; Ambichl, Philipp; Prada, Claire; Rotter, Stefan; Aubry, Alexandre

    2016-07-01

    A wave packet undergoes a strong spatial and temporal dispersion while propagating through a complex medium. This wave scattering is often seen as a nightmare in wave physics whether it be for focusing, imaging, or communication purposes. Controlling wave propagation through complex systems is thus of fundamental interest in many areas, ranging from optics or acoustics to medical imaging or telecommunications. Here, we study the propagation of elastic waves in a cavity and a disordered waveguide by means of laser interferometry. From the direct experimental access to the time-delay matrix of these systems, we demonstrate the existence of particlelike wave packets that remain focused in time and space throughout their complex trajectory. Due to their limited dispersion, their selective excitation will be crucially relevant for all applications involving selective wave focusing and efficient information transfer through complex media.

  6. Controlled Quantum Packets

    NASA Technical Reports Server (NTRS)

    DeMartino, Salvatore; DeSiena, Silvio

    1996-01-01

    We look at time evolution of a physical system from the point of view of dynamical control theory. Normally we solve motion equation with a given external potential and we obtain time evolution. Standard examples are the trajectories in classical mechanics or the wave functions in Quantum Mechanics. In the control theory, we have the configurational variables of a physical system, we choose a velocity field and with a suited strategy we force the physical system to have a well defined evolution. The evolution of the system is the 'premium' that the controller receives if he has adopted the right strategy. The strategy is given by well suited laboratory devices. The control mechanisms are in many cases non linear; it is necessary, namely, a feedback mechanism to retain in time the selected evolution. Our aim is to introduce a scheme to obtain Quantum wave packets by control theory. The program is to choose the characteristics of a packet, that is, the equation of evolution for its centre and a controlled dispersion, and to give a building scheme from some initial state (for example a solution of stationary Schroedinger equation). It seems natural in this view to use stochastic approach to Quantum Mechanics, that is, Stochastic Mechanics [S.M.]. It is a quantization scheme different from ordinary ones only formally. This approach introduces in quantum theory the whole mathematical apparatus of stochastic control theory. Stochastic Mechanics, in our view, is more intuitive when we want to study all the classical-like problems. We apply our scheme to build two classes of quantum packets both derived generalizing some properties of coherent states.

  7. Charles A. Lindbergh Learning Packet.

    ERIC Educational Resources Information Center

    Rodriguez, Charley

    This aerospace education learning packet contains information about the famous pilot, Charles A. Lindbergh. Posters, recommended teaching methods, tests with keys, and task cards are also included. (KHR)

  8. Radiotherapy DICOM packet sniffing.

    PubMed

    Ackerly, T; Gesoand, M; Smith, R

    2008-09-01

    The Digital Imaging and Communications in Medicine (DICOM) standard is meant to allow communication of medical images between equipment provided by different vendors, but when two applications do not interact correctly in a multi-vendor environment it is often first necessary to demonstrate non-compliance of either the sender or the receiver before a resolution to the problem can be progressed. Sometimes the only way to do this is to monitor the network communication between the two applications to find out which one is not complying with the DICOM standard. Packet sniffing is a technique of network traffic analysis by passive observation of all information transiting a point on the network, regardless of the specified sender or receiver. DICOM packet sniffing traps and interprets the network communication between two DICOM applications to determine which is non compliant. This is illustrated with reference to three examples, a radiotherapy planning system unable to receive CT data from a particular CT scanner, a radiotherapy simulator unable to print correctly on a DICOM printer, and a PACS unable to respond when queried about what images it has in its archive by a radiotherapy treatment planning system. Additionally in this work it has been proven that it is feasible to extract DICOM images from the intercepted network data. This process can be applied to determine the cause of a DICOM image being rendered differently by the sender and the receiver.

  9. An Overview of Algorithms for Downlink Transmit Beamforming

    DTIC Science & Technology

    2007-11-02

    Swindlehurst Electrical & Computer Engineering Brigham Young University Vector Modulo Pre-coding Use a perturbation of the form SP =,Cc =t(a+ jb) where -c...constellation "spacing" A. Lee Swindlehurst Electrical & Computer Engineering Brigham Young University Vector Modulo Pre-coding (cont.) * Choose c to solve...An Overview of Algorithms for Downlink Transmit Beamforming A. Lee Swindlehurst and Chris Peel Brigham Young University phone: 801-422-4343 email

  10. Downlink Probability Density Functions for EOS-McMurdo Sound

    NASA Technical Reports Server (NTRS)

    Christopher, P.; Jackson, A. H.

    1996-01-01

    The visibility times and communication link dynamics for the Earth Observations Satellite (EOS)-McMurdo Sound direct downlinks have been studied. The 16 day EOS periodicity may be shown with the Goddard Trajectory Determination System (GTDS) and the entire 16 day period should be simulated for representative link statistics. We desire many attributes of the downlink, however, and a faster orbital determination method is desirable. We use the method of osculating elements for speed and accuracy in simulating the EOS orbit. The accuracy of the method of osculating elements is demonstrated by closely reproducing the observed 16 day Landsat periodicity. An autocorrelation function method is used to show the correlation spike at 16 days. The entire 16 day record of passes over McMurdo Sound is then used to generate statistics for innage time, outage time, elevation angle, antenna angle rates, and propagation loss. The levation angle probability density function is compared with 1967 analytic approximation which has been used for medium to high altitude satellites. One practical result of this comparison is seen to be the rare occurrence of zenith passes. The new result is functionally different than the earlier result, with a heavy emphasis on low elevation angles. EOS is one of a large class of sun synchronous satellites which may be downlinked to McMurdo Sound. We examine delay statistics for an entire group of sun synchronous satellites ranging from 400 km to 1000 km altitude. Outage probability density function results are presented three dimensionally.

  11. Nanosatellite optical downlink experiment: design, simulation, and prototyping

    NASA Astrophysics Data System (ADS)

    Clements, Emily; Aniceto, Raichelle; Barnes, Derek; Caplan, David; Clark, James; Portillo, Iñigo del; Haughwout, Christian; Khatsenko, Maxim; Kingsbury, Ryan; Lee, Myron; Morgan, Rachel; Twichell, Jonathan; Riesing, Kathleen; Yoon, Hyosang; Ziegler, Caleb; Cahoy, Kerri

    2016-11-01

    The nanosatellite optical downlink experiment (NODE) implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10 Mbps. A primary goal of NODE is to leverage commercially available technologies to provide a scalable and cost-effective alternative to radio-frequency-based communications. The NODE transmitter uses a 200-mW 1550-nm master-oscillator power-amplifier design using power-efficient M-ary pulse position modulation. To facilitate pointing the 0.12-deg downlink beam, NODE augments spacecraft body pointing with a microelectromechanical fast steering mirror (FSM) and uses an 850-nm uplink beacon to an onboard CCD camera. The 30-cm aperture ground telescope uses an infrared camera and FSM for tracking to an avalanche photodiode detector-based receiver. Here, we describe our approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system. This includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design. We capture trades and technology development needs and outline plans for integrated system ground testing.

  12. Vocational and Industrial Arts Packets.

    ERIC Educational Resources Information Center

    Maine Audubon Society, Falmouth.

    This book is a teacher's guide to energy alternatives. It is divided into seven informational packets on the following topics: parabolic solar concentrators, solar flat plate collectors, wood as fuel, heat loss, bio-gas, wind, and water. Each packet contains background information for the teachers and learning activities for the students. The…

  13. Tropical Animal Tour Packet. Metro.

    ERIC Educational Resources Information Center

    Metro Washington Park Zoo, Portland, OR. Educational Services Div.

    This packet is designed to assist teachers in creating a tropical animals lesson plan that centers around a visit to the zoo. A teacher packet is divided into eight parts: (1) goals and objectives; (2) what to expect at the zoo; (3) student activities (preparatory activities, on-site activities, and follow-up activities); (4) background…

  14. DS-CDMA satellite diversity reception for personal satellite communication: Downlink performance analysis

    NASA Technical Reports Server (NTRS)

    DeGaudenzi, Riccardo; Giannetti, Filippo

    1995-01-01

    The downlink of a satellite-mobile personal communication system employing power-controlled Direct Sequence Code Division Multiple Access (DS-CDMA) and exploiting satellite-diversity is analyzed and its performance compared with a more traditional communication system utilizing single satellite reception. The analytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. It is shown how the capacity gain provided by diversity reception shrinks considerably in the presence of increasing traffic or in the case of light shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to intra-system interference, no more than two satellites shall be active over the same region. To achieve higher system capacity, differently from terrestrial cellular systems, Multi-User Detection (MUD) techniques are likely to be required in the mobile user terminal, thus considerably increasing its complexity.

  15. Experience with the EURECA Packet Telemetry and Packet Telecommand system

    NASA Technical Reports Server (NTRS)

    Sorensen, Erik Mose; Ferri, Paolo

    1994-01-01

    The European Retrieval Carrier (EURECA) was launched on its first flight on the 31st of July 1992 and retrieved on the 29th of June 1993. EURECA is characterized by several new on-board features, most notably Packet telemetry, and a partial implementation of packet telecommanding, the first ESA packetised spacecraft. Today more than one year after the retrieval the data from the EURECA mission has to a large extent been analysed and we can present some of the interesting results. This paper concentrates on the implementation and operational experience with the EURECA Packet Telemetry and Packet Telecommanding. We already discovered during the design of the ground system that the use of packet telemetry has major impact on the overall design and that processing of packet telemetry may have significant effect on the computer loading and sizing. During the mission a number of problems were identified with the on-board implementation resulting in very strange anomalous behaviors. Many of these problems directly violated basic assumptions for the design of the ground segment adding to the strange behavior. The paper shows that the design of a telemetry packet system should be flexible enough to allow a rapid configuration of the telemetry processing in order to adapt it to the new situation in case of an on-board failure. The experience gained with the EURECA mission control should be used to improve ground systems for future missions.

  16. On-board closed-loop congestion control for satellite based packet switching networks

    NASA Technical Reports Server (NTRS)

    Chu, Pong P.; Ivancic, William D.; Kim, Heechul

    1993-01-01

    NASA LeRC is currently investigating a satellite architecture that incorporates on-board packet switching capability. Because of the statistical nature of packet switching, arrival traffic may fluctuate and thus it is necessary to integrate congestion control mechanism as part of the on-board processing unit. This study focuses on the closed-loop reactive control. We investigate the impact of the long propagation delay on the performance and propose a scheme to overcome the problem. The scheme uses a global feedback signal to regulate the packet arrival rate of ground stations. In this scheme, the satellite continuously broadcasts the status of its output buffer and the ground stations respond by selectively discarding packets or by tagging the excessive packets as low-priority. The two schemes are evaluated by theoretical queuing analysis and simulation. The former is used to analyze the simplified model and to determine the basic trends and bounds, and the later is used to assess the performance of a more realistic system and to evaluate the effectiveness of more sophisticated control schemes. The results show that the long propagation delay makes the closed-loop congestion control less responsive. The broadcasted information can only be used to extract statistical information. The discarding scheme needs carefully-chosen status information and reduction function, and normally requires a significant amount of ground discarding to reduce the on-board packet loss probability. The tagging scheme is more effective since it tolerates more uncertainties and allows a larger margin of error in status information. It can protect the high-priority packets from excessive loss and fully utilize the downlink bandwidth at the same time.

  17. A packet-based concept for spacecraft command planning

    NASA Technical Reports Server (NTRS)

    Barnes, Valerie B.

    1993-01-01

    The current generation of spacecraft being developed and operated by the Applied Physics Laboratory provides users with access to a broad spectrum of scientific instruments on maneuverable platforms that can be oriented for observation of both moving and stationary targets of interest. The capability of these increasingly complex spacecraft to perform data collection operations is approaching one observation per orbit. To enable both rapid configuration and generation of complex spacecraft command sequences, as well as reusability of command sequences among data collection operations, a packet-based concept for spacecraft command planning has been developed. The configuration of the spacecraft for any operation is designed using 'packets' where a packet represents a set of commands that is reusable. The packets can be combined in varying levels of functionality, and in varying time relationships, to create an observation timeline. At the lowest packet level are primitives. Primitives relate the details of command generation for a particular spacecraft to a 'message template.' Thus the packet concept itself is reusable from one spacecraft to the next.

  18. Accessibility

    EPA Pesticide Factsheets

    Federal laws, including Section 508 of the Rehabilitation Act, mandate that people with disabilities have access to the same information that someone without a disability would have. 508 standards cover electronic and information technology (EIT) products.

  19. Design of a Multicast Optical Packet Switch Based on Fiber Bragg Grating Technology for Future Networks

    NASA Astrophysics Data System (ADS)

    Cheng, Yuh-Jiuh; Yeh, Tzuoh-Chyau; Cheng, Shyr-Yuan

    2011-09-01

    In this paper, a non-blocking multicast optical packet switch based on fiber Bragg grating technology with optical output buffers is proposed. Only the header of optical packets is converted to electronic signals to control the fiber Bragg grating array of input ports and the packet payloads should be transparently destined to their output ports so that the proposed switch can reduce electronic interfaces as well as the bit rate. The modulation and the format of packet payloads may be non-standard where packet payloads could also include different wavelengths for increasing the volume of traffic. The advantage is obvious: the proposed switch could transport various types of traffic. An easily implemented architecture which can provide multicast services is also presented. An optical output buffer is designed to queue the packets if more than one incoming packet should reach to the same destination output port or including any waiting packets in optical output buffer that will be sent to the output port at a time slot. For preserving service-packet sequencing and fairness of routing sequence, a priority scheme and a round-robin algorithm are adopted at the optical output buffer. The fiber Bragg grating arrays for both input ports and output ports are designed for routing incoming packets using optical code division multiple access technology.

  20. Hardware packet pacing using a DMA in a parallel computer

    DOEpatents

    Chen, Dong; Heidelberger, Phillip; Vranas, Pavlos

    2013-08-13

    Method and system for hardware packet pacing using a direct memory access controller in a parallel computer which, in one aspect, keeps track of a total number of bytes put on the network as a result of a remote get operation, using a hardware token counter.

  1. High speed packet switching

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This document constitutes the final report prepared by Proteon, Inc. of Westborough, Massachusetts under contract NAS 5-30629 entitled High-Speed Packet Switching (SBIR 87-1, Phase 2) prepared for NASA-Greenbelt, Maryland. The primary goal of this research project is to use the results of the SBIR Phase 1 effort to develop a sound, expandable hardware and software router architecture capable of forwarding 25,000 packets per second through the router and passing 300 megabits per second on the router's internal busses. The work being delivered under this contract received its funding from three different sources: the SNIPE/RIG contract (Contract Number F30602-89-C-0014, CDRL Sequence Number A002), the SBIR contract, and Proteon. The SNIPE/RIG and SBIR contracts had many overlapping requirements, which allowed the research done under SNIPE/RIG to be applied to SBIR. Proteon funded all of the work to develop new router interfaces other than FDDI, in addition to funding the productization of the router itself. The router being delivered under SBIR will be a fully product-quality machine. The work done during this contract produced many significant findings and results, summarized here and explained in detail in later sections of this report. The SNIPE/RIG contract was completed. That contract had many overlapping requirements with the SBIR contract, and resulted in the successful demonstration and delivery of a high speed router. The development that took place during the SNIPE/RIG contract produced findings that included the choice of processor and an understanding of the issues surrounding inter processor communications in a multiprocessor environment. Many significant speed enhancements to the router software were made during that time. Under the SBIR contract (and with help from Proteon-funded work), it was found that a single processor router achieved a throughput significantly higher than originally anticipated. For this reason, a single processor router was

  2. Threatened and Endangered Species: Tour Packet.

    ERIC Educational Resources Information Center

    Coats, Victoria; Samia, Cory

    This resource unit contains a teacher information packet and a middle school student activity packet to be used in creating a threatened and endangered species unit. The packet of student activities is designed to help maximize a field trip to the zoo and build on students' zoo experience in the classroom. The teacher information packet covers the…

  3. Wavelet Packets in Wideband Multiuser Communications

    DTIC Science & Technology

    2004-11-01

    developed doubly orthogonal CDMA user spreading waveforms based on wavelet packets. We have also developed and evaluated a wavelet packet based ...inter symbol interferences. Compared with the existing DFT based multicarrier CDMA systems, better performance is achieved with the wavelet packet...23 3.4 Over Loaded Waveform Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4. Wavelet Packet Based Time-Varying

  4. Building an Energy-efficient Uplink and Downlink Delay Aware TDM-PON System

    NASA Astrophysics Data System (ADS)

    Newaz, S. H. Shah; Jang, Min Seok; Alaelddin, Fuad Yousif Mohammed; Lee, Gyu Myoung; Choi, Jun Kyun

    2016-05-01

    With the increasing concern over the energy expenditure due to rapid ICT expansion and growth of Internet traffic volume, there is a growing trend towards developing energy-efficient ICT solutions. Passive Optical Network (PON), which is regarded as a key enabler to facilitate high speed broadband connection to individual subscribers, is considered as one of the energy-efficient access network technologies. However, an immense amount of research effort can be noticed in academia and industries to make PON more energy-efficient. In this paper, we aim at improving energy saving performance of Time Division Multiplexing (TDM)-PON, which is the most widely deployed PON technology throughout the world. A commonly used approach to make TDM-PON energy-efficient is to use sleep mode in Optical Network Units (ONUs), which are the customer premises equipment of a TDM-PON system. However, there is a strong trade-off relationship between traffic delay performance of an ONU and its energy saving (the longer the sleep interval length of an ONU, the lower its energy consumption, but the higher the traffic delay, and vice versa). In this paper, we propose an Energy-efficient Uplink and Downlink Delay Aware (EUDDA) scheme for TDM-PON system. The prime object of EUDDA is to meet both downlink and uplink traffic delay requirement while maximizing energy saving performance of ONUs as much as possible. In EUDDA, traffic delay requirement is given more priority over energy saving. Even so, it still can improve energy saving of ONUs noticeably. We evaluate performance of EUDDA in front of two existing solutions in terms of traffic delay, jitter, and ONU energy consumption. The performance results show that EUDDA significantly outperforms the other existing solutions.

  5. Packet flow monitoring tool and method

    DOEpatents

    Thiede, David R [Richland, WA

    2009-07-14

    A system and method for converting packet streams into session summaries. Session summaries are a group of packets each having a common source and destination internet protocol (IP) address, and, if present in the packets, common ports. The system first captures packets from a transport layer of a network of computer systems, then decodes the packets captured to determine the destination IP address and the source IP address. The system then identifies packets having common destination IP addresses and source IP addresses, then writes the decoded packets to an allocated memory structure as session summaries in a queue.

  6. Bohmian trajectories of Airy packets

    SciTech Connect

    Nassar, Antonio B.; Miret-Artés, Salvador

    2014-09-15

    The discovery of Berry and Balazs in 1979 that the free-particle Schrödinger equation allows a non-dispersive and accelerating Airy-packet solution has taken the folklore of quantum mechanics by surprise. Over the years, this intriguing class of wave packets has sparked enormous theoretical and experimental activities in related areas of optics and atom physics. Within the Bohmian mechanics framework, we present new features of Airy wave packet solutions to Schrödinger equation with time-dependent quadratic potentials. In particular, we provide some insights to the problem by calculating the corresponding Bohmian trajectories. It is shown that by using general space–time transformations, these trajectories can display a unique variety of cases depending upon the initial position of the individual particle in the Airy wave packet. Further, we report here a myriad of nontrivial Bohmian trajectories associated to the Airy wave packet. These new features are worth introducing to the subject’s theoretical folklore in light of the fact that the evolution of a quantum mechanical Airy wave packet governed by the Schrödinger equation is analogous to the propagation of a finite energy Airy beam satisfying the paraxial equation. Numerous experimental configurations of optics and atom physics have shown that the dynamics of Airy beams depends significantly on initial parameters and configurations of the experimental set-up.

  7. The throughput of packet broadcasting channels

    NASA Technical Reports Server (NTRS)

    Abramson, N.

    1977-01-01

    A unified presentation of packet broadcasting theory is presented. Section II introduces the theory of packet broadcasting data networks. Section III provides some theoretical results on the performance of a packet broadcasting network when users have a variety of data rates. Section IV deals with packet broadcasting networks distributed in space, and in Section V some properties of power-limited packet broadcasting channels are derived, showing that the throughput of such channels can approach that of equivalent point-to-point channels.

  8. New packet scheduling algorithm in wireless CDMA data networks

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Gao, Zhuo; Li, Shaoqian; Li, Lemin

    2002-08-01

    The future 3G/4G wireless communication systems will provide internet access for mobile users. Packet scheduling algorithms are essential for QoS of diversified data traffics and efficient utilization of radio spectrum.This paper firstly presents a new packet scheduling algorithm DSTTF under the assumption of continuous transmission rates and scheduling intervals for CDMA data networks . Then considering the constraints of discrete transmission rates and fixed scheduling intervals imposed by the practical system, P-DSTTF, a modified version of DSTTF, is brought forward. Both scheduling algorithms take into consideration of channel condition, packet size and traffic delay bounds. The extensive simulation results demonstrate that the proposed scheduling algorithms are superior to some typical ones in current research. In addition, both static and dynamic wireless channel model of multi-level link capacity are established. These channel models sketch better the characterizations of wireless channel than two state Markov model widely adopted by the current literature.

  9. Integrated optical buffers for packet-switched networks

    NASA Astrophysics Data System (ADS)

    Burmeister, Emily Frances

    Routers form the backbone of the Internet, directing data to the right locations with huge throughput capacity of terabits/second) and very few errors (1 error allowed in 1012 bits). However, as the Internet continues to grow rapidly, so must the capacity of electronic routers, thereby also growing in footprint and power consumption. The energy bill alone has developers looking for an alternate solution. Today's routers can only operate with electrical signals although Internet data is transmitted optically. This requires the data to be converted from the optical domain to the electrical domain and back again. Optical routers have the potential of saving in power by omitting these conversions, but have been held back in part by the lack of a practical optical memory device. This work presents the first integrated optical buffer for next generation optical packet-switched networks. Buffering is required in a router to move packets of data in order to avoid collisions between packets heading to the same destination at the same time. The device presented here uses an InP-based two-by-two switch with a silica waveguide delay to form a recirculating buffer. Packet storage was shown with 98% packet recovery for 5 circulations. Autonomous contention resolution was demonstrated with two buffered channels to show that the technology is a realistic solution for creating multiple element buffers on multiple router ports. This thesis proposes and demonstrates the first integrated optical random access memory, thereby making a great stride toward high capacity optical routers.

  10. Spacelab uplink/downlink data flow and formats

    NASA Technical Reports Server (NTRS)

    Kandefer, F.

    1978-01-01

    The results of an analysis of the Spacelab (SL) data uplink/downlink structure and those data system elements associated with the support of this data flow are presented. Specific objectives of this report are to present the results of the following analyses: (1) operations of the SL high rate multiplexer, including format structure, data rates, format combinations, format switching, etc.; (2) operations of SL data recorders to include the definition of modes, data rates and forms; (3) operations of the high rate demultiplexer as described above; (4) potential experiment data formats defining formatting parameters to be considered in decommutation analysis; (5) SL computer input/output (I/O) decommutation channels, including the definition of structure, quantity and use of this I/O data; (6) detailed requirements of the data quality monitoring philosophy for this function.

  11. Self-Interfering Wave Packets

    NASA Astrophysics Data System (ADS)

    Colas, David; Laussy, Fabrice P.

    2016-01-01

    We study the propagation of noninteracting polariton wave packets. We show how two qualitatively different concepts of mass that arise from the peculiar polariton dispersion lead to a new type of particlelike object from noninteracting fields—much like self-accelerating beams—shaped by the Rabi coupling out of Gaussian initial states. A divergence and change of sign of the diffusive mass results in a "mass wall" on which polariton wave packets bounce back. Together with the Rabi dynamics, this yields propagation of ultrafast subpackets and ordering of a spacetime crystal.

  12. Sports Medicine. Clinical Rotation. Instructor's Packet and Student Study Packet.

    ERIC Educational Resources Information Center

    Texas Univ., Austin. Extension Instruction and Materials Center.

    The materials in this packet are for a course designed to provide individualized classroom study for a specific area of clinical rotation--sports medicine. The instructor's manual describes the learning objectives together with a list of reference materials that should be provided for completion of the student worksheets, and lists suggested…

  13. Fairness algorithm of the resilient packet ring

    NASA Astrophysics Data System (ADS)

    Tu, Lai; Huang, Benxiong; Zhang, Fan; Wang, Xiaoling

    2004-04-01

    Resilient Packet Ring (RPR) is a newly developed Layer 2 access technology for ring topology based high speed network. Fairness Algorithm (FA), one of its key technologies, takes responsibility for regulating each station access to the ring. Since different methods emphasize particularly on different aspects, the RPR Work Group have tabled several proposals. This paper will discuss two of them and propose an improved algorithm, which can be seen as a generalization of the two schemes proposed in [1] and [2]. The new algorithm is a distributed algorithm, and uses a multi level feedback mechanism. Each station calculates its own fair rate to regulate its access to the ring, and sends fairness control message (FCM) with its bandwidth demand information to the whole ring. All stations keep a bandwidth demand image, which update periodically based on the information of received FCM. The image can be used for local fair rate calculation to achieve fair access. In the properties study section of this paper, we compare our algorithm with the two existing one both in theoretical method and in scenario simulation. Our algorithm has successfully resolve lack of the awareness of multi congestion points in [1] and the drawback of weakness of fault tolerance in [2].

  14. Environment Resource Packets Get Wide Use

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1974

    1974-01-01

    Announces the availability of the resource packet entitled "Noise Pollution," the third in the series prepared by the University of Maryland, and the main topics which will be covered in the remaining three packets. (CC)

  15. A robust coding scheme for packet video

    NASA Technical Reports Server (NTRS)

    Chen, Yun-Chung; Sayood, Khalid; Nelson, Don J.

    1992-01-01

    A layered packet video coding algorithm based on a progressive transmission scheme is presented. The algorithm provides good compression and can handle significant packet loss with graceful degradation in the reconstruction sequence. Simulation results for various conditions are presented.

  16. Alternative packet switch architectures for a 30/20 GHz FDMA/TDMA geostationary communication satellite network

    NASA Technical Reports Server (NTRS)

    Stehle, Roy; Ogier, Richard G.

    1995-01-01

    This study has investigated alternatives for realizing a packet-based network switch for deployment on a communication satellite. The emphasis was on the avoidance of contention problems that can occur due to the simultaneous arrival of an excessive number of packets destined for the same downlink dwell. The study was to look ahead, beyond the current Advanced Communications Technology Satellite (ACTS) capability, to the next generation of satellites. The study has not been limited by currently available technology, but has used university and commercial research efforts as a basis for designs that can be readily constructed and launched within the next five years. Tradeoffs in memory requirement, power requirement, and architecture have been considered as a part of our study.

  17. Alternative packet switch architectures for a 30/20 GHz FDMA/TDMA geostationary communication satellite network

    NASA Astrophysics Data System (ADS)

    Stehle, Roy; Ogier, Richard G.

    1995-06-01

    This study has investigated alternatives for realizing a packet-based network switch for deployment on a communication satellite. The emphasis was on the avoidance of contention problems that can occur due to the simultaneous arrival of an excessive number of packets destined for the same downlink dwell. The study was to look ahead, beyond the current Advanced Communications Technology Satellite (ACTS) capability, to the next generation of satellites. The study has not been limited by currently available technology, but has used university and commercial research efforts as a basis for designs that can be readily constructed and launched within the next five years. Tradeoffs in memory requirement, power requirement, and architecture have been considered as a part of our study.

  18. Dynamics of quantum wave packets

    SciTech Connect

    Gosnell, T.R.; Taylor, A.J.; Rodriguez, G.; Clement, T.S.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was to develop ultrafast laser techniques for the creation and measurement of quantum vibrational wave packets in gas phase diatomic molecules. Moreover, the authors sought to manipulate the constitution of these wave packets in terms of harmonic-oscillator basis wavefunctions by manipulating the time-dependent amplitude and phase of the incident ultrashort laser pulse. They specifically investigated gaseous diatomic potassium (K{sub 2}), and discovered variations in the shape of the wave packets as a result of changing the linear chirp in the ultrashort preparation pulse. In particular, they found evidence for wave-packet compression for a specific degree of chirp. Important ancillary results include development of new techniques for denoising and deconvolution of femtosecond time traces and techniques for diagnosing the phase and amplitude of the electric field of femtosecond laser pulses.

  19. Science and Art, Learning Packet.

    ERIC Educational Resources Information Center

    Singer, Carla Michalove

    Science and art have much in common. Artists as well as scientists carefully observe and communicate their subjects. Throughout time, artists have been involved in experimentation, an important scientific method which can lead to new discoveries. Both scientific developments and the ongoing history of art are cumulative. This learning packet is an…

  20. Recycling Study Guide [Resource Packet].

    ERIC Educational Resources Information Center

    Wisconsin State Dept. of Natural Resources, Madison.

    This resource packet contains six documents developed by the Wisconsin Department of Natural Resources in order to help teachers infuse the environmental education topics of recycling and solid waste into social studies, art, English, health, mathematics, science, and environmental education classes. "Recycling Study Guide" contains 19…

  1. Homelessness: A General Information Packet.

    ERIC Educational Resources Information Center

    Homelessness Exchange, Washington, DC.

    This packet contains documents that provide general information about homelessness and the need for both Federal and local action to help the homeless people in America. Sections 1 and 2 contain the following articles released by the Homelessness Information Exchange: (1) "The Problem of Homelessness Nationwide"; and "Alternative Family Housing…

  2. Information Packet on Surrogate Parents.

    ERIC Educational Resources Information Center

    Moore, Jean J.; Mason, Doris M.

    The information packet focuses on the role of the surrogate parent with emphasis on the rights of the handicapped child as mandated by P.L. 94-142, the Education for All Handicapped Children Act. Included are the following: a discussion of 10 surrogate parent issues identified through a literature search and survey of five states (Connecticut,…

  3. Dissection & Science Fairs. [Information Packet.

    ERIC Educational Resources Information Center

    National Anti-Vivisection Society, Chicago, IL.

    This collection of pamphlets and articles reprinted from other National Anti-Vivisection Society (NAVS) publications was compiled to address the issues of classroom laboratory dissection and the use of animals in science fair projects. Three of the pamphlets contained in this packet are student handbooks designed to help students of elementary,…

  4. Hunger and Development [Issue Packet].

    ERIC Educational Resources Information Center

    American Freedom from Hunger Foundation, Washington, DC.

    A variety of informational materials is compiled in this issue packet concentrating on hunger and development. They have been assembled to understand the issues associated with the facts of world hunger and to try to invent new forms of action and thought necessary to find the possibilities hidden in the hunger issue. Items include: (1) a fact and…

  5. Population and Development [Issue Packet].

    ERIC Educational Resources Information Center

    American Freedom from Hunger Foundation, Washington, DC.

    A variety of informational materials is compiled in this issue packet concentrating on population and development. The materials have been assembled to understand the issues associated with the facts of the world's population and to try to invent new forms of action and thought necessary to find the possibilities hidden in the population issue.…

  6. Ancient Chinese Bronzes: Teacher's Packet.

    ERIC Educational Resources Information Center

    Smithsonian Institution, Washington, DC. Arthur M. Sackler Gallery.

    The focus of this teacher's packet is the bronze vessels made for the kings and great families of the early Chinese dynasties between 1700 B.C. and 200 A.D. The materials in the guide are intended for use by teachers and students visiting the exhibition, "The Arts of China," at the Arthur M. Sackler Gallery of the Smithsonian Institution…

  7. 78 FR 63228 - Determination That Potassium Citrate, 10 Milliequivalents/Packet and 20 Milliequivalents/Packet...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-23

    ... HUMAN SERVICES Food and Drug Administration Determination That Potassium Citrate, 10 Milliequivalents...) has determined that Potassium Citrate, 10 milliequivalents/packet (mEq/packet) and 20 mEq/ packet, was... approve abbreviated new drug applications (ANDAs) for Potassium Citrate, 10 mEq/packet and 20...

  8. [KIND Worksheet Packet: Wild Animals (Junior).

    ERIC Educational Resources Information Center

    National Association for Humane and Environmental Education, East Haddam, CT.

    This packet is the junior part of a series of worksheet packets available at both junior (grades 3-4) and senior (grades 5-6) levels that covers a variety of humane and environmental topics. Each packet includes 10 worksheets, all of which originally appeared in past issues of the annual teaching magazine "KIND (Kids in Nature's Defense)…

  9. [KIND Worksheet Packet: Wild Animals (Senior).

    ERIC Educational Resources Information Center

    National Association for Humane and Environmental Education, East Haddam, CT.

    This packet is the senior part of a series of worksheet packets available at both junior (grades 3-4) and senior (grades 5-6) levels that covers a variety of humane and environmental topics. Each packet includes 10 worksheets, all of which originally appeared in past issues of the annual teaching magazine "KIND (Kids in Nature's Defense)…

  10. Trade Related Reading Packets for Disabled Readers.

    ERIC Educational Resources Information Center

    Davis, Beverly; Woodruff, Nancy S.

    Six trade-related reading packets for disabled readers are provided for these trades: assemblers, baking, building maintenance, data entry, interior landscaping, and warehousing. Each packet stresses from 9 to 14 skills. Those skills common to most packets include context clues, fact or opinion, details, following directions, main idea,…

  11. Coverage Performance of Common/Shared Control Signals Using Transmit Diversity in Evolved UTRA Downlink

    NASA Astrophysics Data System (ADS)

    Taoka, Hidekazu; Morimoto, Akihito; Kawai, Hiroyuki; Higuchi, Kenichi; Sawahashi, Mamoru

    This paper presents the best transmit diversity schemes for three types of common/shared control signals from the viewpoint of the block error rate (BLER) performance in the Evolved UTRA downlink employing OFDM radio access. This paper also presents the coverage performance of the common/shared control signals using transmit diversity with respect to the outage probability that satisfies the required BLER performance, which is a major factor determining the cell configuration. Simulation results clarify that Space-Frequency Block Code (SFBC) and the combination of SFBC and Frequency Switched Transmit Diversity (FSTD) are the best transmit diversity schemes among the open-loop type transmit diversity candidates for two-antenna and four-antenna transmission cases, respectively. Furthermore, we show through system-level simulations that SFBC is very effective in reducing the outage probability at the required BLER for the physical broadcast channel (PBCH), for the common control signal with resource block (RB)-level assignment such as the dynamic broadcast channel (D-BCH) and paging channel (PCH), and in increasing the number of accommodated L1/L2 control signals over one transmission time interval duration, using mini-control channel element (CCE)-level assignment.

  12. Frequency Domain Beamforming for a Deep Space Network Downlink Array

    NASA Technical Reports Server (NTRS)

    Navarro, Robert

    2012-01-01

    This paper describes a frequency domain beamformer to array up to 8 antennas of NASA's Deep Space Network currently in development. The objective of this array is to replace and enhance the capability of the DSN 70m antennas with multiple 34m antennas for telemetry, navigation and radio science use. The array will coherently combine the entire 500 MHz of usable bandwidth available to DSN receivers. A frequency domain beamforming architecture was chosen over a time domain based architecture to handle the large signal bandwidth and efficiently perform delay and phase calibration. The antennas of the DSN are spaced far enough apart that random atmospheric and phase variations between antennas need to be calibrated out on an ongoing basis in real-time. The calibration is done using measurements obtained from a correlator. This DSN Downlink Array expands upon a proof of concept breadboard array built previously to develop the technology and will become an operational asset of the Deep Space Network. Design parameters for frequency channelization, array calibration and delay corrections will be presented as well a method to efficiently calibrate the array for both wide and narrow bandwidth telemetry.

  13. Nonuniform spatially adaptive wavelet packets

    NASA Astrophysics Data System (ADS)

    Carre, Philippe; Fernandez-Maloigne, Christine

    2000-12-01

    In this paper, we propose a new decomposition scheme for spatially adaptive wavelet packets. Contrary to the double tree algorithm, our method is non-uniform and shift- invariant in the time and frequency domains, and is minimal for an information cost function. We prose some-restrictions to our algorithm to reduce the complexity and permitting us to provide some time-frequency partitions of the signal in agreement with its structure. This new 'totally' non-uniform transform, more adapted than Malvar, Packets or dyadic double-tree decomposition, allows the study of all possible time-frequency partitions with the only restriction that the blocks are rectangular. It permits one to obtain a satisfying Time-Frequency representation, and is applied for the study of EEG signals.

  14. Prediction and comparison of downlink electric-field and uplink localised SAR values for realistic indoor wireless planning.

    PubMed

    Plets, David; Joseph, Wout; Aerts, Sam; Vanhecke, Kris; Vermeeren, Günter; Martens, Luc

    2014-12-01

    In this paper, for the first time a heuristic network calculator for both whole-body exposure due to indoor base station antennas or access points (downlink exposure) and localised exposure due to the mobile device (uplink exposure) in indoor wireless networks is presented. As an application, three phone call scenarios are investigated (Universal Mobile Telecommunications System (UMTS) macrocell, UMTS femtocell and WiFi voice-over-IP) and compared with respect to the electric-field strength and localised specific absorption rate (SAR) distribution. Prediction models are created and successfully validated with an accuracy of 3 dB. The benefits of the UMTS power control mechanisms are demonstrated. However, dependent on the macrocell connection quality and on the user's average phone call connection time, also the macrocell solution might be preferential from an exposure point of view for the considered scenario.

  15. Experimental Packet Radio System Design Plan

    DTIC Science & Technology

    1974-03-13

    series of step functions. Rather, it must be viewed as having an irregular shape. The situation at any particular point in time ’ s determined by...it waits a sufficient time to allow devices tudt receive the packet to repeat It. When any of these repeats the packet and the packet is...keeping heat input to any or all burners at a safe level at all times . CLEAN Complete, flameless combustion of the gas results in no soot formation, no

  16. Experimental and trial-based study of Resilient Packet Ring

    NASA Astrophysics Data System (ADS)

    Ramnath, Vasudha; Cheng, Heng Seng; Ngoh, Lek Heng

    2002-08-01

    An experimental study of the Resilient Packet Ring (RPR) media access control (MAC) technology that is optimized for IP traffic in the metropolitan-area-network (MAN) environment is described. The study involved the deployment and trials of a RPR testbed encompassing a public optical fiber infrastructure in which Cisco Systems' Dynamic Packet Transport (DPT) Ring Technology - a prestandard RPR implementation - was used. We focus on a number of important RPR protocol features that are vital to the future success of RPR as a MAN/wide-area-network (WAN) network technology. Related research on RPR/DPT has been done so far through simulation studies only. Standardization of RPR is currently being performed by the Institute of Electrical and Electronics Engineers (IEEE) 802.17 working group and is expected to be completed in 2003. Also, we present and discuss the experiments and tests performed to investigate the key features of RPR, along with the results obtained.

  17. Second Harmonic Generation of Nanoscale Phonon Wave Packets.

    PubMed

    Bojahr, A; Gohlke, M; Leitenberger, W; Pudell, J; Reinhardt, M; von Reppert, A; Roessle, M; Sander, M; Gaal, P; Bargheer, M

    2015-11-06

    Phonons are often regarded as delocalized quasiparticles with certain energy and momentum. The anharmonic interaction of phonons determines macroscopic properties of the solid, such as thermal expansion or thermal conductivity, and a detailed understanding becomes increasingly important for functional nanostructures. Although phonon-phonon scattering processes depicted in simple wave-vector diagrams are the basis of theories describing these macroscopic phenomena, experiments directly accessing these coupling channels are scarce. We synthesize monochromatic acoustic phonon wave packets with only a few cycles to introduce nonlinear phononics as the acoustic counterpart to nonlinear optics. Control of the wave vector, bandwidth, and consequently spatial extent of the phonon wave packets allows us to observe nonlinear phonon interaction, in particular, second harmonic generation, in real time by wave-vector-sensitive Brillouin scattering with x-rays and optical photons.

  18. Causal evolution of wave packets

    NASA Astrophysics Data System (ADS)

    Eckstein, Michał; Miller, Tomasz

    2017-03-01

    Drawing from the optimal transport theory adapted to the relativistic setting we formulate the principle of a causal flow of probability and apply it in the wave-packet formalism. We demonstrate that whereas the Dirac Hamiltonian impels a causal evolution of probabilities, even in the presence of interactions, the relativistic-Schrödinger model is acausal. We quantify the causality breakdown in the latter model and argue that, in contrast to the popular viewpoint, it is not related to the localization properties of the states.

  19. Archaeology: Smithsonian Institution Teacher's Resource Packet.

    ERIC Educational Resources Information Center

    National Museum of Natural History, Washington, DC.

    This archaeology resource packet provides information on frequently asked questions of the National Museum of Natural History (Smithsonian Institution), including the topics of: (1) career information; (2) excavation; (3) fieldwork opportunities; (4) artifact identification; and (5) preservation. The packet is divided into six sections. Section 1…

  20. Energy Conservation Activity Packet, Grade 5.

    ERIC Educational Resources Information Center

    Bakke, Ruth

    This activity packet for grade 5 is one of a series developed in response to concern for energy conservation. It contains activities that stress an energy conservation ethic and includes many values clarification activities for grade five. The packet is divided into two parts and provides the teacher with background information, concepts and…

  1. German Cultural Packets 13 and 14.

    ERIC Educational Resources Information Center

    Atlanta Public Schools, GA.

    These German culture packets are designed to accompany A-LM Level II and include a statement of the rationale behind the unit, the objectives of the packet, the activities themselves, and a brief evaluation by the student. The activities involve the use of the basic text, the student workbook, corresponding tapes, and fellow students as partners…

  2. Power-Aware Cognitive Packet Networks

    DTIC Science & Technology

    2005-04-01

    Power-Aware Cognitive Packet Networks Erol Gelenbe Dennis Gabor Chair Ricardo Lent Research Fellow Department of Electrical and Electronic...intelligent distribution of energy consumption in the network Power-Aware Cognitive Packet Networks Erol Gelenbe Dennis Gabor Chair Ricardo Lent

  3. Jamestown Settlement Museum Teacher Resource Packet.

    ERIC Educational Resources Information Center

    Jamestown-Yorktown Foundation, Williamsburg, VA. Education Dept.

    This teacher's packet provides background materials for teachers to incorporate the study of Jamestown, Virginia, into their classroom. The packet includes the following background essays: (1) "A Short History of Jamestown"; (2) "The Fort"; (3) "Life in an Indian Village"; (4) "Recommended Reading and…

  4. Oral Hygiene. Instructor's Packet. Learning Activity Package.

    ERIC Educational Resources Information Center

    Hime, Kirsten

    This instructor's packet accompanies the learning activity package (LAP) on oral hygiene. Contents included in the packet are a time sheet, suggested uses for the LAP, an instruction sheet, final LAP reviews, a final LAP review answer key, suggested activities, additional resources (student handouts), student performance checklists for both…

  5. Bad data packet capture device

    DOEpatents

    Chen, Dong; Gara, Alan; Heidelberger, Philip; Vranas, Pavlos

    2010-04-20

    An apparatus and method for capturing data packets for analysis on a network computing system includes a sending node and a receiving node connected by a bi-directional communication link. The sending node sends a data transmission to the receiving node on the bi-directional communication link, and the receiving node receives the data transmission and verifies the data transmission to determine valid data and invalid data and verify retransmissions of invalid data as corresponding valid data. A memory device communicates with the receiving node for storing the invalid data and the corresponding valid data. A computing node communicates with the memory device and receives and performs an analysis of the invalid data and the corresponding valid data received from the memory device.

  6. Multidimensional signaling via wavelet packets

    NASA Astrophysics Data System (ADS)

    Lindsey, Alan R.

    1995-04-01

    This work presents a generalized signaling strategy for orthogonally multiplexed communication. Wavelet packet modulation (WPM) employs the basis functions from an arbitrary pruning of a full dyadic tree structured filter bank as orthogonal pulse shapes for conventional QAM symbols. The multi-scale modulation (MSM) and M-band wavelet modulation (MWM) schemes which have been recently introduced are handled as special cases, with the added benefit of an entire library of potentially superior sets of basis functions. The figures of merit are derived and it is shown that the power spectral density is equivalent to that for QAM (in fact, QAM is another special case) and hence directly applicable in existing systems employing this standard modulation. Two key advantages of this method are increased flexibility in time-frequency partitioning and an efficient all-digital filter bank implementation, making the WPM scheme more robust to a larger set of interferences (both temporal and sinusoidal) and computationally attractive as well.

  7. Experiments examining drag in linear droplet packets

    NASA Astrophysics Data System (ADS)

    Nguyen, Q. V.; Dunn-Rankin, D.

    1992-01-01

    This paper presents an experimental study of vertically traveling droplet packets, where the droplets in each packet are aligned linearly, one behind another. The paper describes in detail, an experimental apparatus that produces repeatable, linearly aligned, and isolated droplet packets containing 1 6 droplets per packet. The apparatus is suitable for examining aerodynamic interactions between droplets within each packet. This paper demonstrates the performance of the apparatus by examining the drag reduction and collision of droplets traveling in the wake of a lead droplet. Comparison of a calculated single droplet trajectory with the detailed droplet position versus time data for a droplet packet provides the average drag reduction experienced by the trailing droplets due to the aerodynamic wake of the lead droplet. For the conditions of our experiment (4 droplet packet, 145 μm methanol droplets, 10 m/s initial velocity, initial droplet spacing of 5.2 droplet diameters, Reynolds number approx. 80) the average drag on the first trailing droplet was found to be 75% of the drag on the lead droplet.

  8. Multi-Cell Cooperation with Fairness Constraint in the Downlink OFDMA Cellular Networks

    NASA Astrophysics Data System (ADS)

    Li, Hongxing; Luo, Hanwen; Chen, Wen; Guo, Jia

    In this letter, we study cell cooperation in the downlink OFDMA cellular networks. The proposed cooperation scheme is based on fractional frequency reuse (FFR), where a cooperation group consists of three sector antennas from three adjacent cells and the subchannels of each cooperation group are allocated coordinately to users. Simulation results demonstrate the effectiveness of the proposed schemes in terms of throughput and fairness.

  9. Astronaut Andrew M. Allen, mission commander, sets up systems for a television downlink on the

    NASA Technical Reports Server (NTRS)

    1996-01-01

    STS-75 ONBOARD VIEW --- Astronaut Andrew M. Allen, mission commander, sets up systems for a television downlink on the flight deck of the Space Shuttle Columbia. Allen was joined by four other astronauts and an international payload specialist for more than 16 days of research aboard Columbia. The photograph was taken with a 70mm handheld camera.

  10. Uplink Downlink Rate Balancing and Throughput Scaling in FDD Massive MIMO Systems

    NASA Astrophysics Data System (ADS)

    Bergel, Itsik; Perets, Yona; Shamai, Shlomo

    2016-05-01

    In this work we extend the concept of uplink-downlink rate balancing to frequency division duplex (FDD) massive MIMO systems. We consider a base station with large number antennas serving many single antenna users. We first show that any unused capacity in the uplink can be traded off for higher throughput in the downlink in a system that uses either dirty paper (DP) coding or linear zero-forcing (ZF) precoding. We then also study the scaling of the system throughput with the number of antennas in cases of linear Beamforming (BF) Precoding, ZF Precoding, and DP coding. We show that the downlink throughput is proportional to the logarithm of the number of antennas. While, this logarithmic scaling is lower than the linear scaling of the rate in the uplink, it can still bring significant throughput gains. For example, we demonstrate through analysis and simulation that increasing the number of antennas from 4 to 128 will increase the throughput by more than a factor of 5. We also show that a logarithmic scaling of downlink throughput as a function of the number of receive antennas can be achieved even when the number of transmit antennas only increases logarithmically with the number of receive antennas.

  11. Computer Simulation and Field Experiment for Downlink Multiuser MIMO in Mobile WiMAX System

    PubMed Central

    Yamaguchi, Kazuhiro; Nagahashi, Takaharu; Akiyama, Takuya; Matsue, Hideaki; Uekado, Kunio; Namera, Takakazu; Fukui, Hiroshi; Nanamatsu, Satoshi

    2015-01-01

    The transmission performance for a downlink mobile WiMAX system with multiuser multiple-input multiple-output (MU-MIMO) systems in a computer simulation and field experiment is described. In computer simulation, a MU-MIMO transmission system can be realized by using the block diagonalization (BD) algorithm, and each user can receive signals without any signal interference from other users. The bit error rate (BER) performance and channel capacity in accordance with modulation schemes and the number of streams were simulated in a spatially correlated multipath fading environment. Furthermore, we propose a method for evaluating the transmission performance for this downlink mobile WiMAX system in this environment by using the computer simulation. In the field experiment, the received power and downlink throughput in the UDP layer were measured on an experimental mobile WiMAX system developed in Azumino City in Japan. In comparison with the simulated and experimented results, the measured maximum throughput performance in the downlink had almost the same performance as the simulated throughput. It was confirmed that the experimental mobile WiMAX system for MU-MIMO transmission successfully increased the total channel capacity of the system. PMID:26421311

  12. Computer Simulation and Field Experiment for Downlink Multiuser MIMO in Mobile WiMAX System.

    PubMed

    Yamaguchi, Kazuhiro; Nagahashi, Takaharu; Akiyama, Takuya; Matsue, Hideaki; Uekado, Kunio; Namera, Takakazu; Fukui, Hiroshi; Nanamatsu, Satoshi

    2015-01-01

    The transmission performance for a downlink mobile WiMAX system with multiuser multiple-input multiple-output (MU-MIMO) systems in a computer simulation and field experiment is described. In computer simulation, a MU-MIMO transmission system can be realized by using the block diagonalization (BD) algorithm, and each user can receive signals without any signal interference from other users. The bit error rate (BER) performance and channel capacity in accordance with modulation schemes and the number of streams were simulated in a spatially correlated multipath fading environment. Furthermore, we propose a method for evaluating the transmission performance for this downlink mobile WiMAX system in this environment by using the computer simulation. In the field experiment, the received power and downlink throughput in the UDP layer were measured on an experimental mobile WiMAX system developed in Azumino City in Japan. In comparison with the simulated and experimented results, the measured maximum throughput performance in the downlink had almost the same performance as the simulated throughput. It was confirmed that the experimental mobile WiMAX system for MU-MIMO transmission successfully increased the total channel capacity of the system.

  13. Reduction of ETS-VI Laser Communication Equipment Optical-Downlink Telemetry Collected During GOLD

    NASA Technical Reports Server (NTRS)

    Toyoshima, M.; Araki, K.; Arimoto, Y.; Toyoda, M.; Jeganathan, M.; Wilson, K.; Lesh, J. R.

    1997-01-01

    Free-space laser communications experiments were conducted between the laser communication equipment (LCE) on board the Japanese Engineering Test Satellite VI (ETS-VI) and the ground station located at the Table Mountain Facility (TMF) during late 1995 and early 1996. This article describes the on-line data reduction process used to decode LCE telemetry (called E2) downlinked on the optical carrier during the Ground/Orbiter Lasercomm Demonstration (GOLD) experiments. The LCE has the capability of transmitting real-time sensor and status information at 128 kbps by modulating the onboard diode laser. The optical downlink was detected on the ground, bit synchronized, and the resulting data stream stored on a data recorder. The recorded data were subsequently decoded by on-line data processing that included cross-correlation of the known telemetry data format and the downlink data stream. Signals obtained from the processing can be useful not only in evaluating the characteristics of the LCE but also in understanding uplink and downlink signal quality.

  14. Modeling and performance evaluation of the DPS25 packet switching multiprocessor system

    NASA Astrophysics Data System (ADS)

    Mitropoulos, Spyridon

    1987-05-01

    A packet switching communication network is evaluated via queue network modeling theory. Direct access memory systems, busses linking the network processors, commutation and signal processors, and virtual reference circuits are considered. All models are developed with the help of the QNAP2 program and listings of the models are given. The method is illustrated with results from simulations at the various system levels.

  15. Interconnecting network for switching data packets and method for switching data packets

    SciTech Connect

    Benner, Alan Frederic; Minkenberg, Cyriel Johan Agnes; Stunkel, Craig Brian

    2010-05-25

    The interconnecting network for switching data packets, having data and flow control information, comprises a local packet switch element (S1) with local input buffers (I(1,1) . . . I(1,y)) for buffering the incoming data packets, a remote packet switch element (S2) with remote input buffers (I(2,1) . . . I(2,y)) for buffering the incoming data packets, and data lines (L) for interconnecting the local and the remote packet switch elements (S1, S2). The interconnecting network further comprises a local and a remote arbiter (A1, A2) which are connected via control lines (CL) to the input buffers (I(1,1) . . . I(1,y), I(2,1) . . . I(2,y)), and which are formed such that they can provide that the flow control information is transmitted via the data lines (L) and the control lines (CL).

  16. Protocol Software for a Packet Voice Terminal

    DTIC Science & Technology

    1983-11-16

    III satellite. The PVTs with their attached telephone instrument serve as the interface with the voice user. The PVTs prepare speech for transmission...through a packet network by digitizing the speech, preparing speech data packets, and sending speech data messages. The PVT handles the speech coming...TOTALKin. Thes Foori alControle wilno trani speech message s unlTreessin ithas note rcenie s speehdfr ao sufficentpo toefl erAcofitt cdng atei t pfres

  17. Channel Access in Erlang

    SciTech Connect

    Nicklaus, Dennis J.

    2013-10-13

    We have developed an Erlang language implementation of the Channel Access protocol. Included are low-level functions for encoding and decoding Channel Access protocol network packets as well as higher level functions for monitoring or setting EPICS process variables. This provides access to EPICS process variables for the Fermilab Acnet control system via our Erlang-based front-end architecture without having to interface to C/C++ programs and libraries. Erlang is a functional programming language originally developed for real-time telecommunications applications. Its network programming features and list management functions make it particularly well-suited for the task of managing multiple Channel Access circuits and PV monitors.

  18. Detecting the BAO using Discrete Wavelet Packets

    NASA Astrophysics Data System (ADS)

    Garcia, Noel Anthony; Wu, Yunyun; Kadowaki, Kevin; Pando, Jesus

    2017-01-01

    We use wavelet packets to investigate the clustering of matter on galactic scales in search of the Baryon Acoustic Oscillations. We do so in two ways. We develop a wavelet packet approach to measure the power spectrum and apply this method to the CMASS galaxy catalogue from the Sloan Digital Sky Survey (SDSS). We compare the resulting power spectrum to published BOSS results by measuring a parameter β that compares our wavelet detected oscillations to the results from the SDSS collaboration. We find that β=1 indicating that our wavelet packet methods are detecting the BAO at a similar level as traditional Fourier techniques. We then use wavelet packets to decompose, denoise, and then reconstruct the galaxy density field. Using this denoised field, we compute the standard two-point correlation function. We are able to successfully detect the BAO at r ≈ 105 h-1 Mpc in line with previous SDSS results. We conclude that wavelet packets do reproduce the results of the key clustering statistics computed by other means. The wavelet packets show distinct advantages in suppressing high frequency noise and in keeping information localized.

  19. Comparison of Ring-Buffer-Based Packet Capture Solutions

    SciTech Connect

    Barker, Steven Andrew

    2015-10-01

    Traditional packet-capture solutions using commodity hardware incur a large amount of overhead as packets are copied multiple times by the operating system. This overhead slows sensor systems to a point where they are unable to keep up with high bandwidth traffic, resulting in dropped packets. Incomplete packet capture files hinder network monitoring and incident response efforts. While costly commercial hardware exists to capture high bandwidth traffic, several software-based approaches exist to improve packet capture performance using commodity hardware.

  20. Good Grooming. Cooperative Work Experience Learning Activity Packet: Series on Job Entry and Adjustment; Packet Four.

    ERIC Educational Resources Information Center

    Herschbach, Dennis R.; And Others

    This student booklet is fourth in an illustrated series of eleven learning activity packets for use in teaching job hunting and application procedures and the management of wages to secondary students. Two units are included in this packet, one covering proper dress and grooming for the interview, and the other appearance on the job. Suggestions…

  1. Radiology/Imaging. Clinical Rotation. Instructor's Packet and Student Study Packet.

    ERIC Educational Resources Information Center

    Texas Univ., Austin. Extension Instruction and Materials Center.

    The instructor's packet, the first of two packets, is one of a series of materials designed to help students who are investigating the activities within a radiology department or considering any of the imaging technologies as a career. The material is designed to relate training experience to information studied in the classroom. This packet…

  2. Analysis of wave packet motion in frequency and time domain: oxazine 1.

    PubMed

    Braun, Markus; Sobotta, Constanze; Dürr, Regina; Pulvermacher, Horst; Malkmus, Stephan

    2006-08-17

    Wave packet motion in the laser dye oxazine 1 in methanol is investigated by spectrally resolved transient absorption spectroscopy. The spectral range of 600-690 nm was accessible by amplified broadband probe pulses covering the overlap region of ground-state bleach and stimulated emission signal. The influence of vibrational wave packets on the optical signal is analyzed in the frequency domain and the time domain. For the analysis in the frequency domain an algorithm is presented that accounts for interference effects of neighbored vibrational modes. By this method amplitude, phase and decay time of vibrational modes are retrieved as a function of probe wavelength and distortions due to neighbored modes are reduced. The analysis of the data in the time domain yields complementary information on the intensity, central wavelength, and spectral width of the optical bleach spectrum due to wave packet motion.

  3. Dynamics of Attosecond Electron Wave Packets

    NASA Astrophysics Data System (ADS)

    Mauritsson, Johan

    2005-05-01

    We present results from some of the first experimental studies of attosecond electron wave packets created via the absorption of ultrashort extreme ultraviolet (XUV) light pulses [1]. The pulses, made via high harmonic generation, form an attosecond pulse train (APT) whose properties we can manipulate by a combination of spatial and spectral filtering. For instance, we show that on-target attosecond pulses of 170 as duration, which is close to the single cycle limit, can be produced [2]. The electron wave packets created when such an APT is used to ionize an atom are different from the tunneling wave packets familiar from strong field ionization. We show how to measure the dynamics of these wave packets in a strong infrared (IR) field, where the absorption of energy above the ionization threshold is found to depend strongly on the APT-IR delay [3]. We also demonstrate that altering the properties of the initial electron wave packet by manipulating the APT changes the subsequent continuum electron dynamics. Finally, we show how the phase of a longer, femtosecond electron wave packet can be modulated by a moderately strong IR pulse with duration comparable to or shorter than that of the electron wave packet. This experiment reveals how the normal ponderomotive shift of an XUV ionization event is modified when the IR pulse is shorter than the XUV pulse.[1] The experiments were done at Lund Institute of Technology, Sweden.[2] R. López-Martens, et al., Phys. Rev. Lett. 94, 033001 (2005)[3] P. Johnsson, et al., submitted to Phys. Rev. Lett.

  4. Atomic Electron Wave Packet Interference and Control

    NASA Astrophysics Data System (ADS)

    Noel, Michael W.

    We have used a train of picosecond laser pulses to excite an atomic electron into a coherent superposition of radially localized wave packets. Such superpositions were used in three separate experiments to study interference and control of atomic electron wave packets. The first experiment is an analog of Young's double -slit interferometer using an atomic electron instead of light. The superposition for this experiment consists of two wave packets coherently excited on opposite sides of a common Kepler orbit, which mimic the pair of slits used in Young's experiment. The two wave packets propagate and spread until they completely overlap, then a third laser pulse probes the resulting fringe pattern. The relative phase of the two wave packet can be varied so that the interference produces a single localized electron wave packet on one side of the orbit or the other. In the second experiment we study the same superposition of two separated wave packets, but this time in an analogy to Schrodinger's coherent superposition of live and dead cat. State selective field ionization is used to verify that only every other atomic level is populated in the cat state, and a Ramsey fringe measurement is used to demonstrate the coherence of the superposition. In the third experiment we have made use of the interference studied in the first two in an effort to control the radial distribution of the electron. This is done by controlling the quantum state distribution that is excited with a train of laser pulses. We have developed this control theory for the weak field case to show the simple and unique solutions that result. We have also demonstrated this type of control by showing how the state distribution can be modified for the simple case of a train of three pulses.

  5. Hop Reservation Multiple Access (HRMA) for Multichannel Packet Radio Networks

    DTIC Science & Technology

    1998-01-01

    protocols as FAMA [4][7] and MACAW [5]. To simplify our analysis, a non-persistent policy is used for hop reser- vations; persistent versions of HRMA are...and SPARROW Project. http://www.cse.ucsc.edu/research/ccrg/, Santa Cruz, CA, 1998. [5] V. Bharghavan, A. Demers, S. Shenker, and L. Zhang. Macaw : A

  6. 47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an...

  7. 47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an...

  8. 47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an...

  9. 47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an...

  10. Characterization of fast photoelectron packets in weak and strong laser fields in ultrafast electron microscopy.

    PubMed

    Plemmons, Dayne A; Tae Park, Sang; Zewail, Ahmed H; Flannigan, David J

    2014-11-01

    The development of ultrafast electron microscopy (UEM) and variants thereof (e.g., photon-induced near-field electron microscopy, PINEM) has made it possible to image atomic-scale dynamics on the femtosecond timescale. Accessing the femtosecond regime with UEM currently relies on the generation of photoelectrons with an ultrafast laser pulse and operation in a stroboscopic pump-probe fashion. With this approach, temporal resolution is limited mainly by the durations of the pump laser pulse and probe electron packet. The ability to accurately determine the duration of the electron packets, and thus the instrument response function, is critically important for interpretation of dynamics occurring near the temporal resolution limit, in addition to quantifying the effects of the imaging mode. Here, we describe a technique for in situ characterization of ultrashort electron packets that makes use of coupling with photons in the evanescent near-field of the specimen. We show that within the weakly-interacting (i.e., low laser fluence) regime, the zero-loss peak temporal cross-section is precisely the convolution of electron packet and photon pulse profiles. Beyond this regime, we outline the effects of non-linear processes and show that temporal cross-sections of high-order peaks explicitly reveal the electron packet profile, while use of the zero-loss peak becomes increasingly unreliable.

  11. Weighted unequal error protection for transmitting scalable object-oriented images over packet-erasure networks.

    PubMed

    Gan, Tong; Ma, Kai-Kuang

    2005-02-01

    In this paper, we investigate the problem of transmitting embedded encoded object-oriented images over the packet-erasure networks. After giving a review of the existing combined unequal error protection (CUEP) and individual unequal error protection (IUEP) schemes, a novel weighted unequal error protection (WUEP) packetization scheme is proposed, which serves as an alternative to the existing methods. In our proposed framework, the embedded bitstreams of all concerned image objects are packetized into multiple description packet streams before transmission. Two levels of rate allocation are introduced: intraobject rate allocation provides unequal error protection to the embedded bitstream of each object and minimizes its associated mean distortion; interobject rate allocation aims at minimizing the weighted mean distortion by adaptively allocating the rate budget among different objects according to their importance. Furthermore, our proposed packetization scheme ensures independent access and manipulation of individual image object. A detailed comparison between CUEP, IUEP, and WUEP is presented along with the experimental results, so that one can choose the most suitable approach according to the requirements.

  12. Design of a 10-Gb/s satellite downlink at millimeter-wave frequencies

    NASA Astrophysics Data System (ADS)

    Ridgway, Richard W.; Nippa, David W.; Yen, Stephen; Barnum, Thomas J.

    2011-03-01

    System requirements, including carrier frequency, transmitted power and antenna gain are presented for a 10 Gb/s satellite downlink operating at millimeter-wave frequencies. Telecommunications-grade optical components and a high-speed photodiode are used to generate and modulate millimeter-wave carrier frequencies between 90 GHz and 100 GHz at data rates in excess of 10 Gb/s. Experimental results are presented that determine the minimum received power level needed for error-free wireless data transmission. Commercially available W-band power amplifiers are shown to increase the transmitted power level and extend the error-free propagation distance to distances of 10 km. Experimental results and documented atmospheric attenuation values for clouds, fog and rain are used to estimate link budgets for a wireless downlink located on a low-earth-orbiting satellite operating at an altitude of 350 km.

  13. Performance analysis of MRC spatial diversity receiver system for satellite-to-ground downlink optical transmissions

    NASA Astrophysics Data System (ADS)

    Li, Kangning; Ma, Jing; Tan, Liying; Yu, Siyuan; Cao, Yubin

    2016-10-01

    The performances of satellite-to-ground downlink optical communications over Gamma-Gamma distributed turbulence are studied for multiple apertures receiver system. Maximum ratio combining (MRC) technique is considered as a combining scheme to mitigate the atmospheric turbulence under thermal noise limited conditions. Bit-error rate (BER) performances for on-off keying (OOK) modulated direct detection optical communications are analyzed for MRC diversity receptions through an approximation method. To show the net diversity gain of multiple apertures receiver system, BER performances of MRC receiver system are compared with a single monolithic aperture receiver system with the same total aperture area (same average total incident optical power) for satellite-to-ground downlink optical communications. All the numerical results are also verified by Monte-Carlo (MC) simulations.

  14. An overview of packet-switching communications

    NASA Astrophysics Data System (ADS)

    Heggestad, H. M.

    1984-04-01

    A brief introduction is provided to an alternative computer-based technique for connecting a source to a destination, one which is not an evolutionary improvement in circuit switching but a radical departure from traditional techniques, namely packet switching. It is noted that this mechanism is becoming firmly established as a method for communicating digital data. Advances are also being made rapidly in the transmission of voice by this means, and packet switching may in fact be ideal for some future systems in which voice and data are fully integrated. The distinguishing feature of a packet-switched system is that a computer organizes outgoing digital information into segments which make their way independently to the receiving stations. Here, other computers reassemble them into replicas of the original message. One of the objectives conveniently achieved by packet systems is robustness with respect to blockage on particular links in the network. It is pointed out that two significant limitations affect the design and use of packet-switched systems; one is the need for substantial computer processing and bit manipulation at the network nodes, the other is accumulation of delay for real-time traffic.

  15. Balancing Uplink and Downlink under Asymmetric Traffic Environments Using Distributed Receive Antennas

    NASA Astrophysics Data System (ADS)

    Sohn, Illsoo; Lee, Byong Ok; Lee, Kwang Bok

    Recently, multimedia services are increasing with the widespread use of various wireless applications such as web browsers, real-time video, and interactive games, which results in traffic asymmetry between the uplink and downlink. Hence, time division duplex (TDD) systems which provide advantages in efficient bandwidth utilization under asymmetric traffic environments have become one of the most important issues in future mobile cellular systems. It is known that two types of intercell interference, referred to as crossed-slot interference, additionally arise in TDD systems; the performances of the uplink and downlink transmissions are degraded by BS-to-BS crossed-slot interference and MS-to-MS crossed-slot interference, respectively. The resulting performance unbalance between the uplink and downlink makes network deployment severely inefficient. Previous works have proposed intelligent time slot allocation algorithms to mitigate the crossed-slot interference problem. However, they require centralized control, which causes large signaling overhead in the network. In this paper, we propose to change the shape of the cellular structure itself. The conventional cellular structure is easily transformed into the proposed cellular structure with distributed receive antennas (DRAs). We set up statistical Markov chain traffic model and analyze the bit error performances of the conventional cellular structure and proposed cellular structure under asymmetric traffic environments. Numerical results show that the uplink and downlink performances of the proposed cellular structure become balanced with the proper number of DRAs and thus the proposed cellular structure is notably cost-effective in network deployment compared to the conventional cellular structure. As a result, extending the conventional cellular structure into the proposed cellular structure with DRAs is a remarkably cost-effective solution to support asymmetric traffic environments in future mobile cellular

  16. Joint Minimization of Uplink and Downlink Whole-Body Exposure Dose in Indoor Wireless Networks

    PubMed Central

    Plets, D.; Joseph, W.; Vanhecke, K.; Vermeeren, G.; Wiart, J.; Aerts, S.; Varsier, N.; Martens, L.

    2015-01-01

    The total whole-body exposure dose in indoor wireless networks is minimized. For the first time, indoor wireless networks are designed and simulated for a minimal exposure dose, where both uplink and downlink are considered. The impact of the minimization is numerically assessed for four scenarios: two WiFi configurations with different throughputs, a Universal Mobile Telecommunications System (UMTS) configuration for phone call traffic, and a Long-Term Evolution (LTE) configuration with a high data rate. Also, the influence of the uplink usage on the total absorbed dose is characterized. Downlink dose reductions of at least 75% are observed when adding more base stations with a lower transmit power. Total dose reductions decrease with increasing uplink usage for WiFi due to the lack of uplink power control but are maintained for LTE and UMTS. Uplink doses become dominant over downlink doses for usages of only a few seconds for WiFi. For UMTS and LTE, an almost continuous uplink usage is required to have a significant effect on the total dose, thanks to the power control mechanism. PMID:25793213

  17. Joint minimization of uplink and downlink whole-body exposure dose in indoor wireless networks.

    PubMed

    Plets, D; Joseph, W; Vanhecke, K; Vermeeren, G; Wiart, J; Aerts, S; Varsier, N; Martens, L

    2015-01-01

    The total whole-body exposure dose in indoor wireless networks is minimized. For the first time, indoor wireless networks are designed and simulated for a minimal exposure dose, where both uplink and downlink are considered. The impact of the minimization is numerically assessed for four scenarios: two WiFi configurations with different throughputs, a Universal Mobile Telecommunications System (UMTS) configuration for phone call traffic, and a Long-Term Evolution (LTE) configuration with a high data rate. Also, the influence of the uplink usage on the total absorbed dose is characterized. Downlink dose reductions of at least 75% are observed when adding more base stations with a lower transmit power. Total dose reductions decrease with increasing uplink usage for WiFi due to the lack of uplink power control but are maintained for LTE and UMTS. Uplink doses become dominant over downlink doses for usages of only a few seconds for WiFi. For UMTS and LTE, an almost continuous uplink usage is required to have a significant effect on the total dose, thanks to the power control mechanism.

  18. Digital transceiver implementation for wavelet packet modulation

    NASA Astrophysics Data System (ADS)

    Lindsey, Alan R.; Dill, Jeffrey C.

    1998-03-01

    Current transceiver designs for wavelet-based communication systems are typically reliant on analog waveform synthesis, however, digital processing is an important part of the eventual success of these techniques. In this paper, a transceiver implementation is introduced for the recently introduced wavelet packet modulation scheme which moves the analog processing as far as possible toward the antenna. The transceiver is based on the discrete wavelet packet transform which incorporates level and node parameters for generalized computation of wavelet packets. In this transform no particular structure is imposed on the filter bank save dyadic branching, and a maximum level which is specified a priori and dependent mainly on speed and/or cost considerations. The transmitter/receiver structure takes a binary sequence as input and, based on the desired time- frequency partitioning, processes the signal through demultiplexing, synthesis, analysis, multiplexing and data determination completely in the digital domain - with exception of conversion in and out of the analog domain for transmission.

  19. A versatile model for packet loss visibility and its application to packet prioritization.

    PubMed

    Lin, Ting-Lan; Kanumuri, Sandeep; Zhi, Yuan; Poole, David; Cosman, Pamela C; Reibman, Amy R

    2010-03-01

    In this paper, we propose a generalized linear model for video packet loss visibility that is applicable to different group-of-picture structures. We develop the model using three subjective experiment data sets that span various encoding standards (H.264 and MPEG-2), group-of-picture structures, and decoder error concealment choices. We consider factors not only within a packet, but also in its vicinity, to account for possible temporal and spatial masking effects. We discover that the factors of scene cuts, camera motion, and reference distance are highly significant to the packet loss visibility. We apply our visibility model to packet prioritization for a video stream; when the network gets congested at an intermediate router, the router is able to decide which packets to drop such that visual quality of the video is minimally impacted. To show the effectiveness of our visibility model and its corresponding packet prioritization method, experiments are done to compare our perceptual-quality-based packet prioritization approach with existing Drop-Tail and Hint-Track-inspired cumulative-MSE-based prioritization methods. The result shows that our prioritization method produces videos of higher perceptual quality for different network conditions and group-of-picture structures. Our model was developed using data from high encoding-rate videos, and designed for high-quality video transported over a mostly reliable network; however, the experiments show the model is applicable to different encoding rates.

  20. Design and Performance Analysis of Downlink in Space Communications System for Lunar Exploration

    NASA Astrophysics Data System (ADS)

    Lee, Wooju; Cho, Kyongkuk; Yoon, Dongweon

    2010-03-01

    Korean government made clear that it would make efforts to carry out full-fledged research into space exploration with the aim of developing a Lunar Orbiter (LO) from 2017 to 2020 in the detailed implement guidance of the space development project established in 2007 (Lee 2009). To make the plan realized, basic researches into a space communication link are essential (Kim et al. 2009). However, local researches in Korea were focused on the near-earth satellite communication links and the researches on the deep space communications were hardly founded. This paper designs and analyzes the downlink between a LO and an Earth Station (ES) in space communications system for lunar exploration, and suggests requirements for the communication link design with conforming to international recommendations. In general, among the losses in the calculation of a space communication link budget between the LO and the ES, the largest one is the free space loss comes from the distance between the earth and the moon. Furthermore, an accurate link model should be made up in order to analyze the performance in a more accurate way, with all the other elements influencing on signal quality. In this paper, we design the model of a space communications system considering almost all elements to affect the downlink performance of the space communications system between the LO and the ES, based on detailed requirements by CCSDS (the Consultative Committee for Space Data Systems, 2007), and verify the results with reference to the foreign operation cases of NASA (National Aeronautics and Space Administration) DSN (Deep Space Network) (Slobin 2006, Sniffin 2002, 2008). According to the CCSDS, we assume that the communication links have the line of sight path between the LO and the ES for S, X, Ku, and Ka bands, and an uncoded OQPSK signal is considered for a telemetry transmission. Also, a required target BER (Bit Error Rate) in the downlink space communications systems is assumed to be 10^5. We

  1. Packet radar spectrum recovery for physiological signals.

    PubMed

    Yavari, Ehsan; Padasdao, Bryson; Lubecke, Victor; Boric-Lubecke, Olga

    2013-01-01

    Packet Doppler radar is investigated for extracting physiological signals. System on Chip is employed as a signal source in packet mode, and it transmits signals intermittently at 2.405 GHz to save power. Reflected signals are demodulated directly by spectral analysis of received pulses in the baseband. Spectral subtraction, using data from an empty room, is applied to extract the periodic movement. It was experimentally demonstrated that frequency of the periodic motion can be accurately extracted using this technique. Proposed approach reduces the computation complexity of the signal processing part effectively.

  2. Coding for spread spectrum packet radios

    NASA Technical Reports Server (NTRS)

    Omura, J. K.

    1980-01-01

    Packet radios are often expected to operate in a radio communication network environment where there tends to be man made interference signals. To combat such interference, spread spectrum waveforms are being considered for some applications. The use of convolutional coding with Viterbi decoding to further improve the performance of spread spectrum packet radios is examined. At 0.00001 bit error rates, improvements in performance of 4 db to 5 db can easily be achieved with such coding without any change in data rate nor spread spectrum bandwidth. This coding gain is more dramatic in an interference environment.

  3. Wavelet and wavelet packet compression of electrocardiograms.

    PubMed

    Hilton, M L

    1997-05-01

    Wavelets and wavelet packets have recently emerged as powerful tools for signal compression. Wavelet and wavelet packet-based compression algorithms based on embedded zerotree wavelet (EZW) coding are developed for electrocardiogram (ECG) signals, and eight different wavelets are evaluated for their ability to compress Holter ECG data. Pilot data from a blind evaluation of compressed ECG's by cardiologists suggest that the clinically useful information present in original ECG signals is preserved by 8:1 compression, and in most cases 16:1 compressed ECG's are clinically useful.

  4. Ray Curvature and Refraction of Wave Packets.

    DTIC Science & Technology

    1978-09-01

    1!~~~~~ _ ‘ AD AOM 302 FLORIDA STATE UNIV TALLAHASSEE DEPT OF OCEANOGRAPHY FIG B/3 RAY CURVATURE AND REFRACTION OF WAVE PACKETS. (U) SEP 78 .J E...BREEDING N00014—77—C—0329 UNCLASSIFIED TR JE6 3 NL _ _ _ rwii__ _ ~iU ir!I I -~~ RAYOJR\\1L~[UREAND REFRACI ION OF WAVE F1~\\CKET~S ~y J. Ernest Breeding...01 29 014 -~ Technical Report No. JEB-3 Department of Oceanography • Florida State University RAY CURVATURE AND REFRACTION OF WAVE PACKETS b O G • J

  5. All-optical packet header and payload separation for un-slotted optical packet switched networks

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Zhang, Min; Ye, Peida

    2005-11-01

    A novel all-optical header and payload separation technique that can be utilized in un-slotted optical packet switched networks is presented. The technique uses a modified TOAD for packet header extraction with differential modulation scheme and two SOAs that perform a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue of this system is simple structure and need not any additional continuous pulses. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the parameters of the system are discussed and designed to optimize the operation performance.

  6. The Air We Breathe. Activity Packet.

    ERIC Educational Resources Information Center

    Connecticut State Dept. of Environmental Protection, Hartford.

    This packet of materials is intended to provide teachers with an interdisciplinary approach to integrating air quality education into the existing curriculum of Connecticut schools. The unit is designed to complement the student booklet "The Air We Breathe," which is included. A major portion of the document is comprised of teaching…

  7. Cashier/Checker Learning Activity Packets (LAPs).

    ERIC Educational Resources Information Center

    Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    Twenty-four learning activity packets (LAPs) are provided for six areas of instruction in a cashier/checker program. Section A, Orientation, contains an LAP on exploring the job of cashier-checker. Section B, Operations, has nine LAPs, including those on operating the cash register, issuing trading stamps, and completing the cash register balance…

  8. Yorktown Victory Center Museum Teacher Resource Packet.

    ERIC Educational Resources Information Center

    Jamestown-Yorktown Foundation, Williamsburg, VA. Education Dept.

    This resource packet provides information and activities for teaching abut the historical significance of Yorktown, Virginia in the American Revolution. Teachers' materials include brief background essays on: (1) "Summary of the American Revolution in Virginia"; (2) "Life in the Army"; (3) "Life in Revolutionary…

  9. Peninsula Humane Society Teacher's Packet. Secondary Level.

    ERIC Educational Resources Information Center

    Peninsula Humane Society, San Mateo, CA.

    Activities in this teacher's packet are designed to familiarize secondary school students with the responsibilities involved in pet ownership. Teaching plans are provided for a total of 12 lessons grouped under social studies, language arts, math, and health sciences. Activities focus on pet overpopulation, expressions of social responses in…

  10. Queueing Analysis For Packet Switched Video

    NASA Astrophysics Data System (ADS)

    Sen, Prodip; Rikli, Nasser; Maglaris, Basil

    1987-10-01

    Packet switching of variable bit-rate real-time video sources is a means for the efficient sharing of communication resources, while maintaining a uniform picture quality. Performance analyses for the statistical multiplexing of such video sources are required as a first step towards assessing the feasibility of packet switched video. This paper extends our earlier work in modelling video sources which have been coded using inter-frame coding schemes, and in carrying out buffer queueing analyses for the multiplexing of several such sources. Our previous models and analysis were suitable for relatively uniform activity scenes. Here we consider models and queueing analysis for more realistic scenes with multiple activity levels where the coder output bit-rates may change violently. We present correlated Markov source models for the corresponding sources, and using a flow-equivalent queueing analysis, obtain common buffer queue distributions and probabilities of packet loss. Our results demonstrate efficient resource sharing of packetized video on a single link, due to the smoothing effect of multiplexing several variable-rate video sources.

  11. The Nutcracker--Theater Activity Packet.

    ERIC Educational Resources Information Center

    New York City Board of Education, Brooklyn, NY. Div. of Curriculum and Instruction.

    A part of the New York City Board of Education Early Stages educational program, this activity packet was developed to assist teachers in preparing students for viewing the American Ballet Theatre's production of "The Nutcracker." The guide begins with a section on preparing for the performance, and includes information on the Early…

  12. Humane Education Teachers' Packet (Preschool & Kindergarten).

    ERIC Educational Resources Information Center

    Sammut-Tovar, Dorothy

    Designed to sensitize preschoolers and kindergartners to the responsibilities involved in caring for living things, this teacher's packet provides a variety of student worksheets and activity suggestions. Teaching plans are provided for a total of nine lessons, which can be easily integrated into other learning areas such as numbers, colors,…

  13. The World Around You. Environmental Education Packet.

    ERIC Educational Resources Information Center

    Garden Club of America, New York, NY.

    The Garden Club of America has compiled this environmental education packet of informational materials to help teachers educate their students for survival. The "Study Guide" contains essays by ten authorities on topics of population, soil, air, water, power and energy, solid waste management, open space, public lands, oceans, and wildlife. Each…

  14. Student Problems. Adult Literacy Independent Learning Packet.

    ERIC Educational Resources Information Center

    Koefer, Ann M.

    This independent learning packet, which is designed for administrators, teachers, counselors, and tutors in Pennsylvania's Region 7 Tri-Valley Literacy Staff Development area as well as for their adult students, examines the following seven problems encountered by students: the job market, child care, single parenting/parenting skills, divorce,…

  15. Biological Diversity. Global Issues Education Packet.

    ERIC Educational Resources Information Center

    Holm, Amy E.

    Biological diversity, also commonly called genetic diversity, refers to the variety of organisms on Earth. Scientists are concerned that many species will become extinct because of extensive development in the tropical regions. This packet is designed to increase student's awareness about direct and indirect causes of extinction, endangered…

  16. Solid Waste Activity Packet for Teachers.

    ERIC Educational Resources Information Center

    Illinois Univ., Urbana. Cooperative Extension Service.

    This solid waste activity packet introduces students to the solid waste problem in Illinois. Topics explore consumer practices in the market place, packaging, individual and community garbage generation, and disposal practices. The activities provide an integrated approach to incorporating solid waste management issues into subject areas. The…

  17. Metro College for Living. Workshop Packet.

    ERIC Educational Resources Information Center

    Kreps, Alice Roelofs

    This packet contains information and materials for conducting a training workshop for working with adults who are developmentally disabled. The materials are specifically designed to train volunteer teachers in the College for Living (CFL) program, which supplements residential programs in and around Denver and aids institutions in orienting…

  18. Controlled wave-packet manipulation with driven optical lattices

    SciTech Connect

    Arlinghaus, Stephan; Holthaus, Martin

    2011-12-15

    Motivated by recent experimental progress achieved with ultracold atoms in kilohertz-driven optical lattices, we provide a theoretical discussion of mechanisms governing the response of a particle in a cosine lattice potential to strong forcing pulses with smooth envelope. Such pulses effectuate adiabatic motion of a wave packet's momentum distribution on quasienergy surfaces created by spatiotemporal Bloch waves. Deviations from adiabaticity can then be deliberately exploited for exerting coherent control and for reaching target states which may not be accessible by other means. As one particular example, we consider an analog of the {pi} pulses known from optical resonance. We also suggest adapting further techniques previously developed for controlling atomic and molecular dynamics by laser pulses to the coherent control of matter waves in shaken optical lattices.

  19. PROJECT SUCCESS: Art. (Introductory Packet, Drawing, Claywork, Painting).

    ERIC Educational Resources Information Center

    Petersen, Nancy

    Four packets comprise the art component of an enrichment program for gifted elementary students. The introduction packet reviews identification of children gifted in art through pre and post measures. A drawing packet reviews techniques for such activities as human figure drawing, shading, crayon rubbinqs, experimenting with perspective, and…

  20. Segregation of helicity in inertial wave packets

    NASA Astrophysics Data System (ADS)

    Ranjan, A.

    2017-03-01

    Inertial waves are known to exist in the Earth's rapidly rotating outer core and could be important for the dynamo generation. It is well known that a monochromatic inertial plane wave traveling parallel to the rotation axis (along positive z ) has negative helicity while the wave traveling antiparallel (negative z ) has positive helicity. Such a helicity segregation, north and south of the equator, is necessary for the α2-dynamo model based on inertial waves [Davidson, Geophys. J. Int. 198, 1832 (2014), 10.1093/gji/ggu220] to work. The core is likely to contain a myriad of inertial waves of different wave numbers and frequencies. In this study, we investigate whether this characteristic of helicity segregation also holds for an inertial wave packet comprising waves with the same sign of Cg ,z, the z component of group velocity. We first derive the polarization relations for inertial waves and subsequently derive the resultant helicity in wave packets forming as a result of superposition of two or more waves. We find that the helicity segregation does hold for an inertial wave packet unless the wave numbers of the constituent waves are widely separated. In the latter case, regions of opposite color helicity do appear, but the mean helicity retains the expected sign. An illustration of this observation is provided by (a) calculating the resultant helicity for a wave packet formed by superposition of four upward-propagating inertial waves with different wave vectors and (b) conducting the direct numerical simulation of a Gaussian eddy under rapid rotation. Last, the possible effects of other forces such as the viscous dissipation, the Lorentz force, buoyancy stratification, and nonlinearity on helicity are investigated and discussed. The helical structure of the wave packet is likely to remain unaffected by dissipation or the magnetic field, but can be modified by the presence of linearly stable stratification and nonlinearity.

  1. Effect of Coulomb interaction on multi-electronwave packet dynamics

    SciTech Connect

    Shiokawa, T.; Takada, Y.; Konabe, S.; Hatsugai, Y.; Muraguchi, M.; Endoh, T.; Shiraishi, K.

    2013-12-04

    We have investigated the effect of Coulomb interaction on electron transport in a one-dimensional nanoscale structure using a multi-electron wave packet approach. To study the time evolution, we numerically solve the time-dependent Hartree-Fock equation, finding that the electron wave packet dynamics strongly depends on the Coulomb interaction strength. When the Coulomb interaction is large, each electron wave packet moves separately in the presence of an electric field. With weak Coulomb interaction, however, the electron wave packets overlap, forming and moving as one collective wave packet.

  2. Interference Avoidance and Resource Allocation for OFDMA Downlink of Femtocells with Distributed Power Control

    NASA Astrophysics Data System (ADS)

    Jung, Hyunduk; Han, Jechan; Lee, Jaiyong

    OFDMA femtocells in the macrocellular network of which frequency reuse factor is 1 cause serious interference to macrocell users, while the femtocells improve the performance of indoor users. In this letter, a novel downlink resource allocation algorithm for OFDMA femtocell networks is proposed to reduce interference between the macrocells and the femtocells. This algorithm allocates femtocell subchannels to avoid interference to macrocell users in the femtocell coverage, and minimizes the total transmission power of the femtocell to reduce the negative effect on the performance of the macrocell. Simulation results are provided to present the performance of the proposed algorithm.

  3. Destination-directed, packet-switching architecture for 30/20-GHz FDMA/TDM geostationary communications satellite network

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Shalkhauser, Mary JO

    1992-01-01

    A destination-directed packet switching architecture for a 30/20-GHz frequency division multiple access/time division multiplexed (FDMA/TDM) geostationary satellite communications network is discussed. Critical subsystems and problem areas are identified and addressed. Efforts have concentrated heavily on the space segment; however, the ground segment has been considered concurrently to ensure cost efficiency and realistic operational constraints.

  4. Destination directed packet switch architecture for a 30/20 GHz FDMA/TDM geostationary communication satellite network

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Shalkhauser, Mary JO

    1991-01-01

    Emphasis is on a destination directed packet switching architecture for a 30/20 GHz frequency division multiplex access/time division multiplex (FDMA/TDM) geostationary satellite communication network. Critical subsystems and problem areas are identified and addressed. Efforts have concentrated heavily on the space segment; however, the ground segment was considered concurrently to ensure cost efficiency and realistic operational constraints.

  5. Transporting live video over high packet loss networks

    NASA Astrophysics Data System (ADS)

    Werdin, Dave

    2013-05-01

    Transport of live video requires a robust backbone as live video decoders are subject to dropouts and buffer starvation. A short duration packet loss will many times cause a decoder to go black for many seconds as it reacquires the stream and clock. IP networks due to their connectionless approach and support for variable length packets, inherently display packet delivery variability. These characteristics most typically include packet loss, packet delay variation, and packets being delivered out of order. Deep Packet Recovery (DPR) techniques provide correction to IP network induced errors and issues. DPR can provide a much broader and stronger protection than traditional Forward Error Correction techniques enabling transport of live video across severely impaired networks.

  6. Using Internet Audio to Enhance Online Accessibility

    ERIC Educational Resources Information Center

    Schwartz, Linda Matula

    2004-01-01

    Accessibility to online education programs is an important factor that requires continued research, improvement, and regulation. Particularly valuable in the enhancement of online accessibility is the Voice-over Internet Protocol (VOIP) medium. VOIP compresses analog voice data and converts it into digital packets for transmission over the…

  7. Steering attosecond electron wave packets with light.

    PubMed

    Kienberger, R; Hentschel, M; Uiberacker, M; Spielmann, Ch; Kitzler, M; Scrinzi, A; Wieland, M; Westerwalbesloh, Th; Kleineberg, U; Heinzmann, U; Drescher, M; Krausz, F

    2002-08-16

    Photoelectrons excited by extreme ultraviolet or x-ray photons in the presence of a strong laser field generally suffer a spread of their energies due to the absorption and emission of laser photons. We demonstrate that if the emitted electron wave packet is temporally confined to a small fraction of the oscillation period of the interacting light wave, its energy spectrum can be up- or downshifted by many times the laser photon energy without substantial broadening. The light wave can accelerate or decelerate the electron's drift velocity, i.e., steer the electron wave packet like a classical particle. This capability strictly relies on a sub-femtosecond duration of the ionizing x-ray pulse and on its timing to the phase of the light wave with a similar accuracy, offering a simple and potentially single-shot diagnostic tool for attosecond pump-probe spectroscopy.

  8. A packet switched communications system for GRO

    NASA Technical Reports Server (NTRS)

    Husain, Shabu; Yang, Wen-Hsing; Vadlamudi, Rani; Valenti, Joseph

    1993-01-01

    This paper describes the packet switched Instrumenters Communication System (ICS) that was developed for the Command Management Facility at GSFC to support the Gamma Ray Observatory (GRO) spacecraft. The GRO ICS serves as a vital science data acquisition link to the GRO scientists to initiate commands for their spacecraft instruments. The system is ready to send and receive messages at any time, 24 hours a day and seven days a week. The system is based on X.25 and the International Standard Organization's (ISO) 7-layer Open Systems Interconnection (OSI) protocol model and has client and server components. The components of the GRO ICS are discussed along with how the Communications Subsystem for Interconnection (CSFI) and Network Control Program Packet Switching Interface (NPSI) software are used in the system.

  9. Creating and Transporting Trojan Wave Packets

    NASA Astrophysics Data System (ADS)

    Wyker, B.; Ye, S.; Dunning, F. B.; Yoshida, S.; Reinhold, C. O.; Burgdörfer, J.

    2012-01-01

    Nondispersive localized Trojan wave packets with ni˜305 moving in near-circular Bohr-like orbits are created and transported to localized near-circular Trojan states of higher n, nf˜600, by driving with a linearly polarized sinusoidal electric field whose period is slowly increased. The protocol is remarkably efficient with over 80% of the initial atoms being transferred to the higher n states, a result confirmed by classical trajectory Monte Carlo simulations.

  10. Teleportation of nonclassical wave packets of light.

    PubMed

    Lee, Noriyuki; Benichi, Hugo; Takeno, Yuishi; Takeda, Shuntaro; Webb, James; Huntington, Elanor; Furusawa, Akira

    2011-04-15

    We report on the experimental quantum teleportation of strongly nonclassical wave packets of light. To perform this full quantum operation while preserving and retrieving the fragile nonclassicality of the input state, we have developed a broadband, zero-dispersion teleportation apparatus that works in conjunction with time-resolved state preparation equipment. Our approach brings within experimental reach a whole new set of hybrid protocols involving discrete- and continuous-variable techniques in quantum information processing for optical sciences.

  11. Issues in Satellite Packet Video Communication.

    DTIC Science & Technology

    1983-07-01

    i.o . .. . . _ _: .. ,: -t - .. . ..:’, • ... . . . ... . . . j.. - . ". 4 ISSUES IN SATELLITE PACKET VIDEO COMMUNICATIO \\ For the transmitter: 1. Get...120B, which is interfaced to a Digital Equipment Corporation PDP ," 11/45 minicomputer host. The effects of varying xy and z can be simulated on the AP...plus an encoder/decoder for forward error correction, supplied by Linkabit Corporation - the earth station transmitter, receiver, and antenna supplied by

  12. Relativistic Electron Wave Packets Carrying Angular Momentum

    NASA Astrophysics Data System (ADS)

    Bialynicki-Birula, Iwo; Bialynicka-Birula, Zofia

    2017-03-01

    There are important differences between the nonrelativistic and relativistic description of electron beams. In the relativistic case the orbital angular momentum quantum number cannot be used to specify the wave functions and the structure of vortex lines in these two descriptions is completely different. We introduce analytic solutions of the Dirac equation in the form of exponential wave packets and we argue that they properly describe relativistic electron beams carrying angular momentum.

  13. LEO-to-ground optical communications link using adaptive optics correction on the OPALS downlink

    NASA Astrophysics Data System (ADS)

    Wright, Malcolm W.; Kovalik, Joseph; Morris, Jeff; Abrahamson, Matthew; Biswas, Abhijit

    2016-03-01

    The Optical PAyload for Lasercomm Science (OPALS) experiment on the International Space Station (ISS) recently demonstrated successful optical downlinks to the NASA/JPL 1-m aperture telescope at the Optical Communication Telescope Laboratory (OCTL) located near Wrightwood, CA. A large area (200 μm diameter) free space coupled avalanche photodiode (APD) detector was used to receive video and a bit patterns at 50 Mb/s. We report on a recent experiment that used an adaptive optics system at OCTL to correct for atmospherically-induced refractive index fluctuations so that the downlink from the ISS could be coupled into a single mode fiber receiver. Stable fiber coupled power was achieved over an entire pass using a self-referencing interferometer based adaptive optics system that was provided and operated by Boeing Co. and integrated to OCTL. End-to-end transmission and reconstruction of an HD video signal verified the communication performance as in the original OPALS demonstration. Coupling the signal into a single mode fiber opens the possibility for higher bandwidth and efficiency modulation schemes and serves as a pilot experiment for future implementations.

  14. Investigation of the MQAM modulation schemes in downlink of space optical communication system

    NASA Astrophysics Data System (ADS)

    Li, Mi; Wang, Ning; Li, Bowen; Zhang, Xuping; Song, Yuejiang; Zhang, Yingjie; Tu, Guojie

    2015-10-01

    Based on weak fluctuation theory, the expression of bit-error rate (BER) of Multiple Quadrature Amplitude Modulation (MQAM) with the consideration of detector noise in the downlink of space communication system is discussed in this paper. According to the expression, the performance of three typical modulation schemes, which are 4QAM, 16QAM, 64QAM, are specially analyzed. It is known that the higher the order of the modulation scheme is, the more bits of information per symbol can carry. However, when the transmission power is 1 W and the receiver diameter Dr is 1 m, the BER is 2.12×10-13 for 4QAM, 5.98×10-8 for 16QAM and 6.22×10-5 for 64QAM, which means that a higher order modulation scheme shows a higher bit-error rate (BER). Thus considering bandwidth efficiency as well as bit error rate, 16QAM is highly recommended in the real space optical communication system. In addition, the relationships between BER and optimum divergence angle, transmitter beam radius, receiving aperture for downlink are also suggested respectively in this paper, which has important reference significance for the design of the ground-to-satellite laser communication system.

  15. Spectral Modulation by Rotational Wave Packets

    NASA Astrophysics Data System (ADS)

    Baertschy, Mark; Hartinger, Klaus

    2005-05-01

    Periodic rephasing of molecular rotational wave packets can create rapid fluctuations in the optical properties of a molecular gas which can be used to manipulate the temporal phase and spectral content of ultrashort light pulses. We have demonstrated spectral control of a time-delayed ultrafast probe pulse propagating through the rotational wave packet prepared by a pump laser pulse. The spectrum of the probe pulse can be either broadened or compressed, depending on the relative sign of the temporal phase modulation and the initial chirp of the probe pulse. Adjustment of the spectral phase at the output of the interaction region allows controlled temporal pulse streching^1 and compression^2. The degree to which the spectrum of an ultrafast pulse can be modified depends on the strength and shape of the rotational wavepacket. We are studying the optimization of the rotational wave packet excitation with complex, shaped pump laser pulses for the purpose of optimizing probe pulse spectra modulation. ^1 Klaus Hartinger and Randy A. Bartels, Opt. Lett., submitted (2005). ^2 R.A. Bartels, T.C. Weinacht, N. Wagner, M. Baertschy, Chris H. Greene, M.M. Murnane, and H.C. Kapteyn , Phys. Rev. Lett., 88, 013903 (2002). This work was supported by the NSF.

  16. Optimal channel access protocol with multiple reception capacity

    NASA Astrophysics Data System (ADS)

    Chlamtac, Imrica; Farago, Andras

    1994-04-01

    A multiple access packet communication model is analyzed in which the users can receive packets on more than one common channel. For this type of system, a new channel access protocol is presented. We prove that under heavy homogeneous load the protocol guarantees the maximum achievable throughput among all possible protocols. The general model can be applied to different systems, according to various realizations of the logical channels. For example, in packet radio networks the channels can be realized by different carrier frequencies (FDMA) or by different codes (CDMA). The simplicity and optimality of the protocol make it attractive for practical applications.

  17. 47 CFR 27.19 - Requirements for operation of base and fixed stations in the 600 MHz downlink band in close...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... stations in the 600 MHz downlink band in close proximity to Radio Astronomy Observatories. 27.19 Section 27... base and fixed stations in the 600 MHz downlink band in close proximity to Radio Astronomy Observatories. (a) Licensees must make reasonable efforts to protect the radio astronomy observatory at...

  18. Tracking nuclear wave-packet dynamics in molecular oxygen ions with few-cycle infrared laser pulses

    SciTech Connect

    De, S.; Bocharova, I. A.; Magrakvelidze, M.; Ray, D.; Cao, W.; Thumm, U.; Cocke, C. L.; Bergues, B.; Kling, M. F.; Litvinyuk, I. V.

    2010-07-15

    We have tracked nuclear wave-packet dynamics in doubly charged states of molecular oxygen using few-cycle infrared laser pulses. Bound and dissociating wave packets were launched and subsequently probed via a pair of 8-fs pulses of 790 nm radiation. Ionic fragments from the dissociating molecules were monitored by velocity-map imaging. Pronounced oscillations in the delay-dependent kinetic energy release spectra were observed. The occurrence of vibrational revivals permits us to identify the potential curves of the O{sub 2} dication which are most relevant to the molecular dynamics. These studies show the accessibility to the dynamics of such higher-charged molecules.

  19. Packet spacing : an enabling mechanism for delivering multimedia content in computational grids /

    SciTech Connect

    Feng, A. C.; Feng, W. C.; Belford, Geneva G.

    2001-01-01

    Streaming multimedia with UDP has become increasingly popular over distributed systems like the Internet. Scientific applications that stream multimedia include remote computational steering of visualization data and video-on-demand teleconferencing over the Access Grid. However, UDP does not possess a self-regulating, congestion-control mechanism; and most best-efort traflc is served by congestion-controlled TCF! Consequently, UDP steals bandwidth from TCP such that TCP$ows starve for network resources. With the volume of Internet traffic continuing to increase, the perpetuation of UDP-based streaming will cause the Internet to collapse as it did in the mid-1980's due to the use of non-congestion-controlled TCP. To address this problem, we introduce the counterintuitive notion of inter-packet spacing with control feedback to enable UDP-based applications to perform well in the next-generation Internet and computational grids. When compared with traditional UDP-based streaming, we illustrate that our approach can reduce packet loss over SO% without adversely afecting delivered throughput. Keywords: network protocol, multimedia, packet spacing, streaming, TCI: UDlq rate-adjusting congestion control, computational grid, Access Grid.

  20. Asynchronous broadcast for ordered delivery between compute nodes in a parallel computing system where packet header space is limited

    DOEpatents

    Kumar, Sameer

    2010-06-15

    Disclosed is a mechanism on receiving processors in a parallel computing system for providing order to data packets received from a broadcast call and to distinguish data packets received at nodes from several incoming asynchronous broadcast messages where header space is limited. In the present invention, processors at lower leafs of a tree do not need to obtain a broadcast message by directly accessing the data in a root processor's buffer. Instead, each subsequent intermediate node's rank id information is squeezed into the software header of packet headers. In turn, the entire broadcast message is not transferred from the root processor to each processor in a communicator but instead is replicated on several intermediate nodes which then replicated the message to nodes in lower leafs. Hence, the intermediate compute nodes become "virtual root compute nodes" for the purpose of replicating the broadcast message to lower levels of a tree.

  1. Preliminary Downlink Design and Performance Assessment for Advanced Radio Interferometry Between Space and Earth (ARISE)

    NASA Astrophysics Data System (ADS)

    Yan, T.-Y.; Wang, C. C.; Gray, A.; Hemmati, H.; Mittskus, A.; Golshan, N.; Noca, M.

    1998-10-01

    Advanced Radio Interferometry Between Space and Earth (ARISE) is a space very long baseline interferometry (VLBI) mission with a nominal launch date of 2008. It consists of an inflatable 25-m radio telescope circulating in a highly elliptical Earth orbit with a perigee of 5,000 km and an apogee of 40,000 km. The objective is to observe in conjunction with Earth-based telescopes to obtain high-resolution maps of quasars and active galactic nuclei for science investigations. ARISE requires an 8-Gb/s downlink of science data, which is a challenge using today's technology. In this article, 8-Gb/s systems using both traditional radio frequency (RF) and laser communication are proposed with the goal of minimizing both the cost and the risk of the design. Either option requires appropriate technology investments. The RF system requires the use of dual polarization, high-order modulations such as 32-quadrature amplitude modulation (QAM), and spectrally efficient square-root raised-cosine (SRRC) filters to meet the Federal Communications Commission (FCC) spectral allocation. If additional bandwidth is allocated by the FCC, constant-envelope modulations such as cross-correlated trellis-coded quadrature modulation (XTCQM) can be used in place of SRRC filters and QAM to reduce the power required on the spacecraft. The proposed laser communication system uses on-off keying (OOK) and wavelength division multiplexing (WDM). The wavelength of 1550 nm has the advantage of lower background light subtended at the ground receiver for downlink communications. The critical components of the system are based on mature fiber-optic technologies. The downlink transceiver terminal will be a modified Optical Communications Demonstrator (OCD) that has been in development at JPL over the past 3 years. This article includes a road map on how the 8-Gb/s RF and laser communication systems can be developed with a series of demonstrations between now and the launch date. The demonstrations are

  2. Fairness for Non-Orthogonal Multiple Access in 5G Systems

    NASA Astrophysics Data System (ADS)

    Timotheou, Stelios; Krikidis, Ioannis

    2015-10-01

    In non-orthogonal multiple access (NOMA) downlink, multiple data flows are superimposed in the power domain and user decoding is based on successive interference cancellation. NOMA's performance highly depends on the power split among the data flows and the associated power allocation (PA) problem. In this letter, we study NOMA from a fairness standpoint and we investigate PA techniques that ensure fairness for the downlink users under i) instantaneous channel state information (CSI) at the transmitter, and ii) average CSI. Although the formulated problems are non-convex, we have developed low-complexity polynomial algorithms that yield the optimal solution in both cases considered.

  3. Fast packet switch architectures for broadband integrated services digital networks

    NASA Technical Reports Server (NTRS)

    Tobagi, Fouad A.

    1990-01-01

    Background information on networking and switching is provided, and the various architectures that have been considered for fast packet switches are described. The focus is solely on switches designed to be implemented electronically. A set of definitions and a brief description of the functionality required of fast packet switches are given. Three basic types of packet switches are identified: the shared-memory, shared-medium, and space-division types. Each of these is described, and examples are given.

  4. Measurement and Evaluation Studies of Packet Radio Telecommunications Systems

    DTIC Science & Technology

    2014-01-07

    and to perform, evaluation of Packet Radio Network In support of the evolution of packet radio technology . The (continued) DD ,: FORM AN 71 1473...by the PRNET investi- gation efforts in support of the continuing evolution of packet radio technology . The reliance on simulation and measurement...potentials of such technology . The PRNET Project has involved the efforts of a number of contracting institution. As one of the major participants, this

  5. Development of optical packet and circuit integrated ring network testbed.

    PubMed

    Furukawa, Hideaki; Harai, Hiroaki; Miyazawa, Takaya; Shinada, Satoshi; Kawasaki, Wataru; Wada, Naoya

    2011-12-12

    We developed novel integrated optical packet and circuit switch-node equipment. Compared with our previous equipment, a polarization-independent 4 × 4 semiconductor optical amplifier switch subsystem, gain-controlled optical amplifiers, and one 100 Gbps optical packet transponder and seven 10 Gbps optical path transponders with 10 Gigabit Ethernet (10GbE) client-interfaces were newly installed in the present system. The switch and amplifiers can provide more stable operation without equipment adjustments for the frequent polarization-rotations and dynamic packet-rate changes of optical packets. We constructed an optical packet and circuit integrated ring network testbed consisting of two switch nodes for accelerating network development, and we demonstrated 66 km fiber transmission and switching operation of multiplexed 14-wavelength 10 Gbps optical paths and 100 Gbps optical packets encapsulating 10GbE frames. Error-free (frame error rate < 1×10(-4)) operation was achieved with optical packets of various packet lengths and packet rates, and stable operation of the network testbed was confirmed. In addition, 4K uncompressed video streaming over OPS links was successfully demonstrated.

  6. Packet Forwarding Scheme Based on Interworking Architecture for Future Internet

    NASA Astrophysics Data System (ADS)

    Kim, Seokhoon; Ryoo, Intae

    This paper introduces a packet forwarding scheme based on interworking architecture that can provide quite a good QoS by minimizing processing delay which is the major part of the timeliness factor in New Generation IP-based networks. Based on path and resource reservation mechanism, the POSIA makes routers on the packet forwarding path synchronize with each other and then forward packets. We have shown that the POSIA outperforms the existing packet forwarding schemes like IntServ, DiffServ and MPLS through computer simulations using OPNET.

  7. Square-integrability of multivariate metaplectic wave-packet representations

    NASA Astrophysics Data System (ADS)

    Ghaani Farashahi, Arash

    2017-03-01

    This paper presents a systematic study for harmonic analysis of metaplectic wave-packet representations on the Hilbert function space {{L}2}≤ft({{{R}}d}\\right) . The abstract notions of symplectic wave-packet groups and metaplectic wave-packet representations will be introduced. We then present an admissibility condition on closed subgroups of the real symplectic group \\text{Sp}≤ft({{{R}}d}\\right) , which guarantees the square-integrability of the associated metaplectic wave-packet representation on {{L}2}≤ft({{{R}}d}\\right) .

  8. Ship-Shore Packet Switched Communications System.

    DTIC Science & Technology

    1986-06-01

    AD-RU74 638 SHIP-SHORE PACKET SWITCHED COMMUNICATIONdS SYSTE(U) 1 JUN 86NAVAL POSTGRADUATE SCHOOL MONTEREY CA R A BUDDENLERI UNLSSIFIED F/G 71...FORM 1473,84 MAR 83 APR edition may be used until exhausted SECURITY CLASSIFICATION OF THIS PAGE All other editions are obsolete l iI nl I r .. I I I...UNCLASSIFIED SECUMITV CLASSIICATIOs Or TMI# PAS g% "a s r 19. Abstract (cont’d) 3) HF communications are characterized by low capacity and high

  9. Controlling plasmonic wave packets in silver nanowires.

    SciTech Connect

    Cao, L.; Nome, R.; Montgomery, J. M.; Gray, S. K.; Scherer, N. F.

    2010-09-01

    Three-dimensional finite-difference time-domain simulations were performed to explore the excitation of surface plasmon resonances in long silver (Ag) nanowires. In particular, we show that it is possible to generate plasmonic wave packets that can propagate along the nanowire by exciting superpositions of surface plasmon resonances. By using an appropriately chirped pulse, it is possible to transiently achieve localization of the excitation at the distal end of the nanowire. Such designed coherent superpositions will allow realizing spatiotemporal control of plasmonic excitations for enhancing nonlinear responses in plasmonic 'circuits'.

  10. A Novel Nonlinear Precoding Detection Algorithm for VBLAST in MIMO-MC-CDMA Downlink System

    NASA Astrophysics Data System (ADS)

    Fu, Hongliang; Tao, Yong

    Considering the error propagation effect and high complexity of the Vertical Bell Labs Layered Space Time (V-BLAST), a novel nonlinear ZF-THP algorithm for VBLAST in MIMO-MC-CDMA downlink system is proposed in this paper. QR decomposition is used for precoding matrix, the nonlinear Tomlinson-Harashima Precoding (THP) is used between the sub-carrier channels of MC-CDMA to eliminate interference from other signals at the transmitter, and can obtain frequency diversity gain and eliminate effectively the error propagation effect. At the receiver, zero forcing criterion is used, and the complexity of the receiver can be reduced. Simulation results show that the proposed algorithm is better than the traditional zero forcing algorithm and the linear precoding algorithm in the system BER.

  11. Simple Laser Communications Terminal for Downlink from Earth Orbit at Rates Exceeding 10 Gb/s

    NASA Technical Reports Server (NTRS)

    Kovalik, Joseph M.; Hemmati, Hamid; Biswas, Abhijit; Roberts, William T.

    2013-01-01

    A compact, low-cost laser communications transceiver was prototyped for downlinking data at 10 Gb/s from Earth-orbiting spacecraft. The design can be implemented using flight-grade parts. With emphasis on simplicity, compactness, and light weight of the flight transceiver, the reduced-complexity design and development approach involves: 1. A high-bandwidth coarse wavelength division multiplexed (CWDM) (4 2.5 or 10-Gb/s data-rate) downlink transmitter. To simplify the system, emphasis is on the downlink. Optical uplink data rate is modest (due to existing and adequate RF uplink capability). 2. Highly simplified and compact 5-cm diameter clear aperture optics assembly is configured to single transmit and receive aperture laser signals. About 2 W of 4-channel multiplexed (1,540 to 1,555 nm) optically amplified laser power is coupled to the optical assembly through a fiber optic cable. It contains a highly compact, precision-pointing capability two-axis gimbal assembly to coarse point the optics assembly. A fast steering mirror, built into the optical path of the optical assembly, is used to remove residual pointing disturbances from the gimbal. Acquisition, pointing, and tracking are assisted by a beacon laser transmitted from the ground and received by the optical assembly, which will allow transmission of a laser beam. 3. Shifting the link burden to the ground by relying on direct detection optical receivers retrofitted to 1-m-diameter ground telescopes. 4. Favored mass and volume reduction over power-consumption reduction. The two major variables that are available include laser transmit power at either end of the link, and telescope aperture diameter at each end of the link. Increased laser power is traded for smaller-aperture diameters. 5. Use of commercially available spacequalified or qualifiable components with traceability to flight qualification (i.e., a flight-qualified version is commercially available). An example is use of Telecordia-qualified fiber

  12. Audio-Visual/Communications Teaching Aids Packet. Supplementary Materials. Packet P-8.

    ERIC Educational Resources Information Center

    Peace Corps, Washington, DC. Information Collection and Exchange Div.

    This packet contains three handouts on training theory and the use of audiovisual aids, as well as a section on materials and presentation techniques for use by community development workers concerned with exchanging information and working with the people in a community. The first handout, "Communication in Development," briefly…

  13. Wireless Avionics Packet to Support Fault Tolerance for Flight Applications

    NASA Technical Reports Server (NTRS)

    Block, Gary L.; Whitaker, William D.; Dillon, James W.; Lux, James P.; Ahmad, Mohammad

    2009-01-01

    In this protocol and packet format, data traffic is monitored by all network interfaces to determine the health of transmitter and subsystems. When failures are detected, the network inter face applies its recover y policies to provide continued service despite the presence of faults. The protocol, packet format, and inter face are independent of the data link technology used. The current demonstration system supports both commercial off-the-shelf wireless connections and wired Ethernet connections. Other technologies such as 1553 or serial data links can be used for the network backbone. The Wireless Avionics packet is divided into three parts: a header, a data payload, and a checksum. The header has the following components: magic number, version, quality of service, time to live, sending transceiver, function code, payload length, source Application Data Interface (ADI) address, destination ADI address, sending node address, target node address, and a sequence number. The magic number is used to identify WAV packets, and allows the packet format to be updated in the future. The quality of service field allows routing decisions to be made based on this value and can be used to route critical management data over a dedicated channel. The time to live value is used to discard misrouted packets while the source transceiver is updated at each hop. This information is used to monitor the health of each transceiver in the network. To identify the packet type, the function code is used. Besides having a regular data packet, the system supports diagnostic packets for fault detection and isolation. The payload length specifies the number of data bytes in the payload, and this supports variable-length packets in the network. The source ADI is the address of the originating interface. This can be used by the destination application to identify the originating source of the packet where the address consists of a subnet, subsystem class within the subnet, a subsystem unit

  14. Scattering of wave packets with phases

    NASA Astrophysics Data System (ADS)

    Karlovets, Dmitry V.

    2017-03-01

    A general problem of 2 → N f scattering is addressed with all the states being wave packets with arbitrary phases. Depending on these phases, one deals with coherent states in (3 + 1) D, vortex particles with orbital angular momentum, the Airy beams, and their generalizations. A method is developed in which a number of events represents a functional of the Wigner functions of such states. Using width of a packet σ p /< p> as a small parameter, the Wigner functions, the number of events, and a cross section are represented as power series in this parameter, the first non-vanishing corrections to their plane-wave expressions are derived, and generalizations for beams are made. Although in this regime the Wigner functions turn out to be everywhere positive, the cross section develops new specifically quantum features, inaccessible in the plane-wave approximation. Among them is dependence on an impact parameter between the beams, on phases of the incoming states, and on a phase of the scattering amplitude. A model-independent analysis of these effects is made. Two ways of measuring how a Coulomb phase and a hadronic one change with a transferred momentum t are discussed.

  15. Classical Hamiltonian structures in wave packet dynamics

    NASA Astrophysics Data System (ADS)

    Gray, Stephen K.; Verosky, John M.

    1994-04-01

    The general, N state matrix representation of the time-dependent Schrödinger equation is equivalent to an N degree of freedom classical Hamiltonian system. We describe how classical mechanical methods and ideas can be applied towards understanding and modeling exact quantum dynamics. Two applications are presented. First, we illustrate how qualitative insights may be gained by treating the two state problem with a time-dependent coupling. In the case of periodic coupling, Poincaré surfaces of section are used to view the quantum dynamics, and features such as the Floquet modes take on interesting interpretations. The second application illustrates computational implications by showing how Liouville's theorem, or more generally the symplectic nature of classical Hamiltonian dynamics, provides a new perspective for carrying out numerical wave packet propagation. We show how certain simple and explicit symplectic integrators can be used to numerically propagate wave packets. The approach is illustrated with an application to the problem of a diatomic molecule interacting with a laser, although it and related approaches may be useful for describing a variety of problems.

  16. Wavelet Packet Entropy for Heart Murmurs Classification

    PubMed Central

    Safara, Fatemeh; Doraisamy, Shyamala; Azman, Azreen; Jantan, Azrul; Ranga, Sri

    2012-01-01

    Heart murmurs are the first signs of cardiac valve disorders. Several studies have been conducted in recent years to automatically differentiate normal heart sounds, from heart sounds with murmurs using various types of audio features. Entropy was successfully used as a feature to distinguish different heart sounds. In this paper, new entropy was introduced to analyze heart sounds and the feasibility of using this entropy in classification of five types of heart sounds and murmurs was shown. The entropy was previously introduced to analyze mammograms. Four common murmurs were considered including aortic regurgitation, mitral regurgitation, aortic stenosis, and mitral stenosis. Wavelet packet transform was employed for heart sound analysis, and the entropy was calculated for deriving feature vectors. Five types of classification were performed to evaluate the discriminatory power of the generated features. The best results were achieved by BayesNet with 96.94% accuracy. The promising results substantiate the effectiveness of the proposed wavelet packet entropy for heart sounds classification. PMID:23227043

  17. Michigan Natural History. A Spring Activity Packet for Fourth Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on the natural history of…

  18. Practical distributed video coding in packet lossy channels

    NASA Astrophysics Data System (ADS)

    Qing, Linbo; Masala, Enrico; He, Xiaohai

    2013-07-01

    Improving error resilience of video communications over packet lossy channels is an important and tough task. We present a framework to optimize the quality of video communications based on distributed video coding (DVC) in practical packet lossy network scenarios. The peculiar characteristics of DVC indeed require a number of adaptations to take full advantage of its intrinsic robustness when dealing with data losses of typical real packet networks. This work proposes a new packetization scheme, an investigation of the best error-correcting codes to use in a noisy environment, a practical rate-allocation mechanism, which minimizes decoder feedback, and an improved side-information generation and reconstruction function. Performance comparisons are presented with respect to a conventional packet video communication using H.264/advanced video coding (AVC). Although currently the H.264/AVC rate-distortion performance in case of no loss is better than state-of-the-art DVC schemes, under practical packet lossy conditions, the proposed techniques provide better performance with respect to an H.264/AVC-based system, especially at high packet loss rates. Thus the error resilience of the proposed DVC scheme is superior to the one provided by H.264/AVC, especially in the case of transmission over packet lossy networks.

  19. Nature Prepares for Winter. A Fall Activity Packet for Kindergarten.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on preparations for winter…

  20. Learn about Seabirds. Teaching Packet, Grades 4-6.

    ERIC Educational Resources Information Center

    Fish and Wildlife Service (Dept. of Interior), Anchorage, AK.

    This teaching packet is designed to teach Alaskan students in grades 4-6 about Alaska's seabird populations, the worldwide significance of seabirds, and the environmental conditions to which seabirds are sensitive. The packet includes a curriculum guide (containing a teacher's background story and 12 teaching activities), a separately published…

  1. NIE Credit-Granting Courses and Workshops Information Packet.

    ERIC Educational Resources Information Center

    American Newspaper Publishers Association Foundation, Washington, DC.

    This packet offers information about NIE (Newspaper in Education) credit-granting courses and workshops (some of them cooperative press/school ventures) on the use of newspapers in instructional programs. The packet is in four major sections, containing: (1) case studies of two exceptional programs at the University of Wisconsin-Madison and at…

  2. Spring Birds. A Spring Activity Packet for First Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on the characteristics of…

  3. Sculpture of Indonesia. [Teacher's Packet for a Teacher Workshop.

    ERIC Educational Resources Information Center

    Asian Art Museum of San Francisco, CA.

    This teacher's packet accompanies a slide presentation on the sculpture found in Indonesia. The packet contains: (1) a slide list with descriptions listing time period and dimensions of each piece; (2) an introductory essay describing the setting of Indonesia, the Central Javanese Period and the Eastern Javanese Period; (3) descriptions of how to…

  4. Continuing Development of California State Packet Radio Project.

    ERIC Educational Resources Information Center

    Brownrigg, Edwin

    1992-01-01

    Provides background on the California State Library Packet Radio project, which will use packet radios to deploy a wireless, high-speed, wide-area network of 600 nodes, including 100 libraries, in the San Francisco Bay Area. Project goals and objectives, plan of operation, equipment, and evaluation plans are summarized. (MES)

  5. Dolphin "packet" use during long-range echolocation tasks.

    PubMed

    Finneran, James J

    2013-03-01

    When echolocating, dolphins typically emit a single broadband "click," then wait to receive the echo before emitting another click. However, previous studies have shown that during long-range echolocation tasks, they may instead emit a burst, or "packet," of several clicks, then wait for the packet of echoes to return before emitting another packet of clicks. The reasons for the use of packets are unknown. In this study, packet use was examined by having trained bottlenose dolphins perform long-range echolocation tasks. The tasks featured "phantom" echoes produced by capturing the dolphin's outgoing echolocation clicks, convolving the clicks with an impulse response to create an echo waveform, and then broadcasting the delayed, scaled echo to the dolphin. Dolphins were trained to report the presence of phantom echoes or a change in phantom echoes. Target range varied from 25 to 800 m. At ranges below 75 m, the dolphins rarely used packets. As the range increased beyond 75 m, two of the three dolphins increasingly produced packets, while the third dolphin instead utilized very high click repetition rates. The use of click packets appeared to be governed more by echo delay (target range) than echo amplitude.

  6. Reading the Rocks. A Fall Activity Packet for Fifth Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on various geological…

  7. Do Free Quantum-Mechanical Wave Packets Always Spread?

    ERIC Educational Resources Information Center

    Klein, James R.

    1980-01-01

    The spreading or shrinking of free three-dimensional quantum-mechanical wave packets is addressed. A seeming paradox concerning the time evolution operator and nonspreading wave packets is discussed, and the necessity of taking into account the appropriate mathematical structure of quantum mechanics is emphasized. Teaching implications are given.…

  8. Frogs and Toads. A Spring Activity Packet for Second Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on the characteristics and…

  9. Energy Around Us. A Fall Activity Packet for Fourth Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on energy uses, energy…

  10. Forests and Flowers. A Spring Activity Packet for Third Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on plants and…

  11. Langston Hughes Curriculum Packet: Dig and Be Dug in Return.

    ERIC Educational Resources Information Center

    Danielson, Susan

    Designed in a flexible format for use by college instructors, high school teachers, and community education workers, this curriculum packet serves as an introduction to the life and works of black poet Langston Hughes. The major component of the packet is a critical essay that explores the thematic highlights of Hughes's career. The remaining…

  12. Path Diversity Media Streaming over Best Effort Packet Switched Networks

    DTIC Science & Technology

    2003-01-01

    bandwidth for pre-recorded streaming media by sending packets simultaneously from multiple senders to a single receiver. For interactive and live ... streaming applications, the path diversity framework allows a single sender to send packets simultaneously on both default and redundant paths to the

  13. Assessing To Address Barriers to Learning. An Introductory Packet.

    ERIC Educational Resources Information Center

    California Univ., Los Angeles. Center for Mental Health Schools.

    Schools committed to the success of all children must have an array of activities designed to address barriers to learning. This introductory packet contains some aids to help school staff find new ways of thinking about how schools should assess barriers to learning. The following items are included in the packet: (1) a chart of "Barriers to…

  14. Student Activity Packet for the California State Capitol Museum.

    ERIC Educational Resources Information Center

    2001

    This packet contains materials to help fourth and fifth grade teachers provide their students with background information for field trips to the California State Capitol Museum (Sacramento). The working museum focuses on the theme areas of California history, the state government/legislative process, and state symbols. The packet presents teacher…

  15. The Surgical Scrub. Instructor's Packet. Learning Activity Package.

    ERIC Educational Resources Information Center

    Runge, Lillian

    This instructor's packet accompanies the learning activity package (LAP) on the surgical scrub. Contents included in the packet are a time sheet, suggested uses for the LAP, an instruction sheet, final LAP reviews, a final LAP review answer key, a student performance checklist, suggested activities, an additional resources list, and student…

  16. Nature's Hitchhikers. A Fall Activity Packet for Second Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on the characteristics of…

  17. Image coding based on energy-sorted wavelet packets

    NASA Astrophysics Data System (ADS)

    Kong, Lin-Wen; Lay, Kuen-Tsair

    1995-04-01

    The discrete wavelet transform performs multiresolution analysis, which effectively decomposes a digital image into components with different degrees of details. In practice, it is usually implemented in the form of filter banks. If the filter banks are cascaded and both the low-pass and the high-pass components are further decomposed, a wavelet packet is obtained. The coefficients of the wavelet packet effectively represent subimages in different resolution levels. In the energy-sorted wavelet- packet decomposition, all subimages in the packet are then sorted according to their energies. The most important subimages, as measured by the energy, are preserved and coded. By investigating the histogram of each subimage, it is found that the pixel values are well modelled by the Laplacian distribution. Therefore, the Laplacian quantization is applied to quantized the subimages. Experimental results show that the image coding scheme based on wavelet packets achieves high compression ratio while preserving satisfactory image quality.

  18. Learning packets in nursing education: reviving the past.

    PubMed

    Xu, Yin; Martin, Madeleine; Gribbins, Ashley

    2010-05-01

    Learning packets gained popularity in nursing education in the 1960's. Recently, they have been cited as strategies for distance learning. The aim of this project was to integrate Topic Focused Learning Packets as a complementary teaching strategy for presentation of new content to large classes of undergraduate nursing students. In addition to reducing in-class content presentation time, goals included: fostering critical thinking, actively engaging the student, and providing opportunities for team-based interaction. Rationale, design process and packets will be described. The learning packet was viewed positively by the students and faculty. Among 134 students, 119 strongly agreed or agreed that the learning packet was effective in increasing their understanding of the content and achieving the course objectives.

  19. Priority-based methods for reducing the impact of packet loss on HEVC encoded video streams

    NASA Astrophysics Data System (ADS)

    Nightingale, James; Wang, Qi; Grecos, Christos

    2013-02-01

    The rapid growth in the use of video streaming over IP networks has outstripped the rate at which new network infrastructure has been deployed. These bandwidth-hungry applications now comprise a significant part of all Internet traffic and present major challenges for network service providers. The situation is more acute in mobile networks where the available bandwidth is often limited. Work towards the standardisation of High Efficiency Video Coding (HEVC), the next generation video coding scheme, is currently on track for completion in 2013. HEVC offers the prospect of a 50% improvement in compression over the current H.264 Advanced Video Coding standard (H.264/AVC) for the same quality. However, there has been very little published research on HEVC streaming or the challenges of delivering HEVC streams in resource-constrained network environments. In this paper we consider the problem of adapting an HEVC encoded video stream to meet the bandwidth limitation in a mobile networks environment. Video sequences were encoded using the Test Model under Consideration (TMuC HM6) for HEVC. Network abstraction layers (NAL) units were packetized, on a one NAL unit per RTP packet basis, and transmitted over a realistic hybrid wired/wireless testbed configured with dynamically changing network path conditions and multiple independent network paths from the streamer to the client. Two different schemes for the prioritisation of RTP packets, based on the NAL units they contain, have been implemented and empirically compared using a range of video sequences, encoder configurations, bandwidths and network topologies. In the first prioritisation method the importance of an RTP packet was determined by the type of picture and the temporal switching point information carried in the NAL unit header. Packets containing parameter set NAL units and video coding layer (VCL) NAL units of the instantaneous decoder refresh (IDR) and the clean random access (CRA) pictures were given the

  20. An On-Demand Emergency Packet Transmission Scheme for Wireless Body Area Networks

    PubMed Central

    Al Ameen, Moshaddique; Hong, Choong Seon

    2015-01-01

    The rapid developments of sensor devices that can actively monitor human activities have given rise to a new field called wireless body area network (BAN). A BAN can manage devices in, on and around the human body. Major requirements of such a network are energy efficiency, long lifetime, low delay, security, etc. Traffic in a BAN can be scheduled (normal) or event-driven (emergency). Traditional media access control (MAC) protocols use duty cycling to improve performance. A sleep-wake up cycle is employed to save energy. However, this mechanism lacks features to handle emergency traffic in a prompt and immediate manner. To deliver an emergency packet, a node has to wait until the receiver is awake. It also suffers from overheads, such as idle listening, overhearing and control packet handshakes. An external radio-triggered wake up mechanism is proposed to handle prompt communication. It can reduce the overheads and improve the performance through an on-demand scheme. In this work, we present a simple-to-implement on-demand packet transmission scheme by taking into considerations the requirements of a BAN. The major concern is handling the event-based emergency traffic. The performance analysis of the proposed scheme is presented. The results showed significant improvements in the overall performance of a BAN compared to state-of-the-art protocols in terms of energy consumption, delay and lifetime. PMID:26690161

  1. Enhancing In-Flight Transoceanic Communications Using Swift-64 Packet Mode Service

    NASA Technical Reports Server (NTRS)

    Slywczak, Richard A.

    2004-01-01

    Current aeronautical communications can be divided into two segments. The first provides state of the art, packet switched technology to the cabin passengers so that they have access to e-mail and web services. The second provides basic circuit switch communication technology to the cockpit, which does not use bandwidth as efficiently as packet switching nor promotes resource sharing. This paper explores the research efforts currently being conducted by the NASA/Glenn Research Center (GRC) for transoceanic communications. The goal is to bring packet mode services to both the cabin and the cockpit of the aircraft and be able to attain benefits by sharing the data link with cabin services. First, this paper will outline the goals of the program and detail the benefits and issues related to this research. We will explain our current laboratory setup and show an architecture implemented in the testbed. Finally, we will present a work plan that will show the progression of research over the next year. This plan will describe a complete cycle from conceptual design and laboratory implementation to the final flight testing.

  2. Networked LQG control over lossy channels with computational/packet-transmission delays and coarsely quantised packets

    NASA Astrophysics Data System (ADS)

    Foo, Yung Kuan; Moayedi, Maryam; Chai Soh, Yeng

    2016-04-01

    This article addresses the linear quadratic Gaussian (LQG) control problem of networked multi-input, multi-output systems where computational delay exists and the measurement and control signals are packetised and transmitted through a network within which random delay and packet loss may occur during transmissions. A transmission control protocol (TCP)-like protocol for the communication network is considered in which acknowledgement is sent from the actuator to the controller if and only if the control packet is received, assuming these acknowledgements always reach the estimator in time and without fail. To minimise the data word-length for transmissions over the network and to maximise control system performance, it is proposed that different quantisation resolutions be used for transmission data encapsulation, and control and output signals A/D-D/A conversions at sensor/actuator. To circumvent the problem of disparity between encapsulation and A/D-D/A quantisation resolutions, a pseudo-stochastic approach via subtractive dither is applied to quantise the transmission packets. This also enables us to model the quantisation errors as uncorrelated independent zero-mean additive white noises and apply standard LQG methodology and separation principle to design the estimator and the controller separately. An example is included to demonstrate the effectiveness of the approach.

  3. Performance analysis of satellite-to-ground downlink optical communications with spatial diversity over Gamma-Gamma atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Li, Kangning; Ma, Jing; Belmonte, Aniceto; Tan, Liying; Yu, Siyuan

    2015-12-01

    The performances of satellite-to-ground downlink optical communications over Gamma-Gamma distributed turbulence are studied for a multiple-aperture receiver system. Equal gain-combining (EGC) and selection-combining (SC) techniques are considered as practical schemes to mitigate the atmospheric turbulence under thermal-noise-limited conditions. Bit-error rate (BER) performances for on-off keying-modulated direct detection and outage probabilities are analyzed and compared for SC diversity receptions using analytical results and for EGC diversity receptions through an approximation method. To show the net diversity gain of a multiple-aperture receiver system, BER performances and outage probabilities of EGC and SC receiver systems are compared with a single monolithic-aperture receiver system with the same total aperture area (same average total incident optical power) for satellite-to-ground downlink optical communications. All the numerical results are also verified by Monte-Carlo simulations.

  4. Performance analysis of satellite-to-ground downlink coherent optical communications with spatial diversity over Gamma-Gamma atmospheric turbulence.

    PubMed

    Ma, Jing; Li, Kangning; Tan, Liying; Yu, Siyuan; Cao, Yubin

    2015-09-01

    The performances of satellite-to-ground downlink optical communications over Gamma-Gamma distributed atmospheric turbulence are studied for a coherent detection receiving system with spatial diversity. Maximum ratio combining (MRC) and selection combining (SC) techniques are considered as practical schemes to mitigate the atmospheric turbulence. Bit-error rate (BER) performances for binary phase-shift keying modulated coherent detection and outage probabilities are analyzed and compared for SC diversity using analytical results and for MRC diversity through an approximation method with different numbers of receiving aperture each with the same aperture area. To show the net diversity gain of a multiple aperture receiver system, BER performances and outage probabilities of MRC and SC multiple aperture receiver systems are compared with a single monolithic aperture with the same total aperture area (same total average incident optical power) for satellite-to-ground downlink optical communications. All the numerical results are verified by Monte-Carlo simulations.

  5. Packet loss mitigation for biomedical signals in healthcare telemetry.

    PubMed

    Garudadri, Harinath; Baheti, Pawan K

    2009-01-01

    In this work, we propose an effective application layer solution for packet loss mitigation in the context of Body Sensor Networks (BSN) and healthcare telemetry. Packet losses occur due to many reasons including excessive path loss, interference from other wireless systems, handoffs, congestion, system loading, etc. A call for action is in order, as packet losses can have extremely adverse impact on many healthcare applications relying on BAN and WAN technologies. Our approach for packet loss mitigation is based on Compressed Sensing (CS), an emerging signal processing concept, wherein significantly fewer sensor measurements than that suggested by Shannon/Nyquist sampling theorem can be used to recover signals with arbitrarily fine resolution. We present simulation results demonstrating graceful degradation of performance with increasing packet loss rate. We also compare the proposed approach with retransmissions. The CS based packet loss mitigation approach was found to maintain up to 99% beat-detection accuracy at packet loss rates of 20%, with a constant latency of less than 2.5 seconds.

  6. Instrument for measurement of vacuum in sealed thin wall packets

    DOEpatents

    Kollie, Thomas G.; Thacker, Louis H.; Fine, H. Alan

    1993-01-01

    An instrument for the measurement of vacuum within sealed packets 12, the packets 12 having a wall 14 sufficiently thin that it can be deformed by the application of an external vacuum to small area thereof. The instrument has a detector head 18 for placement against the deformable wall 14 of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall 14, with this deformation or lift monitored by the application of light as via a bifurcated light pipe 20. Retro-reflected light through the light pipe is monitored with a photo detector 26. An abrupt change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the vacuum applied through the head 18 to achieve this initiation of movement is equal to the vacuum Within the packet 12. In a preferred embodiment a vacuum reference plate 44 is placed beneath the packet 12 to ensure that no deformation occurs on the reverse surface 16 of the packet. A packet production line model is also described.

  7. Instrument for measurement of vacuum in sealed thin wall packets

    DOEpatents

    Kollie, T.G.; Thacker, L.H.; Fine, H.A.

    1993-10-05

    An instrument is described for the measurement of vacuum within sealed packets, the packets having a wall sufficiently thin that it can be deformed by the application of an external vacuum to small area thereof. The instrument has a detector head for placement against the deformable wall of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall, with this deformation or lift monitored by the application of light as via a bifurcated light pipe. Retro-reflected light through the light pipe is monitored with a photo detector. An abrupt change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the vacuum applied through the head to achieve this initiation of movement is equal to the vacuum within the packet. In a preferred embodiment a vacuum reference plate is placed beneath the packet to ensure that no deformation occurs on the reverse surface of the packet. A packet production line model is also described. 3 figures.

  8. Quality of service in optical packet switched DWDM transport networks

    NASA Astrophysics Data System (ADS)

    Bjornstad, Steinar; Stol, Norvald; Hjelme, Dag R.

    2002-09-01

    For support of multimedia applications in Internet, at least four service classes are normally outlined. We expect optical packet switching to be of special interest in terabit capacity networks with a high number of wavelengths. Our analysis shows that when the wavelength dimension is used for contention resolution, and number of wavelengths is 32 or higher, node-delay is negligible. However buffering in optical packet switches is a scarce resource which use should be minimized. Based on the requirement of the future network, and on our packet switch performance analysis, we suggest reducing the number of service classes to two: A normal class (NCT) with medium low packet loss and a low need for buffering, and a high class (HCT) with a minimum of packet loss. Performance of a buffer reservation scheme is analyzed by simulation. Assuming the network of today with 10 % HCT traffic, assigning four buffer inputs to the HCT traffic, a difference in optical packet loss ratio of three orders of magnitude can be obtained. The same difference in optical packet loss ratio can be obtained if 50 % HCT traffic is assumed (network of tomorrow), by assigning a higher number of buffer inputs.

  9. Evaluation of the possibility of increasing the downlink E.I.R.P. density limits in the Ku band

    NASA Astrophysics Data System (ADS)

    Kumar, Shriram; Schmitt, Neil M.; Friedman, Robert

    2005-08-01

    The purpose of this paper is to examine the possibility of increasing the downlink E.I.R.P. density limits for operation of Fixed Satellite Service (F.S.S.) links in the Ku band. The Ku band is extensively used for voice, video, data, remote sensing applications and for transmission to VSAT (Very Small Aperture Terminals) networks. However, the limit on downlink E.I.R.P. density is considered to be conservative and it's assumed that much higher E.I.R.P. densities should be possible without causing significant interference to adjacent users. If this is proved, it would be possible to achieve lower Bit Error Rates and thereby increase reliability of satellite links. The increased power transmission capability would also allow transmission of more signals with the available bandwidth or lead to reduction in size of receiving antennas. With the help of existing F.C.C. limits on antenna gain patterns and the I.T.U. interference criterion, an increase in downlink E.I.R.P. density per carrier by more than 66% is shown to be possible. This increase in power would dramatically affect Fixed Satellite Services.

  10. Multipair Two-Way Relay Network With Harvest-Then-Transmit Users: Resolving Pairwise Uplink-Downlink Coupling

    NASA Astrophysics Data System (ADS)

    Wang, Shuai; Xia, Minghua; Wu, Yik-Chung

    2016-12-01

    While two-way relaying is a promising way to enhance the spectral efficiency of wireless networks, the imbalance of relay-user distances may lead to excessive wireless power at the nearby-users. To exploit the excessive power, the recently proposed harvest-then-transmit technique can be applied. However, it is well-known that harvest-then-transmit introduces uplink-downlink coupling for a user. Together with the co-dependent relationship between paired users and interference among multiple user pairs, wirelessly powered two-way relay network suffers from the unique pairwise uplink-downlink coupling, and the joint uplink-downlink network design is nontrivial. To this end, for the one pair users case, we show that a global optimal solution can be obtained. For the general case of multi-pair users, based on the rank-constrained difference of convex program, a convergence guaranteed iterative algorithm with an efficient initialization is proposed. Furthermore, a lower bound to the performance of the optimal solution is derived by introducing virtual receivers at relay. Numerical results on total transmit power show that the proposed algorithm achieves a transmit power value close to the lower bound.

  11. Dual-beam optically injected semiconductor laser for radio-over-fiber downlink transmission with tunable microwave subcarrier frequency

    NASA Astrophysics Data System (ADS)

    Liu, Yuping; Qi, Xiaoqiong; Xie, Liang

    2013-04-01

    We propose a downlink broadcast transmission scheme of radio-over-fiber (RoF) system based on period-one (P1) dynamic of dual-beam optically injected semiconductor laser with tunable microwave subcarrier frequency. The transmission performance of 2.5 Gb/s data in a 60 GHz RoF system is demonstrated through numerical simulations. It is found that the proposed transmission scheme can easily generate a single-sideband (SSB) optical modulation by adjusting the injection strength level of two master lasers (ML), which is favorable to reduce the fading effect due to chromatic dispersion. Furthermore, influences of the pulse amplitudes and duty cycles of the downlink data on the transmission properties are investigated. It is observed that the oscillation of the relative power at the base station induced by fiber dispersion does not vary apparently with the modulation parameters. Once the SSB spectrum is generated by dual-beam optical injection, the downlink transmission performance of the proposed RoF system keeps good stability and reliability.

  12. An Efficient Circulant MIMO Equalizer for CDMA Downlink: Algorithm and VLSI Architecture

    NASA Astrophysics Data System (ADS)

    Guo, Yuanbin; Zhang, Jianzhong(Charlie); McCain, Dennis; Cavallaro, Joseph R.

    2006-12-01

    We present an efficient circulant approximation-based MIMO equalizer architecture for the CDMA downlink. This reduces the direct matrix inverse (DMI) of size[InlineEquation not available: see fulltext.] with[InlineEquation not available: see fulltext.] complexity to some FFT operations with[InlineEquation not available: see fulltext.] complexity and the inverse of some[InlineEquation not available: see fulltext.] submatrices. We then propose parallel and pipelined VLSI architectures with Hermitian optimization and reduced-state FFT for further complexity optimization. Generic VLSI architectures are derived for the[InlineEquation not available: see fulltext.] high-order receiver from partitioned[InlineEquation not available: see fulltext.] submatrices. This leads to more parallel VLSI design with[InlineEquation not available: see fulltext.] further complexity reduction. Comparative study with both the conjugate-gradient and DMI algorithms shows very promising performance/complexity tradeoff. VLSI design space in terms of area/time efficiency is explored extensively for layered parallelism and pipelining with a Catapult C high-level-synthesis methodology.

  13. Rate 8/9 coded 8-PSK system for downlink applications

    NASA Technical Reports Server (NTRS)

    Fang, Russell; Kappes, Mark; Miller, Susan

    1992-01-01

    An advanced Coded Trellis Modulation (CTM) System which achieves a 2 bits/s/Hz bandwidth efficiency at an information rate of 200 Mbit/s while minimizing satellite power requirements, was developed for downlink earth station applications. The CTM system employs a high-speed rate 8/9 convolutional code with Viterbi decoding and an 8-Phase Shift Keying (PSK) modem. The minimum Euclidean distance between the modulated waveforms corresponding to the information sequences are maximized in order to maximize the noise immunity of the system. Nyquist filters with a square-root of 40 percent roll-off are used at the transmit and receive sides of the modem in order to minimize intersymbol interference, adjacent channel interference, and distortion at the nonlinear satellite power amplifier. The use of a coded system here also minimizes the effects of co-channel interference. The developed performance of the hardware system was measured to achieve within 1.5 dB from theory at a bit error rate of 5 x 10(exp -7) over an additive white Gaussian noise channel.

  14. Coordinate Update Algorithms for Robust Power Loading for the MU-MISO Downlink With Outage Constraints

    NASA Astrophysics Data System (ADS)

    Sohrabi, Foad; Davidson, Timothy N.

    2016-06-01

    We consider the problem of power allocation for the single-cell multi-user (MU) multiple-input single-output (MISO) downlink with quality-of-service (QoS) constraints. The base station acquires an estimate of the channels and, for a given beamforming structure, designs the power allocation so as to minimize the total transmission power required to ensure that target signal-to-interference-and-noise ratios at the receivers are met, subject to a specified outage probability. We consider scenarios in which the errors in the base station's channel estimates can be modelled as being zero-mean and Gaussian. Such a model is particularly suitable for time division duplex (TDD) systems with quasi-static channels, in which the base station estimates the channel during the uplink phase. Under that model, we employ a precise deterministic characterization of the outage probability to transform the chance-constrained formulation to a deterministic one. Although that deterministic formulation is not convex, we develop a coordinate descent algorithm that can be shown to converge to a globally optimal solution when the starting point is feasible. Insight into the structure of the deterministic formulation yields approximations that result in coordinate update algorithms with good performance and significantly lower computational cost. The proposed algorithms provide better performance than existing robust power loading algorithms that are based on tractable conservative approximations, and can even provide better performance than robust precoding algorithms based on such approximations.

  15. Tri-state delta modulation system for Space Shuttle digital TV downlink

    NASA Technical Reports Server (NTRS)

    Udalov, S.; Huth, G. K.; Roberts, D.; Batson, B. H.

    1981-01-01

    Future requirements for Shuttle Orbiter downlink communication may include transmission of digital video which, in addition to black and white, may also be either field-sequential or NTSC color format. The use of digitized video could provide for picture privacy at the expense of additional onboard hardware, together with an increased bandwidth due to the digitization process. A general objective for the Space Shuttle application is to develop a digitization technique that is compatible with data rates in the 20-30 Mbps range but still provides good quality pictures. This paper describes a tri-state delta modulation/demodulation (TSDM) technique which is a good compromise between implementation complexity and performance. The unique feature of TSDM is that it provides for efficient run-length encoding of constant-intensity segments of a TV picture. Axiomatix has developed a hardware implementation of a high-speed TSDM transmitter and receiver for black-and-white TV and field-sequential color. The hardware complexity of this TSDM implementation is summarized in the paper.

  16. MMSE precoding for multiuser MISO downlink transmission with non-homogeneous user SNR conditions

    NASA Astrophysics Data System (ADS)

    Nguyen, Duy HN; Le-Ngoc, Tho

    2014-12-01

    This paper is concerned with linear precoding designs for multiuser downlink transmissions. We consider a multiple-input single-output (MISO) system with multiple single-antenna user equipment (UE) experiencing non-homogeneous average signal-to-noise ratio (SNR) conditions. The first part of this work examines different precoding schemes with perfect channel state information (CSI) and average SNR at the base-station (eNB). We then propose a weighted minimum mean squared error (WMMSE) precoder, which takes advantage of the non-homogeneous SNR conditions. Given in a closed-form solution, the proposed WMMSE precoder outperforms other well-known linear precoders, such as zero-forcing (ZF), regularized ZF (RZF), while achieving a close performance to the locally optimal iterative WMMSE (IWMMSE) precoder, in terms of the achievable network sum-rate. In the second part of this work, we consider the non-homogeneous multiuser system with limited and quantized channel quality indicator (CQI) and channel direction indicator (CDI) feedbacks. Based on the CQI and CDI feedback models proposed for the Long-Term Evolution Advanced standard, we then propose a robust WMMSE precoder in a closed-form solution which takes into account the quantization errors. Simulation shows a significant improvement in the achievable network sum-rate by the proposed robust WMMSE precoder, compared to non-robust linear precoder designs.

  17. On the multiuser diversity of relay-aided downlink systems using reduced feedback.

    PubMed

    Jang, Yong-Up; Shin, Won-Yong

    2014-01-01

    We introduce an efficient multiuser scheduling method using amplify-and-forward relaying in relay-aided downlink systems, consisting of one base station (BS), one relay station, and multiple mobile stations (MSs). In our scheme, the BS opportunistically selects both the transmission mode, that is, either one- or two-hop transmission, and the desired user (i.e., the desired MS). Closed-form expressions for the average achievable rates are derived for the two transmission modes with multiuser scheduling, and its asymptotic solutions are also analyzed in the limit of large number of MSs. Based on the analysis, we propose a feedback-efficient two-step multiuser scheduling algorithm: the transmission mode selection followed by the user selection that only needs a partial feedback for instantaneous signal-to-noise ratios (SNRs) to the BS. We also analyze the average SNR condition such that the multiuser diversity gain is fully exploited for two-hop transmission. The proposed two-step scheduling algorithm exhibits the quite comparable achievable rates to those of the optimal one using full feedback information, while its required feedback information is reduced by half of the optimal one.

  18. Amplitude Scintillation due to Atmospheric Turbulence for the Deep Space Network Ka-Band Downlink

    NASA Technical Reports Server (NTRS)

    Ho, C.; Wheelon, A.

    2004-01-01

    Fast amplitude variations due to atmospheric scintillation are the main concerns for the Deep Space Network (DSN) Ka-band downlink under clear weather conditions. A theoretical study of the amplitude scintillation variances for a finite aperture antenna is presented. Amplitude variances for weak scattering scenarios are examined using turbulence theory to describe atmospheric irregularities. We first apply the Kolmogorov turbulent spectrum to a point receiver for three different turbulent profile models, especially for an exponential model varying with altitude. These analytic solutions then are extended to a receiver with a finite aperture antenna for the three profile models. Smoothing effects of antenna aperture are expressed by gain factors. A group of scaling factor relations is derived to show the dependences of amplitude variances on signal wavelength, antenna size, and elevation angle. Finally, we use these analytic solutions to estimate the scintillation intensity for a DSN Goldstone 34-m receiving station. We find that the (rms) amplitude fluctuation is 0.13 dB at 20-deg elevation angle for an exponential model, while the fluctuation is 0.05 dB at 90 deg. These results will aid us in telecommunication system design and signal-fading prediction. They also provide a theoretical basis for further comparison with other measurements at Ka-band.

  19. Networked Robust Predictive Control Systems Design with Packet Loss

    NASA Astrophysics Data System (ADS)

    Nguyen, Quang T.; Veselý, Vojtech; Kozáková, Alena; Pakshin, Pavel

    2014-01-01

    The paper addresses problem of designing a robust output feedback model predictive control for uncertain linear systems over networks with packet-loss. The packet-loss process is arbitrary and bounded by the control horizon of model predictive control. Networked predictive control systems with packet loss are modeled as switched linear systems. This enables us to apply the theory of switched systems to establish the stability condition. The stabilizing controller design is based on sufficient robust stability conditions formulated as a solution of bilinear matrix inequality. Finally, a benchmark numerical example-double integrator is given to illustrate the effectiveness of the proposed method.

  20. All-optical packet header and payload separation based on two TOADs for optical packet switched networks

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Zhang, Min; Ye, Peida

    2006-09-01

    We present a novel all-optical header and payload separation technique that can be utilized in Un-Slotted optical packet switched networks. The technique uses two modified TOADs, one is for packet header extraction with differential modulation scheme and the other performs a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue of this system is simple structure and low power consumption. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the system parameters are discussed and designed to optimize the performance of the proposed scheme.

  1. Packet-Based Protocol Efficiency for Aeronautical and Satellite Communications

    NASA Technical Reports Server (NTRS)

    Carek, David A.

    2005-01-01

    This paper examines the relation between bit error ratios and the effective link efficiency when transporting data with a packet-based protocol. Relations are developed to quantify the impact of a protocol s packet size and header size relative to the bit error ratio of the underlying link. These relations are examined in the context of radio transmissions that exhibit variable error conditions, such as those used in satellite, aeronautical, and other wireless networks. A comparison of two packet sizing methodologies is presented. From these relations, the true ability of a link to deliver user data, or information, is determined. Relations are developed to calculate the optimal protocol packet size forgiven link error characteristics. These relations could be useful in future research for developing an adaptive protocol layer. They can also be used for sizing protocols in the design of static links, where bit error ratios have small variability.

  2. Propagation velocity of Alfven wave packets in a dissipative plasma

    SciTech Connect

    Amagishi, Y.; Nakagawa, H. ); Tanaka, M. )

    1994-09-01

    We have experimentally studied the behavior of Alfven wave packets in a dissipative plasma due to ion--neutral-atom collisions. It is urged that the central frequency of the packet is observed to gradually decrease with traveling distance in the absorption range of frequencies because of a differential damping among the Fourier components, and that the measured average velocity of its peak amplitude is not accounted for by the conventional group velocity, but by the prediction derived by Tanaka, Fujiwara, and Ikegami [Phys. Rev. A 34, 4851 (1986)]. Furthermore, when the initial central frequency is close to the critical frequency in the anomalous dispersion, the wave packet apparently collapses when traveling along the magnetic field; however, we have found that it is decomposed into another two wave packets with the central frequencies being higher or lower than the critical frequency.

  3. Statistics of Gaussian packets on metric and decorated graphs.

    PubMed

    Chernyshev, V L; Shafarevich, A I

    2014-01-28

    We study a semiclassical asymptotics of the Cauchy problem for a time-dependent Schrödinger equation on metric and decorated graphs with a localized initial function. A decorated graph is a topological space obtained from a graph via replacing vertices with smooth Riemannian manifolds. The main term of an asymptotic solution at an arbitrary finite time is a sum of Gaussian packets and generalized Gaussian packets (localized near a certain set of codimension one). We study the number of packets as time tends to infinity. We prove that under certain assumptions this number grows in time as a polynomial and packets fill the graph uniformly. We discuss a simple example of the opposite situation: in this case, a numerical experiment shows a subexponential growth.

  4. Theory of discrete wave packets in the solar wind.

    NASA Technical Reports Server (NTRS)

    Wu, C. S.

    1972-01-01

    Discrete wave packets were observed by Ogo 5 and earlier satellites. These waves were believed to be in the whistler mode. Since their group velocities were found to be smaller than the solar-wind speed, these waves could not have been generated in the bow shock and could not have propagated upstream later. The present theory discusses a mechanism similar to that of the echo phenomenon in plasma physics discovered in recent years. The present theory enables us to explain (a) why the wave packets were associated with the bow shock, (b) why the wave packets were characterized by coherent oscillations, and (c) why the wave packets had group velocities smaller than the solar wind and yet could still occur in the solar wind. In short, our theory is able to interpret all the essential features deduced from the observational data.

  5. Food packets for use on the Gemini 3 flight

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Food packets for use on the Gemini 3 flight including dehydrated beef pot roast, bacon and egg bites, toasted bread cubes, orange juice and a wet wipe. Water is being inserted into the pouch of dehydrated food.

  6. Statistics of Gaussian packets on metric and decorated graphs

    PubMed Central

    Chernyshev, V. L.; Shafarevich, A. I.

    2014-01-01

    We study a semiclassical asymptotics of the Cauchy problem for a time-dependent Schrödinger equation on metric and decorated graphs with a localized initial function. A decorated graph is a topological space obtained from a graph via replacing vertices with smooth Riemannian manifolds. The main term of an asymptotic solution at an arbitrary finite time is a sum of Gaussian packets and generalized Gaussian packets (localized near a certain set of codimension one). We study the number of packets as time tends to infinity. We prove that under certain assumptions this number grows in time as a polynomial and packets fill the graph uniformly. We discuss a simple example of the opposite situation: in this case, a numerical experiment shows a subexponential growth. PMID:24344346

  7. Packet QoS level classifier based on optical binary priority comparison.

    PubMed

    Song, Seoksu; Nguyen, Vancanh; Park, Jinwoo

    2010-07-19

    Next generation High-Speed optical packet switching networks require components capable of classifying incoming packet into the appropriate priority queue according to the service class of the packet. For the first time, we proposed an all-optical packet QoS (Quality of Service) level classifier employing a sequential binary packet priority comparator, which is implemented using the SOA-based optical logic gates. The performance of the optical binary packet priority comparator was verified experimentally at 1 Gbit/s showing that the proposed scheme can operate higher data rates. These packet level classifier structures are attractive for all-optical network and applications.

  8. Embedded wavelet packet transform technique for texture compression

    NASA Astrophysics Data System (ADS)

    Li, Jin; Cheng, Po-Yuen; Kuo, C.-C. Jay

    1995-09-01

    A highly efficient texture compression scheme is proposed in this research. With this scheme, energy compaction of texture images is first achieved by the wavelet packet transform, and an embedding approach is then adopted for the coding of the wavelet packet transform coefficients. By comparing the proposed algorithm with the JPEG standard, FBI wavelet/scalar quantization standard and the EZW scheme with extensive experimental results, we observe a significant improvement in the rate-distortion performance and visual quality.

  9. COMSAT Participation in ARPA Packet Satellite Program (PSP)

    DTIC Science & Technology

    1979-10-01

    the formats of the var- ious packet transmission and reception modes are defined. Test data on the microprocessor- based QPSK modems included in the...miss rate. Based on this line of rea- soning, which is supported by the analysis in Section 6, the seemingly erratic missed packet behavior observed...Planning." The modem is based on a digitally-controlled micropro- cessor implementation and has been specifically designed to mini- mise the time required

  10. Packet utilisation definitions for the ESA XMM mission

    NASA Technical Reports Server (NTRS)

    Nye, H. R.

    1994-01-01

    XMM, ESA's X-Ray Multi-Mirror satellite, due for launch at the end of 1999 will be the first ESA scientific spacecraft to implement the ESA packet telecommand and telemetry standards and will be the first ESOC-controlled science mission to take advantage of the new flight control system infrastructure development (based on object-oriented design and distributed-system architecture) due for deployment in 1995. The implementation of the packet standards is well defined at packet transport level. However, the standard relevant to the application level (the ESA Packet Utilization Standard) covers a wide range of on-board 'services' applicable in varying degrees to the needs of XMM. In defining which parts of the ESA PUS to implement, the XMM project first considered the mission objectives and the derived operations concept and went on to identify a minimum set of packet definitions compatible with these aspects. This paper sets the scene as above and then describes the services needed for XMM and the telecommand and telemetry packet types necessary to support each service.

  11. TCP Packet Trace Analysis. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Shepard, Timothy J.

    1991-01-01

    Examination of a trace of packets collected from the network is often the only method available for diagnosing protocol performance problems in computer networks. This thesis explores the use of packet traces to diagnose performance problems of the transport protocol TCP. Unfortunately, manual examination of these traces can be so tedious that effective analysis is not possible. The primary contribution of this thesis is a graphical method of displaying the packet trace which greatly reduce, the tediousness of examining a packet trace. The graphical method is demonstrated by the examination of some packet traces of typical TCP connections. The performance of two different implementations of TCP sending data across a particular network path is compared. Traces many thousands of packets long are used to demonstrate how effectively the graphical method simplifies examination of long complicated traces. In the comparison of the two TCP implementations, the burstiness of the TCP transmitter appeared to be related to the achieved throughput. A method of quantifying this burstiness is presented and its possible relevance to understanding the performance of TCP is discussed.

  12. Two-point coherence of wave packets in turbulent jets

    NASA Astrophysics Data System (ADS)

    Jaunet, V.; Jordan, P.; Cavalieri, A. V. G.

    2017-02-01

    An experiment has been performed in order to provide support for wave-packet jet-noise modeling efforts. Recent work has shown that the nonlinear effects responsible for the two-point coherence of wave packets must be correctly accounted for if accurate sound prediction is to be achieved for subsonic turbulent jets. We therefore consider the same Mach 0.4 turbulent jet studied by Cavalieri et al. [Cavalieri et al., J. Fluid Mech. 730, 559 (2013), 10.1017/jfm.2013.346], but this time using two independent but synchronized, time-resolved stereo particle-image velocimetry systems. Each system can be moved independently, allowing simultaneous measurement of velocity in two, axially separated, crossflow planes, enabling eduction of the two-point coherence of wave packets. This and the associated length scales and phase speeds are studied and compared with those of the energy-containing turbulent eddies. The study illustrates how the two-point behavior of wave packets is fundamentally different from that of the more usually studied bulk two-point behavior, suggesting that sound-source modeling efforts should be reconsidered in the framework of wave packets. The study furthermore identifies two families of two-point-coherence behavior, respectively upstream and downstream of the end of the potential core, regions where linear theory is, respectively, successful and unsuccessful in predicting the axial evolution of wave-packets fluctuation energy.

  13. Instrument for measurement of vacuum in sealed thin wall packets

    DOEpatents

    Kollie, T.G.; Thacker, L.H.; Fine, H.A.

    1995-04-18

    An instrument is disclosed for the measurement of vacuum within sealed packets, the packets having a wall that it can be deformed by the application of an external dynamic vacuum to an area thereof. The instrument has a detector head for placement against the deformable wall of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall with this deformation or lift monitored by the application of light as via a bifurcated light pipe. Retro-reflected light through the light pipe is monitored with a photo detector. A change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the dynamic vacuum applied through the head be to achieve this initiation of movement is equal to the vacuum within the packet. In a preferred embodiment a vacuum plate is placed beneath the packet to ensure that no deformation occurs on the reverse surface of the packet. A vacuum can be applied to a recess in this vacuum plate, the value of which can be used to calibrate the vacuum transducer in the detector head. 4 figs.

  14. Instrument for measurement of vacuum in sealed thin wall packets

    DOEpatents

    Kollie, Thomas G.; Thacker, Louis H.; Fine, H. Alan

    1995-01-01

    An instrument for the measurement of vacuum within sealed packets 12, the packets 12 having a wall 14 that it can be deformed by the application of an external dynamic vacuum to an area thereof. The instrument has a detector head 18 for placement against the deformable wall 14 of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall 14, with this deformation or lift monitored by the application of light as via a bifurcated light pipe 20. Retro-reflected light through the light pipe is monitored with a photo detector 26. A change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the dynamic vacuum applied through the head be to achieve this initiation of movement is equal to the vacuum within the packet 12. In a preferred embodiment a vacuum plate 44 is placed beneath the packet 12 to ensure that no deformation occurs on the reverse surface 16 of the packet. A vacuum can be applied to a recess in this vacuum plate, the value of which can be used to calibrate the vacuum transducer in the detector head.

  15. Modified weighted fair queuing for packet scheduling in mobile WiMAX networks

    NASA Astrophysics Data System (ADS)

    Satrya, Gandeva B.; Brotoharsono, Tri

    2013-03-01

    The increase of user mobility and the need for data access anytime also increases the interest in broadband wireless access (BWA). The best available quality of experience for mobile data service users are assured for IEEE 802.16e based users. The main problem of assuring a high QOS value is how to allocate available resources among users in order to meet the QOS requirement for criteria such as delay, throughput, packet loss and fairness. There is no specific standard scheduling mechanism stated by IEEE standards, which leaves it for implementer differentiation. There are five QOS service classes defined by IEEE 802.16: Unsolicited Grant Scheme (UGS), Extended Real Time Polling Service (ertPS), Real Time Polling Service (rtPS), Non Real Time Polling Service (nrtPS) and Best Effort Service (BE). Each class has different QOS parameter requirements for throughput and delay/jitter constraints. This paper proposes Modified Weighted Fair Queuing (MWFQ) scheduling scenario which was based on Weighted Round Robin (WRR) and Weighted Fair Queuing (WFQ). The performance of MWFQ was assessed by using above five QoS criteria. The simulation shows that using the concept of total packet size calculation improves the network's performance.

  16. Spatio-Temporal Waveform Design for Multiuser Massive MIMO Downlink With 1-bit Receivers

    NASA Astrophysics Data System (ADS)

    Gokceoglu, Ahmet; Bjornson, Emil; Larsson, Erik G.; Valkama, Mikko

    2017-03-01

    Internet-of-Things (IoT) refers to a high-density network of low-cost low-bitrate terminals and sensors where also low energy consumption is one central feature. As the power-budget of classical receiver chains is dominated by the high-resolution analog-to-digital converters (ADCs), there is a growing interest towards deploying receiver architectures with reduced-bit or even 1-bit ADCs. In this paper, we study waveform design, optimization and detection aspects of multi-user massive MIMO downlink where user terminals adopt very simple 1-bit ADCs with oversampling. In order to achieve spectral efficiency higher than 1 bit/s/Hz per real-dimension, we propose a two-stage precoding, namely a novel quantization precoder followed by maximum-ratio transmission (MRT) or zero-forcing (ZF) type spatial channel precoder which jointly form the multi-user-multiantenna transmit waveform. The quantization precoder outputs are optimized, under appropriate transmitter and receiver filter bandwidth constraints, to provide controlled inter-symbol-interference (ISI) enabling the input symbols to be uniquely detected from 1-bit quantized observations with a low-complexity symbol detector in the absence of noise. An additional optimization constraint is also imposed in the quantization precoder design to increase the robustness against noise and residual inter-user-interference (IUI). The purpose of the spatial channel precoder, in turn, is to suppress the IUI and provide high beamforming gains such that good symbol-error rates (SERs) can be achieved in the presence of noise and interference. Extensive numerical evaluations illustrate that the proposed spatio-temporal precoder based multiantenna waveform design can facilitate good multi-user link performance, despite the extremely simple 1-bit ADCs in the receivers, hence being one possible enabling technology for the future low-complexity IoT networks.

  17. Overcoming CubeSat downlink limits with vitamin: A new variable coded modulation protocol

    NASA Astrophysics Data System (ADS)

    Sielicki, Thomas A.

    Many space missions, including low earth orbit CubeSats, communicate in a highly dynamic environment because of variations in geometry, weather, and interference. At the same time, most missions communicate using fixed channel codes, modulations, and symbol rates, resulting in a constant data rate that does not adapt to the dynamic conditions. When conditions are good, the fixed date rate can be far below the theoretical maximum, called the Shannon limit; when conditions are bad, the fixed data rate may not work at all. To move beyond these fixed communications and achieve higher total data volume from emerging high-tech instruments, this thesis investigates the use of error correcting codes and different modulations. Variable coded modulation (VCM) takes advantage of the dynamic link by transmitting more information when the signal-to-noise ratio (SNR) is high. Likewise, VCM can throttle down the information rate when SNR is low without having to stop all communications. VCM outperforms fixed communications which can only operate at a fixed information rate as long as a certain signal threshold is met. This thesis presents a new VCM protocol and tests its performance in both software and hardware simulations. The protocol is geared towards CubeSat downlinks as complexity is focused in the receiver, while the transmission operations are kept simple. This thesis explores bin-packing as a way to optimize the selection of VCM modes based on expected SNR levels over time. Working end-to-end simulations were created using MATLAB and LabVIEW, while the hardware simulations were done with software defined radios. Results show that a CubeSat using VCM communications will deliver twice the data throughput of a fixed communications system.

  18. Hybrid single-packet IP traceback with low storage and high accuracy.

    PubMed

    Yang, Ming Hour

    2014-01-01

    Traceback schemes have been proposed to trace the sources of attacks that usually hide by spoofing their IP addresses. Among these methods, schemes using packet logging can achieve single-packet traceback. But packet logging demands high storage on routers and therefore makes IP traceback impractical. For lower storage requirement, packet logging and packet marking are fused to make hybrid single-packet IP traceback. Despite such attempts, their storage still increases with packet numbers. That is why RIHT bounds its storage with path numbers to guarantee low storage. RIHT uses IP header's ID and offset fields to mark packets, so it inevitably suffers from fragment and drop issues for its packet reassembly. Although the 16-bit hybrid IP traceback schemes, for example, MORE, can mitigate the fragment problem, their storage requirement grows up with packet numbers. To solve the storage and fragment problems in one shot, we propose a single-packet IP traceback scheme that only uses packets' ID field for marking. Our major contributions are as follows: (1) our fragmented packets with tracing marks can be reassembled; (2) our storage is not affected by packet numbers; (3) it is the first hybrid single-packet IP traceback scheme to achieve zero false positive and zero false negative rates.

  19. Hybrid Single-Packet IP Traceback with Low Storage and High Accuracy

    PubMed Central

    Yang, Ming Hour

    2014-01-01

    Traceback schemes have been proposed to trace the sources of attacks that usually hide by spoofing their IP addresses. Among these methods, schemes using packet logging can achieve single-packet traceback. But packet logging demands high storage on routers and therefore makes IP traceback impractical. For lower storage requirement, packet logging and packet marking are fused to make hybrid single-packet IP traceback. Despite such attempts, their storage still increases with packet numbers. That is why RIHT bounds its storage with path numbers to guarantee low storage. RIHT uses IP header's ID and offset fields to mark packets, so it inevitably suffers from fragment and drop issues for its packet reassembly. Although the 16-bit hybrid IP traceback schemes, for example, MORE, can mitigate the fragment problem, their storage requirement grows up with packet numbers. To solve the storage and fragment problems in one shot, we propose a single-packet IP traceback scheme that only uses packets' ID field for marking. Our major contributions are as follows: (1) our fragmented packets with tracing marks can be reassembled; (2) our storage is not affected by packet numbers; (3) it is the first hybrid single-packet IP traceback scheme to achieve zero false positive and zero false negative rates. PMID:24707197

  20. Distributed reservation control protocols for random access broadcasting channels

    NASA Astrophysics Data System (ADS)

    Greene, E. P.; Ephremides, A.

    1981-05-01

    Attention is given to a communication network consisting of an arbitrary number of nodes which can communicate with each other via a time-division multiple access (TDMA) broadcast channel. The reported investigation is concerned with the development of efficient distributed multiple access protocols for traffic consisting primarily of single packet messages in a datagram mode of operation. The motivation for the design of the protocols came from the consideration of efficient multiple access utilization of moderate to high bandwidth (4-40 Mbit/s capacity) communication satellite channels used for the transmission of short (1000-10,000 bits) fixed length packets. Under these circumstances, the ratio of roundtrip propagation time to packet transmission time is between 100 to 10,000. It is shown how a TDMA channel can be adaptively shared by datagram traffic and constant bandwidth users such as in digital voice applications. The distributed reservation control protocols described are a hybrid between contention and reservation protocols.

  1. Distributed reservation control protocols for random access broadcasting channels

    NASA Technical Reports Server (NTRS)

    Greene, E. P.; Ephremides, A.

    1981-01-01

    Attention is given to a communication network consisting of an arbitrary number of nodes which can communicate with each other via a time-division multiple access (TDMA) broadcast channel. The reported investigation is concerned with the development of efficient distributed multiple access protocols for traffic consisting primarily of single packet messages in a datagram mode of operation. The motivation for the design of the protocols came from the consideration of efficient multiple access utilization of moderate to high bandwidth (4-40 Mbit/s capacity) communication satellite channels used for the transmission of short (1000-10,000 bits) fixed length packets. Under these circumstances, the ratio of roundtrip propagation time to packet transmission time is between 100 to 10,000. It is shown how a TDMA channel can be adaptively shared by datagram traffic and constant bandwidth users such as in digital voice applications. The distributed reservation control protocols described are a hybrid between contention and reservation protocols.

  2. Heterogeneous wireless/wireline optical access networks with the R-EAT as backend component

    NASA Astrophysics Data System (ADS)

    Hagedorn, Klaus; Gindera, Ralf; Stohr, Andreas; Jager, Dieter

    2004-09-01

    A heterogeneous wireless/wireline optical transmission link using a reflection type electroabsorption transceiver (R-EAT) is presented. Simultaneous transmission of full-duplex broadband wireless LAN (WLAN) channels and 1Gb/s base band data is experimentally demonstrated. The system link employs sub-carrier multiplexing (SCM) and two optical channels for full duplex transmission of various analog WLAN channels and downlink digital base band data. The developed link architecture is suitable for simultaneous transmission of broadband wireline and wireless signals, it enables the coexistence and interoperability between wireline and wireless access technologies. The developed R-EAT component employed in this wireline/wireless access system, features "single-chip-component" base stations in access networks with star type topology where only a single optical fiber is used for bidirectional optical transmission. The R-EAT can be used within the optical C-band (1530- 1560nm) and is suitable for (D)WDM networks. Bit error rate measurements demonstrate the capabilities of the R-EAT for 1Gb/s base band transmission. The analog performance for WLAN transmission is characterised by a spurious free dynamic range (SFDR) of more than 75dB and 90dB for uplink and downlink transmission, respectively. The link gain for uplink and downlink transmission is -42dB and -37dB, respectively. The demonstrates the analog performances of the R-EAT for being used in wireless access networks such as W-LAN.

  3. Quasi-light storage for optical data packets.

    PubMed

    Schneider, Thomas; Preußler, Stefan

    2014-02-06

    Today's telecommunication is based on optical packets which transmit the information in optical fiber networks around the world. Currently, the processing of the signals is done in the electrical domain. Direct storage in the optical domain would avoid the transfer of the packets to the electrical and back to the optical domain in every network node and, therefore, increase the speed and possibly reduce the energy consumption of telecommunications. However, light consists of photons which propagate with the speed of light in vacuum. Thus, the storage of light is a big challenge. There exist some methods to slow down the speed of the light, or to store it in excitations of a medium. However, these methods cannot be used for the storage of optical data packets used in telecommunications networks. Here we show how the time-frequency-coherence, which holds for every signal and therefore for optical packets as well, can be exploited to build an optical memory. We will review the background and show in detail and through examples, how a frequency comb can be used for the copying of an optical packet which enters the memory. One of these time domain copies is then extracted from the memory by a time domain switch. We will show this method for intensity as well as for phase modulated signals.

  4. Fiber Fabry-Perot tunable filter for high-speed optical packet switching

    SciTech Connect

    Taranenko, N.L.; Tenbrink, S.C.; Hsu, K.; Miller, C.M.

    1997-01-01

    Tunable optical filters are important building blocks for All-Optical systems and networks. Fast optical tuning in several microseconds is necessary to perform high-speed optical packet switching. Multi- Gigabit/sec packet-switching will provide flexibility and higher network throughput when large numbers of users communicate simultaneously. One approach to achieve fast wavelength tuning is to use high-speed piezoelectrically-driven Fiber Fabry-Perot tunable filters (FFP-TFs). The requirement for tuning in microseconds raises a whole new set of challenges, such as ringing, thermostability and mechanical inertia control. It was shown that correlation between the mechanical resonance and optical response of the filter is important for the filter`s speed and for mounting hardware and control circuitry optimization. These features together with the FFP-TF`s high capacitance (approximately 0.25-0.5 microfarad) are being folded into building a special controller to substantially improve the shape of the driving signal and the response of the filter. The resultant controller enables tuning the high-speed FFP-TF three-orders-of- magnitude faster than that possible with standard commercial FFP-TFS. The fastest switching time achieved is 2.5 microseconds. As the result, a new packet-switched media access control protocol is being designed to minimize the searching time. The filter scans only once through the entire optical region and then tunes to all the required channels one after another in a few microseconds. It can help update Rainbow-2 Broadcast-and-Select High-Speed Wavelength Division Multiplexing All-Optical network that currently has a circuit- switched protocol using standard FFP-TFS.

  5. Semiclassical dynamics of electron wave packet states with phase vortices.

    PubMed

    Bliokh, Konstantin Yu; Bliokh, Yury P; Savel'ev, Sergey; Nori, Franco

    2007-11-09

    We consider semiclassical higher-order wave packet solutions of the Schrödinger equation with phase vortices. The vortex line is aligned with the propagation direction, and the wave packet carries a well-defined orbital angular momentum (OAM) variant Planck's over 2pil (l is the vortex strength) along its main linear momentum. The probability current coils around the momentum in such OAM states of electrons. In an electric field, these states evolve like massless particles with spin l. The magnetic-monopole Berry curvature appears in momentum space, which results in a spin-orbit-type interaction and a Berry/Magnus transverse force acting on the wave packet. This brings about the OAM Hall effect. In a magnetic field, there is a Zeeman interaction, which, can lead to more complicated dynamics.

  6. Accelerating Airy–Gauss–Kummer localized wave packets

    SciTech Connect

    Zhong, Wei-Ping; Belić, Milivoj; Zhang, Yiqi; Huang, Tingwen

    2014-01-15

    A general approach to generating three-dimensional nondiffracting spatiotemporal solutions of the linear Schrödinger equation with an Airy-beam time-dependence is reported. A class of accelerating optical pulses with the structure of Airy–Gauss–Kummer vortex beams is obtained. Our results demonstrate that the optical field contributions to the Airy–Gauss–Kummer accelerating optical wave packets of the cylindrical symmetry can be characterized by the radial and angular mode numbers. -- Highlights: •A general solution of 3D linear Schrödinger equation with an Airy time-dependence is reported. •We find that the Airy–Kummer spatiotemporal wave packets can carry infinite energy. •A class of the accelerating spatiotemporal optical pulses with special structures was found. •The spatiotemporal wave packets retain their energy features over several Rayleigh lengths.

  7. Attosecond Electron Wave Packet Dynamics in Strong Laser Fields

    SciTech Connect

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier, A.; Lopez-Martens, R.; Valentin, C.; Balcou, Ph.; Kazamias, S.; Mauritsson, J.; Gaarde, M. B.; Schafer, K. J.; Mairesse, Y.; Wabnitz, H.; Salieres, P.

    2005-07-01

    We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy ({approx}20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes.

  8. Foreign Material in the Gastrointestinal Tract: Cocaine Packets

    PubMed Central

    Kucukmetin, Nurten Turkel; Gucyetmez, Bulent; Poyraz, Tuncer; Yildirim, Sadik; Boztas, Gungor; Tozun, Nurdan

    2014-01-01

    Smuggling drugs by swallowing or inserting into a body cavity is not only a serious and growing international crime, but can also lead to lethal medical complications. The most common cause of death in ‘body packers’, people transporting drugs by ingesting a packet into the gastrointestinal tract, is acute drug toxicity from a ruptured packet. However, more than 30 years after the initial report of body packing, there is still no definitive treatment protocol for the management of this patient group. The treatment strategy is determined according to the particular condition of the patient and the clinical experience of the treatment center. Surgical intervention is also less common now, due to both the use of improved packaging materials among smugglers and a shift towards a more conservative medical approach. Herein, we report a case of toxicity from ingested packets of cocaine that leaked and, despite surgery, resulted in exitus of the patient. PMID:24574951

  9. Bufferless Ultra-High Speed All-Optical Packet Routing

    NASA Astrophysics Data System (ADS)

    Muttagi, Shrihari; Prince, Shanthi

    2011-10-01

    All-Optical network is still in adolescence to cope up with steep rise in data traffic at the backbone network. Routing of packets in optical network depends on the processing speed of the All-Optical routers, thus there is a need to enhance optical processing to curb the delay in packet forwarding unit. In the proposed scheme, the header processing takes place on fly, therefore processing delay is at its lower limit. The objective is to propose a framework which establishes high data rate transmission with least latency in data routing from source to destination. The Routing table and optical header pulses are converted into Pulse Position (PP) format, thus reducing the complexity and in turn the processing delay. Optical pulse matching is exercised which results in multi-output transmission. This results in ultra-high speed packet forwarding unit. In addition, this proposed scheme includes dispersion compensation unit, which makes the data reliable.

  10. A robust low-rate coding scheme for packet video

    NASA Technical Reports Server (NTRS)

    Chen, Y. C.; Sayood, Khalid; Nelson, D. J.; Arikan, E. (Editor)

    1991-01-01

    Due to the rapidly evolving field of image processing and networking, video information promises to be an important part of telecommunication systems. Although up to now video transmission has been transported mainly over circuit-switched networks, it is likely that packet-switched networks will dominate the communication world in the near future. Asynchronous transfer mode (ATM) techniques in broadband-ISDN can provide a flexible, independent and high performance environment for video communication. For this paper, the network simulator was used only as a channel in this simulation. Mixture blocking coding with progressive transmission (MBCPT) has been investigated for use over packet networks and has been found to provide high compression rate with good visual performance, robustness to packet loss, tractable integration with network mechanics and simplicity in parallel implementation.

  11. On-board congestion control for satellite packet switching networks

    NASA Technical Reports Server (NTRS)

    Chu, Pong P.

    1991-01-01

    It is desirable to incorporate packet switching capability on-board for future communication satellites. Because of the statistical nature of packet communication, incoming traffic fluctuates and may cause congestion. Thus, it is necessary to incorporate a congestion control mechanism as part of the on-board processing to smooth and regulate the bursty traffic. Although there are extensive studies on congestion control for both baseband and broadband terrestrial networks, these schemes are not feasible for space based switching networks because of the unique characteristics of satellite link. Here, we propose a new congestion control method for on-board satellite packet switching. This scheme takes into consideration the long propagation delay in satellite link and takes advantage of the the satellite's broadcasting capability. It divides the control between the ground terminals and satellite, but distributes the primary responsibility to ground terminals and only requires minimal hardware resource on-board satellite.

  12. Semiclassical Dynamics of Electron Wave Packet States with Phase Vortices

    SciTech Connect

    Bliokh, Konstantin Yu.; Bliokh, Yury P.; Savel'ev, Sergey; Nori, Franco

    2007-11-09

    We consider semiclassical higher-order wave packet solutions of the Schroedinger equation with phase vortices. The vortex line is aligned with the propagation direction, and the wave packet carries a well-defined orbital angular momentum (OAM) ({Dirac_h}/2{pi})l (l is the vortex strength) along its main linear momentum. The probability current coils around the momentum in such OAM states of electrons. In an electric field, these states evolve like massless particles with spin l. The magnetic-monopole Berry curvature appears in momentum space, which results in a spin-orbit-type interaction and a Berry/Magnus transverse force acting on the wave packet. This brings about the OAM Hall effect. In a magnetic field, there is a Zeeman interaction, which, can lead to more complicated dynamics.

  13. Fast Packet Classification Using Multi-Dimensional Encoding

    NASA Astrophysics Data System (ADS)

    Huang, Chi Jia; Chen, Chien

    Internet routers need to classify incoming packets quickly into flows in order to support features such as Internet security, virtual private networks and Quality of Service (QoS). Packet classification uses information contained in the packet header, and a predefined rule table in the routers. Packet classification of multiple fields is generally a difficult problem. Hence, researchers have proposed various algorithms. This study proposes a multi-dimensional encoding method in which parameters such as the source IP address, destination IP address, source port, destination port and protocol type are placed in a multi-dimensional space. Similar to the previously best known algorithm, i.e., bitmap intersection, multi-dimensional encoding is based on the multi-dimensional range lookup approach, in which rules are divided into several multi-dimensional collision-free rule sets. These sets are then used to form the new coding vector to replace the bit vector of the bitmap intersection algorithm. The average memory storage of this encoding is Θ (L · N · log N) for each dimension, where L denotes the number of collision-free rule sets, and N represents the number of rules. The multi-dimensional encoding practically requires much less memory than bitmap intersection algorithm. Additionally, the computation needed for this encoding is as simple as bitmap intersection algorithm. The low memory requirement of the proposed scheme means that it not only decreases the cost of packet classification engine, but also increases the classification performance, since memory represents the performance bottleneck in the packet classification engine implementation using a network processor.

  14. Symmetry and conservation laws in semiclassical wave packet dynamics

    SciTech Connect

    Ohsawa, Tomoki

    2015-03-15

    We formulate symmetries in semiclassical Gaussian wave packet dynamics and find the corresponding conserved quantities, particularly the semiclassical angular momentum, via Noether’s theorem. We consider two slightly different formulations of Gaussian wave packet dynamics; one is based on earlier works of Heller and Hagedorn and the other based on the symplectic-geometric approach by Lubich and others. In either case, we reveal the symplectic and Hamiltonian nature of the dynamics and formulate natural symmetry group actions in the setting to derive the corresponding conserved quantities (momentum maps). The semiclassical angular momentum inherits the essential properties of the classical angular momentum as well as naturally corresponds to the quantum picture.

  15. Electron acceleration by Landau resonance with whistler mode wave packets

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Reinleitner, L. A.

    1983-01-01

    Recent observations of electrostatic waves associated with whistler mode chorus emissions provide evidence that electrons are being trapped by Landau resonance interactions with the chorus. In this paper, the trapping, acceleration and escape of electrons in Landau resonance with a whistler mode wave packet are discussed. It is shown that acceleration can occur by both inhomogeneous and dispersive effects. The maximum energy gained is controlled by the points where trapping and escape occur. Large energy changes are possible if the frequency of the wave packet or the magnetic field strength increase between the trapping and escape points. Various trapping and escape mechanisms are discussed.

  16. The Open Host Network Packet Process Correlator for Windows

    SciTech Connect

    2014-06-17

    The Hone sensors are packet-process correlation engines that log the relationships between applications and the communications they are responsible for. Hone sensors are available for a variety of platforms including Linux, Windows, and MacOSX. Hone sensors are designed to help analysts understand the meaning of communications on a deeper level by associating the origin or destination process to the communication. They do this by tracing communications on a per-packet basis, through the kernel of the operating system to determine their ultimate source/destination on the monitored machine.

  17. Symmetry and conservation laws in semiclassical wave packet dynamics

    NASA Astrophysics Data System (ADS)

    Ohsawa, Tomoki

    2015-03-01

    We formulate symmetries in semiclassical Gaussian wave packet dynamics and find the corresponding conserved quantities, particularly the semiclassical angular momentum, via Noether's theorem. We consider two slightly different formulations of Gaussian wave packet dynamics; one is based on earlier works of Heller and Hagedorn and the other based on the symplectic-geometric approach by Lubich and others. In either case, we reveal the symplectic and Hamiltonian nature of the dynamics and formulate natural symmetry group actions in the setting to derive the corresponding conserved quantities (momentum maps). The semiclassical angular momentum inherits the essential properties of the classical angular momentum as well as naturally corresponds to the quantum picture.

  18. Gabor Wave Packet Method to Solve Plasma Wave Equations

    SciTech Connect

    A. Pletzer; C.K. Phillips; D.N. Smithe

    2003-06-18

    A numerical method for solving plasma wave equations arising in the context of mode conversion between the fast magnetosonic and the slow (e.g ion Bernstein) wave is presented. The numerical algorithm relies on the expansion of the solution in Gaussian wave packets known as Gabor functions, which have good resolution properties in both real and Fourier space. The wave packets are ideally suited to capture both the large and small wavelength features that characterize mode conversion problems. The accuracy of the scheme is compared with a standard finite element approach.

  19. Fourier optics and time evolution of de Broglie wave packets

    NASA Astrophysics Data System (ADS)

    Dillon, G.

    2012-06-01

    It is shown that, under the conditions of validity of the Fresnel approximation, diffraction and interference for a monochromatic wave traveling in the z-direction may be described in terms of the spreading in time of the transverse ( x, y wave packet. The time required for the evolved wave packet to yield identical patterns as given by standard optics corresponds to the time for the quantum to cross the optical apparatus. This point of view may provide interesting cues in wave mechanics and quantum physics education.

  20. Zeno dynamics in wave-packet diffraction spreading

    SciTech Connect

    Porras, Miguel A.; Luis, Alfredo; Gonzalo, Isabel; Sanz, Angel S.

    2011-11-15

    We analyze a simple and feasible practical scheme displaying Zeno, anti-Zeno, and inverse-Zeno effects in the observation of wave-packet spreading caused by free evolution. The scheme is valid both in spatial diffraction of classical optical waves and in time diffraction of a quantum wave packet. In the optical realization, diffraction spreading is observed by placing slits between a light source and a light-power detector. We show that the occurrence of Zeno or anti-Zeno effects depends just on the frequency of observations between the source and detector. These effects are seen to be related to the diffraction mode theory in Fabry-Perot resonators.

  1. Short-time Chebyshev wave packet method for molecular photoionization

    NASA Astrophysics Data System (ADS)

    Sun, Zhaopeng; Zheng, Yujun

    2016-08-01

    In this letter we present the extended usage of short-time Chebyshev wave packet method in the laser induced molecular photoionization dynamics. In our extension, the polynomial expansion of the exponential in the time evolution operator, the Hamiltonian operator can act on the wave packet directly which neatly avoids the matrix diagonalization. This propagation scheme is of obvious advantages when the dynamical system has large Hamiltonian matrix. Computational simulations are performed for the calculation of photoelectronic distributions from intense short pulse ionization of K2 and NaI which represent the Born-Oppenheimer (BO) model and Non-BO one, respectively.

  2. IEEE 802.16 Packet Scheduling with Traffic Prioritization and Cross-Layer Optimization

    NASA Astrophysics Data System (ADS)

    Monteiro, João; Sargento, Susana; Gomes, Álvaro; Fontes, Francisco; Neves, Pedro

    WiMAX is emerging as a broadband wireless access technology to satisfy end user expectations, containing a new set of advantages in terms of throughput, coverage and QoS support at the MAC level which allows convergence of several different types of applications and services. For that reason, the allocation of resources or scheduling becomes of greater importance. This paper focuses on a cross-layer scheduling optimization solution for IEEE 802.16. The relevant features of the proposed packet scheduling optimization scheme consist: of prioritization of users within the same traffic class, allowing for example to an operator, differentiated treatment among users, for instance distinguishing between premium or gold users and silver users; and also cross layer optimization which implies radio resource optimization and a more effective scheduler decision. Simulation scenarios are presented to demonstrate how the scheduling solution allocates resources through particular WiMAX MAC layer implementation in the NS-2 simulator. Results show that the new mechanism implementation results in an improvement to the simple Round Robin fashion present in the original simulation model, being able to increase differentiation between different classes and decrease packets delay, due to its cross-layer processing and traffic prioritization.

  3. High-speed IP packet forwarding over Internet using ATM technology

    NASA Astrophysics Data System (ADS)

    Esaki, Hiroshi

    1995-10-01

    Framework of IP packet delivery with high throughput and small latency using ATM technology in large scaled internets is proposed, while keeping the current subnet model. Router has the mapping functionality between flow-identifier (e.g. in IPv6 header) and VPI/VCI value to forward IP packets cell-by-cell, rather than the conventional packet-by- packet forwarding. By using this cut-thru IP packet forwarding, both resource reservation oriented IP packet flows (i.e. IP packet flow provided by RSVP) and nonresource reservation oriented IP packet flows (i.e. best effort service) experience less packet delivery latency and obtain higher throughput, compared to the conventional hop-by-hop packet forwarding does. In order to perform the cut-thru IP packet forwarding using cell relaying capability in the router, routers exchange the information how the IP packet flows are aggregated into ATM- VCC. This information exchanging is hop-by-hop base, and the cut-thru decision is a matter of every router's local decision. With the hop-by-hop cut-thru IP packet forwarding, soft-state oriented and scalable QoS-ed high speed communication platform can be provided.

  4. On board processing for future satellite communications systems: Comparison of FDM, TDM and hybrid accessing schemes

    NASA Technical Reports Server (NTRS)

    Berk, G.; Jean, P. N.; Rotholz, E.

    1982-01-01

    Several satellite uplink and downlink accessing schemes for customer premises service are compared. Four conceptual system designs are presented: satellite-routed frequency division multiple access (FDMA), satellite-switched time division multiple access (TDMA), processor-routed TDMA, and frequency-routed TDMA, operating in the 30/20 GHz band. The designs are compared on the basis of estimated satellite weight, system capacity, power consumption, and cost. The systems are analyzed for fixed multibeam coverage of the continental United States. Analysis shows that the system capacity is limited by the available satellite resources and by the terminal size and cost.

  5. A multi-ring optical packet and circuit integrated network with optical buffering.

    PubMed

    Furukawa, Hideaki; Shinada, Satoshi; Miyazawa, Takaya; Harai, Hiroaki; Kawasaki, Wataru; Saito, Tatsuhiko; Matsunaga, Koji; Toyozumi, Tatuya; Wada, Naoya

    2012-12-17

    We newly developed a 3 × 3 integrated optical packet and circuit switch-node. Optical buffers and burst-mode erbium-doped fiber amplifiers with the gain flatness are installed in the 3 × 3 switch-node. The optical buffer can prevent packet collisions and decrease packet loss. We constructed a multi-ring optical packet and circuit integrated network testbed connecting two single-ring networks and a client network by the 3 × 3 switch-node. For the first time, we demonstrated 244 km fiber transmission and 5-node hopping of multiplexed 14-wavelength 10 Gbps optical paths and 100 Gbps optical packets encapsulating 10 Gigabit Ethernet frames on the testbed. Error-free (frame error rate < 1 × 10(-4)) operation was achieved with optical packets of various packet lengths. In addition, successful avoidance of packet collisions by optical buffers was confirmed.

  6. Joint source coding, transport processing, and error concealment for H.323-based packet video

    NASA Astrophysics Data System (ADS)

    Zhu, Qin-Fan; Kerofsky, Louis

    1998-12-01

    In this paper, we investigate how to adapt different parameters in H.263 source coding, transport processing and error concealment to optimize end-to-end video quality at different bitrates and packet loss rates for H.323-based packet video. First different intra coding patterns are compared and we show that the contiguous rectangle or square block pattern offers the best performance in terms of video quality in the presence of packet loss. Second, the optimal intra coding frequency is found for different bitrates and packet loss rates. The optimal number of GOB headers to be inserted in the source coding is then determined. The effect of transport processing strategies such as packetization and retransmission is also examined. For packetization, the impact of packet size and the effect of macroblock segmentation to picture quality are investigated. Finally, we show that the dejitter buffering delay can be used to the advantage for packet loss recovery with video retransmission without incurring any extra delay.

  7. A CURRICULUM FOR ENGLISH, TEACHER PACKET, GRADE 11.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    UNITS IN THE TEACHER PACKET FOR THE 11TH-GRADE NEBRASKA ENGLISH CURRICULUM ARE ORGANIZED AROUND THREE MAJOR THEMES IN AMERICAN LITERATURE--MAN AND NATURE, MAN AND MORAL LAW, AND MAN AND SOCIETY. THE MAN AND NATURE THEME IS EXAMINED IN TWO UNITS--"INDIVIDUALISM AND IDEALISM, SPIRITUAL AUTOBIOGRAPHY" AND "THE SEARCH FOR FORM."…

  8. An Efficient Conflict Detection Algorithm for Packet Filters

    NASA Astrophysics Data System (ADS)

    Lee, Chun-Liang; Lin, Guan-Yu; Chen, Yaw-Chung

    Packet classification is essential for supporting advanced network services such as firewalls, quality-of-service (QoS), virtual private networks (VPN), and policy-based routing. The rules that routers use to classify packets are called packet filters. If two or more filters overlap, a conflict occurs and leads to ambiguity in packet classification. This study proposes an algorithm that can efficiently detect and resolve filter conflicts using tuple based search. The time complexity of the proposed algorithm is O(nW+s), and the space complexity is O(nW), where n is the number of filters, W is the number of bits in a header field, and s is the number of conflicts. This study uses the synthetic filter databases generated by ClassBench to evaluate the proposed algorithm. Simulation results show that the proposed algorithm can achieve better performance than existing conflict detection algorithms both in time and space, particularly for databases with large numbers of conflicts.

  9. Resonance-assisted decay of nondispersive wave packets.

    PubMed

    Wimberger, Sandro; Schlagheck, Peter; Eltschka, Christopher; Buchleitner, Andreas

    2006-07-28

    We present a quantitative semiclassical theory for the decay of nondispersive electronic wave packets in driven, ionizing Rydberg systems. Statistically robust quantities are extracted combining resonance-assisted tunneling with subsequent transport across chaotic phase space and a final ionization step.

  10. Application of Cellular Automata to Detection of Malicious Network Packets

    ERIC Educational Resources Information Center

    Brown, Robert L.

    2014-01-01

    A problem in computer security is identification of attack signatures in network packets. An attack signature is a pattern of bits that characterizes a particular attack. Because there are many kinds of attacks, there are potentially many attack signatures. Furthermore, attackers may seek to avoid detection by altering the attack mechanism so that…

  11. Using Document Reading Activity Packets (DRAP) in the Classroom.

    ERIC Educational Resources Information Center

    Adomanis, James F.; Schulz, Constance

    1987-01-01

    Reviews a Document Reading Activity Packet (DRAP) revolving around the "Fort Washington Incident" of the War of 1812 and the resulting court martial of Captain Samuel T. Dyson. Explains this exercise is designed to stimulate students' interest in their own state histories as well as stimulate their curiosity for further research. (BSR)

  12. Maintaining Inequality: A Background Packet on Tracking and Ability Grouping.

    ERIC Educational Resources Information Center

    National Coalition of Education Activists, Rosendale, NY.

    This document includes a selection of materials from the National Coalition of Education Activists (NCEA) on tracking and ability grouping designed to be a tool for teachers who wish to organize their school or district against tracking. The packet contains a cover letter, a response/feedback form, and reproductions of the following articles: (1)…

  13. Analysis of a Rumor Routing Protocol with Limited Packet Lifetimes

    DTIC Science & Technology

    2010-03-01

    modified rumor routing protocol system................................................... 29 Figure 3: A MORRP node modeled in OPNET ...41 Table 4: Parameters for OPNET model verification simulations...packet-related parameters can be modeled by an arbitrary distribution. 2. Uses OPNET , a discrete-time network simulator, to analyze the effect each

  14. A CURRICULUM FOR ENGLISH, STUDENT PACKET, GRADE 8.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    THE EIGHTH-GRADE STUDENT PACKET OF THE NEBRASKA ENGLISH CURRICULUM BEGINS WITH A UNIT ON "THE MAKING OF HEROES, THE NOBLEMAN IN WESTERN LITERATURE" WHICH LEADS STUDENTS TO QUESTION WHAT MAKES A HERO, WHAT HE IS LIKE, AND HOW HE EXISTS IN LITERATURE. AFTER READING A NUMBER OF BRIEF SELECTIONS FROM SUCH WORKS AS "THE…

  15. A CURRICULUM FOR ENGLISH, STUDENT PACKET, GRADE 7.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    THE SEVENTH-GRADE STUDENT PACKET, PRODUCED BY THE NEBRASKA CURRICULUM DEVELOPMENT CENTER, BEGINS WITH THE UNIT ENTITLED "THE MAKING OF STORIES" IN WHICH STUDENTS CONSIDER WRITERS' AUDIENCES AND METHODS OF COMPOSITION AND PRESENTATION. SUCH MATERIAL AS "A CHRISTMAS CAROL" AND SELECTIONS FROM "THE…

  16. [Geography Awareness Week Activity Packet, 1987 and 1988.

    ERIC Educational Resources Information Center

    Texas Alliance for Geographic Education, College Station.

    This resource packet contains materials and suggestions to integrate National Geography Awareness Week for 1987 and 1988 into elementary and secondary education in Texas. The materials for 1987 include: (1) a pamphlet for a balloon release; (2) a collection of ideas for student activities; (3) a description of two field experiences; (4) a…

  17. A CURRICULUM FOR ENGLISH, STUDENT PACKET, GRADE 12.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    THE LITERATURE PROGRAM OF THE GRADE 12 STUDENT PACKET OF THE NEBRASKA ENGLISH CURRICULUM CONSISTS OF A SELECTIVE SURVEY OF ENGLISH LITERATURE FROM THE RENAISSANCE TO THE 20TH CENTURY. IT BEGINS WITH A UNIT ON SHAKESPEAREAN TRAGEDY IN WHICH STUDENTS READ REVENGE TRAGEDIES--SENECA'S "THYESTES" AND KYD'S "THE SPANISH TRAGEDY"--AS…

  18. Energy Crisis: Libya's and Nigeria's Role. Resource Packet.

    ERIC Educational Resources Information Center

    African-American Inst., New York, NY. School Services Div.

    This resource packet contains practical suggestions and resource materials to help secondary teachers teach about Libya's and Nigeria's roles in the energy crisis. Students become acquainted with the governments and cultures of the two countries, examine their social problems, and learn how the Libyan and Nigerian governments are using money from…

  19. A CURRICULUM FOR ENGLISH, STUDENT PACKET, GRADE 11.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    THE 11TH-GRADE COURSE OF STUDY IN AMERICAN LITERATURE PRESENTED IN THE STUDENT PACKET FOR THE NEBRASKA ENGLISH CURRICULUM BEGINS WITH A UNIT ENTITLED "INDIVIDUALISM AND IDEALISM" IN WHICH STUDENTS ANALYZE SPIRITUAL AUTOBIOGRAPHIES BY EMERSON, THOREAU, WHITMAN, AND DICKINSON. NEXT, THE THEME OF SIN AND LONELINESS AS IT LIMITS…

  20. Energy Conservation Activity Packet, Grade 5. Revised Edition.

    ERIC Educational Resources Information Center

    Pohlman, Betty; And Others

    This activity notebook for grade 5 is one of a series developed in response to energy conservation. It contains activities that stress an energy conservation ethic and includes many values clarification activities for grade five. The packet is divided into two parts and provides the teacher with background information, concepts and objectives, and…

  1. The Sphinx and the Pyramids at Giza. Educational Packet.

    ERIC Educational Resources Information Center

    Gagliano, Sara; Rapport, Wendy

    This packet of materials was created to accompany the exhibit "The Sphinx and the Pyramids: 100 Years of American Archaeology at Giza" at the Semitic Museum of Harvard University. The lessons and teacher's guide focus on the following: (1) "The Mystery of the Secret Tomb" where students take on the role of an archaeologist by…

  2. Solar Energy Education Packet for Elementary & Secondary Students. Revised Edition.

    ERIC Educational Resources Information Center

    Center for Renewable Resources, Washington, DC.

    The arrangement of this packet is essentially evolutionary, with a conscious effort to alternate reading assignments, activities and experiments. It begins with solar energy facts and terminology as background to introduce the reader to basic concepts. It progresses into a discussion of passive solar systems. This is followed by several projects…

  3. "Macbeth." A Play Packet To Accompany "Elementary, My Dear Shakespeare."

    ERIC Educational Resources Information Center

    Engen, Barbara; Campbell, Joy

    Intended for use by elementary school teachers as a supplement to the book, "Elementary, My Dear Shakespeare," or for use by itself to produce one Shakespeare play, this play packet contains ready-to-reproduce materials for the production of "Macbeth." Materials include: staging suggestions for scenery, props, lighting, and…

  4. Office Reprographics. Instructor's Guide. Student Activity Packet. Office Occupations.

    ERIC Educational Resources Information Center

    Johnson, Diane E.

    This training package, one in a series of instructional modules consisting of an instructor's guide and a student activity packet, deals with office reprographics. Included in the instructor's guide are general directions for implementing the presentation; a detailed guide for teaching the lesson that includes performance objectives, suggestions…

  5. Hardware Realization of an Ethernet Packet Analyzer Search Engine

    DTIC Science & Technology

    2007-11-02

    specific for the home automation industry. This analyzer will be at the gateway of a network and analyze Ethernet packets as they go by. It will keep... home automation and not the computer network. This system is a stand-alone real-time network analyzer capable of decoding Ethernet protocols. The

  6. Marine and Coastal Resources. Global Issues Education Packet.

    ERIC Educational Resources Information Center

    Holm, Amy E.

    At least 70% of the Earth is covered with water. This packet provides background information on eight areas of concern regarding marine and coastal resources. Considered are: (1) "Coastal Resources"; (2) "Mangroves"; (3) "Coral Reefs"; (4) "Ocean Resources"; (5) "Aquaculture"; (6) "Pollution"; (7) "Marine Debris"; and (8) "The Global Commons."…

  7. Texas Wills. Teachers Instructional Packet, TIP No. 14, Spring 1987.

    ERIC Educational Resources Information Center

    Texas A and M Univ., College Station. Texas Real Estate Research Center.

    Part of a series of classroom aids designed for real estate instructors, this instructional packet was developed to help real estate students understand the different types of wills recognized in Texas, their preparation, provisions, and execution. First, information about wills is presented, including definitions of relevant terms and a…

  8. Solar Energy Education Packet for Elementary & Secondary Students.

    ERIC Educational Resources Information Center

    Center for Renewable Resources, Washington, DC.

    The arrangement of this packet is essentially evolutionary, with a conscious effort to alternate reading assignments, activities and experiments. It begins with solar energy facts and terminology as background to introduce the reader to basic concepts. It progresses into a discussion of passive solar systems. This is followed by several projects…

  9. Compression of echocardiographic scan line data using wavelet packet transform

    NASA Technical Reports Server (NTRS)

    Hang, X.; Greenberg, N. L.; Qin, J.; Thomas, J. D.

    2001-01-01

    An efficient compression strategy is indispensable for digital echocardiography. Previous work has suggested improved results utilizing wavelet transforms in the compression of 2D echocardiographic images. Set partitioning in hierarchical trees (SPIHT) was modified to compress echocardiographic scanline data based on the wavelet packet transform. A compression ratio of at least 94:1 resulted in preserved image quality.

  10. Chirp dependence of wave packet motion in oxazine 1.

    PubMed

    Malkmus, Stephan; Dürr, Regina; Sobotta, Constanze; Pulvermacher, Horst; Zinth, Wolfgang; Braun, Markus

    2005-11-24

    The motion of vibrational wave packets in the system oxazine 1 in methanol is investigated by spectrally resolved transient absorption spectroscopy. The spectral properties of the probe pulse from 600 to 700 nm were chosen to cover the overlap region where ground-state bleach and stimulated emission signals are detected. The spectral phase of the pump pulse was manipulated by a liquid crystal display based pulse-shaping setup. Chirped excitation pulses of negative and positive chirp can be used to excite vibrational modes predominantly in the ground or excited state, respectively. To distinguish the observed wave packets in oxazine 1 moving in the ground or excited state, spectrally resolved transient absorption experiments are performed for various values of the linear chirp of the pump pulses. The amplitudes of the wave packet motion show an asymmetric behavior with an optimum signal for a negative chirp of -0.75 +/- 0.2 fs/nm, which indicates that predominantly ground-state wave packets are observed.

  11. A CURRICULUM FOR ENGLISH, TEACHER PACKET, GRADE 12.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    THE TEACHER PACKET FOR THE 12TH-GRADE ENGLISH PROGRAM OF THE NEBRASKA CURRICULUM DEVELOPMENT CENTER COMPRISES, THROUGH THE STUDY OF SELECTED WORKS, A SURVEY OF ENGLISH LITERARY PERIODS FROM THE RENAISSANCE TO THE 20TH CENTURY. UNITS ARE PROVIDED IN THE FOLLOWING AREAS--(1) "SENECAN REVENGE TRAGEDY--'THYESTES,''THE SPANISH TRAGEDY,' AND…

  12. Anti-Litter Curriculum Packet, Interdisciplinary, K-12.

    ERIC Educational Resources Information Center

    Tillis, Richard

    This curriculum packet consists of 20 illustrated cards with 15 activities designed to create "positive feelings" about a clean environment. Activities range from picture coloring for younger students, to lessons such as the economic and health problems litter creates for older students. Objectives include encouraging anti-litter and…

  13. Environmental Education Inservice Training Packet for the Intermediate Level.

    ERIC Educational Resources Information Center

    Upper Mississippi River ECO-Center, Thomson, IL.

    The inservice teacher training packet, developed with help from the environmental education program of the Upper Mississippi River ECO-Center, is designed to help intermediate-level teachers develop teaching skills which will enable them to introduce environmental or outdoor education to their students and develop those concepts, attitudes, and…

  14. Wave packet motion in harmonic potential and computer visualization

    NASA Technical Reports Server (NTRS)

    Tsuru, Hideo; Kobayashi, Takeshi

    1993-01-01

    Wave packet motions of a single electron in harmonic potentials or a magnetic field are obtained analytically. The phase of the wave function which depends on both time and space is also presented explicitly. The probability density of the electron changes its width and central position periodically. These results are visualized using computer animation techniques.

  15. Substance Abuse Prevention Education. Special Topic Curriculum Resources Packet.

    ERIC Educational Resources Information Center

    Connecticut State Dept. of Education, Hartford.

    This curriculum resources packet provides the most current information available in substance abuse prevention education. Its stated purpose is to assist schools in combating the problem of substance abuse through effective prevention/education programs. These topic areas are discussed: (1) drugs and their effects; (2) continuum of drug use; (3)…

  16. A CURRICULUM FOR ENGLISH, STUDENT PACKET, GRADE 9.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    THE FIRST UNIT OF THE STUDENT PACKET FOR GRADE NINE OF THE NEBRASKA ENGLISH CURRICULUM IS A STUDY OF THE RELATIONSHIPS WHICH EXIST BETWEEN AUTHOR AND AUDIENCE, AND AN EXAMINATION OF THE EPIGRAM, LIMERICK, PARABLE, FABLE, AND ODE. WITH THIS BACKGROUND, STUDENTS CONSIDER "ON AVARICE" AND "ANIMAL FARM" AS EXAMPLES OF FORMAL AND…

  17. Canada and the United States. Perspective. Learning Activity Packet.

    ERIC Educational Resources Information Center

    Maine Univ., Orono. New England - Atlantic Provinces - Quebec Center.

    The similarities and differences of Canada and the United States are explored in this Learning Activity Packet (LAP). Ten learning objectives are given which encourage students to examine: 1) the misconceptions Americans and Canadians have about each other and their ways of life; 2) the effect and influence of French and English exploration and…

  18. Customized lifting multiwavelet packet information entropy for equipment condition identification

    NASA Astrophysics Data System (ADS)

    Chen, Jinglong; Zuo, Ming J.; Zi, Yanyang; He, Zhengjia; Yuan, Jing; Chen, Xuefeng

    2013-09-01

    Condition identification of mechanical equipment from vibration measurement data is significant to avoid economic loss caused by unscheduled breakdowns and catastrophic accidents. However, this task still faces challenges due to the complexity of equipment and the harsh environment. This paper provides a possibility for equipment condition identification by proposing a method called customized lifting multiwavelet packet information entropy. Benefiting from the properties of multi-resolution analysis and multiple wavelet basis functions, the multiwavelet method has advantages in characterizing non-stationary vibration signals. In order to realize the accurate detection and identification of the condition features, a customized lifting multiwavelet packet is constructed via a multiwavelet lifting scheme. Then the vibration signal from the mechanical equipment is processed by the customized lifting multiwavelet packet transform. The relative energy in each frequency band of the multiwavelet packet transform coefficients that equals a percentage of the whole signal energy is taken as the probability. The normalized information entropy is obtained based on the relative energy to describe the condition of a mechanical system. The proposed method is applied to the condition identification of a rolling mill and a demountable disk-drum aero-engine. The results support the feasibility of the proposed method in equipment condition identification.

  19. Packet Preparation. Summer Program Academic Resources Coordination Center.

    ERIC Educational Resources Information Center

    State Univ. of New York, Cortland. Coll. at Cortland.

    This teaching guide was developed by the Summer Program Academic Resources Coordination Center (SPARCC) in Loudonville, New York. SPARCC was a migrant education grant that developed and helped implement model summer migrant education programs in New York, Virginia, and Florida. This guide provides directions for preparing learning packets to…

  20. Scattering of wave packets on atoms in the Born approximation

    NASA Astrophysics Data System (ADS)

    Karlovets, D. V.; Kotkin, G. L.; Serbo, V. G.

    2015-11-01

    It has recently been demonstrated experimentally that 200 -300 keV electrons with the unusual spatial profiles can be produced and even focused to a subnanometer scale—namely, electrons carrying nonzero orbital angular momentum and also the so-called Airy beams. Since the wave functions of such electrons do not represent plane waves, the standard Born formula for scattering of them off a potential field is no longer applicable and, hence, needs modification. In the present paper, we address the generic problem of elastic scattering of a wave packet of a fast nonrelativistic particle off a potential field. We obtain simple and convenient formulas for a number of events and an effective cross section in such a scattering, which represent generalization of the Born formula for a case when finite sizes and spatial inhomogeneity of the initial packet should be taken into account. As a benchmark, we consider two simple models corresponding to scattering of a Gaussian wave packet on a Gaussian potential and on a hydrogen atom, and perform a detailed analysis of the effects brought about by the limited sizes of the incident beam and by the finite impact parameter between the potential center and the packet's axis.

  1. SLIAG Advocacy Packet: A Guide for Community-Based Organizations.

    ERIC Educational Resources Information Center

    National Council of La Raza, Washington, DC.

    This packet of materials is designed as a basic guide for community-based organizations (CBOs) interested in tracking the use of State Legalization Impact Assistance Grants (SLIAG) funds and in advocating that they be used efficiently and effectively. The SLIAG program was created under the Immigration Reform and Control Act of 1986 (IRCA) to…

  2. [Principal's Training Simulator in Special Education. Instructor's Packet.

    ERIC Educational Resources Information Center

    Burello, Leonard C.; And Others

    This instructor's packet on collaborative leadership development in special education presents the Principal's Training Simulator in Special Education (PTSSE), designed to provide an orientation to typical situations facing local school district administrators, consideration of major issues in programming for exceptional children, practice in…

  3. Diffraction of Gaussian wave packets by a single slit

    NASA Astrophysics Data System (ADS)

    Zecca, A.

    2011-02-01

    A two-dimensional formulation of particle diffraction by a single slit is proposed within Schrödinger QM. The study is done in terms of Gaussian wave packets. A "confinement" assumption is considered together with a previous "truncation" assumption when the wave packet passes the slit. In the limiting situation of entering Gaussian wave packet peaked in the transverse-momentum probability distribution, the diffraction pattern results in an unaltered central maximum with lateral maxima narrower and higher than in the absence of the confinement assumption. For entering wave packets peaked in the transverse position probability distribution, the diffraction pattern consists of a central Gaussian spot with lateral diffraction maxima, not present in the absence of the "confinement" assumption, whose visibility depends on the configuration of the parameters. With a different analysis, a similar effect was obtained also in G. Kalbermann (J. Phys. A: Math. Gen. 35, 4599 (2002)). Its experimental verification seems of interest to discriminate between Schrödinger QM and stochastic electrodynamics with spin.

  4. Teacher Education Packet for Illinois Core Curriculum in Agriculture.

    ERIC Educational Resources Information Center

    Hemp, Paul; Pepple, Jerry

    Developed for use by teacher educators or state staff, this teaching packet provides preservice or inservice training to teachers and prospective teachers on how to use the Illinois Core Curriculum in Agriculture. (It is recommended that copies of the Illinois core materials be available to the students.) Three problem areas are included:…

  5. Energy Conservation Activity Packet, Grade 6. Revised Edition.

    ERIC Educational Resources Information Center

    Pohlman, Betty; And Others

    This activity notebook for grade 6 is one of a series developed in response to the concern for energy conservation. It contains activities that stress an energy conservation ethic and includes many values clarification activities for grade six. The packet is divided into two parts and provides the teacher with background information, concepts and…

  6. Energy Conservation Activity Packet, Grade 3. Revised Edition.

    ERIC Educational Resources Information Center

    Pohlman, Betty; And Others

    This notebook for grade 3 is one of a series developed in response to the concern for energy conservation. It contains activities that stress an energy conservation ethic and includes many values clarification activities for grade three. The packet is divided into two parts and provides the teacher with background information, concepts and…

  7. Energy Conservation Activity Packet, Grade 4. Revised Edition.

    ERIC Educational Resources Information Center

    Pohlman, Betty; And Others

    This activity notebook for grade 4 is one in a series developed in response to the concern for energy conservation. It contains activities that stress an energy conservation ethic and includes many values clarification activities for grade four. The packet is divided into two parts and provides the teacher with background information, concepts and…

  8. A CURRICULUM FOR ENGLISH, STUDENT PACKET, GRADE 10.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Curriculum Development Center.

    THE STUDENT PACKET FOR GRADE 10 OF THE NEBRASKA ENGLISH CURRICULUM BEGINS WITH FOUR UNITS ON LITERATURE, EACH STRESSING AN ASPECT OF MAN'S CONCEPTION OF THE WORLD. THROUGH A STUDY OF THE LITERATURE OF SEVERAL CULTURES, WRITTEN AT VARIOUS TIMES, STUDENTS FIRST CONSIDER "MAN AND NATURE, MAN'S PICTURE OF NATURE." THE SECOND UNIT, "MAN…

  9. In Her Own Write: Maryland Women's History Resource Packet, 1989.

    ERIC Educational Resources Information Center

    Maryland State Commission for Women, Baltimore.

    This packet is designed to raise precollege students' understanding and awareness of writing by women, to encourage women's studies in the curriculum, and to assist in identifying bias in language use and English/language arts curriculum materials. It can also be used by companies or community organizations interested in similar issues. It…

  10. Sharing Skills: Reach for a Book; Book Week Puzzle Packet.

    ERIC Educational Resources Information Center

    Bauer, Caroline Feller

    1986-01-01

    Reach for a Book is the theme for Children's Book Week 1986, and book presentations, activities, and exhibits to emphasize the joy of reading are listed. A Book Week Puzzle Packet provides two puzzles designed to reinforce the idea of using the card catalog to find materials on specific subjects. (EM)

  11. Business Education: Learning Activities Packet for Office Education.

    ERIC Educational Resources Information Center

    Hawaii State Dept. of Education, Honolulu. Office of Instructional Services.

    These seventeen individualized learning activities packets (LAPs) are intended to relate essential competencies needed for entry or advancement in office occupations to the secondary level office education program and to assist students in achieving occupational proficiency in business careers. Each LAP contains some or all of the following…

  12. On-board B-ISDN fast packet switching architectures. Phase 1: Study

    NASA Technical Reports Server (NTRS)

    Faris, Faris; Inukai, Thomas; Lee, Fred; Paul, Dilip; Shyy, Dong-Jye

    1993-01-01

    The broadband integrate services digital network (B-ISDN) is an emerging telecommunications technology that will meet most of the telecommunications networking needs in the mid-1990's to early next century. The satellite-based system is well positioned for providing B-ISDN service with its inherent capabilities of point-to-multipoint and broadcast transmission, virtually unlimited connectivity between any two points within a beam coverage, short deployment time of communications facility, flexible and dynamic reallocation of space segment capacity, and distance insensitive cost. On-board processing satellites, particularly in a multiple spot beam environment, will provide enhanced connectivity, better performance, optimized access and transmission link design, and lower user service cost. The following are described: the user and network aspects of broadband services; the current development status in broadband services; various satellite network architectures including system design issues; and various fast packet switch architectures and their detail designs.

  13. Children's Literature with a Science Emphasis: Twenty Teacher-Developed K-8 Activity Packets.

    ERIC Educational Resources Information Center

    Butler, Malcolm B.

    This document features 10 science activity packets developed for elementary students by science teachers in a graduate seminar. The activity packets were designed to cover existing commercial children's books on specific content areas. The 10 activity packets are: (1) "Bringing the Rain to Kapiti Plain," which explains the water cycle;…

  14. Symmetric reconfigurable capacity assignment in a bidirectional DWDM access network.

    PubMed

    Ortega, Beatriz; Mora, José; Puerto, Gustavo; Capmany, José

    2007-12-10

    This paper presents a novel architecture for DWDM bidirectional access networks providing symmetric dynamic capacity allocation for both downlink and uplink signals. A foldback arrayed waveguide grating incorporating an optical switch enables the experimental demonstration of flexible assignment of multiservice capacity. Different analog and digital services, such as CATV, 10 GHz-tone, 155Mb/s PRBS and UMTS signals have been transmitted in order to successfully test the system performance under different scenarios of total capacity distribution from the Central Station to different Base Stations with two reconfigurable extra channels for each down and upstream direction.

  15. Modelling and control of Zigbee-based wireless networked control system with both network-induced delay and packet dropout

    NASA Astrophysics Data System (ADS)

    Li, Jian-ning; Su, Hong-ye; Wu, Zheng-guang; Chu, Jian

    2013-06-01

    A new stochastic switched linear model is established to describe the Zigbee-based wireless networked control system (WNCS) with both network-induced delay and packet dropout. The network-induced delay can be less or longer than one sampling period. A sufficient condition is presented for the exponentially mean square stability of the closed-loop WNCS, and corresponding state feedback controller is designed by using the augmenting technique and multi-Lyapunov approach. Then, combined with carrier sense multiple access with collision avoidance (CSMA-CA) algorithm, a method is given to choose proper parameter values. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed method.

  16. Vocational Instructor Teaching Skills Project. Evaluating Your Teaching Effectiveness. Resource Packet. [and] Computer-Based Education. Resource Packet.

    ERIC Educational Resources Information Center

    Portland Community Coll., OR.

    A project was conducted at Mt. Hood (Oregon) Community College to develop modules to upgrade the teaching skills of community college teachers. Two modules developed through this project, Evaluating Your Teaching Effectiveness and Computer-Based Education, are included in this document. The Evaluating Your Teaching Effectiveness packet consists of…

  17. Downlink Training Techniques for FDD Massive MIMO Systems: Open-Loop and Closed-Loop Training With Memory

    NASA Astrophysics Data System (ADS)

    Choi, Junil; Love, David J.; Bidigare, Patrick

    2014-10-01

    The concept of deploying a large number of antennas at the base station, often called massive multiple-input multiple-output (MIMO), has drawn considerable interest because of its potential ability to revolutionize current wireless communication systems. Most literature on massive MIMO systems assumes time division duplexing (TDD), although frequency division duplexing (FDD) dominates current cellular systems. Due to the large number of transmit antennas at the base station, currently standardized approaches would require a large percentage of the precious downlink and uplink resources in FDD massive MIMO be used for training signal transmissions and channel state information (CSI) feedback. To reduce the overhead of the downlink training phase, we propose practical open-loop and closed-loop training frameworks in this paper. We assume the base station and the user share a common set of training signals in advance. In open-loop training, the base station transmits training signals in a round-robin manner, and the user successively estimates the current channel using long-term channel statistics such as temporal and spatial correlations and previous channel estimates. In closed-loop training, the user feeds back the best training signal to be sent in the future based on channel prediction and the previously received training signals. With a small amount of feedback from the user to the base station, closed-loop training offers better performance in the data communication phase, especially when the signal-to-noise ratio is low, the number of transmit antennas is large, or prior channel estimates are not accurate at the beginning of the communication setup, all of which would be mostly beneficial for massive MIMO systems.

  18. Field trial of 160 Gbit/s DWDM-based optical packet switching and transmission.

    PubMed

    Furukawa, Hideaki; Wada, Naoya; Awaji, Yoshinari; Miyazaki, Tetsuya; Kong, Eddie; Chan, Peter; Man, Ray; Cincotti, Gabriella; Kitayama, Ken-ichi

    2008-07-21

    We demonstrated, for the first time, a field trial of 160 (16 lambda x 10) Gbit/s, fine granularity, DWDM-based optical packet switching and transmission by newly-developed burst-mode EDFAs and an optical packet switch prototype with multiple all-optical label processors. We achieved 64 km field transmission and switching of 160 (16 lambda x 10) Gbit/s DWDM-based optical packets encapsulating almost 10 Gbit/s IP packets with error-free operation (IP-packet-loss-rate <10(-6) and bit-error-rate <10(-9)).

  19. Strongly nonlinear evolution of low-frequency wave packets in a dispersive plasma

    NASA Technical Reports Server (NTRS)

    Vasquez, Bernard J.

    1993-01-01

    The evolution of strongly nonlinear, strongly modulated wave packets is investigated in a dispersive plasma using a hybrid numerical code. These wave packets have amplitudes exceeding the strength of the external magnetic field, along which they propagate. Alfven (left helicity) wave packets show strong steepening for p < 1, while fast (fight heIicity) wave packets hardly steepen for any beta. Substantial regions of opposite helicity form on the leading side of steepened Alfven wave packets. This behavior differs qualitatively from that exhibited by the solutions to the derivative nonlinear Schrodinger (DNLS) equation.

  20. Revivals and classical-motion bases of quantum wave packets

    NASA Astrophysics Data System (ADS)

    Aronstein, David L.

    This thesis explores the boundary between classical and quantum mechanics by studying wave packets, coherent superpositions of the stationary states of a quantum system. Such wave packets travel as localized entities along the trajectories predicted by classical mechanics for small windows of time before they spread out and decay away. Our investigations focus on two central issues---the revivals of the shape and classical motion of these wave packets that occur long after their initial decay, and the classical-motion bases that describe the quantum wavefunction in terms of constitutive objects that move classically. We study the infinite square-well potential, a simple model of complete confinement in a one-dimensional interval. The quantum motion seen in this potential is compared with classical models of a particle bouncing between two walls and of a wave traveling along a stretched string with both ends secured. We uncover a remarkable wave-motion basis, with which the wavefunction at any moment in time can be decomposed into a sum of distinct wave propagations of the initial quantum wavefunction in the classical wave equation. These results are extended to the finite square-well potential and we show how the wave-motion basis can be reconciled with the seemingly disparate theory of revivals for highly excited quantum wave packets. We explore the commonalities of the quantum revivals seen in a wide variety of systems by developing a mathematical formalism called phase-difference equations. These equations connect physical models for revivals with the subsequent prediction of revival times in a general way and offer a comprehensive "calculus" for understanding revival phenomena. We apply this calculus to several examples to demonstrate its power and versatility. Using a recently developed semiclassical basis for quantum states, we explore the radial wave packets of the hydrogen atom. Viewed in the semiclassical basis, the revivals of these wave packets are shown

  1. Investigation into the formation of charge packets in polyethylene: Experiment and simulation

    NASA Astrophysics Data System (ADS)

    Zhao, J.; Chen, G.; Lewin, P. L.

    2012-08-01

    The phenomenon of charge packet has been reported in polymeric insulation materials under the application of dc electric fields in recent decades. It is noted that such charge packets could lead to substantial modification of local electric stress, which increases the possibility of failure of insulating materials. The physics of charge packets has not yet been revealed clearly. In this paper, the dynamics of positive charge packets in polyethylene is observed using the pulsed electro-acoustic technique. Negative differential mobility of positive charge carrier is found, which is believed to be crucial to the formation of charge packets. This negative differential mobility is introduced into a bipolar charge transport model to simulate the packet-like space charge in polymers. Simulation results show that not only the negative differential mobility but also weaker trapping characteristic are required to generate a positive charge packet in polyethylene under dc stress.

  2. Reconfigurable Data Communications Packet-Switch Emulation Test Bed Demonstrated

    NASA Technical Reports Server (NTRS)

    Chu, Pong P.; Jones, Robert E.

    1999-01-01

    The Communications Technology Division at the NASA Lewis Research Center has an ongoing program to develop advanced switching and routing technology concepts for future satellite onboard processing systems. Through a university grant as a part of this research, the Cleveland State University is using a flexible reconfigurable data communications packet switch emulation test bed to investigate packet switching techniques. Because of the switching speed and protocol complexity, implementing a data communications network is a tremendous task. Various alternatives should be carefully studied and evaluated in the development stage so that the optimal system configuration can be obtained and implemented later. Therefore, it is desirable to predict the performance of the network before it is actually constructed. This is especially true in the case of satellite systems. In the past, theoretical analysis, software simulation, and prototyping were used to evaluate performance. However, each method has its drawback. There are basic tradeoffs among accuracy, cost, and required evaluation time. No method is completely satisfactory.

  3. Wave packet dynamics in the optimal superadiabatic approximation

    NASA Astrophysics Data System (ADS)

    Betz, V.; Goddard, B. D.; Manthe, U.

    2016-06-01

    We explain the concept of superadiabatic representations and show how in the context of electronically non-adiabatic transitions they lead to an explicit formula that can be used to predict transitions at avoided crossings. Based on this formula, we present a simple method for computing wave packet dynamics across avoided crossings. Only knowledge of the adiabatic potential energy surfaces near the avoided crossing is required for the computation. In particular, this means that no diabatization procedure is necessary, the adiabatic electronic energies can be computed on the fly, and they only need to be computed to higher accuracy when an avoided crossing is detected. We test the quality of our method on the paradigmatic example of photo-dissociation of NaI, finding very good agreement with results of exact wave packet calculations.

  4. Revision of a Non-Preemptive EDF Packet Scheduling Algorithm

    DTIC Science & Technology

    2009-04-24

    arrival time apk ,n within [t, t+ τ ]: t ≤ apk ,n ≤ t+ τ (14) Moreover, from (11) and xmin,k is the minimum interval be- tween the departures of two...successive packets at source gpk − gp′k ≥ xmin,k, we have: apk − ap′k = gpk − gp′k ≥ xmin,k > τ (15) From(14) and (15), we have ap′k < apk −τ ≤ (t+τ)−τ...that the packet pk must arrive after π′pi because it remains at the node in the interval (π′pi , dlpi,n]: π′pi < apk ,n (19) From (18)(19) dlpi,n − π′pi

  5. The Formation of Packets of Hairpins in Shear Flows

    NASA Astrophysics Data System (ADS)

    Cohen, Jacob; Karp, Michael; Shukhman, Ilia

    2009-11-01

    In the present work we utilize a recently developed new method in an attempt to understand the generation of packets of hairpin vortices from a pair of counter rotating streamwise vortices embedded in uniform shear flow. This analytical-based solution method is capable of following (numerically) the evolution of finite-amplitude localized vortical disturbances embedded in shear flows. Due to their localization in space, the surrounding base flow is assumed to have homogeneous shear to leading order. The method can solve in a novel way the interaction between a general family of unbounded planar homogeneous shear flows and any localized disturbance. The solution is carried out using Lagrangian variables in Fourier space which is convenient and enables fast computations. The revealed mechanism for generation of packets of hairpins seems to be universal and has been observed in the past both in fully developed wall-bounded shear flows as well as in wall-bounded transitional shear flows.

  6. Basis for paraxial surface-plasmon-polariton packets

    NASA Astrophysics Data System (ADS)

    Martinez-Herrero, Rosario; Manjavacas, Alejandro

    2016-12-01

    We present a theoretical framework for the study of surface-plasmon polariton (SPP) packets propagating along a lossy metal-dielectric interface within the paraxial approximation. Using a rigorous formulation based on the plane-wave spectrum formalism, we introduce a set of modes that constitute a complete basis set for the solutions of Maxwell's equations for a metal-dielectric interface in the paraxial approximation. The use of this set of modes allows us to fully analyze the evolution of the transversal structure of SPP packets beyond the single plane-wave approximation. As a paradigmatic example, we analyze the case of a Gaussian SPP mode, for which, exploiting the analogy with paraxial optical beams, we introduce a set of parameters that characterize its propagation.

  7. The Interference of the Dynamically Squeezed Vibrational Wave Packets

    NASA Technical Reports Server (NTRS)

    Vinogradov, An. V.; Janszky, J.; Kobayashi, T.

    1996-01-01

    An electronic excitation of a molecule by a sequence of two femtosecond phase-locked laser pulses is considered. In this case the interference between the vibrational wave packets induced by each of the subpulses within a single molecule takes place. It is shown that due to the dynamical squeezing effect of a molecular vibrational state the interference of the vibrational wave packets allows one to measure the duration of a femtosecond laser pulse. This can be achieved experimentally by measuring the dependence of the integral fluorescence of the excited molecule on the delay time between the subpulses. The interference can lead to a sharp peak (or to a down-fall) in that dependence, the width of which is equal to the duration of the laser pulse. It is shown that finite temperature of the medium is favorable for such an experiment.

  8. Stochastic Acceleration of Ions Driven by Pc1 Wave Packets

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Sibeck, D. G.; Tel'nikhin, A. A.; Kronberg, T. K.

    2015-01-01

    The stochastic motion of protons and He(sup +) ions driven by Pc1 wave packets is studied in the context of resonant particle heating. Resonant ion cyclotron heating typically occurs when wave powers exceed 10(exp -4) nT sq/Hz. Gyroresonance breaks the first adiabatic invariant and energizes keV ions. Cherenkov resonances with the electrostatic component of wave packets can also accelerate ions. The main effect of this interaction is to accelerate thermal protons to the local Alfven speed. The dependencies of observable quantities on the wave power and plasma parameters are determined, and estimates for the heating extent and rate of particle heating in these wave-particle interactions are shown to be in reasonable agreement with known empirical data.

  9. Stochastic acceleration of ions driven by Pc1 wave packets

    SciTech Connect

    Khazanov, G. V. Sibeck, D. G.; Tel'nikhin, A. A.; Kronberg, T. K.

    2015-07-15

    The stochastic motion of protons and He{sup +} ions driven by Pc1 wave packets is studied in the context of resonant particle heating. Resonant ion cyclotron heating typically occurs when wave powers exceed 10{sup −4} nT{sup 2}/Hz. Gyroresonance breaks the first adiabatic invariant and energizes keV ions. Cherenkov resonances with the electrostatic component of wave packets can also accelerate ions. The main effect of this interaction is to accelerate thermal protons to the local Alfven speed. The dependencies of observable quantities on the wave power and plasma parameters are determined, and estimates for the heating extent and rate of particle heating in these wave-particle interactions are shown to be in reasonable agreement with known empirical data.

  10. Predictive onboard flow control for packet switching satellites

    NASA Technical Reports Server (NTRS)

    Bobinsky, Eric A.

    1992-01-01

    We outline two alternate approaches to predicting the onset of congestion in a packet switching satellite, and argue that predictive, rather than reactive, flow control is necessary for the efficient operation of such a system. The first method discussed is based on standard, statistical techniques which are used to periodically calculate a probability of near-term congestion based on arrival rate statistics. If this probability exceeds a present threshold, the satellite would transmit a rate-reduction signal to all active ground stations. The second method discussed would utilize a neural network to periodically predict the occurrence of buffer overflow based on input data which would include, in addition to arrival rates, the distributions of packet lengths, source addresses, and destination addresses.

  11. High-performance multicasting schemes in optical packet switched networks

    NASA Astrophysics Data System (ADS)

    Ji, Yuefeng; Liu, Xin; Zhang, Jie; Zhang, Min

    2009-11-01

    Current trends in communications indicate that multicasting is becoming increasingly popular and important in networking applications. Since multicasting can be supported more efficiently in optical domain by utilizing the inherent light-splitting capacity of optical devices, such as optical splitters, than by copying data in electronic domain, issues concerning running multicast sessions in the all-optical networks have received much attention in recent years. In this paper, different multicasting schemes and their performance in the Optical Packet Switched networks are investigated, including the parallel mode, serial mode, and hybrid mode multicasting schemes. Computer simulation results show that compared with the parallel-mode and serial-mode multicasting schemes, hybrid-mode multicasting scheme is the best way to deliver multicast sessions in the Optical Packet Switched networks due to its highest performance.

  12. Organizing Multicast Receivers Deterministically by Packet-Loss Correlation

    DTIC Science & Technology

    1998-01-01

    source with either negative acknowledgments ( Nacks ) requesting lost data and the retransmissions that ensue during packet-loss, or positive...any receiver to respond to a Nack , and the Reliable Multicast Transport Protocol (RMTP) [17] appoints \\designated receivers", or- ganized into a tree... Nacks , and retransmissions, which reduces the load on the source and the network. The question is how to establish such an organized local recovery

  13. Collision Avoidance Techniques for Packet-Radio Networks

    DTIC Science & Technology

    1998-06-01

    results for various con gurations . . . . . . . . . . . . . . . . . 114 4.2 Throughput comprison of FAMA-NCS, IEEE 802.11 and MACAW . . . . . 116 5.1...Kar90] and its modi ed version MACAW (MACA for Wireless) [BDSZ94] were proposed to operate with hidden terminal using a simple three-way dialogue...interference free packets, and does not detect any other type of activity on the channel). However, the performance of MACA and MACAW degrade to

  14. IP- -: A Reduced Internet Protocol for Optical Packet Networking

    NASA Astrophysics Data System (ADS)

    Ohta, Masataka; Fujikawa, Kenji

    IP- - is proposed as an Internet Protocol suitable for optical packet networking. As optical routers require much faster control than electric ones and lack of optical buffers other than those by fiber delay lines requires fixed time control, Internet Protocols must be at least as simple as IPv4 and much simpler than IPv6. IP- - also addresses issues of IP address space exhaustion and IP routing table explosion.

  15. SDN architecture for optical packet and circuit integrated networks

    NASA Astrophysics Data System (ADS)

    Furukawa, Hideaki; Miyazawa, Takaya

    2016-02-01

    We have been developing an optical packet and circuit integrated (OPCI) network, which realizes dynamic optical path, high-density packet multiplexing, and flexible wavelength resource allocation. In the OPCI networks, a best-effort service and a QoS-guaranteed service are provided by employing optical packet switching (OPS) and optical circuit switching (OCS) respectively, and users can select these services. Different wavelength resources are assigned for OPS and OCS links, and the amount of their wavelength resources are dynamically changed in accordance with the service usage conditions. To apply OPCI networks into wide-area (core/metro) networks, we have developed an OPCI node with a distributed control mechanism. Moreover, our OPCI node works with a centralized control mechanism as well as a distributed one. It is therefore possible to realize SDN-based OPCI networks, where resource requests and a centralized configuration are carried out. In this paper, we show our SDN architecture for an OPS system that configures mapping tables between IP addresses and optical packet addresses and switching tables according to the requests from multiple users via a web interface. While OpenFlow-based centralized control protocol is coming into widespread use especially for single-administrative, small-area (LAN/data-center) networks. Here, we also show an interworking mechanism between OpenFlow-based networks (OFNs) and the OPCI network for constructing a wide-area network, and a control method of wavelength resource selection to automatically transfer diversified flows from OFNs to the OPCI network.

  16. A User-Oriented Performance Index for Packet Switched Networks.

    DTIC Science & Technology

    1986-03-01

    network type classification is [ Ref . 1] 1. Circuit-switched 2. Message-switched 3. Packet-switched 1. Circuit Switching In circuit switching, a "call" is...tech- niques used for over a century by telegraph and torn paper tape switching systems [ Ref . 2: p. 1307]. These techniques had traditionally used...was an eleven volume analysis written by Paul Baran of the RAND Corporation [ Ref . 3] in 1964. This report showed significant advantages in the use of

  17. Routing in circuit and Packet Switched Networks: An Annotated Bibliography.

    DTIC Science & Technology

    1981-09-14

    papers. These reviews focus on parts of the papers relevant to the DSN. 2. INDEX TO SELECTED TOPICS 2.1 Circuit-Switched Networks 2.1.1 Routing Bernas and...engineering - Bell System. 2.1.3 Event-by-Event Simulations Bernas and Grieco (1978) POLYGRID vs. adaptive vs. flood search routing - AUTOVON simula- tion...Enhance Survivability Bernas and Grieco (1978) POLYGRID, adaptive and flood search routing. Gafni and Bertsekas (1981) Distributed routing for packet radio

  18. Lossless Compression of Data into Fixed-Length Packets

    NASA Technical Reports Server (NTRS)

    Kiely, Aaron B.; Klimesh, Matthew A.

    2009-01-01

    A computer program effects lossless compression of data samples from a one-dimensional source into fixed-length data packets. The software makes use of adaptive prediction: it exploits the data structure in such a way as to increase the efficiency of compression beyond that otherwise achievable. Adaptive linear filtering is used to predict each sample value based on past sample values. The difference between predicted and actual sample values is encoded using a Golomb code.

  19. The performance analysis of linux networking - packet receiving

    SciTech Connect

    Wu, Wenji; Crawford, Matt; Bowden, Mark; /Fermilab

    2006-11-01

    The computing models for High-Energy Physics experiments are becoming ever more globally distributed and grid-based, both for technical reasons (e.g., to place computational and data resources near each other and the demand) and for strategic reasons (e.g., to leverage equipment investments). To support such computing models, the network and end systems, computing and storage, face unprecedented challenges. One of the biggest challenges is to transfer scientific data sets--now in the multi-petabyte (10{sup 15} bytes) range and expected to grow to exabytes within a decade--reliably and efficiently among facilities and computation centers scattered around the world. Both the network and end systems should be able to provide the capabilities to support high bandwidth, sustained, end-to-end data transmission. Recent trends in technology are showing that although the raw transmission speeds used in networks are increasing rapidly, the rate of advancement of microprocessor technology has slowed down. Therefore, network protocol-processing overheads have risen sharply in comparison with the time spent in packet transmission, resulting in degraded throughput for networked applications. More and more, it is the network end system, instead of the network, that is responsible for degraded performance of network applications. In this paper, the Linux system's packet receive process is studied from NIC to application. We develop a mathematical model to characterize the Linux packet receiving process. Key factors that affect Linux systems network performance are analyzed.

  20. Electronically nonadiabatic wave packet propagation using frozen Gaussian scattering

    SciTech Connect

    Kondorskiy, Alexey D.; Nanbu, Shinkoh

    2015-09-21

    We present an approach, which allows to employ the adiabatic wave packet propagation technique and semiclassical theory to treat the nonadiabatic processes by using trajectory hopping. The approach developed generates a bunch of hopping trajectories and gives all additional information to incorporate the effect of nonadiabatic coupling into the wave packet dynamics. This provides an interface between a general adiabatic frozen Gaussian wave packet propagation method and the trajectory surface hopping technique. The basic idea suggested in [A. D. Kondorskiy and H. Nakamura, J. Chem. Phys. 120, 8937 (2004)] is revisited and complemented in the present work by the elaboration of efficient numerical algorithms. We combine our approach with the adiabatic Herman-Kluk frozen Gaussian approximation. The efficiency and accuracy of the resulting method is demonstrated by applying it to popular benchmark model systems including three Tully’s models and 24D model of pyrazine. It is shown that photoabsorption spectrum is successfully reproduced by using a few hundreds of trajectories. We employ the compact finite difference Hessian update scheme to consider feasibility of the ab initio “on-the-fly” simulations. It is found that this technique allows us to obtain the reliable final results using several Hessian matrix calculations per trajectory.

  1. Wave-packet model for excitation by ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Suominen, Kalle-Antti; Garraway, Barry M.; Stenholm, Stig

    1992-03-01

    In this paper we discuss the excitation of a localized molecular ground-state wave function by a short laser pulse. With a one-dimensional approach we show when it is possible to excite a considerable fraction of the ground state without too much distortion of the shape of the wave packet. This is of interest in time-resolved molecular experiments where an excited wave packet is often taken as the initial state. We solve the two coupled wave equations numerically and compare results to an analytical approximation based on the Rosen-Zener model. The validity of the approximation and its breakdown is considered in detail. Special attention is paid to the effect of lengthening the pulse duration and the consequences of the accompanying number of Rabi flops occurring in the area theorem. When the approximation breaks down, the wave packet becomes distorted and spread out, but there are still interesting coherence effects due to the interplay between the Rabi flopping and the molecular dynamics; these are displayed and discussed. Finally, the relationship to other works and possible generalizations are presented.

  2. Arteriovenous Access

    PubMed Central

    MacRae, Jennifer M.; Dipchand, Christine; Oliver, Matthew; Moist, Louise; Yilmaz, Serdar; Lok, Charmaine; Leung, Kelvin; Clark, Edward; Hiremath, Swapnil; Kappel, Joanne; Kiaii, Mercedeh; Luscombe, Rick; Miller, Lisa M.

    2016-01-01

    Complications of vascular access lead to morbidity and may reduce quality of life. In this module, we review both infectious and noninfectious arteriovenous access complications including neuropathy, aneurysm, and high-output access. For the challenging patients who have developed many complications and are now nearing their last vascular access, we highlight some potentially novel approaches. PMID:28270919

  3. Joint Power and Multiple Access Control for Wireless Mesh Network with Rose Projection Method

    PubMed Central

    Tang, Meiqin; Shang, Lili; Xin, Yalin; Liu, Xiaohua; Wei, Xinjiang

    2014-01-01

    This paper investigates the utility maximization problem for the downlink of the multi-interface multichannel wireless mesh network with orthogonal frequency division multiple access. A cross-layer joint power and multiple access control algorithm are proposed. Rosen projection matrix is combined with Solodov projection techniques to build a three-memory gradient Rosen projection method, which is applied to solve this optimization problem. The convergence analysis is given and simulations show that the proposed solution achieves significant throughput compared with existing approaches. PMID:24883384

  4. Joint power and multiple access control for wireless mesh network with Rose projection method.

    PubMed

    Tang, Meiqin; Shang, Lili; Xin, Yalin; Liu, Xiaohua; Wei, Xinjiang

    2014-01-01

    This paper investigates the utility maximization problem for the downlink of the multi-interface multichannel wireless mesh network with orthogonal frequency division multiple access. A cross-layer joint power and multiple access control algorithm are proposed. Rosen projection matrix is combined with Solodov projection techniques to build a three-memory gradient Rosen projection method, which is applied to solve this optimization problem. The convergence analysis is given and simulations show that the proposed solution achieves significant throughput compared with existing approaches.

  5. Alternatives for the introduction of optical packet switching networks in this internet world

    NASA Astrophysics Data System (ADS)

    Chiaroni, Dominique

    2001-09-01

    With the emergence of new services mixing data, voice and video, the expected increase of the traffic volume together with the modification of its profile creates a need for a high throughput multimedia network. In addition, quality-of- service (QoS) management is currently widely debated at the convergence between ATM and IP communities. In the meantime, WDM is widely deployed, giving access to large transport capacities together with a new dimension for routing purposes. This paper present alternatives for a multi- service optical network infrastructure in this Internet world, where WDM is used not only to increase the throughput but also to differentiate the traffic, to alleviate contention issues and to provide cost-effective solutions. On the same optical infrastructure under a self-sufficient management yet, would coexist different logical sub-networks where different routing techniques are used according to QoS and client protocol requirements. The main objective is to save on the transport cost by optimizing through packet switching techniques the resource utilization according traffic characteristics, while providing enough flexibility to adapt the resources to the evolution of the demand, and maintaining a high transmission quality, as provided by SONET today. This work, capitalizes on InP-based fast optical switching technologies demonstrated within the European ACTS KEIPS project. In this paper, the network concepts, packet format considerations, preferred routing techniques and system architecture will be reported and illustrated through physical and logical analysis. Finally, t < o introduction scenario will be presented: one for the backbone and one for the metro.

  6. Adaptive optics correction into single mode fiber for a low Earth orbiting space to ground optical communication link using the OPALS downlink.

    PubMed

    Wright, Malcolm W; Morris, Jeffery F; Kovalik, Joseph M; Andrews, Kenneth S; Abrahamson, Matthew J; Biswas, Abhijit

    2015-12-28

    An adaptive optics (AO) testbed was integrated to the Optical PAyload for Lasercomm Science (OPALS) ground station telescope at the Optical Communications Telescope Laboratory (OCTL) as part of the free space laser communications experiment with the flight system on board the International Space Station (ISS). Atmospheric turbulence induced aberrations on the optical downlink were adaptively corrected during an overflight of the ISS so that the transmitted laser signal could be efficiently coupled into a single mode fiber continuously. A stable output Strehl ratio of around 0.6 was demonstrated along with the recovery of a 50 Mbps encoded high definition (HD) video transmission from the ISS at the output of the single mode fiber. This proof of concept demonstration validates multi-Gbps optical downlinks from fast slewing low-Earth orbiting (LEO) spacecraft to ground assets in a manner that potentially allows seamless space to ground connectivity for future high data-rates network.

  7. Performance Analysis of Power Saving Class of Type 1 with Both Downlink and Uplink Traffics in IEEE 802.16e

    NASA Astrophysics Data System (ADS)

    Baek, Sangkyu; Choi, Bong Dae

    We investigate power consumption of a mobile station with the power saving class of type 1 in the IEEE 802.16e. We deal with stochastic behavior of mobile station during not only sleep mode period but also awake mode period with both downlink and uplink traffics. Our methods for investigating the power saving class of type 1 are to construct the embedded Markov chain and the semi-Markov chain generated by the embedded Markov chain. To see the effect of the sleep mode, we obtain the average power consumption of a mobile station and the mean queueing delay of a message. Numerical results show that the larger size of the sleep window makes the power consumption of a mobile station smaller and the queueing delay of a downlink message longer.

  8. Exposure assessment of one-year-old child to 3G tablet in uplink mode and to 3G femtocell in downlink mode using polynomial chaos decomposition

    NASA Astrophysics Data System (ADS)

    Liorni, I.; Parazzini, M.; Varsier, N.; Hadjem, A.; Ravazzani, P.; Wiart, J.

    2016-04-01

    So far, the assessment of the exposure of children, in the ages 0-2 years old, to relatively new radio-frequency (RF) technologies, such as tablets and femtocells, remains an open issue. This study aims to analyse the exposure of a one year-old child to these two sources, tablets and femtocells, operating in uplink (tablet) and downlink (femtocell) modes, respectively. In detail, a realistic model of an infant has been used to model separately the exposures due to (i) a 3G tablet emitting at the frequency of 1940 MHz (uplink mode) placed close to the body and (ii) a 3G femtocell emitting at 2100 MHz (downlink mode) placed at a distance of at least 1 m from the infant body. For both RF sources, the input power was set to 250 mW. The variability of the exposure due to the variation of the position of the RF sources with respect to the infant body has been studied by stochastic dosimetry, based on polynomial chaos to build surrogate models of both whole-body and tissue specific absorption rate (SAR), which makes it easy and quick to investigate the exposure in a full range of possible positions of the sources. The major outcomes of the study are: (1) the maximum values of the whole-body SAR (WB SAR) have been found to be 9.5 mW kg-1 in uplink mode and 65 μW kg-1 in downlink mode, i.e. within the limits of the ICNIRP 1998 Guidelines; (2) in both uplink and downlink mode the highest SAR values were approximately found in the same tissues, i.e. in the skin, eye and penis for the whole-tissue SAR and in the bone, skin and muscle for the peak SAR; (3) the change in the position of both the 3G tablet and the 3G femtocell significantly influences the infant exposure.

  9. Exposure assessment of one-year-old child to 3G tablet in uplink mode and to 3G femtocell in downlink mode using polynomial chaos decomposition.

    PubMed

    Liorni, I; Parazzini, M; Varsier, N; Hadjem, A; Ravazzani, P; Wiart, J

    2016-04-21

    So far, the assessment of the exposure of children, in the ages 0-2 years old, to relatively new radio-frequency (RF) technologies, such as tablets and femtocells, remains an open issue. This study aims to analyse the exposure of a one year-old child to these two sources, tablets and femtocells, operating in uplink (tablet) and downlink (femtocell) modes, respectively. In detail, a realistic model of an infant has been used to model separately the exposures due to (i) a 3G tablet emitting at the frequency of 1940 MHz (uplink mode) placed close to the body and (ii) a 3G femtocell emitting at 2100 MHz (downlink mode) placed at a distance of at least 1 m from the infant body. For both RF sources, the input power was set to 250 mW. The variability of the exposure due to the variation of the position of the RF sources with respect to the infant body has been studied by stochastic dosimetry, based on polynomial chaos to build surrogate models of both whole-body and tissue specific absorption rate (SAR), which makes it easy and quick to investigate the exposure in a full range of possible positions of the sources. The major outcomes of the study are: (1) the maximum values of the whole-body SAR (WB SAR) have been found to be 9.5 mW kg(-1) in uplink mode and 65 μW kg(-1) in downlink mode, i.e. within the limits of the ICNIRP 1998 Guidelines; (2) in both uplink and downlink mode the highest SAR values were approximately found in the same tissues, i.e. in the skin, eye and penis for the whole-tissue SAR and in the bone, skin and muscle for the peak SAR; (3) the change in the position of both the 3G tablet and the 3G femtocell significantly influences the infant exposure.

  10. Implementation of a Data Packet Generator Using Pattern Matching for Wearable ECG Monitoring Systems

    PubMed Central

    Noh, Yun Hong; Jeong, Do Un

    2014-01-01

    In this paper, a packet generator using a pattern matching algorithm for real-time abnormal heartbeat detection is proposed. The packet generator creates a very small data packet which conveys sufficient crucial information for health condition analysis. The data packet envelopes real time ECG signals and transmits them to a smartphone via Bluetooth. An Android application was developed specifically to decode the packet and extract ECG information for health condition analysis. Several graphical presentations are displayed and shown on the smartphone. We evaluate the performance of abnormal heartbeat detection accuracy using the MIT/BIH Arrhythmia Database and real time experiments. The experimental result confirm our finding that abnormal heart beat detection is practically possible. We also performed data compression ratio and signal restoration performance evaluations to establish the usefulness of the proposed packet generator and the results were excellent. PMID:25029280

  11. Storage-efficient 16-Bit Hybrid IP traceback with Single Packet.

    PubMed

    Yang, Ming Hour

    2014-01-01

    Since adversaries may spoof their source IPs in the attacks, traceback schemes have been proposed to identify the attack source. However, some of these schemes' storage requirements increase with packet numbers. Some even have false positives because they use an IP header's fragment offset for marking. Thus, we propose a 16-bit single packet hybrid IP traceback scheme that combines packet marking and packet logging with high accuracy and low storage requirement. The size of our log tables can be bounded by route numbers. We also set a threshold to determine whether an upstream interface number is stored in a log table or in a marking field, so as to balance the logging frequency and our computational loads. Because we store user interface information on small-degree routers, compared with current single packet traceback schemes, ours can have the lowest storage requirements. Besides, our traceback achieves zero false positive/negative rates and guarantees reassembly of fragmented packets at the destination.

  12. A Busy-Tone-Multiple-Access-Type Scheme for Packet-Radio Networks,

    DTIC Science & Technology

    1981-06-01

    is applied in each of the L distinct channels. In addition a node that senses activity on the subchannel Z (where lstL), transmits a signal over a...transmission. From the above description, it is clear that the probability of completed transmission at a node i that uses the subchannel Z for...transmission is given here by : Sm Ps 1- - (12) mCB(i) 11m𔄀 where B(i) is the collection of all nodes in A(i) that use the subchannel I for transmission and 6

  13. All optical contention detection and resolution for asynchronous variable length optical packets switching

    NASA Astrophysics Data System (ADS)

    Farhat, Rim; Farhat, Amel; Menif, Mourad

    2016-04-01

    We proposed a novel 2×2 all optical packet switching router architecture supporting asynchronous, labelled and variablelength packet. A proof of concept through Matlab Simulink simulation is validated. Then we discussed the three possible scenarios to demonstrate the contention resolution technique based on deflection routing. We have showing that the contending packet is detected and forwarded according FIFO (First In First Out) strategy to another output.

  14. An Experimental Exploration of the Impact of Network-Level Packet Loss on Network Intrusion Detection

    DTIC Science & Technology

    2015-08-01

    Experimental environment 5 Table 1 Hardware specifications Name Manufacture Model CPU Memory Hard Drive IP Address Bilbo Dell PowerEdge R610 Intel...10 we replayed the same hour of network traffic from the CDX 20093 that we used in our theoretical2 exploration to show the impact of our packet... replay the traffic at arbitrary speeds. Table 3 lists the speed multiplier that we used and the packet loss we observed. Table 3 Network packet loss

  15. An Experimental Exploration of the Impact of Sensor-Level Packet Loss on Network Intrusion Detection

    DTIC Science & Technology

    2015-07-01

    analyzing the packets are bound by available central processing unit (CPU) cycles and not buffer memory . Allocating the bulk of the CPU time to the...ways this is similar to the Tcpreplay14 command, which will take packets from a file saved in Tcpdump format and replay them on the network at any...bit bucket end if end while To validate that Pcapreplay is actually replaying packets at the specified multiple of the orginal speed, we will use the

  16. General expressions for downlink signal to interference and noise ratio in homogeneous and heterogeneous LTE-Advanced networks.

    PubMed

    Ali, Nora A; Mourad, Hebat-Allah M; ElSayed, Hany M; El-Soudani, Magdy; Amer, Hassanein H; Daoud, Ramez M

    2016-11-01

    The interference is the most important problem in LTE or LTE-Advanced networks. In this paper, the interference was investigated in terms of the downlink signal to interference and noise ratio (SINR). In order to compare the different frequency reuse methods that were developed to enhance the SINR, it would be helpful to have a generalized expression to study the performance of the different methods. Therefore, this paper introduces general expressions for the SINR in homogeneous and in heterogeneous networks. In homogeneous networks, the expression was applied for the most common types of frequency reuse techniques: soft frequency reuse (SFR) and fractional frequency reuse (FFR). The expression was examined by comparing it with previously developed ones in the literature and the comparison showed that the expression is valid for any type of frequency reuse scheme and any network topology. Furthermore, the expression was extended to include the heterogeneous network; the expression includes the problem of co-tier and cross-tier interference in heterogeneous networks (HetNet) and it was examined by the same method of the homogeneous one.

  17. Packet Randomized Experiments for Eliminating Classes of Confounders

    PubMed Central

    Pavela, Greg; Wiener, Howard; Fontaine, Kevin R.; Fields, David A.; Voss, Jameson D.; Allison, David B.

    2014-01-01

    Background Although randomization is considered essential for causal inference, it is often not possible to randomize in nutrition and obesity research. To address this, we develop a framework for an experimental design—packet randomized experiments (PREs), which improves causal inferences when randomization on a single treatment variable is not possible. This situation arises when subjects are randomly assigned to a condition (such as a new roommate) which varies in one characteristic of interest (such as weight), but also varies across many others. There has been no general discussion of this experimental design, including its strengths, limitations, and statistical properties. As such, researchers are left to develop and apply PREs on an ad hoc basis, limiting its potential to improve causal inferences among nutrition and obesity researchers. Methods We introduce PREs as an intermediary design between randomized controlled trials and observational studies. We review previous research that used the PRE design and describe its application in obesity-related research, including random roommate assignments, heterochronic parabiosis, and the quasi-random assignment of subjects to geographic areas. We then provide a statistical framework to control for potential packet-level confounders not accounted for by randomization. Results PREs have successfully been used to improve causal estimates of the effect of roommates, altitude, and breastfeeding on weight outcomes. When certain assumptions are met, PREs can asymptotically control for packet-level characteristics. This has the potential to statistically estimate the effect of a single treatment even when randomization to a single treatment did not occur. Conclusions Applying PREs to obesity-related research will improve decisions about clinical, public health, and policy actions insofar as it offers researchers new insight into cause and effect relationships among variables. PMID:25444088

  18. Semiclassical wave-packets emerging from interaction with an environment

    SciTech Connect

    Recchia, Carla; Teta, Alessandro

    2014-01-15

    We study the quantum evolution in dimension three of a system composed by a test particle interacting with an environment made of N harmonic oscillators. At time zero the test particle is described by a spherical wave, i.e., a highly correlated continuous superposition of states with well localized position and momentum, and the oscillators are in the ground state. Furthermore, we assume that the positions of the oscillators are not collinear with the center of the spherical wave. Under suitable assumptions on the physical parameters characterizing the model, we give an asymptotic expression of the solution of the Schrödinger equation of the system with an explicit control of the error. The result shows that the approximate expression of the wave function is the sum of two terms, orthogonal in L{sup 2}(R{sup 3(N+1)}) and describing rather different situations. In the first one, all the oscillators remain in their ground state and the test particle is described by the free evolution of a slightly deformed spherical wave. The second one consists of a sum of N terms where in each term there is only one excited oscillator and the test particle is correspondingly described by the free evolution of a wave packet, well concentrated in position and momentum. Moreover, the wave packet emerges from the excited oscillator with an average momentum parallel to the line joining the oscillator with the center of the initial spherical wave. Such wave packet represents a semiclassical state for the test particle, propagating along the corresponding classical trajectory. The main result of our analysis is to show how such a semiclassical state can be produced, starting from the original spherical wave, as a result of the interaction with the environment.

  19. Modelling of quasi-periodic oscillations with wave packets

    NASA Astrophysics Data System (ADS)

    Alpar, M. A.; Yilmaz, A.

    1997-08-01

    Model dispersion relations are introduced to explore power spectra of the normal-branch (NB) and horizontal-branch (HB) quasi-periodic oscillations (QPOs; for reviews see Van der Klis (1989)[ARA&A, 27, 517], (1992) [Proc. of NATO ASI X-Ray Binaries and Recycled Pulsars, eds. E.P.J. Van den Heuvel & S.A. Rappaport, Kluwer, Dordrecht], (1995)[Proc. of NATO ASI The Lives of the Neutron Stars, eds. M.A. Alpar, Ümit Kiziloğlu, & J. van Paradijs, Kluwer, Dordrecht]) of low mass X-ray binaries (LMXBs) in terms of wave packets and to illustrate the presence of frequency bands around the Kepler and beat frequencies. For the NB QPOs wave packets of sound waves in a thick middle disk state, with frequencies determined by the rotation frequency, have wavelengths comparable to the size of the middle disk. For Z-sources on the HB, the wave packets result from disturbances in the inner disk induced by the neutron star magnetic field which rotates at the beat frequency with respect to the inner disk. For both the NB and the HB QPOs, we construct simple model dispersion relations, and show that the QPO peaks in the observed power spectra correspond to reasonable wavelengths and system parameters. The kilohertz QPOs, which were discovered after the original version of this paper was submitted, are also discussed as a possible realization of the Kepler and beat frequency bands. Problems of integrating the kHz and HB QPOs in a disk model are briefly noted. It is tentatively suggested that supersonic and wave propagation regions of the inner disk have complementary functions for the origin of kHz and HB QPOs respectively.

  20. Sampled-Data Consensus of Linear Multi-agent Systems With Packet Losses.

    PubMed

    Zhang, Wenbing; Tang, Yang; Huang, Tingwen; Kurths, Jurgen

    2016-08-17

    In this paper, the consensus problem is studied for a class of multi-agent systems with sampled data and packet losses, where random and deterministic packet losses are considered, respectively. For random packet losses, a Bernoulli-distributed white sequence is used to describe packet dropouts among agents in a stochastic way. For deterministic packet losses, a switched system with stable and unstable subsystems is employed to model packet dropouts in a deterministic way. The purpose of this paper is to derive consensus criteria, such that linear multi-agent systems with sampled-data and packet losses can reach consensus. By means of the Lyapunov function approach and the decomposition method, the design problem of a distributed controller is solved in terms of convex optimization. The interplay among the allowable bound of the sampling interval, the probability of random packet losses, and the rate of deterministic packet losses are explicitly derived to characterize consensus conditions. The obtained criteria are closely related to the maximum eigenvalue of the Laplacian matrix versus the second minimum eigenvalue of the Laplacian matrix, which reveals the intrinsic effect of communication topologies on consensus performance. Finally, simulations are given to show the effectiveness of the proposed results.

  1. Time delay of wave packets during their tunnelling through a quantum diode

    SciTech Connect

    Ivanov, N A; Skalozub, V V

    2014-04-28

    A modified saddle-point method is used to investigate the process of propagation of a wave packet through a quantum diode. A scattering matrix is constructed for the structure in question. The case of tunnelling of a packet with a Gaussian envelope through the diode is considered in detail. The time delay and the shape of the wave packet transmitted are calculated. The dependence of the delay time on the characteristics of the input packet and the internal characteristics of the quantum diode is studied. Possible applications of the results obtained are discussed. (laser applications and other topics in quantum electronics)

  2. Feature extraction for EEG-based brain-computer interfaces by wavelet packet best basis decomposition.

    PubMed

    Yang, Bang-hua; Yan, Guo-zheng; Yan, Rong-guo; Wu, Ting

    2006-12-01

    A method based on wavelet packet best basis decomposition (WPBBD) is investigated for the purpose of extracting features of electroencephalogram signals produced during motor imagery tasks in brain-computer interfaces. The method includes the following three steps. (1) Original signals are decomposed by wavelet packet transform (WPT) and a wavelet packet library can be formed. (2) The best basis for classification is selected from the library. (3) Subband energies included in the best basis are used as effective features. Three different motor imagery tasks are discriminated using the features. The WPBBD produces a 70.3% classification accuracy, which is 4.2% higher than that of the existing wavelet packet method.

  3. Time behavior of a Gaussian wave packet accompanying the generalized coherent state for the inverted oscillator

    NASA Astrophysics Data System (ADS)

    Maamache, Mustapha; Bouguerra, Yacine; Choi, Jeong Ryeol

    2016-06-01

    A Gaussian wave packet of the inverted oscillator is investigated using the invariant operator method together with the unitary transformation method. A simple wave packet directly derived from the eigenstates of the invariant operator of the system corresponds to a plane wave that is fully delocalized. However, we can construct a weighted wave packet in terms of such plane waves, which corresponds to a Gaussian wave. This wave packet is associated with the generalized coherent state, which can be crucially utilized for investigating the classical limit of quantum wave mechanics. Various quantum properties of the system, such as fluctuations of the canonical variables, the uncertainty product, and the motion of the wave packet or quantum particle, are analyzed by means of this wave packet. We have confirmed that the time behavior of such a wave packet is very similar to the counterpart classical state. The wave packet runs away from the origin in the positive or negative direction in the 1D coordinate depending on the condition of the initial state. We have confirmed that this wave packet not only moves acceleratively but also spreads out during its propagation.

  4. Localization of a matter wave packet in a disordered potential

    SciTech Connect

    Piraud, M.; Bouyer, P.; Aspect, A.; Sanchez-Palencia, L.; Lugan, P.

    2011-03-15

    We theoretically study the Anderson localization of a matter wave packet in a one-dimensional disordered potential. We develop an analytical model which includes the initial phase-space density of the matter wave and the spectral broadening induced by the disorder. Our approach predicts a behavior of the localized density profile significantly more complex than a simple exponential decay. These results are confirmed by large-scale and long-time numerical calculations. They shed new light on recent experiments with ultracold atoms and may impact their analysis.

  5. Electroencephalography data analysis by using discrete wavelet packet transform

    NASA Astrophysics Data System (ADS)

    Karim, Samsul Ariffin Abdul; Ismail, Mohd Tahir; Hasan, Mohammad Khatim; Sulaiman, Jumat; Muthuvalu, Mohana Sundaram; Janier Josefina, B.

    2015-05-01

    Electroencephalography (EEG) is the electrical activity generated by the movement of neurons in the brain. It is categorized into delta waves, theta, alpha, beta and gamma. These waves exist in a different frequency band. This paper is a continuation of our previous research. EEG data will be decomposed using Discrete Wavelet Packet Transform (DWPT). Daubechies wavelets 10 (D10) will be used as the basic functions for research purposes. From the main results, it is clear that the DWPT able to characterize the EEG signal corresponding to each wave at a specific frequency. Furthermore, the numerical results obtained better than the results using DWT. Statistical analysis support our main findings.

  6. Multi-Resource Fair Queueing for Packet Processing

    DTIC Science & Technology

    2012-06-19

    Since processing happens with increasing start tags , all backlogged packets p must have maxr S(p, r) ≥ vt. Since each flow has strictly non-zero...statistical monitoring, and IPSec encryption. Because our machine only had one 1 Gbps link, we throttled its outgoing bandwidth to 200 Mbps to emulate a...Flow 2 (CPU-bound) Running alone 191 Mbps 33 Mbps Per-res. fairness 75 Mbps 32 Mbps DRFQ 160 Mbps 28 Mbps Table 7: Throughput of bandwidth and CPU

  7. Detection of gastric drug packet by ultrasound scanning.

    PubMed

    Chung, Chin Hung; Fung, Wing Tak

    2006-10-01

    A 53-year-old male drug user was brought to the emergency department by police for suspected drug smuggling by body packing. The abdominal X-ray revealed suspicion of the presence of a drug packet in the gastric antrum, but the patient strongly denied body packing. Abdominal ultrasonography confirmed the presence of a 4.0 x 2.8 cm(2) oval-shaped echogenic mass with posterior shadowing in the gastric antrum. A small plastic bag with many blue tablets was later retrieved by endoscopy. Ultrasonography is recommended in similar cases with doubtful radiological findings.

  8. Effects of wireless packet loss in industrial process control systems.

    PubMed

    Liu, Yongkang; Candell, Richard; Moayeri, Nader

    2017-02-09

    Timely and reliable sensing and actuation control are essential in networked control. This depends on not only the precision/quality of the sensors and actuators used but also on how well the communications links between the field instruments and the controller have been designed. Wireless networking offers simple deployment, reconfigurability, scalability, and reduced operational expenditure, and is easier to upgrade than wired solutions. However, the adoption of wireless networking has been slow in industrial process control due to the stochastic and less than 100% reliable nature of wireless communications and lack of a model to evaluate the effects of such communications imperfections on the overall control performance. In this paper, we study how control performance is affected by wireless link quality, which in turn is adversely affected by severe propagation loss in harsh industrial environments, co-channel interference, and unintended interference from other devices. We select the Tennessee Eastman Challenge Model (TE) for our study. A decentralized process control system, first proposed by N. Ricker, is adopted that employs 41 sensors and 12 actuators to manage the production process in the TE plant. We consider the scenario where wireless links are used to periodically transmit essential sensor measurement data, such as pressure, temperature and chemical composition to the controller as well as control commands to manipulate the actuators according to predetermined setpoints. We consider two models for packet loss in the wireless links, namely, an independent and identically distributed (IID) packet loss model and the two-state Gilbert-Elliot (GE) channel model. While the former is a random loss model, the latter can model bursty losses. With each channel model, the performance of the simulated decentralized controller using wireless links is compared with the one using wired links providing instant and 100% reliable communications. The sensitivity of the

  9. Color coded multiple access scheme for bidirectional multiuser visible light communications in smart home technologies

    NASA Astrophysics Data System (ADS)

    Tiwari, Samrat Vikramaditya; Sewaiwar, Atul; Chung, Yeon-Ho

    2015-10-01

    In optical wireless communications, multiple channel transmission is an attractive solution to enhancing capacity and system performance. A new modulation scheme called color coded multiple access (CCMA) for bidirectional multiuser visible light communications (VLC) is presented for smart home applications. The proposed scheme uses red, green and blue (RGB) light emitting diodes (LED) for downlink and phosphor based white LED (P-LED) for uplink to establish a bidirectional VLC and also employs orthogonal codes to support multiple users and devices. The downlink transmission for data user devices and smart home devices is provided using red and green colors from the RGB LEDs, respectively, while uplink transmission from both types of devices is performed using the blue color from P-LEDs. Simulations are conducted to verify the performance of the proposed scheme. It is found that the proposed bidirectional multiuser scheme is efficient in terms of data rate and performance. In addition, since the proposed scheme uses RGB signals for downlink data transmission, it provides flicker-free illumination that would lend itself to multiuser VLC system for smart home applications.

  10. Packet Drop Avoidance for High-speed network transmission protocol

    SciTech Connect

    Jin, Guojun

    2004-05-01

    As network bandwidth continues to grow and longer paths are used to exchange large scientific data between storage systems and GRID computation, it has become increasingly obvious that there is a need to deploy a packet drop avoidance mechanism into network transmission protocols. Current end-to-end congestion avoidance mechanisms used in Transmission Control Protocol (TCP) have worked well on low bandwidth delay product networks, but with newer high-bandwidth delay networks they have shown to be inefficient and prone to unstable. This is largely due to increased network bandwidth coupled with changes in internet traffic patterns. These changes come from a variety of new network applications that are being developed to take advantage of the increased network bandwidth. This paper will examine the end-to-end congestion avoidance mechanism and perform a step-by-step analysis of its theory. In addition we will propose an alternative approach developed as part of a new network transmission protocol. Our alternative protocol uses a packet drop avoidance (PDA) mechanism built on top of the maximum burst size (MBS) theory combined with a real-time available bandwidth algorithm.

  11. Adaptive P2P video streaming via packet labeling

    NASA Astrophysics Data System (ADS)

    Chakareski, Jacob; Frossard, Pascal

    2007-01-01

    We consider the scenario of video streaming in peer-to-peer networks. A single media server delivers the video content to a large number of peer hosts by taking advantage of their forwarding capabilities. We propose a scheme that enables the peers to efficiently distribute the media stream among them. Each of the peers connects to the streaming server via multiple multicast trees that provide for robustness in the event of peer disconnection. Moreover, adaptive forwarding of the media content at each peer is enabled by labeling the packets with their importance for the reconstruction of the media stream. We study the performance of the proposed scheme as a function of system parameters such as the play-out delay of the media application, the peer population size and the number of multicast trees employed by the scheme. We show that by placing priorities on forwarding the individual packets at each peer an improved performance is achieved over conventional peer-to-peer systems where no such prioritization is deployed. The gains in performance are particularly significant for low-delay applications and large peer populations.

  12. Web Accessibility and Accessibility Instruction

    ERIC Educational Resources Information Center

    Green, Ravonne A.; Huprich, Julia

    2009-01-01

    Section 508 of the Americans with Disabilities Act (ADA) mandates that programs and services be accessible to people with disabilities. While schools of library and information science (SLIS*) and university libraries should model accessible Web sites, this may not be the case. This article examines previous studies about the Web accessibility of…

  13. Simulation of satellite-supported packet radio networks in the laboratory - Modular experimental system simplifies the design of packet radio networks for land-mobile applications

    NASA Astrophysics Data System (ADS)

    Boettcher, Axel; Dippold, Michael; Jahn, Axel; Schaefer, Wolfgang

    1992-05-01

    A modular simulation system with hardware and software components is described which can be used for planning and testing land-mobile packet radio data networks. The system is shown to be simple, robust, and suitable for inner city environment.

  14. Fade detector for the FODA-TDMA access scheme

    NASA Astrophysics Data System (ADS)

    Celandroni, Nedo; Ferro, Erina; Marzoli, Antonio

    1989-05-01

    The First in first out Ordered Demand Assignment-Time Division Multiple Access (FODA-TDMA) satellite access scheme designed for simultaneous transmissions of real time data, like packetized voice and slow-scan images (stream traffic) and data coming from standard EDP applications, such as bulk data tansfer, interactive computer access, mailing, data base enquiry and updating (datagram traffic) is described. When deep fades are experienced due to rain attenuation, the system is able to counter the fade. Techniques to detect the fade are presented.

  15. Next generation communications satellites: Multiple access and network studies

    NASA Technical Reports Server (NTRS)

    Stern, T. E.; Schwartz, M.; Meadows, H. E.; Ahmadi, H. K.; Gadre, J. G.; Gopal, I. S.; Matsmo, K.

    1980-01-01

    Following an overview of issues involved in the choice of promising system architectures for efficient communication with multiple small inexpensive Earth stations serving hetergeneous user populations, performance evaluation via analysis and simulation for six SS/TDMA (satellite-switched/time-division multiple access) system architectures is discussed. These configurations are chosen to exemplify the essential alternatives available in system design. Although the performance evaluation analyses are of fairly general applicability, whenever possible they are considered in the context of NASA's 30/20 GHz studies. Packet switched systems are considered, with the assumption that only a part of transponder capacit is devoted to packets, the integration of circuit and packet switched traffic being reserved for further study. Three types of station access are distinguished: fixed (FA), demand (DA), and random access (RA). Similarly, switching in the satellite can be assigned on a fixed (FS) or demand (DS) basis, or replaced by a buffered store-and-forward system (SF) onboard the satellite. Since not all access/switching combinations are practical, six systems are analyzed in detail: three FS SYSTEMS, FA/FS, DA/ES, RA/FS; one DS system, DA/DS; and two SF systems, FA/SF, DA/SF. Results are presented primarily in terms of delay-throughput characteristics.

  16. Black History at Your Doorstep: Resource Packet 1985-1986. Volume 1.

    ERIC Educational Resources Information Center

    Maryland Commission on Afro-American History and Culture, Annapolis.

    This packet of resource materials was compiled to help teachers infuse the study of Afro-American history and culture into the curriculum throughout the school year. The packet contains both informational materials and sample activities. In order to assist teachers in studying the Afro-American experience in their own communities, special emphasis…

  17. Packet Switching Networks: An Introduction with Some Attention to Selected Vendors.

    ERIC Educational Resources Information Center

    Sanchez, James Joseph

    The purpose of this paper is to provide an overview of the history, development, and services of the packet switching network services that currently exist in the United States. The character of packet switching, a computerized method of transmitting data, is used as the basis for tracing the development of the industry itself. Contending that the…

  18. Least Intervention Needed: Toward Appropriate Inclusion of Students with Special Needs. An Introductory Packet.

    ERIC Educational Resources Information Center

    California Univ., Los Angeles. Center for Mental Health Schools.

    Inclusion is the practice of educating children who have disabilities in classes together with their peers who do not have disabilities. This packet on "least intervention" contains resource materials that help ensure appropriate inclusion. The first section of this packet contains discussions of appropriate inclusion and a description of the…

  19. Wave analysis of the evolution of a single wave packet in supersonic boundary layer

    NASA Astrophysics Data System (ADS)

    Yermolaev, Yury G.; Yatskikh, Aleksey A.; Kosinov, Alexander D.; Semionov, Nickolay V.

    2016-10-01

    The evolution of the artificial wave packet in laminar flat-plate boundary layer was experimentally studied by hot-wire measurements at M=2. The localized disturbances were generated by pulse glow discharge. The wave analysis of evolution of wave packet was provided. It was found, that the most unstable waves are oblique, that consistent with results of linear theory.

  20. Learning Disabilities in the Workplace: A Professional Development Packet. Session 1 & 2.

    ERIC Educational Resources Information Center

    Corley, Mary Ann; Tibbetts, John

    This field-tested training packet, which was designed for adult literacy providers, contains preparation materials, facilitator's notes, handout masters, and transparency masters for two 3-hour sessions on learning disabilities (LD) in the workplace. (At the end of the first session supported by the packet, participants will be able to do the…

  1. Personal Skills. Facilitator's Skill Packets 1-7. Social Skills Training.

    ERIC Educational Resources Information Center

    Model Classrooms, Bellevue, WA.

    This document contains the following seven facilitators' skill packets on personal skills: (1) personal hygiene; (2) personal appearance; (3) locker hygiene; (4) dorm cleanliness; (5) punctuality and attendance; (6) responding to supervision; and (7) teamwork. Each packet contains the following sections: definition of personal skills; objective;…

  2. Easements in Texas. Teachers Instructional Packet, TIP No. 5, Spring 1985.

    ERIC Educational Resources Information Center

    Texas A and M Univ., College Station. Texas Real Estate Research Center.

    Part of a series of classroom aids designed for real estate instructors, this instructional packet was developed to help real estate students understand public and private easements, which most commonly entail the right of a person (or the public) to use the land of another in a certain manner. Following an evaluation form for the packet, a…

  3. Simulation on the electronic wave packet cyclotron motion in a Weyl semimetal slab

    NASA Astrophysics Data System (ADS)

    Yao, Haibo; Zhu, Mingfeng; Jiang, Liwei; Zheng, Yisong

    2017-04-01

    We perform a numerical simulation on the time evolution of an electronic wave packet in a Weyl semimetal (WSM) slab driven by a magnetic field. We find that the evolution trajectory of the wave packet depends sensitively on its initial spin state. Only with initial spin state identical to that of the Fermi arc state at the surface it localized, does the wave packet evolution demonstrate the characteristic cyclotron orbit of WSM previously predicted from a semiclassical viewpoint. By analyzing the eigen-expansion of the electronic wave packet, we find the chiral Landau levels (LLs) of the WSM slab, as ingredients of the wave packet, to be responsible for establishing the characteristic WSM cyclotron orbit. In contrast, the nonchiral LLs contribute irregular oscillations to the wave packet evolution, going against the formation of a well-defined cyclotron orbit. In addition, the tilted magnetic field does not affect the motion of the electronic wave packet along the Fermi arcs in the momentum space. It does, however, alter the evolution trajectory of the electronic wave packet in real space and spin space. Finally, the energy disalignment of the Weyl nodes results in a 3D cyclotron orbit in real space.

  4. The Landlord's and Tenant's Guide. Teachers Instructional Packet, TIP No. 10, Spring 1986.

    ERIC Educational Resources Information Center

    Texas A and M Univ., College Station. Texas Real Estate Research Center.

    Part of a series of classroom aids designed for real estate instructors, this instructional packet was designed to give real estate students a balanced view of the landlord-tenant relationship in Texas. Following an evaluation form for the instructional packet, a summary presentation explores the topic, explains the rules that govern and the…

  5. Guide to Alternative Mortgage Instruments. Teachers Instructional Packet, TIP No. 4, Spring 1985.

    ERIC Educational Resources Information Center

    Texas A and M Univ., College Station. Texas Real Estate Research Center.

    Part of a series of classroom aids designed for real estate instructors, this instructional packet was developed to help real estate students understand the various alternative mortgage instruments, including their major advantages and disadvantages. First, an evaluation form for the packet is presented. Next, a summary presentation on four basic…

  6. A multi-function IEC 61850 packet generator based on FPGA

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Li, Hong-bin; Cheng, Han-miao

    2016-07-01

    An IEC 61850 packet generator is used to produce IEC 61850-9-2 packets by simulating the merging unit and testing the IEC 61850 digital device. While the existing IEC packet generator can produce ideal digital without any noise, it does not take into account the fact that the merging unit output signal packets will be inevitably superimposed with noise. Since the International Electrical Commission standard of the electronic current transformer specifies the minimum output signal-to-noise ratio of the merging unit to be 30 dB, and the signal superimposed with noise will influence the operation performance of the digital device, it is necessary to design a multi-function IEC 61850-9-2 packet generator for a digital device test. Therefore, in this paper, a multi-function IEC 61850 packet generator has been developed, which not only can output various IEC 61850-9-2 packets, but also can add white Gaussian noise to the signal for digital device testing. By testing three digital electricity meters from different manufacturers, we showed that the error of the digital electricity meter is significantly larger when the signal packet is superimposed with noise. Also when the signal-to-noise ration is 30 dB, the error of one of the meters exceeds the allowed range of the accuracy class. This indicates that the noise testing and the noise setting function of the system has an important role in the testing of a digital device.

  7. Scholastic Journalism Week, February 20-26, 1994. Information and Information and Activities Packet.

    ERIC Educational Resources Information Center

    Journalism Education Association.

    Designed to help Journalism Education Association members and their students plan observances and involve the local media, this packet of information offers suggestions for celebrating Scholastic Journalism Week. The packet of information is designed to raise awareness of student publications in schools; promote First Amendment rights of high…

  8. Multiwavelet packet entropy and its application in transmission line fault recognition and classification.

    PubMed

    Liu, Zhigang; Han, Zhiwei; Zhang, Yang; Zhang, Qiaoge

    2014-11-01

    Multiwavelets possess better properties than traditional wavelets. Multiwavelet packet transformation has more high-frequency information. Spectral entropy can be applied as an analysis index to the complexity or uncertainty of a signal. This paper tries to define four multiwavelet packet entropies to extract the features of different transmission line faults, and uses a radial basis function (RBF) neural network to recognize and classify 10 fault types of power transmission lines. First, the preprocessing and postprocessing problems of multiwavelets are presented. Shannon entropy and Tsallis entropy are introduced, and their difference is discussed. Second, multiwavelet packet energy entropy, time entropy, Shannon singular entropy, and Tsallis singular entropy are defined as the feature extraction methods of transmission line fault signals. Third, the plan of transmission line fault recognition using multiwavelet packet entropies and an RBF neural network is proposed. Finally, the experimental results show that the plan with the four multiwavelet packet energy entropies defined in this paper achieves better performance in fault recognition. The performance with SA4 (symmetric antisymmetric) multiwavelet packet Tsallis singular entropy is the best among the combinations of different multiwavelet packets and the four multiwavelet packet entropies.

  9. PROJECT SUCCESS: Marine Science. (Introductory Packet, Basic Marine Science Laboratory Techniques, Oceanographic Instruments, Individual Projects, Bibliography).

    ERIC Educational Resources Information Center

    Demaray, Bryan

    Five packets comprise the marine science component of an enrichment program for gifted elementary students. Considered in the introductory section are identification (pre/post measure) procedures. Remaining packets address the following topics (subtopics in parentheses): basic marine science laboratory techniques (microscope techniques and metric…

  10. Spacelab Program: Conversion of Spacelab to packet data format. Flight system study

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A study of packetization of the Spacelab data handling system, including the alternate approaches considered and the supporting rationale, is described. It is concluded that it is well within today's state of the art in microelectronics to implement either a full or hybrid packet data system on board the Spacelab. Of the two, the hybrid system is preferred because of the significant cost saving.

  11. In the Public Interest: Law, Government, and Media. Maryland Women's History Resource Packet--1986.

    ERIC Educational Resources Information Center

    Maryland State Commission for Women, Baltimore.

    Designed to be used for National Women's History Week (March 2-8), this 1986 Maryland women's history resource packet centers around Maryland women who have made significant volunteer and career contributions in the areas of government, law, and the public interest media. The packet begins with suggested student activity lists and activity sheets…

  12. Quantum dynamics of charge transfer on the one-dimensional lattice: Wave packet spreading and recurrence

    NASA Astrophysics Data System (ADS)

    V, N. Likhachev; O, I. Shevaleevskii; G, A. Vinogradov

    2016-01-01

    The wave function temporal evolution on the one-dimensional (1D) lattice is considered in the tight-binding approximation. The lattice consists of N equal sites and one impurity site (donor). The donor differs from other lattice sites by the on-site electron energy E and the intersite coupling C. The moving wave packet is formed from the wave function initially localized on the donor. The exact solution for the wave packet velocity and the shape is derived at different values E and C. The velocity has the maximal possible group velocity v = 2. The wave packet width grows with time ˜ t1/3 and its amplitude decreases ˜ t-1/3. The wave packet reflects multiply from the lattice ends. Analytical expressions for the wave packet front propagation and recurrence are in good agreement with numeric simulations.

  13. Test particle simulation study of whistler wave packets observed near Comet Giacobini-Zinner

    NASA Technical Reports Server (NTRS)

    Kaya, N.; Matsumoto, H.; Tsurutani, B. T.

    1989-01-01

    Nonlinear interactions of water group ions with large-amplitude whistler wave packets detected at the leading edge of steepened magnetosonic waves observed near Comet Giacobini-Zinner (GZ) are studied using test particle simulations of water-ion interactions with a model wave based on GZ data. Some of the water ions are found to be decelerated in the steepened portion of the magnetosonic wave to the resonance velocity with the whistler wave packets. Through resonance and related nonlinear interaction with the large-amplitude whistler waves, the water ions become trapped by the packet. An energy balance calculation demonstrates that the trapped ions lose their kinetic energy during the trapped motion in the packet. Thus, the nonlinear trapping motion in the wave structure leads to effective energy transfer from the water group ions to the whistler wave packets in the leading edge of the steepened MHD waves.

  14. Magnetic helicity conservation and inverse energy cascade in electron magnetohydrodynamic wave packets.

    PubMed

    Cho, Jungyeon

    2011-05-13

    Electron magnetohydrodynamics (EMHD) provides a fluidlike description of small-scale magnetized plasmas. An EMHD wave propagates along magnetic field lines. The direction of propagation can be either parallel or antiparallel to the magnetic field lines. We numerically study propagation of three-dimensional (3D) EMHD wave packets moving in one direction. We obtain two major results. (1) Unlike its magnetohydrodynamic (MHD) counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave packets traveling in one direction create opposite-traveling wave packets via self-interaction and cascade energy to smaller scales. (2) EMHD wave packets traveling in one direction clearly exhibit inverse energy cascade. We find that the latter is due to conservation of magnetic helicity. We compare inverse energy cascade in 3D EMHD turbulence and two-dimensional (2D) hydrodynamic turbulence.

  15. Interception and modification of network authentication packets with the purpose of allowing alternative authentication modes

    DOEpatents

    Kent, Alexander Dale

    2008-09-02

    Methods and systems in a data/computer network for authenticating identifying data transmitted from a client to a server through use of a gateway interface system which are communicately coupled to each other are disclosed. An authentication packet transmitted from a client to a server of the data network is intercepted by the interface, wherein the authentication packet is encrypted with a one-time password for transmission from the client to the server. The one-time password associated with the authentication packet can be verified utilizing a one-time password token system. The authentication packet can then be modified for acceptance by the server, wherein the response packet generated by the server is thereafter intercepted, verified and modified for transmission back to the client in a similar but reverse process.

  16. Non-intrusive Packet-Layer Model for Monitoring Video Quality of IPTV Services

    NASA Astrophysics Data System (ADS)

    Yamagishi, Kazuhisa; Hayashi, Takanori

    Developing a non-intrusive packet-layer model is required to passively monitor the quality of experience (QoE) during service. We propose a packet-layer model that can be used to estimate the video quality of IPTV using quality parameters derived from transmitted packet headers. The computational load of the model is lighter than that of the model that takes video signals and/or video-related bitstream information such as motion vectors as input. This model is applicable even if the transmitted bitstream information is encrypted because it uses transmitted packet headers rather than bitstream information. For developing the model, we conducted three extensive subjective quality assessments for different encoders and decoders (codecs), and video content. Then, we modeled the subjective video quality assessment characteristics based on objective features affected by coding and packet loss. Finally, we verified the model's validity by applying our model to unknown data sets different from training data sets used above.

  17. A Solution for Irregular IP Multicast Packet Flooding — For Heavy Traffic IP Multicast Communication

    NASA Astrophysics Data System (ADS)

    Misumi, Makoto; Nakagawa, Shin-Ichi; Chinen, Ken-Ichi; Shinoda, Yoichi; Yamaoka, Katsunori

    When an IP Multicast network is constructed on a switch-based network, many IP Multicast packet broadcasts are generated, and these broadcasts cause trouble for all of the other kinds of communication. To solve this problem, implementing IGMP Snooping on various switches has been proposed. However, some switches have insufficient IP Multicast packet-handling capability. This problem is also mentioned in RFC4541. In this paper, we propose the IGMP Snooping Activator (ISA) mechanism as a way to solve the IP Multicast packet-handling problem. The ISA transmits dummy IGMP Queries to maintain the IP Multicast network, and it joins the flooding IP Multicast group to activate IGMP Snooping in switches that are unable to handle IP Multicast packets. The experimental evaluation shows the effectiveness of our proposed method: the network load decreases because of the method's effective restraint of IP Multicast packet flooding.

  18. Dispatching packets on a global combining network of a parallel computer

    DOEpatents

    Almasi, Gheorghe; Archer, Charles J.

    2011-07-19

    Methods, apparatus, and products are disclosed for dispatching packets on a global combining network of a parallel computer comprising a plurality of nodes connected for data communications using the network capable of performing collective operations and point to point operations that include: receiving, by an origin system messaging module on an origin node from an origin application messaging module on the origin node, a storage identifier and an operation identifier, the storage identifier specifying storage containing an application message for transmission to a target node, and the operation identifier specifying a message passing operation; packetizing, by the origin system messaging module, the application message into network packets for transmission to the target node, each network packet specifying the operation identifier and an operation type for the message passing operation specified by the operation identifier; and transmitting, by the origin system messaging module, the network packets to the target node.

  19. Source Authentication for Code Dissemination Supporting Dynamic Packet Size in Wireless Sensor Networks †

    PubMed Central

    Kim, Daehee; Kim, Dongwan; An, Sunshin

    2016-01-01

    Code dissemination in wireless sensor networks (WSNs) is a procedure for distributing a new code image over the air in order to update programs. Due to the fact that WSNs are mostly deployed in unattended and hostile environments, secure code dissemination ensuring authenticity and integrity is essential. Recent works on dynamic packet size control in WSNs allow enhancing the energy efficiency of code dissemination by dynamically changing the packet size on the basis of link quality. However, the authentication tokens attached by the base station become useless in the next hop where the packet size can vary according to the link quality of the next hop. In this paper, we propose three source authentication schemes for code dissemination supporting dynamic packet size. Compared to traditional source authentication schemes such as μTESLA and digital signatures, our schemes provide secure source authentication under the environment, where the packet size changes in each hop, with smaller energy consumption. PMID:27409616

  20. Scattering of intense laser radiation by a single-electron wave packet

    SciTech Connect

    Corson, John P.; Peatross, Justin; Mueller, Carsten; Hatsagortsyan, Karen Z.

    2011-11-15

    A quantum theoretical description of photoemission by a single laser-driven electron wave packet is presented. Energy-momentum conservation ensures that the partial emissions from individual momentum components of the electron wave packet do not interfere when the driving field is unidirectional. In other words, light scattering by an electron packet is independent of the phases of the pure momentum states comprising the packet; the size of the electron wave packet does not matter. This result holds also in the case of high-intensity multiphoton scattering. Our analysis is first presented in the QED framework. Since QED permits the second-quantized entangled electron-photon final state to be projected onto pure plane-wave states, the Born probability interpretation requires these projections to be first squared and then summed to find an overall probability of a scattering event. The QED treatment indicates how a semiclassical framework can be developed to recover the key features of the correct result.

  1. Scattering of intense laser radiation by a single-electron wave packet

    NASA Astrophysics Data System (ADS)

    Corson, John P.; Peatross, Justin; Müller, Carsten; Hatsagortsyan, Karen Z.

    2011-11-01

    A quantum theoretical description of photoemission by a single laser-driven electron wave packet is presented. Energy-momentum conservation ensures that the partial emissions from individual momentum components of the electron wave packet do not interfere when the driving field is unidirectional. In other words, light scattering by an electron packet is independent of the phases of the pure momentum states comprising the packet; the size of the electron wave packet does not matter. This result holds also in the case of high-intensity multiphoton scattering. Our analysis is first presented in the QED framework. Since QED permits the second-quantized entangled electron-photon final state to be projected onto pure plane-wave states, the Born probability interpretation requires these projections to be first squared and then summed to find an overall probability of a scattering event. The QED treatment indicates how a semiclassical framework can be developed to recover the key features of the correct result.

  2. A scalable control plane for optical-packet-switched networks

    NASA Astrophysics Data System (ADS)

    Kang, J.; Reed, M. J.

    2005-02-01

    This paper describes the design considerations and architecture of a Generalized Multi-Protocol Label Switching (GMPLS)-based scalable control plane that we are prototyping for optical packet switched (OPS) networks. Functional components of the control plane include a user network interface (UNI), optical label coding, multi-layer routing/traffic engineering algorithm and integrated signaling protocol. Initial implementation and experimentation has demonstrated the feasibility of our prototype as a testbed for various control schemes for OPS networks. One key element of the architecture proposed is the use of external MPLS labeling controlled by the UNI. This proposal reduces the load on the OPS domain header processing while having little impact on the MPLS domain.

  3. Design and implementation considerations of a MSAT packet data network

    NASA Astrophysics Data System (ADS)

    Karam, Fouad G.; Hearn, Terry; Rohr, Doug; Guibord, Arthur F.

    The Mobile Data System, which is intended to provide for packet switched data services is currently under development. The system is based on a star network topology consisting of a centralized Data Hub (DH) serving a large number of mobile terminals. Through the Data Hub, end-to-end connections can be established between terrestrial users on public or private data networks and mobile users. The MDS network will be capable of offering a variety of services some of which are based on the standard X.25 network interface protocol, and others optimized for short messages and broadcast messages. A description of these services and the trade-offs in the DH design are presented.

  4. Silicon-Germanium Fast Packet Switch Developed for Communications Satellites

    NASA Technical Reports Server (NTRS)

    Quintana, Jorge A.

    1999-01-01

    Emerging multimedia applications and future satellite systems will require high-speed switching networks to accommodate high data-rate traffic among thousands of potential users. This will require advanced switching devices to enable communication between satellites. The NASA Lewis Research Center has been working closely with industry to develop a state-of-the-art fast packet switch (FPS) to fulfill this requirement. Recently, the Satellite Industry Task Force identified the need for high-capacity onboard processing switching components as one of the "grand challenges" for the satellite industry in the 21st century. In response to this challenge, future generations of onboard processing satellites will require low power and low mass components to enable transmission of services in the 100 gigabit (1011 bits) per second (Gbps) range.

  5. Design and implementation considerations of a MSAT packet data network

    NASA Technical Reports Server (NTRS)

    Karam, Fouad G.; Hearn, Terry; Rohr, Doug; Guibord, Arthur F.

    1993-01-01

    The Mobile Data System, which is intended to provide for packet switched data services is currently under development. The system is based on a star network topology consisting of a centralized Data Hub (DH) serving a large number of mobile terminals. Through the Data Hub, end-to-end connections can be established between terrestrial users on public or private data networks and mobile users. The MDS network will be capable of offering a variety of services some of which are based on the standard X.25 network interface protocol, and others optimized for short messages and broadcast messages. A description of these services and the trade-offs in the DH design are presented.

  6. Access Denied

    ERIC Educational Resources Information Center

    Villano, Matt

    2008-01-01

    Building access control (BAC)--a catchall phrase to describe the systems that control access to facilities across campus--has traditionally been handled with remarkably low-tech solutions: (1) manual locks; (2) electronic locks; and (3) ID cards with magnetic strips. Recent improvements have included smart cards and keyless solutions that make use…

  7. Open Access

    ERIC Educational Resources Information Center

    Suber, Peter

    2012-01-01

    The Internet lets us share perfect copies of our work with a worldwide audience at virtually no cost. We take advantage of this revolutionary opportunity when we make our work "open access": digital, online, free of charge, and free of most copyright and licensing restrictions. Open access is made possible by the Internet and copyright-holder…

  8. Choice of FDMA/SCPC access technique for aeronautical satellite voice system

    NASA Technical Reports Server (NTRS)

    Smith, G. K.

    1989-01-01

    A worldwide aeronautical mobile satellite system is about to become operational. The system architecture and access methods have been debated extensively, resulting in the selection of Time Division Multiplexing/Time Division Multiple Access (TDM/TDMA) access for packet data, and Single Channel Per Carrier (SCPC) for voice. These have become standards for airline use, and also satisfy the known requirements of ICAO for safety related communications. Voice communications are expected to absorb a high proportion of satellite bandwidth and power in the future. Here, it is explained why INMARSAT selected Frequency Division Multiple Access/SCPC satellite access for this application.

  9. Greedy data transportation scheme with hard packet deadlines for wireless ad hoc networks.

    PubMed

    Lee, HyungJune

    2014-01-01

    We present a greedy data transportation scheme with hard packet deadlines in ad hoc sensor networks of stationary nodes and multiple mobile nodes with scheduled trajectory path and arrival time. In the proposed routing strategy, each stationary ad hoc node en route decides whether to relay a shortest-path stationary node toward destination or a passing-by mobile node that will carry closer to destination. We aim to utilize mobile nodes to minimize the total routing cost as far as the selected route can satisfy the end-to-end packet deadline. We evaluate our proposed routing algorithm in terms of routing cost, packet delivery ratio, packet delivery time, and usability of mobile nodes based on network level simulations. Simulation results show that our proposed algorithm fully exploits the remaining time till packet deadline to turn into networking benefits of reducing the overall routing cost and improving packet delivery performance. Also, we demonstrate that the routing scheme guarantees packet delivery with hard deadlines, contributing to QoS improvement in various network services.

  10. Application of single flux quantum technology to a next-generation photonic packet switch core

    NASA Astrophysics Data System (ADS)

    Yorozu, S.; Harai, H.; Kameda, Y.; Terai, H.; Hashimoto, Y.

    2004-10-01

    Internet traffic is still growing rapidly. Link capacity is easily increased by bundling optical fibers, but the packet switching capacity at a node is limited by the performance of a semiconductor switch facing problems of packaging density, operation speed, and power consumption. Photonic technology is therefore emerging from the link technology into the packet switch technology. A photonic packet switch can analyze the packet label optically and control optical switches, but packet scheduling must be done in the non-optical domain because photonic technology lacks arithmetic characteristics. Increases in the line speed and the number of ports will make this scheduling a bottleneck. Because single flux quantum (SFQ) circuits can operate at several tens of gigahertz, a speed comparable to optical link speed, they will be able to eliminate this bottleneck. To improve the performance of the nodes in the photonic network, we propose an SFQ-circuit-controlled optical packet switch core. Here we describe and discuss two photonic packet switch architectures using SFQ-circuit-controlled photonic switches.

  11. Experimental evaluation of the impact of packet capturing tools for web services.

    SciTech Connect

    Choe, Yung Ryn; Mohapatra, Prasant; Chuah, Chen-Nee; Chen, Chao-Chih

    2011-10-01

    Network measurement is a discipline that provides the techniques to collect data that are fundamental to many branches of computer science. While many capturing tools and comparisons have made available in the literature and elsewhere, the impact of these packet capturing tools on existing processes have not been thoroughly studied. While not a concern for collection methods in which dedicated servers are used, many usage scenarios of packet capturing now requires the packet capturing tool to run concurrently with operational processes. In this work we perform experimental evaluations of the performance impact that packet capturing process have on web-based services; in particular, we observe the impact on web servers. We find that packet capturing processes indeed impact the performance of web servers, but on a multi-core system the impact varies depending on whether the packet capturing and web hosting processes are co-located or not. In addition, the architecture and behavior of the web server and process scheduling is coupled with the behavior of the packet capturing process, which in turn also affect the web server's performance.

  12. Optical node for fast packet-switching networks in the KEOPS project: structure and performance aspects

    NASA Astrophysics Data System (ADS)

    Chiaroni, Dominique; Lavigne, Bruno; Tran, Tri; Hamon, Laure; Jourdan, Amaury

    1998-10-01

    The future telecommunication network will have to face the dramatic increase of subscribers as well as the increase of the user bandwidth through new services. All-optical packet switching techniques can become a strategic objective to offer on an unique technology a service-transparent network. In this paper, we will describe in detail the structure of an optical packet switching node developed in the framework of the ACTS 043 KEOPS project. An analysis of the key functions will be reported to fulfill system requirements including cascadability. In particular the input synchronization, the Broadcast-and-select switching matrix and the output regenerative interface will be described and physical performance will be assessed through theoretical analysis: quality of the signal, packet jitter and packet power fluctuation. The electronic circuitry for the control of the components of each sub-block will be described. Finally, experimental validations of a 160 Gbit/s throughput node will be reported. In order to complete the analysis, the logical performance in a Bernoulli-type traffic will be regarded. In particular an optimized buffer including a recirculation loop will be studied. Logical performance exhibiting a packet loss rate lower than 10-9 for a 0.8 load and mean packet delay as low as 3 packet slots will be illustrated, thereby demonstrating full compatibility with ATM constraints. Finally, new perspectives in terms of throughput potential through cascading will be drawn.

  13. An NMR log echo data de-noising method based on the wavelet packet threshold algorithm

    NASA Astrophysics Data System (ADS)

    Meng, Xiangning; Xie, Ranhong; Li, Changxi; Hu, Falong; Li, Chaoliu; Zhou, Cancan

    2015-12-01

    To improve the de-noising effects of low signal-to-noise ratio (SNR) nuclear magnetic resonance (NMR) log echo data, this paper applies the wavelet packet threshold algorithm to the data. The principle of the algorithm is elaborated in detail. By comparing the properties of a series of wavelet packet bases and the relevance between them and the NMR log echo train signal, ‘sym7’ is found to be the optimal wavelet packet basis of the wavelet packet threshold algorithm to de-noise the NMR log echo train signal. A new method is presented to determine the optimal wavelet packet decomposition scale; this is within the scope of its maximum, using the modulus maxima and the Shannon entropy minimum standards to determine the global and local optimal wavelet packet decomposition scales, respectively. The results of applying the method to the simulated and actual NMR log echo data indicate that compared with the wavelet threshold algorithm, the wavelet packet threshold algorithm, which shows higher decomposition accuracy and better de-noising effect, is much more suitable for de-noising low SNR-NMR log echo data.

  14. Theory of probing attosecond electron wave packets via two-path interference of angle-resolved photoelectrons

    SciTech Connect

    Choi, N. N.; Jiang, T. F.; Morishita, T.; Lee, M.-H.; Lin, C. D.

    2010-07-15

    We study theoretically the electron wave packet generated by an attosecond pulse train (APT) which is probed with a time-delayed infrared (IR) laser pulse. The APT creates an excited state and a continuum electron wave packet. By ionizing the excited state with an IR, a delayed new continuum electron wave packet is created. The interference of the wave packets from the two paths, as reflected in angle-resolved photoelectron spectra, is analyzed analytically. Using the analytical expressions, we examine the possibility of retrieving information on the electron wave packet generated by the APT.

  15. Equal Access.

    ERIC Educational Resources Information Center

    De Patta, Joe

    2003-01-01

    Presents an interview with Stephen McCarthy, co-partner and president of Equal Access ADA Consulting Architects of San Diego, California, about designing schools to naturally integrate compliance with the Americans with Disabilities Act (ADA). (EV)

  16. Oak Ridge Environmental Information System (ORIES) site workstation information packet for OREIS V1. 2

    SciTech Connect

    Voorhees, L.D.; McCord, R.A.; Durfee, R.C.; Land, M.L.; Olson, R.J.; Palmer, M.R.; Thomas, J.K.; Tinnel, E.P.; Zygmunt, B.C.

    1993-02-01

    The OREIS site workstation information packet was developed to accompany the OREIS site workstations, which are being delivered to the Environmental Restoration programs at the five DOE-OR sites. The packet is written specifically for the Site ER program staff at each of the five Sites who have been designated the OREIS contact by their ER program manager, and is not intended for general distribution. The packet provides an overview of the components of OREIS, points to more detailed information provided in the accompanying vendor and OREIS developed manuals, and includes information on training opportunities and user support.

  17. High-capacity packet-switched fabrics: introduction to the focus issue

    NASA Astrophysics Data System (ADS)

    Smiljanic, Aleksandra

    2003-07-01

    Growth in Internet Protocol (IP) traffic is bringing about a need for larger packet switches. Merely adding more small switches to the network to handle the increased IP traffic is an inefficient solution, since the effective capacity of a router falls when packets must pass through many routers—the number of futile transit ports falls with increased switch size. In addition, control is simpler in networks with a smaller number of nodes. In this Focus Issue, authors from NEC, Alcatel, Lucent Technologies, and Chiaro Networks examine designs that enable high-capacity packet switches.

  18. Modelling and performance of packet synchronization in a data communications system

    NASA Astrophysics Data System (ADS)

    Boettcher, Axel

    1992-12-01

    This paper deals with some problems of packet synchronization in a slotted packet-radio communications system. The problems considered are bit-synchronization and unique word detection for bursty systems. The necessary overhead for synchronization purposes is dimensioned for applications in land-mobile satellite communication systems. The performance of synchronization is evaluated using hardware measurement equipment, including a commercial bit-synchronizer. Using these results, the performance loss of communication systems due to packet synchronization effects can be estimated. This is done for the additive white Gaussian noise channel and the class of land-mobile satellite channels.

  19. Research on the key technology and application of the packet transmission network

    NASA Astrophysics Data System (ADS)

    Yun, Xiang; Wang, Zhong

    2009-08-01

    In proportion to the rapid development of telecommunication service, Telecom Operators already have made a strategic transition from "Network, Communication Operators" into "integrated information service provider" to provide customer with varied information service, such as the BT "21st century plan", "Next" plan proposed by France Telecom, FNE and BMS plan by Australia Telstra, RANE Programs by NTT. Domestic Carries also made strategic transition plans. And the priority of network transition is to find the way to build a unified and integrated network supporting carrier-grade Ethernet service also compatible with the conventional network service. The division of the service results in the Packet transmission, namely packet technology, makes Packet-based Transmission Network keeping the virtues of transmission network. The virtues are good scalability, varied operation and maintenance, high-speed protection switching, connection-oriented feature, and building up connection with NMS. At the same time, it adds some characteristics to adapt the statistical multiplexing in the packet service, for instance: connection-oriented label switching, QoS mechanism, dynamic and flexible control plane. The Packet Transmission Network (PTN) can be divided into four layers: packet transmission channel layer (PTC), packet transmission path layer (PTP), and optional packet transmission section Layer (PTS) and physical layer. The key technologies of PTN are as follows: the connection-oriented based label transmission and the statistical multiplexing on packet switching. The use of layer and sub-domain is to provide good scalability. Supporting for fault detection and performance testing and other Operation, Management and Maintenance (OAM) function, linear protection switching, ring protection, dynamics survival technology of pre-placed re-route, QoS, circuit emulation for TDM service, ATM based on PWE3 technique, and MAC layer or physical layer based packet clock synchronization

  20. Statistical Mechanics-Inspired Modeling of Heterogeneous Packet Transmission in Communication Networks

    DTIC Science & Technology

    2012-08-01

    a remarkable similarity with two-component mixtures , e.g., Fig. 7. Network phase diagram with two packet types. The transmission probability of...packet type i is denoted as Pi under the constraint P1 + P2 = 1. The arrival rate for packets of type i is denoted at λi. a mixture of olivine (i.e., an...isolated tetrahedra) and pyroxene (i.e., single chain tetrahedra). The corresponding phase diagram is known as the binary eutectic phase diagram [20

  1. Efficient rate-distortion optimized media streaming for tree-reducible packet dependencies

    NASA Astrophysics Data System (ADS)

    Röder, Martin; Cardinal, Jean; Hamzaoui, Raouf

    2006-01-01

    In packetized media streaming systems, packet dependencies are often modeled as a directed acyclic graph called the dependency graph. We consider the situation where the dependency graph is reducible to a tree. This occurs, for instance, in MPEG1 video streams that are packetized at the frame level. Other video coding standards such as H.264 also allow tree-reducible dependencies. We propose in this context efficient dynamic programming algorithms for finding rate-distortion optimal transmission policies. The proposed algorithms are much faster than previous exact algorithms developed for arbitrary dependency graphs.

  2. Formation of ground-state vibrational wave packets in intense ultrashort laser pulses.

    PubMed

    Goll, Erich; Wunner, Günter; Saenz, Alejandro

    2006-09-08

    The formation of coherent vibrational wave packets in the electronic ground state of neutral molecules in intense ultrashort laser pulses and their subsequent detection by means of recently developed pump-probe experiments are discussed. The wave packet formation is due to the pronounced dependence of the strong-field ionization rate on the internuclear distance. This leads to a deformation of the initial wave function due to an internuclear-distance dependent depletion. The phenomenon is demonstrated with a time-dependent wave packet study for molecular hydrogen.

  3. A Fully Implemented 12 × 12 Data Vortex Optical Packet Switching Interconnection Network

    NASA Astrophysics Data System (ADS)

    Shacham, Assaf; Small, Benjamin A.; Liboiron-Ladouceur, Odile; Bergman, Keren

    2005-10-01

    A fully functional optical packet switching (OPS) interconnection network based on the data vortex architecture is presented. The photonic switching fabric uniquely capitalizes on the enormous bandwidth advantage of wavelength division multiplexing (WDM) wavelength parallelism while delivering minimal packet transit latency. Utilizing semiconductor optical amplifier (SOA)-based switching nodes and conventional fiber-optic technology, the 12-port system exhibits a capacity of nearly 1 Tb/s. Optical packets containing an eight-wavelength WDM payload with 10 Gb/s per wavelength are routed successfully to all 12 ports while maintaining a bit error rate (BER) of 10-12 or better. Median port-to-port latencies of 110 ns are achieved with a distributed deflection routing network that resolves packet contention on-the-fly without the use of optical buffers and maintains the entire payload path in the optical domain.

  4. Field trial of 160 Gb/s all-optical packet switching

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Herrera, J.; Raz, O.; Tangdiongga, E.; Marti, J.; Ramos, F.; Maxwell, G.; Poustie, A.; Mulvad, H. C. H.; Hill, M. T.; de Waardt, H.; Khoe, G. D.; Koonen, A. M. J.; Dorren, H. J. S.

    2007-11-01

    We present the results of a transmission experiment, over 110 km of field installed fiber, for an all-optical 160 Gb/s packet switching system. The system uses in-band optical labels which are processed entirely in the optical domain using a narrow-band all-optical filter. The label decision information is stored by an optical flip-flop, which output controls a high-speed wavelength converter based on ultra-fast cross-phase modulation in a single semiconductor optical amplifier. The packet switched node is located in between two different fiber sections, each having a length of 54.3-km. The field installed fibers are located around the city of Eindhoven in the Netherlands. The results show how the all-optical switch can effectively route the packets based on the optical information and that such packets may be transmitted across the fiber with an acceptable penalty level.

  5. A scheme for synchronizing clocks connected by a packet communication network

    NASA Astrophysics Data System (ADS)

    dos Santos, R. V.; Monteiro, L. H. A.

    2012-07-01

    Consider a communication system in which a transmitter equipment sends fixed-size packets of data at a uniform rate to a receiver equipment. Consider also that these equipments are connected by a packet-switched network, which introduces a random delay to each packet. Here we propose an adaptive clock recovery scheme able of synchronizing the frequencies and the phases of these devices, within specified limits of precision. This scheme for achieving frequency and phase synchronization is based on measurements of the packet arrival times at the receiver, which are used to control the dynamics of a digital phase-locked loop. The scheme performance is evaluated via numerical simulations performed by using realistic parameter values.

  6. Discrete Packet Analysis for Improved Atmospheric Rejection on Modulated Laser Signals

    SciTech Connect

    O'Neill, M., McKenna, I., DiBenedetto, J., Capelle, G., Trainham, R.

    2012-07-19

    This slide-show discusses how the method of discrete packet analysis improves atmospheric compensation for quasi-CW fluorescence detection methods. This is key to improving remote sensing capabilities.

  7. Adaptive sampling rate control for networked systems based on statistical characteristics of packet disordering.

    PubMed

    Li, Jin-Na; Er, Meng-Joo; Tan, Yen-Kheng; Yu, Hai-Bin; Zeng, Peng

    2015-09-01

    This paper investigates an adaptive sampling rate control scheme for networked control systems (NCSs) subject to packet disordering. The main objectives of the proposed scheme are (a) to avoid heavy packet disordering existing in communication networks and (b) to stabilize NCSs with packet disordering, transmission delay and packet loss. First, a novel sampling rate control algorithm based on statistical characteristics of disordering entropy is proposed; secondly, an augmented closed-loop NCS that consists of a plant, a sampler and a state-feedback controller is transformed into an uncertain and stochastic system, which facilitates the controller design. Then, a sufficient condition for stochastic stability in terms of Linear Matrix Inequalities (LMIs) is given. Moreover, an adaptive tracking controller is designed such that the sampling period tracks a desired sampling period, which represents a significant contribution. Finally, experimental results are given to illustrate the effectiveness and advantages of the proposed scheme.

  8. Scattering of Light by Electron Wave Packets: Size Doesn't Matter

    NASA Astrophysics Data System (ADS)

    Corson, John; Glasgow, Scott; Acosta, Sebastian; Ware, Michael; Peatross, Justin

    2011-05-01

    In support of a current experiment, we investigate light scattering by individual free electrons in an intense laser focus using full second quantization. This addresses the question of whether emission from a large electron packet will be suppressed owing to interference between different parts of the packet. Textbook treatments of Compton scattering generally use exact momentum states, but packets necessarily superpose many momentum states with the possibility of quantum interference (see J. Peatross, C. Muller, K. Hatsagortsyan, and C. H. Keitel, Phys. Rev. Lett. 100, 153601, 2008). We investigate the details of this interference for both single- photon and coherent-state scattering. Kinematic constraints eliminate interference in the case of unidirectional stimulation, whether the scattering is single- or multi-photon in nature. To all orders of perturbation theory, the scattering exhibits no dependence on the relative phases of constituent momenta, and thus no dependence on wave packet size.

  9. Wide-band packet radio for multipath environments

    NASA Astrophysics Data System (ADS)

    Fischer, Jeffrey H.; Cafarella, John H.; Bouman, Charles A.; Flynn, Gerard T.; Dolat, Victor S.

    1988-05-01

    A direct-sequence spread-spectrum packet radio is described that has versatile signal-processing and local-control capabilities designed to support the functions required of a robust mobile communications network. Noteworthy capabilities include eleven selectable data rates with accurate range measurements in a fading multipath channel. The radio uses a hybrid analog/digital signal processor and nonrepeating spreading codes for suppression of intersymbol interference and jamming. It incorporates two sets of monolithic surface-acoustic-wave convolvers as programmable matched filters with time-bandwidth products of 64 and 2000. The analog matched filters are coupled with binary postprocessing for the functions of detection, RAKE demodulation, and ranging measurements over a wide multipath spread. The data rate can be varied in response to channel conditions from 1.45 Mb/s down to 44 b/s with an almost ideal tradeoff in signal-processing gain from 18 dB up to 61 dB prior to multipath combining.

  10. Riemann {zeta} function from wave-packet dynamics

    SciTech Connect

    Mack, R.; Schleich, W. P.; Dahl, J. P.; Moya-Cessa, H.; Strunz, W. T.; Walser, R.

    2010-09-15

    We show that the time evolution of a thermal phase state of an anharmonic oscillator with logarithmic energy spectrum is intimately connected to the generalized Riemann {zeta} function {zeta}(s,a). Indeed, the autocorrelation function at a time t is determined by {zeta}({sigma}+i{tau},a), where {sigma} is governed by the temperature of the thermal phase state and {tau} is proportional to t. We use the JWKB method to solve the inverse spectral problem for a general logarithmic energy spectrum; that is, we determine a family of potentials giving rise to such a spectrum. For large distances, all potentials display a universal behavior; they take the shape of a logarithm. However, their form close to the origin depends on the value of the Hurwitz parameter a in {zeta}(s,a). In particular, we establish a connection between the value of the potential energy at its minimum, the Hurwitz parameter and the Maslov index of JWKB. We compare and contrast exact and approximate eigenvalues of purely logarithmic potentials. Moreover, we use a numerical method to find a potential which leads to exact logarithmic eigenvalues. We discuss possible realizations of Riemann {zeta} wave-packet dynamics using cold atoms in appropriately tailored light fields.

  11. Wavelet Packets-Based Blind Watermarking for Medical Image Management

    PubMed Central

    Mostafa, Salwa A.K.; El-sheimy, Naser; Tolba, A.S.; Abdelkader, F.M.; Elhindy, Hisham M.

    2010-01-01

    The last decade has witnessed an explosive use of medical images and Electronics Patient Record (EPR) in the healthcare sector for facilitating the sharing of patient information and exchange between networked hospitals and healthcare centers. To guarantee the security, authenticity and management of medical images and information through storage and distribution, the watermarking techniques are growing to protect the medical healthcare information. This paper presents a technique for embedding the EPR information in the medical image to save storage space and transmission overheads and to guarantee security of the shared data. In this paper a new method for protecting the patient information in which the information is embedded as a watermark in the discrete wavelet packet transform (DWPT) of the medical image using the hospital logo as a reference image. The patient information is coded by an error correcting code (ECC), BCH code, to enhance the robustness of the proposed method. The scheme is blind so that the EPR can be extracted from the medical image without the need of the original image. Therefore, this proposed technique is useful in telemedicine applications. Performance of the proposed method was tested using four modalities of medical images; MRA, MRI, Radiological, and CT. Experimental results showed no visible difference between the watermarked and the original image. Moreover, the proposed watermarking method is robust against a wide range of attacks such as JPEG coding, Gaussian noise addition, histogram equalization, gamma correction, contrast adjustment, and sharpen filter and rotation. PMID:20700520

  12. Packets or ports: the decisions of IP switching

    NASA Astrophysics Data System (ADS)

    Ilvesmaeki, Mika; Kilkki, Kalevi; Luoma, Marko

    1997-10-01

    One of the most important network elements in the Internet are the routers which do relaying of IP packets. Because of growth of the Internet routers currently experience serious problems in relaying traffic in a satisfying speed. The idea of switching Internet traffic flows has recently been introduced and a new technology called IP switching has emerged. Several differing technological solutions have been suggested. In this paper we describe and compare two methods in flow-based IP switching to make the decisions whether to switch internet traffic flows to separate ATM-connections. Traffic measurements are made in two networks of varying size and based on a specific three-stage flow analysis we suggest that the decision to switch should be made as flexible as possible due to the expected diversity of traffic profiles in different parts of the network. This way the optimal service cluster could be switched and router resources could be optimally utilized. A simple model to determine workload to an IP switch is introduced. Using this model we see that the workload of the flow setup component and the routing component may be optimized, if we use flexible methods to determine the flows that are to be separately switched.

  13. Coriolis-coupled wave packet dynamics of H + HLi reaction.

    PubMed

    Padmanaban, R; Mahapatra, S

    2006-05-11

    We investigated the effect of Coriolis coupling (CC) on the initial state-selected dynamics of H+HLi reaction by a time-dependent wave packet (WP) approach. Exact quantum scattering calculations were obtained by a WP propagation method based on the Chebyshev polynomial scheme and ab initio potential energy surface of the reacting system. Partial wave contributions up to the total angular momentum J=30 were found to be necessary for the scattering of HLi in its vibrational and rotational ground state up to a collision energy approximately 0.75 eV. For each J value, the projection quantum number K was varied from 0 to min (J, K(max)), with K(max)=8 until J=20 and K(max)=4 for further higher J values. This is because further higher values of K do not have much effect on the dynamics and also because one wishes to maintain the large computational overhead for each calculation within the affordable limit. The initial state-selected integral reaction cross sections and thermal rate constants were calculated by summing up the contributions from all partial waves. These were compared with our previous results on the title system, obtained within the centrifugal sudden and J-shifting approximations, to demonstrate the impact of CC on the dynamics of this system.

  14. 4x4 optical packet switching of asynchronous burst optical packets with a prototype, 4x4 label processing and switching sub-system.

    PubMed

    Urata, Ryohei; Nakahara, Tatsushi; Takenouchi, Hirokazu; Segawa, Toru; Ishikawa, Hiroshi; Ohki, Akira; Sugiyama, Hiroki; Nishihara, Susumu; Takahashi, Ryo

    2010-07-19

    We report a prototype, 4x4 (4 input/4 output) label processing and switching sub-system for 10-Gb/s asynchronous burst variable-length optical packets. With the prototype, we perform a 4x4 optical packet switching demonstration, achieving error-free (BER<10(-12)) label processing and switching operation for all possible input/output combinations (16 switching paths) simultaneously. Power consumption and latency of the entire, self-contained sub-system is 83 W (includes fan power) and 300 ns, respectively.

  15. New hybrid frequency reuse method for packet loss minimization in LTE network

    PubMed Central

    Ali, Nora A.; El-Dakroury, Mohamed A.; El-Soudani, Magdi; ElSayed, Hany M.; Daoud, Ramez M.; Amer, Hassanein H.

    2014-01-01

    This paper investigates the problem of inter-cell interference (ICI) in Long Term Evolution (LTE) mobile systems, which is one of the main problems that causes loss of packets between the base station and the mobile station. Recently, different frequency reuse methods, such as soft and fractional frequency reuse, have been introduced in order to mitigate this type of interference. In this paper, minimizing the packet loss between the base station and the mobile station is the main concern. Soft Frequency Reuse (SFR), which is the most popular frequency reuse method, is examined and the amount of packet loss is measured. In order to reduce packet loss, a new hybrid frequency reuse method is implemented. In this method, each cell occupies the same bandwidth of the SFR, but the total system bandwidth is greater than in SFR. This will provide the new method with a lot of new sub-carriers from the neighboring cells to reduce the ICI which represents a big problem in many applications and causes a lot of packets loss. It is found that the new hybrid frequency reuse method has noticeable improvement in the amount of packet loss compared to SFR method in the different frequency bands. Traffic congestion management in Intelligent Transportation system (ITS) is one of the important applications that is affected by the packet loss due to the large amount of traffic that is exchanged between the base station and the mobile node. Therefore, it is used as a studied application for the proposed frequency reuse method and the improvement in the amount of packet loss reached 49.4% in some frequency bands using the new hybrid frequency reuse method. PMID:26644933

  16. Nonreciprocal emission of spin-wave packet in FeNi film

    NASA Astrophysics Data System (ADS)

    Sekiguchi, K.; Yamada, K.; Seo, S. M.; Lee, K. J.; Chiba, D.; Kobayashi, K.; Ono, T.

    2010-07-01

    We report a time-resolved propagating spin wave spectroscopy for Fe19Ni81 film. We show that the amplitude of the spin-wave packet depends on the direction of magnetization and that its phase can be controlled by the polarity of pulsed magnetic field for the excitation. The nonreciprocal emission of spin-wave packet can be utilized for the binary spin-wave input into the spin-wave logic circuit.

  17. Architecture and Design of a CMOS IC for Packet Switching Multi-Gigabit Data Streams

    DTIC Science & Technology

    2005-01-01

    such as store-and-forward, wormhole routing, and virtual cut-through. Further characteristics of packet switches and its variants will be presented...outside of the switch fabric [11]. Wormhole routing was first proposed in 1986 by Dally and Seitz and is a technique whereby packets traveling through...interleaved. Wormhole routing is a modification of virtual cut-through routing. The primary difference between the two is that in wormhole routing

  18. Characteristics of Wave Packets in the Upper Troposphere. Part I: Northern Hemisphere Winter.

    NASA Astrophysics Data System (ADS)

    Chang, Edmund K. M.; Yu, Daniel B.

    1999-06-01

    Gridded data produced by the ECMWF reanalysis project have been analyzed to document the properties of wave packets in the Northern Hemisphere winter midlatitude upper troposphere. Based on results from earlier investigations, 300-hPa meridional wind variations were chosen for analysis. Wave packet envelopes were also defined by performing complex demodulation on the wind data. The properties of the wave packets are mainly illustrated using time-lagged one-point correlation maps performed both on and wave packet envelopes.The results show that, over most regions in the Northern Hemisphere winter, with the exception of the deep Tropics and near the Aleutian low, medium-scale waves (dominant wavenumber 5-8) exhibit the characteristics of downstream development and occur within wave trains that propagate with eastward group velocities much faster than the phase speeds of individual phases of the waves. Their group velocity is highly correlated with the local time mean 200-400-hPa wind, while the phase speed is well correlated with the 500-700-hPa flow.A wave coherence index has been defined to show the geographical variations in the downstream development tendency of wave propagation. The results show that wave packets are most coherent along a band that extends from North Africa into southern Asia, toward the Pacific storm track, across North America, then over the central North Atlantic back toward North Africa. The maximum coherence occurs over southern Asia. This band can be regarded as the waveguide for upper-tropospheric wave packets in the Northern Hemisphere winter. Over this band, wave packets generally stay coherent significantly longer than individual troughs and ridges. There is also a secondary waveguide across Russia toward the Pacific, acting as a second source of waves that propagate across the Pacific storm track. Away from the primary waveguide, while wave packet coherence is less, the waves still show the characteristics of downstream development.

  19. All-optical packet routing scheme for optical label-swapping networks

    NASA Astrophysics Data System (ADS)

    Clavero, R.; Martínez, J. M.; Ramos, F.; Martí, J.

    2004-09-01

    A novel scheme for all-optical label reading and packet routing is proposed. The architecture is comprised of all-optical logic XOR gates and all-optical flip-flops based on single Mach-Zehnder interferometers incorporating semiconductor optical amplifiers (SOA-MZIs). The simulation results show that a very small penalty (less than 0.45 dB) for 10 Gbit/s packet processing can be achieved.

  20. New hybrid frequency reuse method for packet loss minimization in LTE network.

    PubMed

    Ali, Nora A; El-Dakroury, Mohamed A; El-Soudani, Magdi; ElSayed, Hany M; Daoud, Ramez M; Amer, Hassanein H

    2015-11-01

    This paper investigates the problem of inter-cell interference (ICI) in Long Term Evolution (LTE) mobile systems, which is one of the main problems that causes loss of packets between the base station and the mobile station. Recently, different frequency reuse methods, such as soft and fractional frequency reuse, have been introduced in order to mitigate this type of interference. In this paper, minimizing the packet loss between the base station and the mobile station is the main concern. Soft Frequency Reuse (SFR), which is the most popular frequency reuse method, is examined and the amount of packet loss is measured. In order to reduce packet loss, a new hybrid frequency reuse method is implemented. In this method, each cell occupies the same bandwidth of the SFR, but the total system bandwidth is greater than in SFR. This will provide the new method with a lot of new sub-carriers from the neighboring cells to reduce the ICI which represents a big problem in many applications and causes a lot of packets loss. It is found that the new hybrid frequency reuse method has noticeable improvement in the amount of packet loss compared to SFR method in the different frequency bands. Traffic congestion management in Intelligent Transportation system (ITS) is one of the important applications that is affected by the packet loss due to the large amount of traffic that is exchanged between the base station and the mobile node. Therefore, it is used as a studied application for the proposed frequency reuse method and the improvement in the amount of packet loss reached 49.4% in some frequency bands using the new hybrid frequency reuse method.

  1. Composable Flexible Real-time Packet Scheduling for Networks on-Chip

    DTIC Science & Technology

    2012-05-16

    should not affect the behaviors of existing applications. In this paper , we propose a composable and flexible work-conserving packet scheduling...to be composable in the sense that new incoming applications should not affect the behaviors of existing applications. In this paper , we propose a...words, real-time flows need to be composable. We set this as the design goal for our packet scheduling discipline developed in this paper . B. Motivating

  2. Radio-Parameter Selection Algorithm for Receiver-Directed Packet-Radio Networks (SRNTN-73)

    DTIC Science & Technology

    1990-01-01

    errors are overcome to some extent by the interleaving capabilities of the LPRs operating in FEC mode . FEC In the SURAP environment a link implements FEC...blocking or channel noise. In contention situations the appropriate action is to minimize packet overlap at the transceiver, and to minimize transmission...receiving node and/or the packet overhead due to coding and channel bit rate. In the second situation the appropriate action is to increase channel gain

  3. Flexible-rate optical packet generation/detection and label swapping for optical label switching networks

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    In recent years, optical label switching (OLS) gains lots of attentions due to its intrinsic advantages to implement protocol, bit-rate, granularity and data format transparency packet switching. In this paper, we propose a novel scheme to realize flexible-rate optical packet switching for OLS networks. At the transmitter node, flexible-rate packet is generated by parallel modulating different combinations of optical carriers generated from the optical multi-carrier generator (OMCG), among which the low-speed optical label occupies one carrier. At the switching node, label is extracted and re-generated in label processing unit (LPU). The payloads are switched based on routing information and new label is added after switching. At the receiver node, another OMCG serves as local oscillators (LOs) for optical payloads coherent detection. The proposed scheme offers good flexibility for dynamic optical packet switching by adjusting the payload bandwidth and could also effectively reduce the number of lasers, modulators and receivers for packet generation/detection. We present proof-of-concept demonstrations of flexible-rate packet generation/detection and label swapping in 12.5 GHz grid. The influence of crosstalk for cascaded label swapping is also investigated.

  4. Trajectory description of the quantum–classical transition for wave packet interference

    SciTech Connect

    Chou, Chia-Chun

    2016-08-15

    The quantum–classical transition for wave packet interference is investigated using a hydrodynamic description. A nonlinear quantum–classical transition equation is obtained by introducing a degree of quantumness ranging from zero to one into the classical time-dependent Schrödinger equation. This equation provides a continuous description for the transition process of physical systems from purely quantum to purely classical regimes. In this study, the transition trajectory formalism is developed to provide a hydrodynamic description for the quantum–classical transition. The flow momentum of transition trajectories is defined by the gradient of the action function in the transition wave function and these trajectories follow the main features of the evolving probability density. Then, the transition trajectory formalism is employed to analyze the quantum–classical transition of wave packet interference. For the collision-like wave packet interference where the propagation velocity is faster than the spreading speed of the wave packet, the interference process remains collision-like for all the degree of quantumness. However, the interference features demonstrated by transition trajectories gradually disappear when the degree of quantumness approaches zero. For the diffraction-like wave packet interference, the interference process changes continuously from a diffraction-like to collision-like case when the degree of quantumness gradually decreases. This study provides an insightful trajectory interpretation for the quantum–classical transition of wave packet interference.

  5. Trajectory description of the quantum-classical transition for wave packet interference

    NASA Astrophysics Data System (ADS)

    Chou, Chia-Chun

    2016-08-01

    The quantum-classical transition for wave packet interference is investigated using a hydrodynamic description. A nonlinear quantum-classical transition equation is obtained by introducing a degree of quantumness ranging from zero to one into the classical time-dependent Schrödinger equation. This equation provides a continuous description for the transition process of physical systems from purely quantum to purely classical regimes. In this study, the transition trajectory formalism is developed to provide a hydrodynamic description for the quantum-classical transition. The flow momentum of transition trajectories is defined by the gradient of the action function in the transition wave function and these trajectories follow the main features of the evolving probability density. Then, the transition trajectory formalism is employed to analyze the quantum-classical transition of wave packet interference. For the collision-like wave packet interference where the propagation velocity is faster than the spreading speed of the wave packet, the interference process remains collision-like for all the degree of quantumness. However, the interference features demonstrated by transition trajectories gradually disappear when the degree of quantumness approaches zero. For the diffraction-like wave packet interference, the interference process changes continuously from a diffraction-like to collision-like case when the degree of quantumness gradually decreases. This study provides an insightful trajectory interpretation for the quantum-classical transition of wave packet interference.

  6. Kelvin wave packets and flow acceleration - A comparison of modeling and observations

    NASA Technical Reports Server (NTRS)

    Coy, L.; Hitchman, M.

    1984-01-01

    Atmospheric Kelvin waves, as revealed by temperatures obtained from the recent Limb Infrared Monitor of the Stratosphere (LIMS) experiment, commonly occur in packets. A simple two-dimensional gravity-wave model is used to study the upward propagation of these packets through different zonal mean wind profiles derived from the LIMS data. The observed prevalence of high frequency waves in the lower mesosphere and low frequency waves in the lower stratosphere can be exlained by dispersion of energy associated with the range of frequencies comprising a packet. Dominant wave frequencies at upper and lower levels are more distinctly separated if the packet propagates through a layer of westerly winds. Due to dispersion and shear effects, a packet of short temporal length at low levels will have a considerably extended impact on a layer of westerly winds at higher levels. Observed and modeled westerly accelerations resulting from packet absorption occur in the same layer, and are similar in magnitude and duration. These results support the theory that Kelvin waves are responsible for the westerly phase of the semiannual oscillation.

  7. Two-tiered partial buffering for contention resolution in optical packet switched networks

    NASA Astrophysics Data System (ADS)

    Dash, Arabind; Jain, Shubham; Gahlot, Amar; Gangopadhyay, Ranjan

    2005-02-01

    The main challenge concerning the design of an optical packet switch is the issue of contention resolution. This paper introduces an optical packet switch architecture, with a two-tiered partially shared buffer using a novel buffer scheduling scheme. The traffic scheduling in the partially shared buffers is done in a hierarchical fashion to ensure the maximum router throughput. We compare the performance of the proposed strategy with single and multiple groups of partially shared buffers, keeping the overall buffer size constant. The performance analysis has been done for a Bernoulli distributed traffic at varying loads. The simulation results indicate a significant improvement in the packet loss probability. A remarkable advantage of the suggested architecture is that it obviates the need for wavelength conversion, thereby achieving a reduction in the infrastructural cost involved in the employment of wavelength converters. The secondary benefits include the elimination of the delay incurred due to searching for the appropriate wavelength and tuning of the wavelength converter. Also, the complexity associated with the accommodation of packets in partially shared buffers is reduced from O(n) to O(1) in comparison to n-groups of partially shared buffers as the search for the least queued partial buffer is replaced by a Boolean decision for every contending packet. Thus, in addition to enhancing the router performance in terms of the packet loss probability, the proposed strategy also augments the router speed.

  8. Storage-Efficient 16-Bit Hybrid IP Traceback with Single Packet

    PubMed Central

    Yang, Ming Hour

    2014-01-01

    Since adversaries may spoof their source IPs in the attacks, traceback schemes have been proposed to identify the attack source. However, some of these schemes' storage requirements increase with packet numbers. Some even have false positives because they use an IP header's fragment offset for marking. Thus, we propose a 16-bit single packet hybrid IP traceback scheme that combines packet marking and packet logging with high accuracy and low storage requirement. The size of our log tables can be bounded by route numbers. We also set a threshold to determine whether an upstream interface number is stored in a log table or in a marking field, so as to balance the logging frequency and our computational loads. Because we store user interface information on small-degree routers, compared with current single packet traceback schemes, ours can have the lowest storage requirements. Besides, our traceback achieves zero false positive/negative rates and guarantees reassembly of fragmented packets at the destination. PMID:25386612

  9. Wave packet dynamics for Gross-Pitaevskii equation in one dimension: Dependence on initial conditions

    NASA Astrophysics Data System (ADS)

    Pal, Sukla; Bhattacharjee, Jayanta K.

    2015-10-01

    The propagation of an initially Gaussian wave packet of width Δ0 in Gross-Pitaevskii equation is extensively studied both for attractive and repulsive interactions. It is predicted analytically and verified numerically that for a free particle with attractive interaction, the dynamics of the width is governed by an effective potential which is sensitive to initial conditions. If Δ0 is equal to a corresponding critical width Δc, then the packet will propagate in time with very little change in shape. These are in essence like coherent states. Whereas, if Δ≠Δc, depending on the nature of the effective potential for chosen Δ0 and the interaction strength (|g|), the width of the packet in course of time, either oscillates with bounded width or will spread like a free particle. For a simple harmonic oscillator (SHO) also, we find that for Δ0 smaller than a critical value, there always exists a coupling strength for which the packet simply oscillates about the mean position without changing its shape, once again providing a resemblance to a coherent state. We also consider the Morse potential, which interpolates between the free particle and the oscillator. For large attractive interactions, the two limiting dynamics (free and simple harmonic) are indeed observed but in the intermediate form of the potential where the nonlinear terms dominate in the dynamics, an initial Gaussian wave packet does not retain its shape. For repulsive interaction, the Gaussian packet always changes shape no matter what the system parameters are.

  10. A novel optoelectronic serial-to-parallel converter for 25-Gbps burst-mode optical packets.

    PubMed

    Ibrahim, Salah; Ishikawa, Hiroshi; Nakahara, Tatsushi; Takahashi, Ryo

    2014-01-13

    A new optoelectronic serial-to-parallel converter (SPC) has been developed to interface 25-Gbps asynchronous optical packets to CMOS circuitry. Other than all previous optoelectronic SPCs that are limited to single-shot operation and hence that can only be used for packet label processing, the SPC presented here can operate repeatedly with a period of as low as 640 ps to perform 1:16 conversion for an entire burst-mode 25-Gbps optical packet. The new SPC adopts a shared-trigger configuration and hence a single device can either convert a single packet or dual packets simultaneously. In this paper, the design and operation of the new SPC is explained after reviewing the fundamentals of performing bit-by-bit serial-to-parallel conversion by using HEMT-arrays and MSM-PDs. The response of the fabricated SPC device is presented and explained, together with the experimental work done to demonstrate 1:16 dual packet conversion at 25 Gbps.

  11. 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.

  12. Expanding Access

    ERIC Educational Resources Information Center

    Roach, Ronald

    2007-01-01

    There is no question that the United States lags behind most industrialized nations in consumer access to broadband Internet service. For many policy makers and activists, this shortfall marks the latest phase in the struggle to overcome the digital divide. To remedy this lack of broadband affordability and availability, one start-up firm--with…

  13. Easy Access

    ERIC Educational Resources Information Center

    Gettelman, Alan

    2009-01-01

    School and university restrooms, locker and shower rooms have specific ADA accessibility requirements that serve the needs of staff, students and campus visitors who are disabled as a result of injury, illness or age. Taking good care of them is good for the reputation of a sensitive community institution, and fosters positive public relations.…

  14. Access Denied

    ERIC Educational Resources Information Center

    Raths, David

    2012-01-01

    As faculty members add online and multimedia elements to their courses, colleges and universities across the country are realizing that there is a lot of work to be done to ensure that disabled students (and employees) have equal access to course material and university websites. Unfortunately, far too few schools consider the task a top priority.…

  15. General Solution for Theoretical Packet Data Loss Rate

    NASA Technical Reports Server (NTRS)

    Lansdowne, Chatwin; Schlesinger, Adam

    2006-01-01

    Communications systems which transfer blocks ("frames") of data must use a marker ("frame synchronization pattern") for identifying where a block begins. A technique ("frame synchronization strategy") is used to locate the start of each frame and maintain synchronization as additional blocks are processed. A device which strips out the frame synchronization pattern [FSP] and provides an "end of frame" pulse is called a frame synchronizer. As clock and data errors are introduced into the system, the start-of-block marker becomes displaced and/or corrupted. The capability of the frame synchronizer to stay locked to the pattern under these conditions is a figure of merit for the frame synchronization strategy. It is important to select a strategy which will stay locked nearly all the time at bit error rates where the data is usable. ("Bit error rate" [BER] is the fraction of binary bits which are inverted by passage through a communication system.) The fraction of frames that are discarded because the frame synchronizer is not locked is called "Percent Data Loss" or "Packet Data Loss rate" [PDL]. A general approach for accurately predicting PDL given BER was developed in Theoretical Percent Data Loss Calculation and Measurement Accuracy, T. P. Kelly, LESC-30554, December 1992. Kelly gave a solution in terms of matrix equations, and only addressed "level" channel encoding. This paper goes on to give a closed-form polynomial solution for the most common class of frame synchronizer strategies, and will also address "mark" and "space" (differential) channel encoding, and burst error environments. The paper is divided into four sections and follows a logically ordered presentation, with results developed before they are evaluated. However, most readers will derive the greatest benefit from this paper by treating the results as reference material. The result developed for differential encoding can be extended to other applications (like block codes) where the probability is

  16. Pilot-Aided Channel Estimation for WiMAX 802.16e Downlink Partial Usage of Subchannel System Using Least Squares Line Fitting

    NASA Astrophysics Data System (ADS)

    Pham, Phuong Thi Thu; Wada, Tomohisa

    This paper presents a pilot-aided channel estimation method which is particularly suitable for mobile WiMAX 802.16e Downlink Partial Usage of Subchannel mode. Based on this mode, several commonly used channel estimation methods are studied and the method of least squares line fitting is proposed. As data of users are distributed onto permuted clusters of subcarriers in the transmitted OFDMA symbol, the proposed channel estimation method utilizes these advantages to provide better performance than conventional approaches while offering remarkably low complexity in practical implementation. Simulation results with different ITU-channels for mobile environments show that depending on situations, enhancement of 5dB or more in term of SNR can be achieved.

  17. Portable color multimedia training systems based on monochrome laptop computers (CBT-in-a-briefcase), with spinoff implications for video uplink and downlink in spaceflight operations

    NASA Technical Reports Server (NTRS)

    Scott, D. W.

    1994-01-01

    This report describes efforts to use digital motion video compression technology to develop a highly portable device that would convert 1990-91 era IBM-compatible and/or MacIntosh notebook computers into full-color, motion-video capable multimedia training systems. An architecture was conceived that would permit direct conversion of existing laser-disk-based multimedia courses with little or no reauthoring. The project did not physically demonstrate certain critical video keying techniques, but their implementation should be feasible. This investigation of digital motion video has spawned two significant spaceflight projects at MSFC: one to downlink multiple high-quality video signals from Spacelab, and the other to uplink videoconference-quality video in realtime and high quality video off-line, plus investigate interactive, multimedia-based techniques for enhancing onboard science operations. Other airborne or spaceborne spinoffs are possible.

  18. Long-term exposure to mobile communication radiation: an analysis of time-variability of electric field level in GSM900 downlink channels.

    PubMed

    Miclaus, Simona; Bechet, Paul; Gheorghevici, Marius

    2013-04-01

    Interest for knowing long-term human exposure levels due to mobile communications has increased in the last years. It has been shown that short-term exposure assessment made under standard procedural restrictions is not reliable when it comes to conclusions on long-term exposure levels. The present work is the result of a several week analysis of time variability of electric field level inside traffic and control channels of the GSM900 mobile communication downlink band and it indicates that a temporal model to allow future predictions of exposure on the long run is obtainable. Collecting, processing and statistically analysing the data provide expression of the maximum and weighted field strengths and their evolution in time. Specific electromagnetic footprints of the channels have been extracted, differentiations between their characteristics have been emphasised and practical advice is provided, with the scope of contributing to the development of reliable procedures for long-term exposure assessment.

  19. Multi-function all optical packet switch by periodic wavelength arrangement in an arrayed waveguide grating and wideband optical filters.

    PubMed

    Feng, Kai-Ming; Wu, Chung-Yu; Wen, Yu-Hsiang

    2012-01-16

    By utilizing the cyclic filtering function of an NxN arrayed waveguide grating (AWG), we propose and experimentally demonstrate a novel multi-function all optical packet switching (OPS) architecture by applying a periodical wavelength arrangement between the AWG in the optical routing/buffering unit and a set of wideband optical filters in the switched output ports to achieve the desired routing and buffering functions. The proposed OPS employs only one tunable wavelength converter at the input port to convert the input wavelength to a designated wavelength which reduces the number of active optical components and thus the complexity of the traffic control is simplified in the OPS. With the proposed OPS architecture, multiple optical packet switching functions, including arbitrary packet switching and buffering, first-in-first-out (FIFO) packet multiplexing, packet demultiplexing and packet add/drop multiplexing, have been successfully demonstrated.

  20. Investigation of the photodetached electronic wave packet dynamics in a magnetic field near a surface

    NASA Astrophysics Data System (ADS)

    Chen, Zhaohang; Wang, Dehua; Cheng, Shaohao

    2017-01-01

    The electronic wave packet dynamics photodetached from H- ion in a magnetic field near an elastic surface has been studied by using the time-dependent perturbation theory combined with the semiclassical closed orbit theory for the first time. Firstly, we put forward an analytic formula for calculating the autocorrelation function of this system. Then we calculate and analyze the autocorrelation function in great detail. It is demonstrated that the quantum wave packet revival phenomenon is significant when the laser pulse width is far less than the period of the detached electron's closed orbit. As the pulse width is close to the period of the detached electron's closed orbit, the quantum wave packet revival phenomenon becomes weakened. When the laser pulse width is bigger than the period of the closed orbit of the detached electron, the adjacent revival peaks in the autocorrelation function begin to merge and the quantum revival phenomenon disappears. In addition, the magnetic field strength can also affect the autocorrelation function of this system. As the magnetic field strength is relatively small, the quantum wave packet revival phenomenon is weak. With the increase of the magnetic field strength, the number of the reviving peaks in the autocorrelation function becomes increased and the quantum wave packet revival phenomenon becomes significant. Therefore, we can control the quantum wave packet revival in the autocorrelation function of this system by changing the laser pulse width and the external magnetic field strength. This study can guide the future experimental research on the wave packet dynamics of atoms or ions in the external fields or surfaces.

  1. On the Performance of Non-Orthogonal Multiple Access in 5G Systems with Randomly Deployed Users

    NASA Astrophysics Data System (ADS)

    Ding, Zhiguo; Yang, Zheng; Fan, Pingzhi; Poor, H. Vincent

    2014-12-01

    In this letter, the performance of non-orthogonal multiple access (NOMA) is investigated in a cellular downlink scenario with randomly deployed users. The developed analytical results show that NOMA can achieve superior performance in terms of ergodic sum rates; however, the outage performance of NOMA depends critically on the choices of the users' targeted data rates and allocated power. In particular, a wrong choice of the targeted data rates and allocated power can lead to a situation in which the user's outage probability is always one, i.e. the user's targeted quality of service will never be met.

  2. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - hemodialysis access; dialysis - hemodialysis ...

  3. Phase-shift migration with wave-packet algorithms

    NASA Astrophysics Data System (ADS)

    Mosher, Charles C.; Foster, Douglas J.; Wu, Ru-Shan

    1996-10-01

    Wavelet transforms have a simple representation in the frequency domain (Daubchies, 1992; Veterlli and Herley, 1992; Mosher and Foster, 1995). Since wave propagation also has a simple representation in the frequency domain, frequency domain wavelet transforms provide a useful framework for studying the nature of wave propagation in the wavelet domain. In this paper, we study phase shift extrapolators for 2-dimensional wavefields that have been Fourier transformed over time and wavelet transformed over space. The wavelet transform over the space axis is implemented in the wavenumber-frequency domain by complex multiplication of low and high pass wavenumber filter functions to form wave packet trees. To differentiate this operation from time-frequency wavelet transforms, we refer to the space-wavenumber-frequency transform as the 'beamlet transform.' The interaction of beamlet transform filter banks and phase shift wavefield extrapolators are simple complex multiplications. Wavefield propagation in the beamlet domain is complicated, however, by the digital implementation of decimation and upsampling operators used in orthogonal wavelet transforms. Unlike the filter functions, which can be viewed as diagonal matrix operators, the decimation and upsampling operators have significant off-diagonal terms. Since these operators do not commute with the filter and phase shift operators, the effects of the non-diagonal operators must be accounted for in the application of wave propagation operators. A simple (but unsatisfying) solution would be to apply forward-inverse transforms at each extrapolation step. Beamlet transforms with compact support in the wavenumber domain (Mosher and Foster, 1995) provide an alternate solution. Analysis of phase shift migration in the beamlet domain yields a simple matrix representation defining the interaction of filters, phase operators, and decimation/upsampling. The effects of decimation/upsampling are represented by simple folding

  4. Support for non-locking parallel reception of packets belonging to a single memory reception FIFO

    DOEpatents

    Chen, Dong [Yorktown Heights, NY; Heidelberger, Philip [Yorktown Heights, NY; Salapura, Valentina [Yorktown Heights, NY; Senger, Robert M [Yorktown Heights, NY; Steinmacher-Burow, Burkhard [Boeblingen, DE; Sugawara, Yutaka [Yorktown Heights, NY

    2011-01-27

    A method and apparatus for distributed parallel messaging in a parallel computing system. A plurality of DMA engine units are configured in a multiprocessor system to operate in parallel, one DMA engine unit for transferring a current packet received at a network reception queue to a memory location in a memory FIFO (rmFIFO) region of a memory. A control unit implements logic to determine whether any prior received packet destined for that rmFIFO is still in a process of being stored in the associated memory by another DMA engine unit of the plurality, and prevent the one DMA engine unit from indicating completion of storing the current received packet in the reception memory FIFO (rmFIFO) until all prior received packets destined for that rmFIFO are completely stored by the other DMA engine units. Thus, there is provided non-locking support so that multiple packets destined for a single rmFIFO are transferred and stored in parallel to predetermined locations in a memory.

  5. Phase Structure of Strong-Field Tunneling Wave Packets from Molecules.

    PubMed

    Liu, Ming-Ming; Li, Min; Wu, Chengyin; Gong, Qihuang; Staudte, André; Liu, Yunquan

    2016-04-22

    We study the phase structure of the tunneling wave packets from strong-field ionization of molecules and present a molecular quantum-trajectory Monte Carlo model to describe the laser-driven dynamics of photoelectron momentum distributions of molecules. Using our model, we reproduce and explain the alignment-dependent molecular frame photoelectron spectra of strong-field tunneling ionization of N_{2} reported by M. Meckel et al. [Nat. Phys. 10, 594 (2014)]. In addition to modeling the low-energy photoelectron angular distributions quantitatively, we extract the phase structure of strong-field molecular tunneling wave packets, shedding light on its physical origin. The initial phase of the tunneling wave packets at the tunnel exit depends on both the initial transverse momentum distribution and the molecular internuclear distance. We further show that the ionizing molecular orbital has a critical effect on the initial phase of the tunneling wave packets. The phase structure of the photoelectron wave packet is a key ingredient for modeling strong-field molecular photoelectron holography, high-harmonic generation, and molecular orbital imaging.

  6. Using optical wavelet packet transform to improve the performance of an optoelectronic iris recognition system

    NASA Astrophysics Data System (ADS)

    Cai, De; Tan, Qiaofeng; Yan, Yingbai; Jin, Guofan; He, Qingsheng

    2005-01-01

    Iris, one important biometric feature, has unique advantages: it has complex texture and is almost unchanged for the lifespan. So iris recognition has been widely studied for intelligent personal identification. Most of researchers use wavelets as iris feature extractor. And their systems obtain high accuracy. But wavelet transform is time consuming, so the problem is to enhance the useful information but still keep high processing speed. This is the reason we propose an opto-electronic system for iris recognition because of high parallelism of optics. In this system, we use eigen-images generated corresponding to optimally chosen wavelet packets to compress the iris image bank. After optical correlation between eigen-images and input, the statistic features are extracted. Simulation shows that wavelet packets preprocessing of the input images results in higher identification rate. And this preprocessing can be fulfilled by optical wavelet packet transform (OWPT), a new optical transform introduced by us. To generate the approximations of 2-D wavelet packet basis functions for implementing OWPT, mother wavelet, which has scaling functions, is utilized. Using the cascade algorithm and 2-D separable wavelet transform scheme, an optical wavelet packet filter is constructed based on the selected best bases. Inserting this filter makes the recognition performance better.

  7. A Hybrid CPU/GPU Pattern-Matching Algorithm for Deep Packet Inspection

    PubMed Central

    Chen, Yaw-Chung

    2015-01-01

    The large quantities of data now being transferred via high-speed networks have made deep packet inspection indispensable for security purposes. Scalable and low-cost signature-based network intrusion detection systems have been developed for deep packet inspection for various software platforms. Traditional approaches that only involve central processing units (CPUs) are now considered inadequate in terms of inspection speed. Graphic processing units (GPUs) have superior parallel processing power, but transmission bottlenecks can reduce optimal GPU efficiency. In this paper we describe our proposal for a hybrid CPU/GPU pattern-matching algorithm (HPMA) that divides and distributes the packet-inspecting workload between a CPU and GPU. All packets are initially inspected by the CPU and filtered using a simple pre-filtering algorithm, and packets that might contain malicious content are sent to the GPU for further inspection. Test results indicate that in terms of random payload traffic, the matching speed of our proposed algorithm was 3.4 times and 2.7 times faster than those of the AC-CPU and AC-GPU algorithms, respectively. Further, HPMA achieved higher energy efficiency than the other tested algorithms. PMID:26437335

  8. Parametric Packet-Layer Model for Evaluation Audio Quality in Multimedia Streaming Services

    NASA Astrophysics Data System (ADS)

    Egi, Noritsugu; Hayashi, Takanori; Takahashi, Akira

    We propose a parametric packet-layer model for monitoring audio quality in multimedia streaming services such as Internet protocol television (IPTV). This model estimates audio quality of experience (QoE) on the basis of quality degradation due to coding and packet loss of an audio sequence. The input parameters of this model are audio bit rate, sampling rate, frame length, packet-loss frequency, and average burst length. Audio bit rate, packet-loss frequency, and average burst length are calculated from header information in received IP packets. For sampling rate, frame length, and audio codec type, the values or the names used in monitored services are input into this model directly. We performed a subjective listening test to examine the relationships between these input parameters and perceived audio quality. The codec used in this test was the Advanced Audio Codec-Low Complexity (AAC-LC), which is one of the international standards for audio coding. On the basis of the test results, we developed an audio quality evaluation model. The verification results indicate that audio quality estimated by the proposed model has a high correlation with perceived audio quality.

  9. A Hybrid CPU/GPU Pattern-Matching Algorithm for Deep Packet Inspection.

    PubMed

    Lee, Chun-Liang; Lin, Yi-Shan; Chen, Yaw-Chung

    2015-01-01

    The large quantities of data now being transferred via high-speed networks have made deep packet inspection indispensable for security purposes. Scalable and low-cost signature-based network intrusion detection systems have been developed for deep packet inspection for various software platforms. Traditional approaches that only involve central processing units (CPUs) are now considered inadequate in terms of inspection speed. Graphic processing units (GPUs) have superior parallel processing power, but transmission bottlenecks can reduce optimal GPU efficiency. In this paper we describe our proposal for a hybrid CPU/GPU pattern-matching algorithm (HPMA) that divides and distributes the packet-inspecting workload between a CPU and GPU. All packets are initially inspected by the CPU and filtered using a simple pre-filtering algorithm, and packets that might contain malicious content are sent to the GPU for further inspection. Test results indicate that in terms of random payload traffic, the matching speed of our proposed algorithm was 3.4 times and 2.7 times faster than those of the AC-CPU and AC-GPU algorithms, respectively. Further, HPMA achieved higher energy efficiency than the other tested algorithms.

  10. Higher order dispersion in the propagation of a gravity wave packet

    NASA Technical Reports Server (NTRS)

    Yeh, K. C.; Dong, B.

    1989-01-01

    To the first order of approximation, the complex amplitude of a wave packet in an anisotropic and dispersive medium is convected with the group of velocity. However, a gravity wave is a vector wave. Its wave packet must be formed by superposition of various wave numbers with corresponding frequencies, as is the case for scalar waves, and additionally by superposing many eigenmodes which also depend on the wave number. To represent the vector wave packet self-consistently, it is found that a gradient term must be included in the expansion. For a Guassian wave packet, this gradient term is shown to have important implications on the velocity vector as represented by its hodograph. Numerical results show that the hodograph is influenced by the location of the relative position of interest from the center of a Gaussian pulse. Higher order expansion shows that an initial Gaussian wave packet will retain its Gaussian shape as it propagates, but the pulse will spread in all directions with its major axis undergoing a rotation. Numerical results indicate that these higher order dispersive effects may be marginally observable in the atmosphere.

  11. Full-duplex RoF link with broadband mm-wave signal in W-band based on WDM-PON access network with optical mm-wave local oscillator broadcasting

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin; Zhang, Ruijiao; Li, Yanjie; Zhang, Qi; Yu, Jianguo

    2015-02-01

    A novel full-duplex link with an optical mm-wave local oscillator broadcasting for broadband millimeter (mm)-wave wireless access in W-band is proposed based on the WDM-PON-RoF. In our scheme, a universal optical mm-wave local oscillator in W-band is distributed over the whole network to up-convert the downlink IF optical signal, which not only improves the spectrum efficiency by reducing the bandwidth requirement of each downlink, but also decreases the degradation caused by the fiber chromatic dispersion. Moreover, since the incoherently down-converted uplink signal is modulated on the reused blank optical carrier extracted from the downlink signal, the base stations (BSs) need no optical source, and so its structure is simplified. The numerical simulation results agree well with the theoretical analysis and show that the proposed full-duplex link for the W-band wireless access based on WDM-PON-RoF maintains good performance with cost effective implement.

  12. Adaptive control of the packet transmission period with solar energy harvesting prediction in wireless sensor networks.

    PubMed

    Kwon, Kideok; Yang, Jihoon; Yoo, Younghwan

    2015-04-24

    A number of research works has studied packet scheduling policies in energy scavenging wireless sensor networks, based on the predicted amount of harvested energy. Most of them aim to achieve energy neutrality, which means that an embedded system can operate perpetually while meeting application requirements. Unlike other renewable energy sources, solar energy has the feature of distinct periodicity in the amount of harvested energy over a day. Using this feature, this paper proposes a packet transmission control policy that can enhance the network performance while keeping sensor nodes alive. Furthermore, this paper suggests a novel solar energy prediction method that exploits the relation between cloudiness and solar radiation. The experimental results and analyses show that the proposed packet transmission policy outperforms others in terms of the deadline miss rate and data throughput. Furthermore, the proposed solar energy prediction method can predict more accurately than others by 6.92%.

  13. Moving the boundary between wavelength resources in optical packet and circuit integrated ring network.

    PubMed

    Furukawa, Hideaki; Miyazawa, Takaya; Wada, Naoya; Harai, Hiroaki

    2014-01-13

    Optical packet and circuit integrated (OPCI) networks provide both optical packet switching (OPS) and optical circuit switching (OCS) links on the same physical infrastructure using a wavelength multiplexing technique in order to deal with best-effort services and quality-guaranteed services. To immediately respond to changes in user demand for OPS and OCS links, OPCI networks should dynamically adjust the amount of wavelength resources for each link. We propose a resource-adjustable hybrid optical packet/circuit switch and transponder. We also verify that distributed control of resource adjustments can be applied to the OPCI ring network testbed we developed. In cooperation with the resource adjustment mechanism and the hybrid switch and transponder, we demonstrate that automatically allocating a shared resource and moving the wavelength resource boundary between OPS and OCS links can be successfully executed, depending on the number of optical paths in use.

  14. Stability of linear dynamic systems over the packet erasure channel: a co-design approach

    NASA Astrophysics Data System (ADS)

    Farhadi, Alireza

    2015-12-01

    This paper is concerned with the stability of linear time-invariant dynamic systems over the packet erasure channel subject to minimum bit rate constraint when an encoder and a decoder are unaware of the control signal. This assumption results in co-designing the encoder, decoder and controller. The encoder, decoder, controller and conditions relating transmission rate to packet erasure probability and eigenvalues of the system matrix A are presented for almost sure asymptotic stability of linear time-invariant dynamic systems over the packet erasure channel with feedback acknowledgment. When the eigenvalues of the system matrix A are real valued, it is shown that the obtained condition for stability is tight. Simulation result illustrates the satisfactory performance of the proposed encoder, decoder and controller for almost sure asymptotic stability.

  15. Output-feedback MRAC of networked control systems with packet dropout

    NASA Astrophysics Data System (ADS)

    Tahoun, A. H.

    2013-09-01

    In this article, a technique of output-feedback model reference adaptive control for networked control systems is developed. The key issues of networked control systems such as channel bandwidth and data-packets dropout induced by the insertion of data networks in the feedback adaptive control loops are considered. The advantage of this article over earlier ones is that the combination of different aspects in networked control systems, output-feedback model reference control of systems with unknown parameters, and unknown data-packets dropout. Error models, adaptive laws, and stability analysis are derived in the case of uncertainty due to data-packets dropout. The applicability of the approach is demonstrated in a practical numerical example of a ship-steering adaptive system.

  16. Finite-time boundedness and stabilisation of networked control systems with bounded packet dropout

    NASA Astrophysics Data System (ADS)

    Sun, Yeguo

    2014-09-01

    In this paper, the finite-time boundedness and stabilisation problems of a class of networked control systems (NCSs) with bounded packet dropout are investigated. The main results provided in the paper are sufficient conditions for finite-time boundedness and stability via state feedback. An iterative approach is proposed to model NCSs with bounded packet dropout as jump linear systems (JLSs). Based on Lyapunov stability theory and JLSs theory, the sufficient conditions for finite-time boundedness and stabilisation of the underlying systems are derived via linear matrix inequalities (LMIs) formulation. Moreover, both sensor-to-controller and controller-to-actuator packet dropouts are considered simultaneously. Lastly, an illustrative example is given to demonstrate the effectiveness of the proposed results.

  17. Juxtaposing density matrix and classical path-based wave packet dynamics

    PubMed Central

    Aghtar, Mortaza; Liebers, Jörg; Strümpfer, Johan; Schulten, Klaus; Kleinekathöfer, Ulrich

    2012-01-01

    In many physical, chemical, and biological systems energy and charge transfer processes are of utmost importance. To determine the influence of the environment on these transport processes, equilibrium molecular dynamics simulations become more and more popular. From these simulations, one usually determines the thermal fluctuations of certain energy gaps, which are then either used to perform ensemble-averaged wave packet simulations, also called Ehrenfest dynamics, or to employ a density matrix approach via spectral densities. These two approaches are analyzed through energy gap fluctuations that are generated to correspond to a predetermined spectral density. Subsequently, density matrix and wave packet simulations are compared through population dynamics and absorption spectra for different parameter regimes. Furthermore, a previously proposed approach to enforce the correct long-time behavior in the wave packet simulations is probed and an improvement is proposed. PMID:22697524

  18. Packet Format Design and Decision Directed Tracking Methods for Filter Bank Multicarrier Systems

    NASA Astrophysics Data System (ADS)

    Amini, Peiman; Farhang-Boroujeny, Behrouz

    2010-12-01

    Packetized data transmission is commonly used in wireless communication systems. Each packet starts with a preamble which is used to synchronize the receiver with carrier frequency of the incoming signal, to find a good timing phase, and to identify the channel impulse response or to adjust a set of channel equalizer parameters. In this paper, following the same philosophy, we develop a packet format for multicarrier systems that operate based on filter banks, filter bank multicarrier (FBMC) systems. The related algorithms for carrier frequency and timing recovery as well as channel identification/equalizer adjustment and methods for carrier and timing tracking loops are proposed. The proposed ideas are evaluated and their satisfactory performance are presented through computer simulations.

  19. Adaptive wavelet packet-based de-speckling of ultrasound images with bilateral filter.

    PubMed

    Esakkirajan, Sankaralingam; Vimalraj, Chinna Thambi; Muhammed, Rashad; Subramanian, Ganapathi

    2013-12-01

    A new adaptive wavelet packet-based approach to minimize speckle noise in ultrasound images is proposed. This method combines wavelet packet thresholding with a bilateral filter. Here, the best bases after wavelet packet decomposition are selected by comparing the first singular value of all sub-bands, and the noisy coefficients are thresholded using a modified NeighShrink technique. The algorithm is tested with various ultrasound images, and the results, in terms of peak signal-to-noise ratio and mean structural similarity values, are compared with those for some well-known de-speckling techniques. The simulation results indicate that the proposed method has better potential to minimize speckle noise and retain fine details of the ultrasound image.

  20. Three-dimensional time-dependent wave-packet calculations of OBrO absorption spectra

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Sun, Zhigang; Cong, Shu-Lin; Lou, Nanquan

    2005-08-01

    The absorption spectra of the C(A22)←X(B12) transition of the OBrO molecule are calculated using three-dimensional time-dependent wave-packet method in Radau coordinates for a total angular momentum J =0. The wave packet is propagated using the split operator technique associated with fast Fourier transform. Employing the basis functions obtained by one-dimensional Fourier grid Hamiltonian method, the initial wave packet is calculated directly on the three-dimensional Fourier grid. The numerical model is characterized by simplicity and efficiency. The ab initio potential surfaces for the C(A22) and X(B12) states are used in the calculation. The calculated absorption spectra of the C(A22)←X(B12) transition of OBrO molecule agree well with the experimental results.