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IEEE International Conference on Personal Wireless Communication

作者： Hasung Kim G.L. Struber Wireless Systems Laboratory School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA USA

ISBN: (纸本)0780358937

3G mobile multimedia communication systems based on W-CDMA support a flexible and adaptive transmission capability to provide packet data service as well as voice service. Mobile multimedia communication requires a coding scheme that can accommodate varying code rate requirements. RCPC (rate compatible punctured convolutional) codes are one practical solution to adaptive coding. RCPC codes use a single rate-1/n convolutional encoder/decoder pair and the transmitter and receiver only need to share a puncturing table. RCPT (rate compatible punctured turbo) codes can be used in a similar way to RCPC codes. This paper considers the application of concatenated RS-RCPT codes and RCPT-HARQ (hybrid ARQ) schemes to W-CDMA.

关键词： Turbo codes Multiaccess communication Multimedia communication Convolutional codes Multimedia systems Mobile communication adaptive coding Decoding Transmitters Concatenated codes

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ATM and Internet via satellite

ATM and Internet via satellite

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MILCOM, Military Communications Conference

作者： P. Chitre COMSAT Laboratories Clarksburg MD USA

ISBN: (纸本)0780365216

The twenty-first century military communications will depend critically on satellite systems for their global reach. The two major networking technologies underlying the global information infrastructure (GII) will be asynchronous transfer mode (ATM) and Internet (IP). The seamless operation of ATM and Internet over the hybrid (satellite and terrestrial) GII will be essential for the unhampered access, dissemination and exchange of information. However, there are major challenges to achieve seamless operation for ATM and Internet via satellite systems. Specific issues related to asynchronous transfer mode (ATM) and internet standards to function efficiently and provide high-quality service over satellite links and networks are discussed. Standardization activities for terrestrial and satellite interoperability of ATM and Internet Protocols (IP) are described. New technologies developed to address these issues are presented, including dynamic adaptive coding, data compression, Transmission Control Protocol (TCP) Proxy, bandwidth on demand, and traffic management. These technologies are currently incorporated in COMSAT Laboratories products such as COMSAT Link Accelerators for ATM and IP and the LINKWAY/sup TM/ 2000.

关键词： Asynchronous transfer mode Military satellites IP networks Protocols Military communication Artificial satellites Web and internet services Standardization adaptive coding Data compression

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Low complexity adaptive code tracking with improved multipath resolution for DS-CDMA communications over fading channels

Low complexity adaptive code tracking with improved multipat...

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IEEE International Symposium on Spread Spectrum Techniques and Applications

作者： P. Schulz-Rittich G. Fock J. Baltersee H. Meyr Institute for Integrated Signal Processing Systems RWTH Aachen University of Technology Aachen Germany

A new adaptive timing error detector (TED) embedded in a code-tracking loop for RAKE reception of direct sequence-CDMA signals is presented. The loop consists of a digital coherent TED and a loop filter with lowpass characteristic. In a multipath fading environment, one such loop can be allocated for each finger in a RAKE receiver and the interference from adjacent paths can be mitigated by adaptively prefiltering the signal prior to the correlation process. The filter coefficients are computed online in order to minimize an interference cost function. Multipaths whose delays differ by as little as one chip duration become resolvable and can be tracked, resulting in significant performance gains of the overall system, especially if the channel delay spread is small. The tracking performance of the proposed loop is assessed by computer simulation.

关键词： adaptive coding Fading Interference Delay Timing adaptive signal detection Detectors Digital filters Fingers Multipath channels

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Combined power/code rate adaptation in Reed-Solomon coded frequency-hopped spread-spectrum multiple access communications

Combined power/code rate adaptation in Reed-Solomon coded fr...

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IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： Jik Dong Kim Sang Wu Kim Department of Electrical Engineering Korea Advanced Institute of Science and Technology Daejeon South Korea

We consider a combined power/code rate adaptation in Reed-Solomon (RS) coded frequency-hopped spread-spectrum multiple access (FH/SSMA) communications, where the transmission power and code rate are adapted simultaneously relative to the channel traffic and channel fading. We investigate the optimal transmission strategy that minimizes the required signal-to-noise ratio for a given error performance, and the performance improvement provided by the optimal strategy over adaptive code rate control and adaptive power control. We show that the combined power/rate control provides an asymptotic power gain of 5.67 dB over adaptive code rate control.

关键词： Reed-Solomon codes adaptive coding Frequency Spread spectrum communication Communication system traffic control Fading Signal to noise ratio Error correction codes Optimal control Communication system control

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A spatially-adaptive bus interface for low-switching communication

A spatially-adaptive bus interface for low-switching communi...

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International Symposium on Low Power Electronics and Design (ISLPED)

作者： A. Acquaviva R. Scarsi Universita di Bologna Bologna Italy Politecnico di Turino Torino Italy

adaptive encoding has been shown to be an effective approach to bus power minimization in situations where characterization of the input statistics is not available. In this paper, we propose a novel technique for adaptive bus encoding that, conversely from existing solutions, exploits spatial correlations in the input data being transmitted to increase the accuracy in the dynamic selection of the encoding function. We discuss the encoding algorithm and we describe an architecture for its implementation as bus interface. We present experimental data collected in a realistic simulation framework on a number of meaningful benchmarks, and we compare them to those obtained through the application of existing encoding schemes.

关键词： Encoding Statistics Codecs Decoding adaptive coding Permission Capacitance Communication switching Logic design Decorrelation

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A scalable architecture for active networks

A scalable architecture for active networks

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IEEE Conference on Open Architectures and Network Programming

作者： R. Sivakumar Sung-Wook Han V. Bharghavan Coordinated Science Laboratory University of Illinois Urbana-Champaign USA

Explores the network-level issues that deal with the organization, interaction and deployment of active routers in a network. We have identified and answered four sets of questions: (i) Where should active routers be placed in the network? What is the network organization of active routers that achieves a good tradeoff between scalability and flexibility? (ii) If all routers in the network are not active, then how can we abstract the state of the "non-active" portion of the network for services that reside in active routers? (iii) How do active routers discover and communicate with other active routers? What is the infrastructure for the management, discovery and communication of active routers? (iv) How do users discover the available (third-party) active services in the network? What is the infrastructure for the dissemination, discovery and composition of active services? We present a network organization of active routers and describe two key network-level constructs-the equivalent link abstraction and the spine network management infrastructure-that enable the deployment of a scalable and flexible active network. We finally present some preliminary simulation and implementation results to demonstrate the efficacy of the proposed architecture.

关键词： Scalability adaptive coding Quality of service

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Single sided MPI implementations for SUN MPI

Single sided MPI implementations for SUN MPI

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Supercomputing Conference

作者： S. Booth E. Mourao EPCC University of Edinburgh Edinburgh UK

This paper describes an implementation of generic MPI-2 single sided communications for SUN-MPI. Our implementation is layered on top of point-to-point MPI communications and therefore can be adapted to other MPI implementations. The code is designed to co-exist with other MPI-2 single sided implementations (for example direct use of shared memory) providing a generic fall-back implementation for those communication paths where an optimised single-sided implementation is not available. MPI-2 single sided communications require the transfer of data-type information as well as user data. We describe a type packing and caching mechanism used to optimise the transfer of data-type information. The performance of this implementation is measured in comparison to equivalent point to point operations and the shared memory implementation provided by SUN.

关键词： Sun Protocols Application software Software libraries Communication standards Buildings Design optimization Message passing adaptive coding Data structures

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Comparative study of adaptive-rate CDMA transmission employing joint-detection and interference cancellation

Comparative study of adaptive-rate CDMA transmission employi...

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IEEE Conference on Vehicular Technology (VTC)

作者： E.L. Kuan L. Hanzo Department of Electronics and Computer Science University of Southampton Southampton UK

Spread adaptive quadrature amplitude modulation (AQAM) is proposed as a powerful means of exploiting the time variant channel capacity fluctuations of wireless channels and studied in comparison to the variable spreading factor (VSF) method. These two adaptive rate transmission methods are compared in the context of joint detection and interference cancellation assisted adaptive code division multiple access (ACDMA) systems. More explicitly, these exploit the time-variant channel quality of mobile channels by switching either the modulation mode (AQAM) or the spreading factor (VSF) on a burst-by-burst basis. The most appropriate modulation mode or spreading factor is chosen based on the instantaneous channel quality estimated. The chosen AQAM mode or spreading factor is communicated to the remote receiver either through explicit signalling or extracted at the receiver using blind detection techniques. The multiuser joint detector (JD) and the successive interference cancellation (SIC) receiver are compared in the context of these adaptive schemes with the conclusion that JD outperformed the SIC receiver in the ACDMA schemes, at the cost of increased complexity.

关键词： Multiaccess communication Interference cancellation Silicon carbide Quadrature amplitude modulation Channel capacity Fluctuations adaptive coding Detectors Context Costs

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An integrated framework for adaptive subband image coding

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 1999年第4期47卷 1024-1038页

作者： Pavlovic, V Moulin, P Ramchandran, K Compaq Comp Corp Cambridge Res Lab Cambridge MA 02139 USA Univ Illinois Beckman Inst Urbana IL 61801 USA Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA

Recent work on filter banks and related expansions has revealed an interesting insight: Different filter bank trees can be regarded as different ways of constructing orthonormal bases: for linear signal expansion, In particular, fast algorithms for finding best bases in an operational rate-distortion (R/D) sense hare been successfully used in image coding, Independently of this work, recent research has also explored the design of filter banks that optimize energy compaction for a single signal or a class of signals. In this paper, we integrate these two different but complementary approaches to best-basis design and propose a coding paradigm in which subband filters, tree structure, and quantizers are chosen to optimize R/D performance, These coder attributes represent side information. They are selected from a codebook designed off-line from training data, using RID as the design criterion. This approach provides a rational framework in which to explore alternatives to empirical design of filter banks, quantizers, and other coding parameters. The on-line coding algorithm is a relatively simple extension of current R/D-optimal coding algorithms that operate,vith fixed filter banks and empirically designed quantizer codebooks. In particular, it is shown that selection of the best adapted filter bank from the codebook is computationally elementary.

关键词： adaptive coding best basis methods filter banks image compression rate-distortion methods subband coding vector quantization

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Dynamic codebook adaptive vector quantization for image coding

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IEEE TRANSACTIONS ON CONSUMER ELECTRONICS 1999年第2期45卷 327-332页

作者： Feng, J Lo, KT City Univ Hong Kong Dept Elect Engn Tat Che Ave Kowloon Peoples R China Hong Kong Polytech Univ Dept Elect & Informat Engn Kowloon Peoples R China

In this paper, a new image coding scheme called dynamic codebook adaptive vector quantization (DCAVQ) is proposed. DCAVQ is designed to minimize the transmission overhead and computational complexity of existing adaptive vector quantization systems. Simulation results using real images demonstrate both subjective and objective performance of decoded images are improved using the proposed method. On the ether hand, the execution time of the system is being comparable to that of a standard universal VQ system.

关键词： Vector quantization Image coding Image reconstruction Statistics Rate-distortion Character generation Bit rate Transform coding adaptive coding

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