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AN adaptive coding SCHEME WITH CODE COMBINING FOR MOBILE RADIO SYSTEMS

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 1993年第4期42卷 469-476页

作者： DENG, RH ZHOU, H Department of Electrical Engineering National University of Singapore Singapore

In this paper, we propose and study an adaptive error-control coding scheme for binary digital FM (BFM) mobile radio transmission. The scheme employs code combining through packet retransmissions. The number of transmissions of a packet is in proportion to the channel fading/noise levels, which is in contrast to time diversity techniques where a fixed number of repetitions of a data packet is performed even in the absence of channel errors. Furthermore, the receiver uses received signal envelopes as channel state information (CSI), which significantly improves the throughput and bit error rate (BER) performance. Performance of the proposed scheme is analyzed for frequency-flat Rayleigh fading channels with additive white Gaussian noise (AWGN), co-channel interference (CI), and random FM noise.

关键词： Scheme transmission Packet Channel state information code combining Radio systems data packets Mobile radio systems signal envelope adaptive coding AWGN

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CONCATENATED WAVELET MHDCT coding OF IMAGES 2

CONCATENATED WAVELET MHDCT CODING OF IMAGES

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2nd Conference on Wavelet Applications

作者： BARAZANDEPOUR, M MARK, JW UNIV WATERLOO DEPT ELECT & COMP ENGNWATERLOOON N2L 3G1CANADA

ISBN: (纸本)0819418447

Wavelet transform (WT) is concatenated with the modified Hadamard-structured discrete cosine transform (MHDCT) to encode image signals. As the outer code, the WT decomposes the image signals into uncorrelated low resolution and detailed signal components. As inner codes, the MHDCT adaptively encodes the low resolution signal, while the detailed signals axe encoded using pulse code modulation (PCM). The concatenated coding approach offers the possibility of regulated coding for progressive transmission of the image signals over communication networks. Results of image coding using the concatenated WT/MHDCT coder axe presented. © 1995 SPIE. All rights reserved.

关键词： WAVELET TRANSFORM TRANSFORM coding DCT MHDCT adaptive coding PROGRESSIVE TRANSMISSION

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An ASBVQ codec for VLBR video coding

An ASBVQ codec for VLBR video coding

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IEE Colloquium on Low Bit Image coding

作者： S.P. Voukelatos J.J. Soraghan Signal Processing Division Department of Electronic and Electrica Engineering University of Strathclyde Glasgow UK

A new adaptive subband vector quantisation (ASBVQ) codec for the encoding of video sequences at very low bit rates is presented. The block diagram of the complete system is shown. Overlapped block motion compensation (OBMC) is employed to generate a prediction of the current frame from the previously decoded frame. The OBMC method generates a prediction error signal which can be compressed more efficiently when a subband based coder is used. A 2D discrete wavelet transform is applied to decompose the prediction error frame into 7 subbands. An adaptive subband VQ scheme is employed to quantize the wavelet coefficients and distribute the available bit budget among the subband vector quantizers. For applications where constant bit rate is required this is provided by the adaptive VQ algorithm, eliminating the need for a buffer.< >

关键词： adaptive coding Image sequence analysis Motion compensation Prediction methods Vector quantization Video coding Wavelet transforms

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Highly efficient coding schemes for contour line drawings

Highly efficient coding schemes for contour line drawings

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IEEE International Conference on Image Processing

作者： Yuk-Hee Chan Wan-Chi Siu Department of Electronic Engineering Hong Kong Polytechnic University Hong Kong China

ISBN: (纸本)0780331222

In this paper, adaptive coding schemes for contour line drawings based on chain code representation is presented. In this scheme, the chain code or the chain-difference code of a contour is modeled as an n-order Markov sequence and then coded with an arithmetic coding scheme adaptively. Experimental result shows that the proposed approach is better than some other conventional approaches.

关键词： Arithmetic Encoding Statistics Engineering drawings Huffman coding Decorrelation Entropy adaptive coding Probability Filters

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A Bayes coding algorithm for FSM sources

A Bayes coding algorithm for FSM sources

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IEEE International Symposium on Information Theory

作者： T. Matsushima S. Hirasawa School of Science and Engineering Waseda University Shinjuku Tokyo Japan

The optimal universal code for FSMX sources (Rissanen 1981) with respect to Bayes redundancy criterion (Davison 1973) is deduced under the condition that the model, the probabilistic parameters and the initial state are unknown. The algorithm is not only Bayes optimal for FSMX sources but also asymptotically optimal for stationary ergodic sources. Moreover the algorithm is regarded as a generalisation of the Ziv-Lempel algorithm. In the basic CTW algorithm, the algorithm needs the initial context x/sub 1-d/x/sub 2-d/...x/sub 0/ where: a finite constant d is the depth of the context tree, for calculating the coding probability of x/sub 1/. For the problem of the initial situation and the infinite depth tree, the extensions to the CTW algorithm have been proposed in Willems (1994). The optimal algorithm proposed in the present paper gives a solution against these problems from another new point of view.

关键词： Probability adaptive coding Arithmetic Context modeling Hafnium

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A multiple trellis-coded hybrid-ARQ scheme for land mobile communication channels

A multiple trellis-coded hybrid-ARQ scheme for land mobile c...

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MILCOM, Military Communications Conference

作者： M. Eroz T. Fuja Electrical Engineering Department Inst it ut e for Systems Research University of Maryland College Park USA

A multiple trellis-coded scheme that adapts itself to varying channel conditions is proposed and simulated over a land mobile radio channel. The scheme can be classified as a type-II hybrid ARQ protocol that makes use of incremental redundancy. A multiple trellis code is one in which each trellis branch is associated with k/spl ges/2 transmitted baud. Simon and Divsalar (1988) have described a method for constructing multiple trellis codes suited for fading environments. Their design technique is used to create rate-compatible punctured trellis codes-analogous to the rate-compatible punctured convolutional codes of Hagenauer (1988)-that vary their redundancy in response to feedback from the demodulator to the transmitter. Specifically, we use a multiple trellis code of multiplicity k=3, designed for fading channels, as our "mother" code. Depending on the channel conditions, this code is punctured to get another code of multiplicity k=2 with a higher bandwidth efficiency. Both the mother and the punctured codes are shown to satisfy the design procedure of Simon et al. The proposed protocol does not require the transmitter to anticipate the channel quality before transmission. Moreover, the protocol requires only a low-rate feedback channel, with significant delay acceptable. The performance of the adaptive code is compared to a "static" code of the same bandwidth efficiency and complexity designed by Schlegel and Costello (1989). Simulations show that the adaptive code gives a coding gain of about 3 dB over the Schlegel-Costello code at a bit error probability of 10/sup -5/.

关键词： Convolutional codes Protocols Redundancy Fading Feedback Radio transmitters Bandwidth adaptive coding Land mobile radio Automatic repeat request

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adaptive error correcting codes based on cooperative play of the game of "twenty questions with a liar"

Adaptive error correcting codes based on cooperative play of...

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Data Compression Conference (DCC)

作者： E.L. Lawler S. Sarkissian Department of Electrical Engineering and Computer Sciences Computer Science Division University of California Berkeley CA USA

Summary form only given. The existence of a noiseless, delayless feedback channel permits the transmitter to detect transmission errors at the time they occur. Such a feedback channel does not increase channel capacity, but it does permit the use of adaptive codes with significantly enhanced error correction capabilities. It is well known that codes of this type can be based on cooperative play of the game of "twenty questions with a liar". However, it is perhaps not so well appreciated that it is practicable to implement codes of this type on general purpose computers. We describe a simple and fast implementation in which the transmitter makes reference to a fully worked out game tree. In the worst case, storage requirements grow exponentially with block length. For many cases of interest, storage requirements are not excessive. For example, a 4-error correcting code with 8 information bits and 13 check bits requires only 103.2 kilobytes of storage. By contrast, an 8-error correcting code with 6 information bits and 25 check bits requires 21.2 megabytes of storage. However, no nonadaptive code is capable of correcting as many as 8 errors when 6 information bits are encoded in a block of length 31.

关键词： Error correction codes Feedback Transmitters Computer science Delay effects Computer errors Channel capacity adaptive coding

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adaptive change of code rate in DS-SSMA communication systems

Adaptive change of code rate in DS-SSMA communication system...

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URSI International Symposium on Signals, Systems, and Electronics (ISSSE)

作者： Youngkwon Ryu Suk Chan Kim Iickho Song Seong Ill Park Hyung Myung Kim WLL Research Laboratory Daejeon South Korea Electrical Engineering Korea Advanced Institute of Science and Technology Daejeon South Korea

ISBN: (纸本)0780325168

An adaptive code rate change scheme in DS-SSMA systems is proposed. In the proposed scheme, the error correcting code rate is changed according to the channel state, the effective number of users. The channel state is estimated based on retransmission requests. The criterion for the change of the code rate is to maximize the throughput under given error bound.

关键词： Error probability Signal to noise ratio Error correction codes Throughput Signal processing Fading State estimation Reed-Solomon codes Frequency adaptive coding

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Adaptation for non-stationary binary sources for data compression

Adaptation for non-stationary binary sources for data compre...

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Asilomar Conference on Signals, Systems & Computers

作者： A. Zandi G.G. Langdon Ricoh California Research Center CA USA Baskin Center of Computer Engineering University of California Santa Cruz CA USA

In static entropy coding schemes such as static Huffman coding, the data is entropy coded under a fixed probability distribution. These methods are usually referred to as two pass, since the probability distribution is often, but not always, computed from the data in a first pass. In contrast, in the dynamic or adaptive, which is sometimes called one pass, the fixed probability distribution is generally too inefficient to be acceptable. The motivation for this work is to define a quantity corresponding to the intuitive concept of "speed of adaptation". With the use of Bayesian framework and the inefficiency penalty function, adaptation risk is defined, and shown to have the desired properties. Since in an adaptive scheme the probability distribution is not fixed, the adaptation risk serves also the role of the "second order" quantity. Hence coding under fixed adaptation risk can be thought of as the simplest generalization of coding under fixed probability distribution. Of course variable adaptation risk is a valid and interesting possibility. As applications several adaptive coding methods are presented and their adaptation risks are analyzed.

关键词： Data compression Probability distribution Decoding Arithmetic Distributed computing Image coding Entropy coding Huffman coding Bayesian methods adaptive coding

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Capacity of advanced TDMA systems for fixed radio access

Capacity of advanced TDMA systems for fixed radio access

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IEE Colloquium on Local Loop Fixed Radio Access

作者： A.G. Burr S.J. Baines T.C. Tozer Department of Electronics University of York York UK Dept. of Electron. York Univ. UK

We review the potential of advanced TDMA systems for fixed radio access. We highlight the differences between the fixed radio access (FRA) environment and the cellular mobile environment, and show that there are significant advantages in a system designed specifically for FRA over mobile and personal systems adapted for this purpose. The features of an advanced TDMA system for FRA are discussed, including the use of directional antennas, and adaptive rate coding and modulation. In particular we consider the capacity improvement possible by the use of directional antennas. Even if 99.9% availability is required, a system spectral efficiency of 0.7 bits/s/Hz/cell is possible, a factor of two improvement on a system with isotropic antennas. The advantages of adaptivity are shown by considering a simple adaptive protocol which is able to improve on this figure by a factor of four.

关键词： Subscriber loops Land mobile radio cellular systems Information rates Time division multiaccess Personal communication networks adaptive coding Modulation Directive antennas

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