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Date 22-26 June 1998

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Displaying Results 1 - 25 of 79
  • 1998 Information Theory Workshop (Cat. No.98EX131)

    Publication Year: 1998
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    Freely Available from IEEE
  • On the frame error rate of turbo-codes

    Publication Year: 1998, Page(s):118 - 119
    Cited by:  Papers (3)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (262 KB)

    In spite of the excellent bit error rate performance of the original turbo-code, simulations indicate that this code yields relatively poor frame error rate performance. In this paper we show that "primitive" turbo-codes and "asymmetric" turbo-codes provides both good bit error rate and frame error rate performance. View full abstract»

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  • Author index

    Publication Year: 1998, Page(s):161 - 162
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    Freely Available from IEEE
  • Toric surfaces and codes

    Publication Year: 1998, Page(s):42 - 43
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (160 KB)

    From an integral convex polytope in R2 we give an explicit description of an error-correcting code over the finite field F q of length (q-1)2. The parameters of the code are read from the polytope. The codes are obtained from toric surfaces and the results are proved using the cohomology and intersection theory of such surfaces View full abstract»

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  • Iterative min-sum decoding of tail-biting codes

    Publication Year: 1998, Page(s):68 - 69
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (192 KB)

    By invoking a form of the Perron-Frobenius theorem for the “min-sum” semi-ring, we obtain a union bound on the performance of iterative decoding of tail-biting codes. This bound shows that for the Gaussian channel, iterative decoding will be optimum, at least for high SNRs, if and only if the minimum “pseudo-distance” of the code is larger than the ordinary minimum distance View full abstract»

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  • Recent results in the decoding of algebraic geometry codes

    Publication Year: 1998, Page(s):35 - 36
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (128 KB)

    We analyse the known decoding algorithms for algebraic geometry codes in the case where the number of errors is [(dFR-1)/2]+1, where dFR is the Feng-Rao distance View full abstract»

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  • On epicyclic Hermitian codes

    Publication Year: 1998
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (76 KB)

    The class of Hermitian codes is a popular and well-studied class of codes on planar curves over GF(2m). These codes have large blocklength, and may soon find engineering importance. In contrast to Reed-Solomon codes, which were discovered by engineers, Hermitian codes were introduced by mathematicians as an example of algebraic geometry codes. We re-introduce Hermitian codes as if they ... View full abstract»

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  • Decoding algebraic geometric codes

    Publication Year: 1998, Page(s):40 - 41
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (196 KB)

    We present a new algorithm for decoding AG-codes significantly beyond the error-correction bound. Specifically, given a word y whose distance to the AG-code is at most e, where e is a parameter depending on the block length and the dimension of the code, our algorithm produces all codewords that have distance ⩽e from y. We also discuss modifications of our general algorithm and show how to obt... View full abstract»

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  • Universal sequential decoding

    Publication Year: 1998
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (108 KB)

    An algorithm is proposed for universal decoding of convolutional/trellis codes employed over unknown channels. On discrete memoryless channels and at rates below the computational cut-off rate (corresponding to a uniform input distribution), the algorithm achieves an asymptotic complexity-vs.-performance tradeoff similar to the tradeoff achieved by the Viterbi (1979) algorithm, but with the benefi... View full abstract»

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  • Correlation attacks on stream ciphers and related decoding problems

    Publication Year: 1998, Page(s):156 - 157
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (208 KB)

    Relations between correlation attacks on stream ciphers and certain decoding problems are investigated. Methods of reducing the decoding complexity are proposed View full abstract»

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  • Coding for the block-fading channel: optimum and suboptimum power-allocation schemes

    Publication Year: 1998, Page(s):96 - 97
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (168 KB)

    Power allocation schemes for the block-fading Gaussian (BF-AWGN) channel with side-information at the transmitter and the receiver are considered. Several power allocation strategies are studied by evaluating the corresponding random coding error exponents. A very simple scheme (selective channel inversion) is shown to provide excellent performance and robustness to variations of the fading statis... View full abstract»

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  • Decoding of codes on surfaces

    Publication Year: 1998, Page(s):33 - 34
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (136 KB)

    The generalization of the Berlekamp-Massey algorithm to codes defined over surfaces is discussed. An example surface in 3-space whose planar sections are Hermitian curves is presented, given in some detail View full abstract»

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  • Analytic properties of contention tree-algorithms

    Publication Year: 1998, Page(s):128 - 129
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (184 KB)

    This article studies the statistical properties of multiple-access contention tree-algorithms with ternary feedback for an arbitrary degree of node. Accurate analytical approximations are given for the expectation value of the number of levels required for a random contender to have successful access, as well as of the number of levels and of the number of contention frames required to provide acc... View full abstract»

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  • Spectral efficiency of direct-sequence spread-spectrum multiaccess with random spreading

    Publication Year: 1998, Page(s):64 - 65
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (196 KB)

    Information theoretic aspects of code division multiple access (CDMA) random direct-sequence spread-spectrum (DSSS) are investigated. The CDMA-DSSS channel with randomly and independently chosen spreading sequences accurately models the situation where pseudo-noise sequences span many symbol periods. We analyze the spectral efficiency (total capacity per chip) as a function of the number of users,... View full abstract»

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  • Maximum likelihood and multistage decoding for optimised multilevel coded modulation

    Publication Year: 1998, Page(s):81 - 82
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (184 KB)

    We consider maximum likelihood trellis decoding of multilevel coded modulation optimised for finite BER. We introduce a class of optimised block coded modulation (BCM) schemes for 8-PSK with a very simple trellis decoder, and show they perform significantly better than conventionally-designed BCM schemes View full abstract»

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  • Relationships between different error-correcting capabilities of a code

    Publication Year: 1998, Page(s):122 - 123
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (196 KB)

    SID channels are discrete channels represented by expressions that involve combinations of the error types substitution, insertion, and deletion. Based on the SID channel model, a simple distance is defined that generalizes the Hamming and Levenshtein distances. For a certain class of SID channels, the distance is used to obtain a unifying necessary and sufficient condition for the error correctin... View full abstract»

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  • Turing complexity of fixed-rate quantization

    Publication Year: 1998, Page(s):20 - 21
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (216 KB)

    The rate of increase of quantization complexity, as the rate of quantization increases, is investigated under a Turing machine framework. It is shown that the problem of asymptotically optimal scalar quantization has polynomial encoding complexity if the distribution function corresponding to the one-third power of the source density is polynomially computable with high probability View full abstract»

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  • Construction of minimal tail-biting trellises

    Publication Year: 1998, Page(s):72 - 74
    Cited by:  Papers (12)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (340 KB)

    The subject of tail-biting trellis representation of block codes has attracted a lot of interest. One of the major open problems in this area is how to construct a minimal tail-biting trellis for a given linear code. We present a solution to this problem. Given a linear block code C, we show how to construct a linear tail-biting trellis for C that minimizes the product of vertex-space sizes among ... View full abstract»

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  • Min-max power allocation for successive decoding

    Publication Year: 1998, Page(s):56 - 57
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (152 KB)

    This paper studies resource allocation in the multi-access, fading channel, with power constraints. Given a desired bit rate vector R* , we wish to determine if it is possible to achieve it with a power budget P¯: the call admissions problem. If so, we wish to achieve it using “minimal” power: the resource allocation problem. We take a min-max fairness approach to deter... View full abstract»

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  • How to encode a stationary source

    Publication Year: 1998, Page(s):86 - 87
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (160 KB)

    We study the problem of constructing messages of the form ω 1, ω2, ..., where each ωk is a letter from a finite alphabet, so that the statistics of ω 1, ω2, ... correspond to a given stationary probability distribution View full abstract»

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  • Information theory and secure multi-party computation

    Publication Year: 1998, Page(s):152 - 153
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (220 KB)

    Two types of generalizations in secure multi-party computation are described. First, we report on a new general adversary model: while previous protocols were designed to tolerate misbehavior of one of two types (active or passive adversaries) the new protocols tolerate mixed types of adversaries, i.e. an adversary that can corrupt players actively, passively, or can let them crash (i.e. stop exec... View full abstract»

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  • Extraction of optimally unbiased bits from a biased source

    Publication Year: 1998, Page(s):90 - 91
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (200 KB)

    We explore the problem of transforming n independent and identically biased {-1,1}-valued random variables, X1, ..., X n, into a single {-1,1} value, f(X1, ..., Xn ), so that this result is as unbiased as possible. In general, no function f produces a completely unbiased result. We perform the first study of the relationship between the bias b of these X... View full abstract»

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  • On visual cryptography schemes

    Publication Year: 1998, Page(s):154 - 155
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (208 KB)

    We consider visual cryptography schemes in which two pixels combine in an arbitrary way. We analyze the pixel expansion and the contrast of (2,n)-threshold visual cryptography schemes, that is schemes in which any pair of n shares can visually reconstruct the secret image, but any single share has no information on the secret image View full abstract»

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  • Higher layer perspectives on modeling the wireless channel

    Publication Year: 1998, Page(s):137 - 138
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (224 KB)

    We present previous findings that reveal the importance of higher order error statistics in assessing the impact of particular forms of error control on services as seen by the higher layers of a protocol stack. In an effort to generalize our past work on the sensitivity of higher layer protocols to channel errors, we examine ways to capture the behavior of realistic channels with tractable models... View full abstract»

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  • Joint source-channel decoding of variable-length encoded sources

    Publication Year: 1998, Page(s):94 - 95
    Cited by:  Papers (45)  |  Patents (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (212 KB)

    In systems that employ source coding, imperfect compression may leave some redundancy in the data at the input to the channel encoder. This paper presents a new method for exploiting that redundancy via joint source-channel maximum a posteriori (MAP) decoding. The technique may be applied to systems that employ a variable-length source code in conjunction with a channel code; the decoder uses the ... View full abstract»

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