IEEE Transactions on Information Theory

Volume 42 Issue 2 • March 1996

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Displaying Results 1 - 25 of 37
  • Classification with finite memory

    Publication Year: 1996, Page(s):337 - 347
    Cited by:  Papers (18)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (917 KB)

    Consider the following situation. A device called a classifier observes a probability law P on l-vectors from an alphabet of size A. Its task is to observe a second probability law Q and decide whether P/spl equiv/Q or P and Q are sufficiently different according to some appropriate criterion. If the classifier has available an unlimited memory (so that it can remember P(z) exactly for all z), thi... View full abstract»

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  • Universal portfolios with side information

    Publication Year: 1996, Page(s):348 - 363
    Cited by:  Papers (119)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1437 KB)

    We present a sequential investment algorithm, the /spl mu/-weighted universal portfolio with side information, which achieves, to first order in the exponent, the same wealth as the best side-information dependent investment strategy (the best state-constant rebalanced portfolio) determined in hindsight from observed market and side-information outcomes. This is an individual sequence result which... View full abstract»

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  • A rate-splitting approach to the Gaussian multiple-access channel

    Publication Year: 1996, Page(s):364 - 375
    Cited by:  Papers (198)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1425 KB)

    It is shown that any point in the capacity region of a Gaussian multiple-access channel is achievable by single-user coding without requiring synchronization among users, provided that each user "splits" data and signal into two parts. Based on this result, a new multiple-access technique called rate-splitting multiple accessing (RSMA) is proposed. RSMA is a code-division multiple-access scheme fo... View full abstract»

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  • A new universal random coding bound for the multiple-access channel

    Publication Year: 1996, Page(s):376 - 386
    Cited by:  Papers (45)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (898 KB)

    The minimum average error probability achievable by block codes on the two-user multiple-access channel is investigated. A new exponential upper bound is found which can be achieved universally for all discrete memoryless multiple-access channels with given input and output alphabets. It is shown that the exponent of this bound is greater than or equal to those of previously known bounds. Moreover... View full abstract»

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  • Nearly optimal multiuser codes for the binary adder channel

    Publication Year: 1996, Page(s):387 - 398
    Cited by:  Papers (17)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1199 KB)

    Coding schemes for the T-user binary adder channel are investigated. Recursive constructions are given for two families of mixed-rate, multiuser codes. It is shown that these basic codes can be combined by time-sharing to yield codes approaching most rates in the T-user capacity region. In particular, the best codes constructed herein achieve a sum-rate, R/sub 1/+...+R/sub T/, which is higher than... View full abstract»

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  • An upper bound on the distribution of computation of a sequential decoder for multiple-access channels

    Publication Year: 1996, Page(s):399 - 408
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (694 KB)

    The computational distribution of sequential decoding for discrete memoryless multiple-access channels is examined. It is shown that all possible collections of incorrect paths in the code tree may be described by bipartite graphs. Using this fact and a new decoding metric it is proved that the number of computations in the first incorrect subtree is a Paretean random variable, and that the parame... View full abstract»

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  • Unveiling turbo codes: some results on parallel concatenated coding schemes

    Publication Year: 1996, Page(s):409 - 428
    Cited by:  Papers (769)  |  Patents (59)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1771 KB)

    A parallel concatenated coding scheme consists of two simple constituent systematic encoders linked by an interleaver. The input bits to the first encoder are scrambled by the interleaver before entering the second encoder. The codeword of the parallel concatenated code consists of the input bits to the first encoder followed by the parity check bits of both encoders. This construction can be gene... View full abstract»

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  • Iterative decoding of binary block and convolutional codes

    Publication Year: 1996, Page(s):429 - 445
    Cited by:  Papers (1504)  |  Patents (207)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1649 KB)

    Iterative decoding of two-dimensional systematic convolutional codes has been termed "turbo" (de)coding. Using log-likelihood algebra, we show that any decoder can be used which accepts soft inputs-including a priori values-and delivers soft outputs that can be split into three terms: the soft channel and a priori inputs, and the extrinsic value. The extrinsic value is used as an a priori value fo... View full abstract»

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  • Asymptotic distribution of the errors in scalar and vector quantizers

    Publication Year: 1996, Page(s):446 - 460
    Cited by:  Papers (33)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1467 KB)

    High-rate (or asymptotic) quantization theory has found formulas for the average squared length (more generally, the qth moment of the length) of the error produced by various scalar and vector quantizers with many quantization points. In contrast, this paper finds an asymptotic formula for the probability density of the length of the error and, in certain special cases, for the probability densit... View full abstract»

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  • On the asymptotic distribution of the errors in vector quantization

    Publication Year: 1996, Page(s):461 - 468
    Cited by:  Papers (11)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (739 KB)

    In a recent paper, Lee and Neuhoff (see ibid., vol.42, no.2, p446-60, 1996) found an asymptotic formula for the distribution of the length of the errors produced by a vector quantizer with many quantization points. This distribution depends on the source probability density, the quantizer point density, and the quantizer shape profile. (The latter characterizes the shapes of the quantization cells... View full abstract»

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  • Lower bound on the mean-squared error in oversampled quantization of periodic signals using vector quantization analysis

    Publication Year: 1996, Page(s):469 - 479
    Cited by:  Papers (25)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1002 KB)

    Oversampled analog-to-digital conversion is a technique which permits high conversion resolution using coarse quantization. Classically, by lowpass filtering the quantized oversampled signal, it is possible to reduce the quantization error power in proportion to the oversampling ratio R. In other words, the reconstruction mean-squared error (MSE) is in /spl Oscr/(R/sup -1/). It was recently found ... View full abstract»

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  • On the cost of finite block length in quantizing unbounded memoryless sources

    Publication Year: 1996, Page(s):480 - 487
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (781 KB)

    The problem of fixed-rate block quantization of an unbounded real memoryless source is studied. It is proved that if the source has a finite sixth moment, then there exists a sequence of quantizers Q/sub n/ of increasing dimension n and fixed rate R such that the mean squared distortion /spl Delta/(Q/sub n/) is bounded as /spl Delta/(Q/sub n/)/spl les/D(R)+O(/spl radic/(log n/n)), where D(R) is th... View full abstract»

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  • Spread-response precoding for communication over fading channels

    Publication Year: 1996, Page(s):488 - 501
    Cited by:  Papers (45)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1567 KB)

    Interleaving is an important technique for improving the effectiveness of traditional error-correcting codes in data transmission systems that exhibit multipath fading. Such channels often arise in mobile wireless communications. We present an alternative to interleaving for such systems, which we term "spread-response precoding". From the perspective of the coded symbol stream, spread-response pr... View full abstract»

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  • Good lattice constellations for both Rayleigh fading and Gaussian channels

    Publication Year: 1996, Page(s):502 - 518
    Cited by:  Papers (182)  |  Patents (17)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1632 KB)

    Recent work on lattices matched to the Rayleigh fading channel has shown how to construct good signal constellations with high spectral efficiency. We present a new family of lattice constellations, based on complex algebraic number fields, which have good performance on Rayleigh fading channels. Some of these lattices also present a reasonable packing density and thus may be used at the same time... View full abstract»

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  • Group codes generated by finite reflection groups

    Publication Year: 1996, Page(s):519 - 528
    Cited by:  Papers (15)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1091 KB)

    Slepian-type group codes generated by finite Coxeter groups are considered. The resulting class of group codes is a generalization of the well-known permutation modulation codes of Slepian (1965), it is shown that a restricted initial-point problem for these codes has a canonical solution that can easily be computed. This allows one to enumerate all optimal group codes in this restricted sense and... View full abstract»

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  • MDS array codes with independent parity symbols

    Publication Year: 1996, Page(s):529 - 542
    Cited by:  Papers (103)  |  Patents (13)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1406 KB)

    A new family of maximum distance separable (MDS) array codes is presented. The code arrays contain p information columns and r independent parity columns, each column consisting of p-1 bits, where p is a prime. We extend a previously known construction for the case r=2 to three and more parity columns. It is shown that when r=3 such extension is possible for any prime p. For larger values of r, we... View full abstract»

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  • A soft-output decoding algorithm for concatenated systems

    Publication Year: 1996, Page(s):543 - 553
    Cited by:  Papers (15)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1187 KB)

    In order to fully utilize the SDD (soft-decision decoding) capacity of the outer codes in a concatenated system, reliability information on the inner decoder outputs (called soft outputs) needs to be provided to the outer decoder. This paper shows that a modified MAP algorithm can be effectively and accurately used to generate such information. In the course of the presentation, a metric based on ... View full abstract»

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  • Location-correcting codes

    Publication Year: 1996, Page(s):554 - 565
    Cited by:  Papers (7)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1364 KB)

    We study codes over GF(q) that can correct t channel errors assuming the error values are known. This is a counterpart to the well-known problem of erasure correction, where error values are found assuming the locations are known. The correction capabilities of these so-called t-location correcting codes (t-LCCs) are characterized by a new metric, the decomposability distance, which plays a role a... View full abstract»

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  • On the cardinality of systematic authentication codes via error-correcting codes

    Publication Year: 1996, Page(s):566 - 578
    Cited by:  Papers (15)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1286 KB)

    In both open and private communication the participants face potential threats from a malicious enemy who has access to the communication channel and can insert messages (impersonation attack) or alter already transmitted messages (substitution attack). Authentication codes (A-codes) have been developed to provide protection against these threats. In this paper we introduce a new distance, called ... View full abstract»

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  • Large families of quaternary sequences with low correlation

    Publication Year: 1996, Page(s):579 - 592
    Cited by:  Papers (76)  |  Patents (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (918 KB)

    A family of quaternary (Z/sub 4/-alphabet) sequences of length L=2/sup r/-1, size M/spl ges/L/sup 2/+3L+2, and maximum nontrivial correlation parameter C/sub max//spl les/2/spl radic/(L+1)+1 is presented. The sequence family always contains the four-phase family /spl Ascr/. When r is odd, it includes the family of binary Gold sequences. The sequence family is easily generated using two shift regis... View full abstract»

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  • Time discretization of continuous-time filters and smoothers for HMM parameter estimation

    Publication Year: 1996, Page(s):593 - 605
    Cited by:  Papers (38)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1842 KB)

    In this paper we propose algorithms for parameter estimation of fast-sampled homogeneous Markov chains observed in white Gaussian noise. Our algorithms are obtained by the robust discretization of stochastic differential equations involved in the estimation of continuous-time hidden Markov models (HMM's) via the EM algorithm. We present two algorithms: the first is based on the robust discretizati... View full abstract»

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  • Stochastic processes that generate polygonal and related random fields

    Publication Year: 1996, Page(s):606 - 617
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1047 KB)

    A reversible, ergodic, Markov process taking values in the space of polygonally segmented images is constructed. The stationary distribution of this process can be made to correspond to a Gibbs-type distribution for polygonal random fields as introduced by Arak and Surgailis (1989) and a few variants thereof, such as those arising in Bayesian analysis of random fields. Extensions to generalized po... View full abstract»

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  • The effect of decision delay in finite-length decision feedback equalization

    Publication Year: 1996, Page(s):618 - 621
    Cited by:  Papers (58)  |  Patents (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (425 KB)

    In this correspondence we derive the finite-length, minimum mean-squared error decision feedback equalizer (MMSE-DFE). We include decision delay as an explicit parameter. Our derivation yields an algebraic interpretation of the effect of decision delay on DFE performance (measured by mean-squared error). It also allows the fast computation of the MMSE-DFE for several different values of both decis... View full abstract»

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  • Some counterexamples in the theory of Weyl-Heisenberg frames

    Publication Year: 1996, Page(s):621 - 623
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (286 KB)

    We present an example of a positive function g with a positive Fourier transform g/spl circ/ and reasonable smoothness and decay properties such that (-1)/sup nm/exp(/spl pi/itm)g(t-n), n, m/spl isin/Z does not constitute a frame for L/sup 2/(R). We also give counterexamples for the statement that one can tell (in)definiteness of a Weyl-Heisenberg frame operator from (in)definiteness of its Weyl s... View full abstract»

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  • Irregular sampling for spline wavelet subspaces

    Publication Year: 1996, Page(s):623 - 627
    Cited by:  Papers (37)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (401 KB)

    Spline wavelets /spl psi//sub m/(t) are important in time-frequency localization due to (i) /spl psi//sub m/ can be arbitrarily close to the optimal case as m is sufficiently large, (ii) /spl psi//sub m/ has compact support and simple analytic expression, which lead to effective computation. Although the spline wavelet subspaces are so simple, Walter's well-known sampling theorem does not hold if ... View full abstract»

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Aims & Scope

IEEE Transactions on Information Theory publishes papers concerned with the transmission, processing, and utilization of information.

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Meet Our Editors

Editor-in-Chief
Alexander Barg

Department of Electrical and Computer Engineering and the Institute for Systems Research, University of Maryland

email: abarg-ittrans@ece.umd.edu