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Information Theory Workshop, 2001. Proceedings. 2001 IEEE

Date 2-7 Sept. 2001

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Displaying Results 1 - 25 of 54
  • Proceedings 2001 IEEE Information Theory Workshop [front matter]

    Page(s): i - vii
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    Freely Available from IEEE
  • Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)

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    Freely Available from IEEE
  • New low-complexity turbo-like codes

    Page(s): 70 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    We discuss the design of new low-complexity turbo-like codes based on a multiple parallel concatenation of 4-state and 2-state constituent codes. The new code designs take advantage of the big-numerator/little-denominator principle along with specially designed interleavers to outperform previously designed turbo codes over the entire range of signal-to-noise ratios. Puncturing at the encoder is used to produce low-complexity codes with excellent performance at code rates of 1/2 and 1/3. The multiple parallel concatenation and puncturing results in turbo-like encoders which are either partially systematic or completely nonsystematic. Comparisons with the proposed 8-state turbo coding standard and with other low-complexity alternative code designs are included. View full abstract»

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  • Author index

    Page(s): 0_1
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    Freely Available from IEEE
  • Time varying convolutional codes revisited

    Page(s): 67 - 69
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    There are several cases where the maximum free distance (MFD) time-invariant convolutional code of a given rate and total encoder memory does not meet the Heller bound or where the encoder that does meet the Heller bound is catastrophic. In order to find codes that meet the Heller bound, it is sometimes necessary to use time-varying convolutional codes. Some periodic time-varying convolutional codes with free distance greater than the best known time-invariant code of the same rate and total encoder memory are presented. These codes also achieve the Heller bound for the given code parameters. In addition, the use of time-varying encoders in order to achieve "spectral thinning" is explored View full abstract»

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  • Capacity considerations for trellis code multiple access systems

    Page(s): 153 - 155
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    Trellis code multiple access (TCMA) is a narrow-band multiple access scheme. There is no bandwidth expansion, so K users are using the same bandwidth as one single user. The load (the number of bits per channel use) of the system is therefore much higher than the load in, for example, conventional CDMA systems. It is shown here that the maximum number of users in a TCMA system is usually modest. This fact is based on constellation-constrained capacity, i.e., the maximum capacity of a system with a specific constellation of the transmitted symbols. The minimum required signal-to-noise ratio for reliable transmission is also given for different code rates View full abstract»

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  • Message-passing decoders and their application to storage systems

    Page(s): 12 - 13
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    Message-passing has been proposed for decoding parity check codes, especially low density parity check (LDPC) codes. We propose using message-passing detectors for partial response channels. Furthermore, we investigate how a single message-passing detector/decoder can be matched to a combination of a partial response channel and a LDPC code View full abstract»

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  • Iterative multiuser joint detection and parameter estimation: a factor-graph approach

    Page(s): 36 - 38
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB) |  | HTML iconHTML  

    We examine a multiple-access AWGN channel with synchronous DS-CDMA in which the channel amplitude and noise variance parameters are unknown a priori. We derive an iterative joint multiuser decoder and parameter estimator based on soft interference cancellation and on soft decision-driven least-squares estimation. Our derivation is obtained by applying the sum-product algorithm to the factor graph of the joint a posteriori probability measure of the information bits and of the unknown channel parameters View full abstract»

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  • Unequal error protection applied to JPEG image transmission using turbo codes

    Page(s): 64 - 66
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    An investigation of unequal error protection (UEP) methods applied to JPEG image transmission using turbo codes is presented. The JPEG image is partitioned into two groups, i.e., DC components and AC components according to their respective sensitivity to channel noise. The highly sensitive DC components are better protected with a lower coding rate, while the less sensitive AC components use a higher coding rate. Simulation results are given to demonstrate how the UEP schemes outperforms the equal error protection (EEP) scheme in terms of bit error rate (BER) and peak signal to noise ratio (PSNR) View full abstract»

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  • Generation of binary vectors that optimize a given weight function with application to soft-decision decoding

    Page(s): 138 - 140
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    Many decoding algorithms need to compute some lists of binary vectors that minimize a given weight function. Furthermore, it is often desirable that these vectors are generated by increasing weight. The considered weight function is usually decreasing in the a priori likelihood that the vector yields correct decoding. We present a new technique to generate candidates for error patterns from the most a priori likely to the least, that proves significantly more efficient than any other known method View full abstract»

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  • Design of space-time turbo TCM on fading channels

    Page(s): 123 - 125
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB) |  | HTML iconHTML  

    Novel code design criteria for space-time codes on slow Rayleigh fading channels are presented. It is shown that the code performance is dominated by the minimum rank r and the minimum determinant of the codeword distance matrix when the product of the minimum rank r and the number of receive antennas nR is less than 4. However, when r·nR is greater than or equal to 4, the code error performance is dominated by the minimum trace of the codeword distance matrix. Furthermore, we present recursive spacetime trellis coded modulation (STTC) which outperforms feedforward STTC on slow and fast fading channels. A substantial increase in performance can be obtained by constructing spacetime turbo trellis coded modulation (ST turbo TCM) which consists of concatenated recursive STTC, decoded by iterative decoding algorithm. The proposed recursive STTC are used as constituent codes in this scheme. The proposed ST turbo TCM significantly outperforms the best known STTC on both slow and fast fading channels View full abstract»

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  • Asymptotic analysis of widely linear MMSE multiuser detection-complex vs real modulation

    Page(s): 55 - 57
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    We give the asymptotic signal-to-interference ratio for the so-called widely linear minimum mean-squared error multiuser receiver for transmission of multiple users to a common receiver with DS-CDMA. Observing that widely linear multiuser detection virtually doubles the spreading factor, we show that transmission with real-valued channel symbols can lead to a higher spectral efficiency than with complex-valued channel symbols when each user employs its own complex-valued random spreading sequence View full abstract»

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  • On interference cancellation and iterative techniques

    Page(s): 39 - 41
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    Recent research activities in the area of mobile radio communications have moved to third generation (3G) cellular systems to achieve higher quality with variable transmission rate of multimedia information. In this paper, an overview is presented of various interference cancellation and iterative detection techniques that are believed to be suitable for 3G wireless communications systems. Key concepts are space-time processing and space-division multiple access (or SDMA) techniques. SDMA techniques are possible with software antennas. Furthermore, to reduce receiver implementation complexity, iterative detection techniques are considered. A particularly attractive method uses tentative hard decisions, made on the received positions with the highest reliability, according to some criterion, and can potentially yield an important reduction in the computational requirements of an iterative receiver, with minimum penalty in error performance. A study of the tradeoffs between complexity and performance loss of iterative multiuser detection techniques is a good research topic View full abstract»

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  • Weak variable-length Slepian-Wolf coding with linked encoders for mixed sources

    Page(s): 82 - 84
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    Slepian and Wolf (see IEEE Trans. Inform. Theory, vol.19, p.471-80, July 1973) first considered the data compression of correlated sources called the SW system, where two sequences emitted from correlated sources are separately encoded to codewords, and sent to a single decoder which has to output original sequence pairs. Recently, Oohama (see IEEE Trans. Inform. Theory, vol.42, p.837-47, May 1996) has extended the SW system and investigated a more general case where there are some mutual linkages between two encoders of the SW system. In this paper, we investigate variable-length coding which allows asymptotically vanishing probability of error for the system considered by Oohama. We clarify the admissible rate region for mixed sources characterized by two ergodic sources, and show that this region is strictly wider than that for fixed-length codes View full abstract»

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  • Concatenated tree codes and related schemes

    Page(s): 76 - 78
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    We report the progress in concatenated tree (CT) codes and related schemes, including low rate codes for CDMA applications and bandwidth efficient coded modulation schemes. It is shown that CT codes provide efficient solutions for various situations. Near capacity performances (within about 0.5 dB) can be achieved at significantly reduced decoding costs View full abstract»

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  • A class of systematic t/B-error correcting codes for semiconductor memory systems

    Page(s): 85 - 86
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    This paper proposes a class of systematic codes called single t/B-error correcting - single b-bit byte error correcting - single b-bit block error detecting (StB/EC-SbEC-SBED) codes for high speed semiconductor memory systems. The proposed codes correct multiple random t-bit errors occurring within a chip and b-bit byte errors caused by sub-array data faults while simultaneously indicating B-bit block errors caused by complete chip failures View full abstract»

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  • A random matrix model for the antenna array channel with decaying power delay profile

    Page(s): 144 - 146
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    The random matrix model for multipath propagation on the antenna array channel is generalised to decaying power delay profiles. Results are given in terms of Stieltjes transforms of the eigenvalue distributions of the channel's space-time covariance matrix View full abstract»

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  • Analog decoding and beyond

    Page(s): 126 - 127
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    In 1998, Hagenauer and Loeliger et al. independently proposed to decode error correcting codes by analog electronic networks. In contrast to previous work on analog Viterbi decoders, the work both by Hagenauer and by Loeliger et al. was inspired by turbo-style decoding of codes described by graphs. Large gains, in terms of speed or power consumption, over digital implementations were envisaged. Since 1998, much effort has been spent towards turning these ideas into working chips. While only decoders of "toy" codes have so far been successfully manufactured, extensive simulations of such circuits have not revealed any fundamental problems. Some progress has also been made in analyzing the effects of transistor mismatch. While much remains to be learned, the author feels confident that analog decoders will eventually find their way into applications. The present paper, rather than reporting on circuit details, offers some thoughts on "the bigger picture"- the underlying principles, motivations, and possible directions of future research View full abstract»

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  • Achievable rate of MIMO channels with data-aided channel estimation

    Page(s): 150 - 152
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB) |  | HTML iconHTML  

    The achievable rate of a coherent coded modulation (CM) digital communication system with data-aided channel estimation and a discrete, equiprobable symbol alphabet is derived under the assumption that the system operates on a flat fading MIMO channel and uses an interleaver to combat the bursty nature of the channel. It is shown that linear minimum mean square error (LMMSE) channel estimation directly follows from the derivation, and links average mutual information to the channel dynamics. Based on the assumption that known training symbols are transmitted, the achievable rate of the system is optimized with respect to the amount of training information needed View full abstract»

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  • Random CDMA in the multiple cell uplink environment: the effect of fading on various receivers

    Page(s): 42 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    A simple multi-cell Rayleigh fading uplink communication model is suggested and analyzed for optimally coded randomly spread DS-CDMA with multiuser detection. The model adheres to Wyner's (1994) infinite linear cell-array setting, according to which only adjacent-cell interference is present, and characterized by a single parameter 0⩽α⩽1. The discussion is confined to asymptotic analysis where both the number of users per cell and the processing gain go to infinity, while their ratio goes to some finite constant. The spectral efficiency of various multiuser detection strategies is evaluated assuming single cell-site processing, and equal transmit powers for all users in all cells. Comparative results demonstrate how performance is affected by the introduction of inter-cell interference (with and without fading), and what is the penalty associated with the randomly spread coded DS-CDMA strategy View full abstract»

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  • Design of low-density parity-check codes for bandwidth efficient modulation

    Page(s): 24 - 26
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    We design low-density parity-check (LDPC) codes for bandwidth efficient modulation using a multilevel coding (MLC) technique. We develop a method to analyze the asymptotic performance of the LDPC codes using message-passing decoding at each level of the MLC scheme as the codeword length goes to infinity. Simulation of very large block size LDPC codes verifies the accuracy of the analytical results. We jointly optimize the code rates and code parameters of the LDPC codes at each level of the MLC scheme, and the asymptotic performance of the optimized irregular LDPC codes is very close to the channel capacity of the additive white Gaussian noise (AWGN) channel View full abstract»

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  • Regular low-density parity-check codes from combinatorial designs

    Page(s): 90 - 92
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    Analytically constructed LDPC codes comprise only a very small subset of possible codes and as a result LDPC codes are still, for the most part, constructed randomly. This paper extends the class of LDPC codes that can be systematically generated by presenting a construction method for regular LDPC codes based on combinatorial designs known as Kirkman triple systems. We construct (3, ρ)-regular codes whose Tanner graph is free of 4-cycles for any integer ρ, and examine girth and minimum distance properties of several classes of LDPC codes obtained from combinatorial designs View full abstract»

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  • Robust space-time codes for time-selective fading

    Page(s): 112 - 114
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    We consider the design of robust codes that exploit both space and time diversity, using bit-interleaved coded modulation. Under quasi-static fading conditions, codes constructed in this way achieve full diversity and perform close to the best space-time trellis codes of comparable complexity. Under fast-fading conditions, these same codes achieve higher diversity than previously known codes of the same complexity View full abstract»

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  • Analog decoders for high rate convolutional codes

    Page(s): 128 - 130
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB) |  | HTML iconHTML  

    Recently, several VLSI implementations of analog decoders have been reported for rate 1/2 tailbiting convolutional codes. The main advantages of analog decoders are much higher decoding speed, smaller chip size and lower power consumption when compared to an equivalent digital decoder. Since many high speed applications require code rates well above 1/2 we focus on high rate tailbiting convolutional codes. For digital decoder implementations it has been shown by C. Weiss and J. Berkmann (see Proc. 3rd ITG Conf. Source and Channel Coding, Munich, Germany, p.199-207, Jan. 2000) that it is advantageous to use the trellis of the dual code which is less complex for high rate codes. The novel analog decoder design proposed in this paper can be seen as a direct analog implementation of the algorithm described by Weiss and Berkman View full abstract»

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  • On the spectral efficiency of CDMA with multiple antennas

    Page(s): 101 - 103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    We consider the impact of transmit diversity on the capacity of synchronous, randomly-spread code-division multiple-access, in the presence of frequency-flat fading. For large user populations, we characterize the spectral efficiency (capacity per chip) of two systems that use different spreading sequences on each antenna: a theoretically optimal system in which each transmit antenna is fed by independent data streams, and a code sequence diversity scheme that transmits the same data on each antenna View full abstract»

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