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A modified Viterbi decoding algorithm for high-rate convolutional codes

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS 2005年第6期16卷 527-536页

作者： Amat, AGI Benedetto, S Siegel, PH Politecn Torino Dipartimento Elettron I-10129 Turin Italy Univ Pompeu Fabra Dept Tecnol Barcelona 08003 Spain Univ Calif San Diego ECE Dept La Jolla CA 92093 USA

It is well-known that the computational complexity of the Viterbi decoding algorithm for an (n, k, V) convolutional code grows exponentially with k and the code memory v, and thus it becomes quickly impractical as the code rate increases. A solution, so far, has been to use punctured convolutional codes, which strongly reduces the decoding complexity but leads to a slightly worse performance. Recently, it has been pointed out that every non-punctured high-rate convolutional code (with 2(k) > 2(v)) can be viewed as the concatenation of a block code and a simpler convolutional code. In this paper, we exploit this property of high-rate codes to facilitate the implementation of the Viterbi algorithm. We propose a modification of the Viterbi decoding algorithm for non-punctured high-rate convolutional codes which results in very significant computational savings. Copyright (c) 2005 AEIT.

关键词： Block codes complexity classes code rate algorithms Viterbi algorithm Viterbi decoding decoding algorithm code memory convolutional coding punctured convolutional code

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BLMS adaptive receiver for direct-sequence code division multiple access systems

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JOURNAL OF COMMUNICATIONS AND NETWORKS 2005年第3期7卷 243-247页

作者： Hamouda, W McLane, PJ Concordia Univ Dept Elect & Comp Engn Montreal PQ HEG 1M8 Canada Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

We propose an efficient block least-mean-square (BLMS) adaptive algorithm, in conjunction with error control coding, for direct-sequence code division multiple access (DS-CDMA) systems. The proposed adaptive receiver incorporates decision feedback detection and channel encoding in order to improve the performance of the standard LMS algorithm in convolutionally coded systems. The BLMS algorithm involves two modes of operation: (i) The training mode where an uncoded training sequence is used for initial filter tap-weights adaptation, and (ii) the decision-directed where the filter weights are adapted, using the BLMS algorithm, after decoding/encoding operation. It is shown that the proposed adaptive receiver structure is able to compensate for the signal-to-noise ratio (SNR) loss incurred due to the switching from uncoded training mode to coded decision-directed mode. Our results show that by using the proposed adaptive receiver (with decision feedback block adaptation) one can achieve a much better performance than both the coded LMS with no decision feedback employed. The convergence behavior of the proposed BLMS receiver is simulated and compared to the standard LMS with and without channel coding. We also examine the steady-state bit-error rate (BER) performance of the proposed adaptive BLMS and standard LMS, both with convolutional coding, where we show that the former is more superior than the latter especially at large SNRs (SNR >= 9 dB).

关键词： adaptive filtering block least-mean-square (BLMS) adaptation code division multiple access (CDMA) convolutional coding interference cancellation

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Signal design and convolutional coding for noncoherent space-time communication on the block-Rayleigh-fading channel

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IEEE TRANSACTIONS ON INFORMATION THEORY 2002年第5期48卷 1186-1194页

作者： McCloud, ML Brehler, M Varanasi, MK Univ Colorado Dept Elect & Comp Engn Boulder CO 80309 USA

We consider the problem of designing signal constellations for the multiple transmit-multiple receive antenna Rayleigh-fading communication channel, when neither the transmitter nor the receiver know the fading. In particular, by employing the asymptotic union bound (AUB) on the probability of error, we give a new formulation of the problem of signal design for the noncoherent fading channel. Since unitary signals are optimal for this channel (in the limit of large signal-to-noise ratios SNRs), the problem can be posed in terms of packings on the Grassmanian manifold. A key difference in our approach from that of other authors is that we use a notion of distance on this manifold that is suggested by the union bound. As a consequence of our use of this distance measure, we obtain signal designs that are guaranteed to achieve the full diversity order of the channel, a result that does not hold when the chordal distance is used. We introduce a new method of recursively designing signals, termed successive updates, to approximately optimize this performance measure. We then examine the use of our signals with several convolutional codes over the fading channel. An upper bound on the bit error probability of the maximum-likelihood decoder is presented together with an asymptotic analysis of that bound.

关键词： convolutional coding fading channels noncoherent communication signal design space-time modulation

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Improved convolutional code design for 3GPP TDD systems

Improved convolutional code design for 3GPP TDD systems

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IEEE Wireless Communications and Networking Conference

作者： Wu, G Li, YH Philips Res E Asia Shanghai 200070 Peoples R China

ISBN: (纸本)0780389662

convolutional code is one of important channel codes to combat fading and noise in 3GPP 3.84/1.28Mcps TDD systems. However, the design of the convolutional codes used in current specifications just obtain the best performance for BPSK modulation and AWGN propagation channel. In 3GPP 3.84/1.28Mcps TDD systems, QPSK modulation is adopted. Moreover, multipath fading channels are often encountered in the practical communication environments. Therefore, convolutional codes used in the specifications cannot always achieve the best performance in the practical 3GP 3.84/1.28Mcps TDD systems. In this paper, we proposed an improved convolutional encoder for 3GPP 3.84/1.28Mcps TDD downlink system by analyzing the integration effects of QPSK modulation and multipath fading channels on the code design. Performance analysis and simulation show that better system performance can be achieved by using the proposed encoder.

关键词： convolutional coding 3GPP TDD rayleigh fading channel

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Construction, analysis and performance of generalised woven codes

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EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS 2004年第2期15卷 79-90页

作者： Bossert, M Dieterich, H Schnug, W Shavgulidze, S Univ Ulm Dept Telecommun & Appl Informat Theory D-89081 Ulm Germany Siemens AG D-89081 Ulm Germany Georgian Tech Univ Dept Digital Commun GE-380075 Tbilisi Georgia

Generalised woven codes (WC) are constructed by combining the woven code structure with the idea of generalised concatenated codes, also known as multi-level codes. The required nested inner convolutional code is analysed. The encoder structure of this new class of codes is described and fundamental code parameters are derived. It is shown that generalised WC have a free distance which is superior to that of comparable WC. Several iterative and non-iterative decoding strategies are discussed. It is shown that the decoding complexity of the nested inner code is not larger than the decoding complexity of its mother code. Finally, bit error rates obtained from simulations are discussed and compared with other code structures like WC. Copyright (C) 2004 AEI.

关键词： Toilets DEcoding Concatenated codes Codes New classes Mother convolutional coding

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Turbo equalization

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IEEE SIGNAL PROCESSING MAGAZINE 2004年第1期21卷 67-80页

作者： Koetter, R Singer, AC Tüchler, M Univ Illinois Coordinated Sci Lab Urbana IL 61801 USA Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA Tech Univ Munich Inst Commun Engn D-8000 Munich Germany

Turbo equalization is an iterative equalization and decoding technique that can achieve equally impressive performance gains for communication systems that send digital data over channels that require equalization, i.e., those that suffer from intersymbol interference (ISI). In this article, we discuss the turbo equalization approach to coded data transmission over ISI channels, with emphasis on the basic ideas and some of the practical details. The original system introduced by Douillard et al. can be viewed as an extension of the turbo decoding algorithm by considering the effect of the ISI channel as another form of error protection, i.e., as a rate-1 convolutional code.

关键词： turbo codes equalisers telecommunication channels iterative decoding data communication intersymbol interference convolutional codes channel coding turbo equalization iterative equalization iterative decoding technique digital data coded data transmission ISI channels turbo decoding algorithm convolutional code digital data data communication decoding algorithm data transmission Communication channels convolutional coding intersymbolic interference Equalizers Iterative decoding turbo codes Channel coding Equalization

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Near-optimal decoding for coded and power-controlled DS-CDMA downlink

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IEEE TRANSACTIONS ON COMMUNICATIONS 2004年第5期52卷 701-705页

作者： Kim, BH GCT Semicond Inc Seoul 150877 South Korea

We first present the traditional decoding approach that employs the common pilot-channel-based maximal ratio combining and the Viterbi or iterative decoding cannot achieve the optimal error-rate performance for downlink direct-sequence code-division multiple-access (CDMA) signals when a fast power control technique is applied together with a convolutional or turbo coding. Then, as an efficient method to realize a nearly optimal decoding, we propose a branch metric power readjustment (BMPR) technique, where the downlink power control command generated by the mobile station is used not only to adjust the base station power in the transmitter side, but also to readjust the decoder input branch metric power in the receiver side. Numerical results show that the BMPR technique applied to the IMT-2000 wideband-CDMA system can improve the transmit power utilization by up to 0.4 dB for the block-error rate of 10(-2).

关键词： branch metric power readjustment (BMPR) convolutional coding iterative decoding maximal ratio combining (MRC) turbo coding Viterbi decoding

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Woven coded continuous phase frequency shift keying

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EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS 2004年第4期15卷 323-336页

作者： Kempf, S Bossert, M Shavgulidze, S Univ Ulm Dept Telecommun & Appl Informat Theory D-89081 Ulm Germany Georgian Tech Univ Dept Digital Commun Theory GE-380075 Tbilisi Georgia

We introduce woven coded continuous phase frequency shift keying (WCCPFSK) as a serial concatenation of several outer convolutional codes and inner continuous phase frequency shift keying (CPFSK). WCCPFSK is a generalization of the serially concatenated CPFSK modulation scheme which uses only one outer convolutional code. We compute the active burst distances of CPFSK and estimate the free distance of systems with one outer code and of WCCPFSK with several outer codes. We show that WCCPFSK with several outer codes achieves the larger free distance. This results in better performance at low bit error rates, which we demonstrate in simulations. Copyright (C) 2004 AEI.

关键词： FREQUENCY SHIFT convolutional coding Bit error rate Weaving frequency shift keying

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Multiple symbol differential detection in jammed FH systems

Multiple symbol differential detection in jammed FH systems

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15th IEEE International Symposium on Personal, Indoor, Mobile, Radio Communications (PIMRC 2004)

作者： Koivu, S Siltala, S Iinatti, J Univ Oulu Ctr Wireless Commun FI-90014 Oulu Finland

ISBN: (纸本)0780385233

Non-coherent detection is usually applied in frequency hopping (FH) systems, because reliable coherent detection is very difficult. With multiple symbol differential detection (MSDD) a non-coherent system can achieve the performance of coherent differentially encoded systems. Due to its is complexity, two computationally simpler hard-decision feedback algorithms, multiple-symbol based decision-feedback differential detection (MSD DF-DD) and multiple symbol observation interval (MSOI), are studied and compared in partial-band jammed FH system. Additionally the system which uses maximum- a-posteriori (MAP) algorithm as inner decoder is studied and its performance is compared to MSD DF-DD and MSOI. The performance improvement of the MSD DF-DD and MSOI using two simple limiters are also studied. The non-iterative versions of MSD DF-DD and MSOI have very similar performance. MSD DF-DD benefits from the iterative processing more effectively than MSOI in jammed and non-jammed simulations. The impact of jamming depends strongly on its bandwidth. The narrower the jamming band is, the more the performance of the alaorithms decrease. MAP-based decoding performs significantly better than either of the algorithms.

关键词： convolutional coding hard decision feedback limiter partial-band jamming

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A turbo decoder architecture with scalable parallelism

A turbo decoder architecture with scalable parallelism

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IEEE Workshop on Signal Processing Systems Design and Implementation

作者： Engin, N Philips Res Labs Eindhoven Netherlands

ISBN: (纸本)0780385047

A scalable, programmable turbo decoder architecture is presented in this paper. The starting point is a comparison of the existing techniques on basis of scalability, area and power consumption. The results from these comparisons lead to a hybrid technique on which our architecture concept is based. The architecture is consisting of clusters each of which is a VLIW architecture. The upsizing is possible by adding a cluster and dividing the two data memories in banks. The window size is chosen according to the number of banks to prevent the conflicts. At the end of the paper, a short evaluation of the architecture is presented.

关键词： iterative decoding convolutional codes maximum likelihood decoding turbo codes parallel architectures programmable circuits convolutional decoders MAP decoder turbo decoder architecture scalable parallelism programmable turbo decoder scalability VLIW architecture clusters data memory banks data window size Iterative decoding Scalability programmable circuits Window Size maximum likelihood decoding Parallel architectures convolutional coding turbo codes ARCHITECTURE Building construction VLIW architecture Turbo Worm gears decoders

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