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Turbo space-time codes with time varying linear transformations

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2007年第2期6卷 486-493页

作者： Chen, Hangjun Haimovich, Alexander Sjogren, Jon A. New Jersey Inst Technol Dept Elect & Comp Engn Newark NJ 07102 USA USAF Off Sci Res NM Arlington VA 22203 USA

Turbo space-time codes with symbols precoded by randomly chosen unitary time variant linear transformations (TVLT) are investigated in this paper. It is shown that turbo codes with TVLT achieve full diversity gain and do not require exhaustive tests of the rank criterion. We prove that the coding gain performance of turbo space-time codes with TVLT improves with the Hamming distance between codewords (number of different columns). As an additional benefit of the application of TVLT, with the removal of the constant modulation condition, we prove that throughput rates achieved by these codes are significantly higher than those for conventional space-time codes. Numerical results are provided to demonstrate diversity gains, coding gains and rates of turbo space-time codes with TVLT.

关键词： MIMO concatenated coding

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Performance analysis of wireless multimedia DS/CDMA communications with power control and hybrid ARQ

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WIRELESS PERSONAL COMMUNICATIONS 2002年第3期20卷 205-218页

作者： Letaief, KB Melanie, YF Hong Kong Univ Sci & Technol Elect & Elect Engn Dept Ctr Wireless Informat Technol Kowloon Hong Kong Peoples R China

In this paper, we present a performance analysis of a wireless multimedia direct-sequence code-division multiple-access (DS/CDMA) system based on different error control schemes and an optimal power control algorithm over multipath Rayleigh fading channels. The error control schemes consist of Forward Error Correction (FEC), diversity, and Automatic Repeat reQuest (ARQ). The concatenated codes with a Reed-Solomon outer code and convolutional inner code are used as FEC. Since a multimedia system is required to support services with different rates and Quality of Services (QoS), different error control schemes are used to satisfy the requirements of different media. In particular, a power control algorithm which can optimize the capacity performance of the integrated system is presented. Numerical results will show that power optimization can increase the capacity and decrease the total transmission power. By incorporating diversity and hybrid ARQ along with appropriate code rates in the optimal power controlled system, dramatic increase in system capacity can also be achieved.

关键词： wireless multimedia communications multipath fading channels concatenated coding CDMA power control

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On iterative decoding in some existing systems

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2001年第5期19卷 883-890页

作者： Bajcsy, J Chong, CV Garr, DA Hunziker, J Kobayashi, H McGill Univ Dept Elect & Comp Sci Montreal PQ H3A 2A7 Canada MIT Dept Elect Engn & Comp Sci Cambridge MA 02139 USA Princeton Univ Dept Elect Engn Princeton NJ 08544 USA

Iterative decoding is used to achieve backward compatible performance improvement in several existing systems. concatenated coding and iterative decoding are first set up using composite mappings, so that various applications in digital communication and recording can be described in a concise and uniform manner. An ambiguity zone detection (AZD) based iterative decoder, operating on generalized erasures, Is described as an alternative for concatenated systems where turbo decoding cannot be performed. Described iterative decoding techniques are then applied to selected wireless communication and digital recording systems. Simulation results and utilization of decoding gains are briefly discussed.

关键词： concatenated coding digital recording systems iterative decoding wireless communication systems

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An Improved Bound on the Fraction of Correctable Deletions

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IEEE TRANSACTIONS ON INFORMATION THEORY 2017年第1期63卷 93-103页

作者： Bukh, Boris Guruswami, Venkatesan Hastad, Johan Carnegie Mellon Univ Dept Math Sci Pittsburgh PA 15213 USA Carnegie Mellon Univ Dept Comp Sci Pittsburgh PA 15213 USA Royal Inst Technol Sch Comp Sci & Commun SE-10044 Stockholm Sweden

We consider codes over fixed alphabets against worst case symbol deletions. For any fixed k >= 2, we construct a family of codes over alphabet of size k with positive rate, which allow efficient recovery from a worst case deletion fraction approaching 1 - (2/(k + root k)). In particular, for binary codes, we are able to recover a fraction of deletions approaching 1/(root 2+1) = root 2-1 approximate to 0.414. Previously, even non-constructively, the largest deletion fraction known to be correctable with positive rate was 1 - Theta (1/root k), and around 0.17 for the binary case. Our result pins down the largest fraction of correctable deletions for k-ary codes as 1 - Theta (1/k), since 1 - 1/k is an upper bound even for the simpler model of erasures where the locations of the missing symbols are known. Closing the gap between (root 2 - 1) and 1/2 for the limit of worst case deletions correctable by binary codes remains a tantalizing open question.

关键词： Error-correction deletion codes combinatorics concatenated coding

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A Broadband Power-Line Communication System Design Scheme for Typical Tanzanian Low-Voltage Network

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IEEE TRANSACTIONS ON POWER DELIVERY 2009年第3期24卷 1218-1224页

作者： Anatory, Justinian Theethayi, Nelson Thottappillil, Rajeev Mvungi, Nerey H. Univ Dodoma Coll Informat & Virtual Educ Dodoma Tanzania Uppsala Univ Div Elect Uppsala Sweden Royal Inst Technol Stockholm Sweden

Information and communications technologies (ICTs) are gaining importance in developing countries. Power-line network is a potential infrastructure for ICT services provision. Power-lines are highly interconnected network with stochastic variation in number of branches. Under such distributed network conditions the design of a broadband power-line communication (BPLC) system is a challenge. In this paper a case study of an actual power-line network, representative of a low-voltage BPLC channel in Dar es Salaam, Tanzania is considered. We shall investigate the performance of such a low-voltage channel that uses orthogonal frequency division multiplexing (OFDM) technique with binary phase shift keying (BPSK) modulation scheme for communication. For sensitivity analysis, three different transmitter locations were chosen and receiver points were varied to identify the possible degraded performance scenarios. Analysis show that in the frequency bands of 100 MHz, the channel delay spread for such networks is about 4 mu s, giving a maximum number of subchannels 4096 with 512 cyclic prefix. To improve the degraded performance scenarios, the concatenated Reed Solomon outer code with punctured convolution inner code was applied to the network. It was found that when the branches were terminated by its corresponding characteristic impedances the performance is improved by 1.0-20 dB compared to a corresponding uncoded system. On the contrary for a coded system when the branches were terminated either in low or higher impedances compared to branch characteristic impedances the improvement was greater than 2-15 dB. This study demonstrates that the specification proposed by IEEE-802.16 Broadband wireless access working groups can be used for performance improvement of distributed low-voltage systems.

关键词： Broadband power-line communication channel model concatenated coding impulsive noise interleaving multipath channel punctured convolutional codes Reed Solomon codes transfer function

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Coded modulation for E²PR4 and ME²PR4 channels

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IEEE TRANSACTIONS ON MAGNETICS 2000年第6期36卷 4036-4043页

作者： Kuznetsov, AV Data Storage Inst Singapore 117608 Singapore

We consider a multilevel modulation scheme based on: 1) a structured set partition (SSP) of partial-response (PR) channel output words;2) a set of conventional block codes with different error-correcting capabilities, and 3) a Viterbi detector searching for the two best paths on the channel trellis. For the classic and modified:target polynomials, examples of SSPs with the good spectra of minimum-Euclidean:distances are given. Bit error rates (BERs) of the Proposed scheme ate investigated for the conventional(E(2)PR4) and modified (ME(2)PR4) channels with the target polynomials 1 + 2D - 2D(3) D-4 and 5 + 4D - 3D(2) - 4D(3) - 2D(4), respectively. Results of simulations show that a gain of 3.4 dB fan be achieved for linear densities of 2.5 to 3.0 and BER of 10(-6) without using any additional distance enhancing constraints [such as d = 1, maximum transition run (MTR), or;quasi-MTR].

关键词： concatenated coding iterative decoding list decoding modulation codes partial response channels recording codes set partitions turbo decoding

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Turbo decoding for partial response channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2000年第8期48卷 1297-1308页

作者： Souvignier, TV Öberg, M Siegel, PH Swanson, RE Wolf, JK Texas Instruments Inc Longmont CO 80503 USA Marvell Semicond Inc Sunnyvale CA 94085 USA Univ Calif San Diego Dept Elect & Comp Engn La Jolla CA 92093 USA Seagate Technol Corp Fremont CA 94538 USA Univ Calif San Diego Ctr Magnet Recording Res La Jolla CA 92039 USA

The partial response channel can be viewed as a rate-1 encoder in which the output alphabet differs from the input alphabet. In serially concatenated coding schemes, the partial response channel can serve as the inner encoder, Recent work on the application of turbo decoding techniques to partial response channels has focused on using a parallel concatenation of convolutional encoders as the outer code and the partial response channel as the inner code. This system requires three a posteriori probability (APP) detectors-one matched to the channel and two matched to the constituent encoders. A simplified system will be presented that uses as its outer code a single convolutional code and as its inner code the partial response channel. The simplified system requires only two APP detectors, offering significant savings in complexity and computation time. This single convolutional code system will be shown to perform as well as the more complicated system, offering substantial gains over uncoded systems. Simulation results for three magnetic recording channel models will be presented: a partial response channel with additive white Gaussian noise, an equalized Lorentzian channel model, and a media noise model called the microtrack model, Since the use of an outer Reed-Solomon code is anticipated in an actual system, the burst-error statistics are investigated. System performance with various interleaver designs and precoders is also investigated.

关键词： concatenated coding iterative methods partial response signaling turbo codes

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Iterative decoding of compound codes by probability propagation in graphical models

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1998年第2期16卷 219-230页

作者： Kschischang, FR Frey, BJ Univ Toronto Dept Elect & Comp Engn Toronto ON Canada Univ Illinois Beckman Inst Urbana IL 61801 USA

We present a unified graphical model framework for describing compound codes and deriving iterative decoding algorithms, After reviewing a variety of graphical models (Markov random fields, Tanner graphs, and Bayesian networks), we derive a general distributed marginalization algorithm far functions described by factor graphs. From this general algorithm, Pearl's belief propagation algorithm is easily derived as a special case, We point out that recently developed iterative decoding algorithms for various codes, including "turbo decoding" of parallel-concatenated convolutional codes, may be viewed as probability propagation in a graphical model of the code, We focus on Bayesian network descriptions of codes, which give a natural input/state/output/channel description of a code and channel, and we indicate how iterative decoders can be developed for parallel- and serially concatenated coding systems, product codes, and low-density parity-check codes.

关键词： concatenated coding decoding graph theory iterative methods product codes

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Channel combining and splitting for cutoff rate improvement

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IEEE TRANSACTIONS ON INFORMATION THEORY 2006年第2期52卷 628-639页

作者： Arikan, E Bilkent Univ Dept Elect Elect Engn TR-06800 Ankara Turkey

The cutoff rate R-0 (W) of a discrete memoryless channel (DMC) W is often used as a figure of merit alongside the channel capacity C(W). If a channel W is split into two possibly correlated subchannels W-1, W-2, the capacity function always satisfies C(W-1) + C(W-2): <= C(W), while there are examples for which R-0 (W-1) + R-0 (W-2) > R-0 (W). The fact that cutoff rate can be '' created '' by channel splitting was noticed by Massey in his study of an optical modulation system. This paper gives a general framework for achieving similar gains in the cutoff rate of arbitrary DMCs by methods of channel combining and splitting. The emphasis is on simple schemes that can be implemented in practice. We give several examples that achieve significant gains in cutoff rate at little extra system complexity. Theoretically, as the complexity grows without bound, the proposed framework is capable of boosting the cutoff rate of a channel to arbitrarily close to its capacity in a sense made precise in the paper. Apart from Massey's work, the methods studied here have elements in common with Forney's concatenated coding idea, a method by Pinsker for cutoff rate improvement, and certain coded-modulation techniques, namely, Ungerboeck's set-partitioning idea and Imai-Hirakawa multilevel coding;these connections are discussed in the paper.

关键词： channel combining channel splitting coded modulation concatenated coding cutoff rate error exponent multilevel coding random-coding exponent reliability exponent set partitioning successive cancellation decoding

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Multilevel Transmission in Dimmable Visible Light Communication Systems

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2013年第20期31卷 3267-3276页

作者： Lee, Sang Hyun Ahn, Kang-Il Kwon, Jae Kyun Univ Texas Austin Dept Elect & Comp Engn Austin TX 78712 USA Yeungnam Univ LED IT Fus Technol Res Ctr Gyongsan 712749 South Korea Yeungnam Univ Dept Elect Engn Gyongsan 712749 South Korea

This paper proposes a multilevel transmission scheme for dimmable visible light communication systems. To provide dimming control of the multilevel modulation, the concatenation of different pulse-amplitude-modulated symbols is used to yield the overall signal with an average amplitude that matches the dimming requirement. This scheme also aims at arbitrary dimming adaptation by adjusting the composition of concatenated differently modulated symbols. To this end, the problem is formulated into linear programming with the objective of maximizing the transmission data rate and satisfying the dimming requirements. We present an achievable data rate of this transmission scheme and demonstrate the error performance under iterative decoding.

关键词： concatenated coding dimming linear codes pulse amplitude modulation visible light communication

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