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Neural network implementation of the BCJR algorithm

DIGITAL SIGNAL PROCESSING 2007年第1期17卷 353-359页

作者： Sazli, Murat Husnu Isik, Can Ankara Univ Fac Engn Dept Elect Engn TR-06100 Ankara Turkey Syracuse Univ LC Smith Coll Engn & Comp Sci Dept Elect Engn Syracuse NY 13244 USA

In this paper, we first show that the BCJR algorithm (or Bahl algorithm) can be implemented via some matrix manipulations. As a direct result of this, we also show that this algorithm is equivalent to a feedforward neural network structure. We verified through computer simulations that this novel neural network implementation yields identical results with the BOR algorithm. (c) 2006 Elsevier Inc. All rights reserved.

关键词： turbo codes turbo coding/decoding channel coding Bahl algorithm BCJR algorithm map algorithm neural networks

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Code recognition for dual N-ary orthogonal hybrid modulation systems

Code recognition for dual <i>N</i>-ary orthogonal hybrid mod...

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International Symposium on Intelligent Signal Processing and Communication Systems

作者： Qiao, Xiaoqiang Zhao, Hangsheng Cai, Yueming Nanjing Telecommun Technol Inst Nanjing Peoples R China Nanjing Inst Commun Engn Nanjing Jiangsu Peoples R China

ISBN: (纸本)9781424414468

Dual N-ary orthogonal hybrid modulation system can increase the data rate greatly compared with conventional N-ary orthogonal spread spectrum system, so it can be used for high rate data communication. In this paper, three code recognition algorithms are presented for dual N-ary orthogonal hybrid modulation system. Then the performance of the system in AWGN and flat Rayleigh fading channel with the three different code recognition algorithms is simulated. The simulation results show that the simplified map algorithm is best for the system with a compromise between the performance and the complexity.

关键词： code recognition N-axy orthogonal SS hybrid modulation map algorithm

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A Reliability-Based SNR Estimation Method in Turbo Detection Systems

A Reliability-Based SNR Estimation Method in Turbo Detection...

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IEEE Vehicular Technology Conference

作者： Li Qiang Shaoqian Li Nion Key Lb of Counicion Universiy of Eecronic Science nd Technoogy of Chin Chengdu 610054 P.R. Chin

ISBN: (纸本)1424402638;9781424402632;1424402646

In this paper, we analyze the sensitivity of map algorithm and its reduced ones, as Max-Log-map and Scaled Max-Log-map, to SNR mismatch in turbo detection systems. And then, we propose a new reliability-based SNR estimation method using the soft extrinsic information output from SMLM decoder. Next, a new turbo equalization scheme is also provided with the new SNR estimation algorithm. Finally, the performance of turbo equalization systems are evaluated using our new scheme. The simulation results show that our equalization scheme performs very close to the LM algorithm with known channel SNR, although it does not need pilot symbols.

关键词： equalisers maximum likelihood detection maximum likelihood estimation turbo codes LM algorithm map algorithm SMLM decoder log maximum a posteriori algorithm reliability-based SNR estimation method scaled max-log-map soft extrinsic information output turb Equalizers maximum likelihood detection turbo codes maximum likelihood estimation Detection systems Least mean square algorithm Worm gears Turbo

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Punctured turbo codes for bandwidth-efficient transmission

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DEFENCE SCIENCE JOURNAL 2006年第4期56卷 585-590页

作者： Rekh, Shobha Rani, S. Subha Shanmugam, A. Joshua, John Kulothungan PSG Coll Technol Coimbatore Tamil Nadu India Karunya Deemed Univ Coimbatore 641028 Tamil Nadu India Bannari Amman Inst Technol Coimbatore Tamil Nadu India

Turbo codes are the error-coding schemes applied nowadays in wireless networks. In naval applications, the information is mostly sent through wireless networks and the data is more prone to noise. Since very important data has to be communicated, it is necessary to get back the original data in the receiver. In military applications also, the soldiers wear electronic jackets which are connected by wireless networks. In such applications, the data loss is not affordable and - there is also a need to utilise the bandwidth efficiently through puncturing by means of which certain bits are deleted before transmission from the output of encoder. By,means of this punctured turbo codes, bandwidth-efficient coding is achieved. Hence, it is necessary to design turbo codes with an efficient puncturing pattern so that the performance of the punctured code is also improved in spite of deletion of few bits before transmission. This paper deals in choosing the puncturing patterns that lead to systematic rate-compatible punctured turbo codes (RCPTCs) which also give a reduction in bit-error rate. ' The design criterion for choosing the best puncturing patterns is based on the minimum weight of code words and their multiplicities. The best puncturing pattern chosen is tested for its performance by simulating turbo codes for an additive white Gaussian noise (AWGN) channel. Compared with the existing puncturing pattern;the pattern proposed is able to achieve a gain of 0.5 dB at a bit-error rate of 10(-3).

关键词： wireless transmission turbo codes error-coding schemes rate-compatible punctured turbo codes additive white Gaussian noise map algorithm soft output viterbi algorithm RCPC rate-compatible punctured codes recursive systematic convolutional encoders

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Exploring general memory structures in turbo decoders using sliding-window map algorithm

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IEICE TRANSACTIONS ON COMMUNICATIONS 2003年第11期E86B卷 3163-3173页

作者： Wu, CM Shieh, MD Wu, CH Natl Cheng Kung Univ Dept Elect Engn Tainan 70101 Taiwan

Turbo coding is a powerful coding technique that can provide highly reliable data transmission at extremely low signal-to-noise ratios. Owing to the computational complexity of the employed decoding algorithm, the realization of turbo decoders usually takes a large amount of memory space and potentially long decoding delay. Therefore, an efficient memory management strategy becomes one of the key factors toward successfully implementing turbo decoders. This paper focuses on the development of general structures for efficient memory management of turbo decoders employing the sliding-window (Log-)map algorithm. Three different structures and the associated mathematic representations are derived to evaluate the required memory size, average decoding rate, and latency based on the speed and the number of the adopted processors. Comparative results show the dependency of the resulting performance based on a set of parameters;thus provide useful and general information on practical implementations of turbo decoders.

关键词： turbo code BCJR algorithm map algorithm sliding window algorithm memory management

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An improved sliding window algorithm for Max-Log-map turbo decoder and its programmable LSI implementation

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IEICE TRANSACTIONS ON ELECTRONICS 2005年第3期E88C卷 403-412页

作者： Gambe, H Tanaka, Y Ohbuchi, K Ishihara, T Li, JF Fujitsu Labs Ltd Kawasaki Kanagawa 2118588 Japan

Thanks to the possibility of being able to implement them in decoders in relatively simple ways, turbo codes are being applied to various areas of engineering. Wireless communications is one of the most important applications, where various types of data communications are required and the speed of information and data capacity need to be changed with different rates of parity bit puncturing being adopted to obtain highly efficient transmission. In such applications, adaptation to various turbo-coding specifications on a real-time basis is needed as well as good bit-error-rate performance. We present a new concept for simplifying metric computation and programmable circuit configurations that focuses on the convolutional decoder, which occupies a significant portion of allocated hardware, and we fundamentally treat a simplified log-domain version of the maximum a posteriori (map) algorithm, usually know as the Max-Log-map (MLM), as a base algorithm. The sliding window method provides an attractive way of computing metric values for the Max-Log-map. However, this algorithm does cause degradation, especially when a high rate code is used, generated by bit puncturing. We propose a new means of avoiding this problem and demonstrate that the sliding window, and a modified version as well as other methods, should be flexibly selected to utilize hardware resources depending on turbo specifications. We demonstrated that our proposed methods provide almost the same BER performance as MLM even when a high rate puncturing rate of 5/6 is applied. Finally, we describe the new hardware architecture that we invented to cope with these programmability issues. We show that a turbo-decoding circuit can be implemented in the processor core and its associated unit to configure an LSI macro circuit. The proposed unit has about 60-K gates. We demonstrate that this architecture can be applied to about the 1.5-Mbps information bit throughput of turbo decoding with a 200-MHz clock cycle, wh

关键词： turbo coding map algorithm Max-Log-map sliding window

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VLSI architectural design tradeoffs for sliding-window Log-map decoders

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IEEE TRANSACTIONS ON VERY LARGE SCALE INTEGRATION (VLSI) SYSTEMS 2005年第4期13卷 439-447页

作者： Wu, CM Shieh, MD Wu, CH Hwang, YT Chen, JH Natl Appl Res Labs CIC Hsinchu 300 Taiwan Natl Cheng Kung Univ Dept Elect Engn Tainan 70101 Taiwan Natl Chung Cheng Univ Dept Elect Engn Chiayi 621 Taiwan Natl Yunlin Univ Sci & Technol Dept Elect Engn Yunlin 640 Taiwan

Turbo codes have received tremendous attention and have commenced their practical applications due to their excellent error-correcting capability. Investigation of efficient iterative decoder realizations is of particular interest because the underlying soft-input soft-output decoding algorithms usually lead to highly complicated implementation. This paper describes the architectural design and analysis of sliding-window (SW) Log-map decoders in terms of a set of predetermined parameters. The derived mathematical representations can be applied to construct a variety of VLSI architectures for different applications. Based on our development, a SW-Log-map decoder complying with the specification of third-generation mobile radio systems is realized to demonstrate the performance tradeoffs among latency, average decoding rate, area/computation complexity, and memory power consumption. This paper thus provides useful and general information on practical implementation of SW-Log-map decoders.

关键词： iterative decoding map algorithm sliding window algorithm turbo code VLSI architecture and design

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VHDL implementation of a turbo decoder with log-map-based iterative decoding

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2004年第4期53卷 1268-1278页

作者： Tong, YH Yeap, TH Chouinard, JY Univ Ottawa Sch Informat Technol & Engn Ottawa ON K1N 6N5 Canada Univ Laval Dept Elect & Comp Engn Quebec City PQ G1K 7P4 Canada

Turbo code is one of the most significant achievements in coding theory during the last decade. By concatenating two simple convolutional codes in parallel, it has been shown that transmission systems employing turbo codes could offer near-capacity performance. More importantly, by employing a suboptimal iterative decoding structure with soft-in/soft-out (SISO) maximum a posteriori-probability (APP) decoding algorithm, the near-capacity performance is achievable at a feasible decoding complexity. Given the outstanding performance of turbo code, the challenge now is to implement it into various communication systems at affordable decoding complexity using current very large scale integration (VLSI) technologies. In this paper, we first investigated the existing four different turbo decoding algorithms. Comparisons of both their performances and implementation complexities were performed. Log-maximum a posteriori (map) -based turbo decoding was found to offer the best performance-complexity compromise. A register-transfer-level (RTL) 12-bit fixed-point turbo decoder based on Log-map algorithm was then designed and simulated using VHDL as the hardware description language. The implemented RTL model was verified by comparing its performances with those obtained from a C-language implementation of the same turbo decoder.

关键词： iterative decoding map algorithm soft-in/soft-out (SISO) decoder turbo code very large scale integration (VLSI) VHDL

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Performance evaluation for map state estimate fusion

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 2004年第2期40卷 706-714页

作者： Chang, KC Tian, Z Mori, S Chong, CY George Mason Univ Dept SEOR Fairfax VA 22030 USA Michigan Technol Univ Dept Elect & Comp Engn Houghton MI 49931 USA ALPHATECH Inc San Diego CA 92121 USA

This paper presents a quantitative performance evaluation method for the maximum a posteriori (map) state estimate fusion algorithm. Under ideal conditions where data association is assumed to be perfect, it has been shown that the map or best linear unbiased estimate (BLUE) fusion formula provides the best linear minimum mean squared estimate (LMMSE) given local estimates under the linear Gaussian assumption for a static system. However, for a dynamic system where fusion is recursively performed by the fusion center on local estimates generated from local measurements, it is not obvious how the map algorithm will perform. In the past, several performance evaluation methods have been proposed for various fusion algorithms, including simple convex combination, cross-covariance combination, information matrix, and map fusion. However, not much has been done to quantify the steady state behavior of these fusion methods for a dynamic system. The goal of this work is to present analytical fusion performance results for map state estimate fusion without extensive Monte Carlo simulations, using an approach developed for steady state performance evaluation for track fusion. Two different communication strategies are considered: fusion with and without feedback to the sensors. Analytic curves for the steady state performance of the fusion algorithm for various communication patterns are presented under different operating conditions.

关键词： .fusion algorithm LMMSE local estimates linear Gaussian map algorithm map fusion steady state performance track fusion various communication sensor measurements

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On the iterative decoding of concatenated partial unit memory codes structures

On the iterative decoding of concatenated partial unit memor...

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1st International Symposium on Wireless Communication Systems (ISWCS 04)

作者： Fagoonee, L Honary, B Univ Lancaster Fac Sci Appl Dept Commun Syst Lancaster LA1 4YW England

ISBN: (纸本)0780384725

The aim of this paper is to describe in detail the iterative decoding algorithm used during the implementation of concatenated Partial Unit Memory (PUM) code structures, such as turbo and woven turbo constructions based on PUM codes. Previous published research by the authors have shown that such concatenated PUM code structures have better distance properties and performance than equivalent structures based on convolutional codes. The decoding algorithm presented is based on the max-log map algorithm used for classical turbo codes with component convolutional codes. Unlike the trellis of a convolutional code, the trellis of PUM codes is characterised by parallel branches between state pairs and multiple input branch labels. We show how the original max-log map algorithm is adapted to cope with the unusual trellis structure of PUM codes. The proof that our algorithm performs satisfactorily is illustrated by the relative performance, for different iterations, of turbo and woven turbo structures based on PUM codes, which approach the Shannon limit.

关键词： iterative decoding map algorithm turbo codes woven turbo codes PUM codes

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