• Title/Summary/Keyword: Turbo decoding

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LLR Based Generalization of Soft Decision Iterative Decoding Algorithms for Block Turbo Codes (LLR 기반 블록 터보 부호의 연판정 복호 알고리즘 일반화)

  • Im, Hyun-Ho;Kwon, Kyung-Hoon;Heo, Jun
    • Journal of Broadcast Engineering
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    • v.16 no.6
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    • pp.1026-1035
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    • 2011
  • This paper presents generalization and application for the conventional SISO decoding algorithm of Block Turbo Codes. R. M. Pyndiah suggested an iterative SISO decoding algorithm for Product Codes, two-dimensionally combined linear block codes, on AWGN channel. It wascalled Block Turbo Codes. Based on decision of Chase algorithm which is SIHO decoding method, SISO decoder for BTC computes soft decision information and transfers the information to next decoder for iterative decoding. Block Turbo Codes show Shannon limit approaching performance with a little iteration at high code rate on AWGN channel. In this paper we generalize the conventional decoding algorithm of Block Turbo Codes, under BPSK modulation and AWGN channel transmission assumption, to the LLR value based algorithm and suggest an application example such as concatenated structure of LDPC codes and Block Turbo Codes.

A Study on Symbol-based Decoding for Turbo Codes (심볼 단위로 복호화가 이루어지는 터보부호에 관한 연구)

  • 김태국;심용걸
    • Proceedings of the IEEK Conference
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    • 2001.06a
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    • pp.273-276
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    • 2001
  • In this thesis we propose symbol-based decoding for turbo codes which is used SOVA as a decoding algorithm. The proposed turbo codes that is interleaved on symbol-by-symbol basis and inputted as n-bit symbols to the decoder. This method makes that the stages of the original trellis are merged together and the trellis depth is reduced by 1/n. We research turbo codes with symbol size n=2 in this paper and its performance.

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Turbo Decoding for Precoded Systems over Multipath Fading Channels

  • Zhang, Qing;Le-Ngoc, THo
    • Journal of Communications and Networks
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    • v.6 no.3
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    • pp.203-208
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    • 2004
  • A combined precoding and turbo decoding strategy for multi-path frequency-selective fading channels is presented. The precoder and multi-path fading channel are jointly modeled as a finite-state probabilistic channel to provide the multi-stage turbo decoder with its statistics information. Both a priori and a posteriori probabilities are used in the metric computation to improve the system performance. Structures of the combined turbo-encoder, interleaver, and precoder in the transmitter and two-stage turbo decoder in the receiver are described. Performance of the proposed scheme in fixed, Rician and Rayleigh multi-path fading channels are evaluated by simulation. The results indicate that the combined precoding and two-stage turbo decoding strategy provides a considerable performance improvement while maintaining the same inner structure of a conventional turbo decoder.

A 18-Mbp/s, 8-State, High-Speed Turbo Decoder

  • Jung Ji-Won;Kim Min-Hyuk;Jeong Jin-Hee
    • Journal of electromagnetic engineering and science
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    • v.6 no.3
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    • pp.147-154
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    • 2006
  • In this paper, we propose and present implementation results of a high-speed turbo decoding algorithm. The latency caused by (de) interleaving and iterative decoding in a conventional maximum a posteriori(MAP) turbo decoder can be dramatically reduced with the proposed design. The source of the latency reduction is come from the combination of the radix-4, dual-path processing, parallel decoding, and rearly-stop algorithms. This reduced latency enables the use of the turbo decoder as a forward error correction scheme in real-time wireless communication services. The proposed scheme results in a slight degradation in bit-error rate(BER) performance for large block sizes because the effective interleaver size in a radix-4 implementation is reduced to half, relative to the conventional method. Fixed on the parameters of N=212, iteration=3, 8-states, 3 iterations, and QPSK modulation scheme, we designed the adaptive high-speed turbo decoder using the Xilinx chip (VIRTEX2P (XC2VP30-5FG676)) with the speed of 17.78 Mb/s. From the results, we confirmed that the decoding speed of the proposed decoder is faster than conventional algorithms by 8 times.

Iterative Decoding for a Turbo-Coded OFDM/CDMA System

  • Kim, Jin-Young
    • Proceedings of the IEEK Conference
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    • 2001.06a
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    • pp.213-216
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    • 2001
  • In this paper, the performance of an OFDM/CDMA system with turbo coding is analyzed and simulated in a multipath fading channel. Bit error probability is derived fDr a Rayleigh fading channel. In an OFDM/CDMA system, an OFDM and a CDMA techniques are combined to exploit the advantages of both techniques. For decoding of turbo code, MAP decoding algorithm is employed. From the simulation results. it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding/decoding complexity. Also, it is shown that the BER performance is substantially improved by increasing the interleaver length for a fixed code rate and the increasing number of iterations used in the decoding process. The results in the paper can be applied to the design of OFDM-based CDMA system.

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Trellis-Based Decoding of High-Dimensional Block Turbo Codes

  • Kim, Soo-Young;Yang, Woo-Seok;Lee, Ho-Jin
    • ETRI Journal
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    • v.25 no.1
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    • pp.1-8
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    • 2003
  • This paper introduces an efficient iterative decoding method for high-dimensional block turbo codes. To improve the decoding performance, we modified the soft decision Viterbi decoding algorithm, which is a trellis-based method. The iteration number can be significantly reduced in the soft output decoding process by applying multiple usage of extrinsic reliability information from all available axes and appropriately normalizing them. Our simulation results reveal that the proposed decoding process needs only about 30% of the iterations required to obtain the same performance with the conventional method at a bit error rate range of $10^{-5}\;to\;10^{-6}$.

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High Speed Turbo Product Code Decoding Algorithm (고속 Turbo Product 부호 복호 알고리즘 및 구현에 관한 연구)

  • Choi Duk-Gun;Lee In-Ki;Jung Ji-Won
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.6C
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    • pp.442-449
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    • 2005
  • In this paper, we introduce three kinds of simplified high-speed decoding algorithms for turbo product decoder. First, A parallel decoder structure, the row and column decoders operate in parallel, is proposed. Second, HAD(Hard Decision Aided) algorithm is used for early-stopping algorithm. Lastly, P-Parallel TPC decoder is a parallel decoding scheme, processing P rows and P columns in parallel instead of decoding one by one as that in the original scheme.

An Efficient Method that Incorporate a Channel Reliability to the Log-MAP-based Turbo Decoding (Log-MAP 방식의 Turbo 복호를 위한 효과적인 채널 신뢰도 부과방식)

  • 고성찬;정지원
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.3B
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    • pp.464-471
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    • 2000
  • The number of quantization bits of the input signals $X_k$,$Y_k$ need to be optimally determined through the trade-off between the H/W complexity and the BER performance in Turbo codes applications. Also, an effective means to incorporate a channel reliability $L_c$ in the Log-MAP-based Turbo decoding is highly required. because it has a major effect on both the complexity and the performance. In this paper, a novel bit-shifting approach that substitutes for the multiplying is proposed so as to effectively incorporate. $L_c$ in Turbo decoding. The optimal number of quantization bits of $X_k$,$Y_k$ is investigated through Monte-Carlo simulations assuming that bit-shifting approach is adopted. In addition. The effects of an incorrect estimation of noise variance on the performance of Turbo codes is investigated. There is a confined range in which the effects of an incorrect estimation can be ignored.

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New Stop Criterion for Reduce of Decoding Delay of Turbo Codes (터보부호의 복호지연 감소를 위한 새로운 반복중단 알고리즘)

  • Shim B. S.;Lee W. B.;Jeong D. H.;Lim S. J.;Kim T. H.;Kim H. Y.
    • Proceedings of the IEEK Conference
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    • 2004.06a
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    • pp.39-42
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    • 2004
  • Turbo codes, proposed by Berrou, that increase the interleaver size and the number of iteration have better than conventional convolutional codes, in case of BER performance. However, because turbo codes has been required much decoding delay to increase iteration number, it demands unnecessary iterative decoding. Therefore, in this paper, we propose iterative decoding stop criterion that uses the variance of absolute value of LLR. This algorithm can be reduced average iterative decoding number and had lossless performance of BER, because of decreasing unnecessary iterative decoding.

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Turbo Codes with DC-Free Trellis Codes as Constituent Codes (무직류 격자형부호를 구성부호기로 가지는 터보부호)

  • 이병길;정창기배상재주언경
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.175-178
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    • 1998
  • In this paper, turbo codes with the DC-free trellis codes based on partition chain as constituent codes are presente. And efficient methods to design the DC-free turbo codes are introduced. An iterative decoding with the MAP algorithm is used for the decoding of the turbo codes designed by various methods. As results of simulations, the presented DC-free turbo codes show better error performances than the DC-free trellis codes.

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