• Title/Summary/Keyword: Low Density Parity Check

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LDPC Generation and Decoding concatenated to Viterbi Decoder based on Sytematic Convolutional Encoder (길쌈부호기를 이용한 LDPC 패리티검사 행렬생성 및 비터비 복호 연계 LDPC 복호기)

  • Lee, Jongsu;Hwang, Eunhan;Song, Sangseob
    • Smart Media Journal
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    • v.2 no.2
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    • pp.39-43
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    • 2013
  • In this paper, we suggest a new technique for WPC parity-check matrix (H-matrix) generation and a corresponding decoding process. The key idea is to construct WPC H-matrix by using a convolutional encoder. It is easy to have many different coderates from a mother code with convolutional codes. However, it is difficult to have many different coderates with LDPC codes. Constructing LDPC Hmatrix based on a convolutional code can easily bring the advantage of convolutional codes to have different coderates. Moreover, both LDPC and convolutional decoding algorithms can be applied altogether in the decoding part. This process prevents the performance degradation of short-length WPC code.

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Comparison of EXIT chart generation for LDPC and turbo codes (시뮬레이션 기법을 이용한 LDPC 부호와 터보부호에 대한 EXIT 차트 생성 비교)

  • Nyamukondiwa, Ramson Munyaradzi;Kim, Sooyoung
    • Journal of Satellite, Information and Communications
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    • v.10 no.3
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    • pp.73-77
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    • 2015
  • In this paper, we present two simulation methods to investigate the effect of excluding bit errors on generating the extrinsic information transfer (EXIT) chart for low density parity check (LDPC) and turbo codes. We utilized the simulation methods including and excluding bit errors to generate EXIT chart which was originally proposed for turbo codes. The generated EXIT charts for LDPC and turbo codes shows that the presented methods appropriately demonstrates the performance behaviours of iterative decoding for LDPC and turbo codes. Analysis on the simulation results demonstrates that the EXIT chart excluding the bit errors shows only a small part of the curves where the amount of information is too large.

An analysis of Multi-mode LDPC Decoder Performance for IEEE 802.11n WLAN (IEEE 802.11n WLAN용 Multi-mode LDPC 복호기의 성능 분석)

  • Park, Hae-Won;Na, Young-Heon;Shin, Kyung-Wook
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2010.10a
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    • pp.80-83
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    • 2010
  • This paper describes an analysis of decoding performance of multi-mode LDPC(Low Density Parity Check) decoder which supports three block lengths (648, 1296, 1944) and four code rates (1/2, 2/3,3/4, 5/6) for IEEE 802.11n WLAN system. A fixed-point model of LDPC decoder which adopts min-sum algorithm and layered decoding scheme is implemented using Matlab. From fixed-point simulation results for various bit-width parameters such as internal bit-width, bit-width of integer and fractional parts, an optimal design condition and decoding performance of LDPC decoder are analyzed.

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Build-in Wiretap Channel I with Feedback and LDPC Codes

  • Wen, Hong;Gong, Guang;Ho, Pin-Han
    • Journal of Communications and Networks
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    • v.11 no.6
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    • pp.538-543
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    • 2009
  • A wiretap channel I is one of the channel models that was proved to achieve unconditional security. However, it has been an open problem in realizing such a channel model in a practical network environment. The paper is committed to solve the open problem by introducing a novel approach for building wiretap channel I in which the eavesdropper sees a binary symmetric channel (BSC) with error probability p while themain channel is error free. By taking advantage of the feedback and low density parity check (LDPC) codes, our scheme adds randomness to the feedback signals from the destination for keeping an eavesdropper ignorant; on the other hand, redundancy is added and encoded by the LDPC codes such that a legitimate receiver can correctly receive and decode the signals. With the proposed approach, unconditionallysecure communication can be achieved through interactive communications, in which the legitimate partner can realize the secret information transmission without a pre-shared secret key even if the eavesdropper has better channel from the beginning.

Pipeline-Aware QC-IRA-LDPC Code and Efficient Decoder Architecture (Pipeline-Aware QC-IRA-LDPC 부호 및 효율적인 복호기 구조)

  • Ajaz, Sabooh;Lee, Hanho
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.10
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    • pp.72-79
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    • 2014
  • This paper presents a method for constructing a pipeline-aware quasi-cyclic irregular repeat accumulate low-density parity-check (PA-QC-IRA-LDPC) codes and efficient rate-1/2 (2016, 1008) PA-QC-IRA-LDPC decoder architecture. A novel pipeline scheduling method is proposed. The proposed methods efficiently reduce the critical path using pipeline without any bit error rate (BER) degradation. The proposed pipeline-aware LDPC decoder provides a significant improvement in terms of throughput, hardware efficiency, and energy efficiency. Synthesis and layout of the proposed architecture is performed using 90-nm CMOS standard cell technology. The proposed architecture shows more than 53% improvement of area efficiency and much better energy efficiency compared to the previously reported architectures.

Parallel LDPC Decoder for CMMB on CPU and GPU Using OpenCL (OpenCL을 활용한 CPU와 GPU 에서의 CMMB LDPC 복호기 병렬화)

  • Park, Joo-Yul;Hong, Jung-Hyun;Chung, Ki-Seok
    • IEMEK Journal of Embedded Systems and Applications
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    • v.11 no.6
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    • pp.325-334
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    • 2016
  • Recently, Open Computing Language (OpenCL) has been proposed to provide a framework that supports heterogeneous computing platforms. By using an OpenCL framework, digital communication systems can support various protocols in a unified computing environment to achieve both high portability and high performance. This article introduces a parallel software decoder of Low Density Parity Check (LDPC) codes for China Multimedia Mobile Broadcasting (CMMB) on a heterogeneous platform. Each step of LDPC decoding has different parallelization characteristics. In this paper, steps suitable for task-level parallelization are executed on the CPU, and steps suitable for data-level parallelization are processed by the GPU. To improve the performance of the proposed OpenCL kernels for LDPC decoding operations, explicit thread scheduling, loop-unrolling, and effective data transfer techniques are applied. The proposed LDPC decoder achieves high performance by using heterogeneous multi-core processors on a unified computing framework.

Performance Analysis of DVB-T2 Turbo Equalization with LDPC and MAP Detector (LDPC 복호와 MAP 등화기를 결합한 DVB-T2 터보 등화기법의 성능분석)

  • Tai, Qing Song;Han, Dong-Seog
    • Journal of Broadcast Engineering
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    • v.15 no.5
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    • pp.665-671
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    • 2010
  • In this paper, a turbo equalizer is proposed for the digital video broadcasting for terrestrial - 2nd generation (DVB-T2) system. The proposed turbo equalizer is consisted with the maximum a posteriori (MAP) and low density parity check (LDPC) decoder. The channel information for the soft-input-soft-output (SISO) MAP equalizer is based on the least square (LS) channel estimator. The performance is analyzed through computer simulations in terms of the iteration number.

Construction of Structured q-ary LDPC Codes over Small Fields Using Sliding-Window Method

  • Chen, Haiqiang;Liu, Yunyi;Qin, Tuanfa;Yao, Haitao;Tang, Qiuling
    • Journal of Communications and Networks
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    • v.16 no.5
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    • pp.479-484
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    • 2014
  • In this paper, we consider the construction of cyclic and quasi-cyclic structured q-ary low-density parity-check (LDPC) codes over a designated small field. The construction is performed with a pre-defined sliding-window, which actually executes the regular mapping from original field to the targeted field under certain parameters. Compared to the original codes, the new constructed codes can provide better flexibility in choice of code rate, code length and size of field. The constructed codes over small fields with code length from tenths to hundreds perform well with q-ary sum-product decoding algorithm (QSPA) over the additive white Gaussian noise channel and are comparable to the improved spherepacking bound. These codes may found applications in wireless sensor networks (WSN), where the delay and energy are extremely constrained.

Optimal Bit Split Methods and Performance Analysis for Applying to Multilevel Modulation of Iterative Codes (반복 부호의 다치 변조방식 적용을 위한 최적의 비트 분리 방법 및 성능평가)

  • Bae, Jong-Tae;Jung, Ji-Won;Choi, Seok-Soon;Kim, Min-Hyuk;Chang, Dae-Ig
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.3C
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    • pp.216-225
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    • 2007
  • This paper presents bit splitting methods to apply multilevel modulation to iterative codes such as turbo code, low density parity check code and turbo product code. Log-likelihood ratio method splits multilevel symbols to bits using the received in-phase and quadrature component based on Gaussian approximation. However it is too complicate to calculate and implement hardware due to exponential and log calculation. therefore this paper presents Euclidean, MAX and Sector method to reduce the high complexity of LLR method. We propose optimal bit splitting method for three iterative codes.

Complexity of Distributed Source Coding using LDPCA Codes (LDPCA 부호를 이용한 실용적 분산 소스 부호화의 복호복잡도)

  • Jang, Min;Kang, Jin-Whan;Kim, Sang-Hyo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.4C
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    • pp.329-336
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    • 2010
  • Distributed source coding (DSC) system moves computational burden from encoder to decoder, so it takes higher decoding complexity. This paper explores the problem of reducing the decoding complexity of practical Slepian-Wolf coding using low-density parity check accumulate (LDPCA) codes. It is shown that the convergence of mean magnitude (CMM) stopping criteria for LDPC codes help reduce the 85% of decoding complexity under the 2% of compression rate loss, and marginal initial rate request reduces complexity below complexity minimum bound. Moreover, inter-rate stopping criterion, modified for rate-adaptable characteristic, is proposed for LDPCA codes, and it makes decoder perform less iterative decoding than normal stopping criterion does when channel characteristic is unknown.