共查询到18条相似文献,搜索用时 187 毫秒
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规则RA码在远程光纤通信系统中的应用研究 总被引:1,自引:0,他引:1
远程光纤通信系统需要高效、高性能的前向纠错码.采用组合设计构造了RA码交织器,得到无4环、高码率的系统规则RA码,将其应用在远程光纤通信系统中,在三种光纤信道模型下进行了仿真.结果表明,基于组合设计的RA码在光纤信道中具有较好的性能,且在x2信道模型下的性能优于高斯信道. 相似文献
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光纤通信系统中的前向纠错技术 总被引:1,自引:0,他引:1
本文介绍了前向纠错技术(FEC)在高速光纤通信系统中应用的必要性,以及FEC采用的BCH-3码和RS-8码的编码技术,带内FEC、带外FEC和并行FEC三种实现方式及特点。最后阐述了FEC技术对光纤通信系统性能的改善。 相似文献
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QC-LDPC(伪循环-低密度奇偶校验)码在AWGN信道下具有优异的性能,但是在光纤信道下,信道模型不是AWGN模型,而是非对称高斯模型,将QC-LDPC码应用在光纤信道的非对称高斯模型下,若想取得最优的性能,需要修正相应的译码方法。给出了在非对称高斯模型下的修正译码方法,并对算法进行了仿真。仿真结果表明,对译码算法修正后,QC-LDPC码在非对称高斯下能够取得较好的译码性能,在误码率BER为10-6,相对未编码系统,能够获得约7dB净编码增益。同时在非对称高斯模型下译码性能要优于在AWGN模型下译码性能。 相似文献
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一种LDPC码在光纤通信系统中的性能分析 总被引:1,自引:1,他引:1
针对超强前向纠错(FEC)技术在光纤通信系统中的应用,文章提出了一种构造简单、编码容易实现的低密度奇偶校验(LDPC)码的构造方法,并仿真验证了该LDPC码在光纤信道环境下的译码性能.与常用的RS(255,239)码相比,在相同的码效率下,所构造的码长为4 080的LDPC码能够获得比RS码高2 dB的编码增益. 相似文献
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介绍了LMDS(LocalMultipointDistributionService)系统结构及系统的信道模型和前向纠错(FEC—ForwardErrorCorrection)机制。易受环境影响的LMDS系统信道特性决定了需要采用纠错能力强的纠错编码方法,在IEEE802.16工作组草案建议的MSUI(ModifiedStanfordUniversityIn-terim)信道模型下,分析了LMDS系统前向纠错采用Turbo码时的译码性能并仿真比较了RS(Reed-Solomon)码和Turbo码的误码率,同时也比较了不同Turbo码译码方法的性能。从仿真结果来看,Turbo码能够明显提高LMDS系统的前向纠错性能,可以应用到实际LMDS系统中去。 相似文献
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空间光通信APD接收机下LDPC码译码方法及性能分析 总被引:6,自引:6,他引:0
准循环-低密度奇偶校验(QC-LDPC)码具有优异的性能,但在译码时需根据具体的信道模型修正对应的译码算法。本文分析了QC-LDPC码在空间光通信中的雪崩光电二极管(APD)接收机下的译码方法及译码性能,提出了在APD接收机信道下计算译码初始化所需的对数似然比(LLR)的方法。仿真结果表明,对APD接收机信道下的译码进行修正后,基本上不增加额外复杂度情况下,QC-LDPC码在精确的韦伯-高斯(Webb-Gaussian)模型下译码性能优于近似的非对称高斯模型;在信道比较理想的条件下,误码率(BER)为10-6时,韦伯-高斯模型与非对称高斯模型译码性能相比有1dB以上的净编码增益。 相似文献
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On turbo code decoder performance in optical-fiber communication systems with dominating ASE noise 总被引:8,自引:0,他引:8
In this paper, we study the effects of different ASE noise models on the performance of turbo code (TC) decoders. A soft-decoding algorithm, the Bahl, Cocke, Jelinek, and Raviv (BCJR) decoding algorithm, is generally used in TC decoders. The BCJR algorithm is a maximum a posteriori probability (MAP) algorithm, and is very sensitive to noise statistics. The Gaussian approximation of ASE noise is widely used in the study of optical-fiber communication systems, and there exist standard TCs for additive white Gaussian noise (AWGN) channels. We show that using a MAP decoding algorithm based on the Gaussian noise assumptions, however, may significantly degrade the TC decoder performance in an optical-fiber channel with non-Gaussian ASE noise. To take full advantage of TC, accurate noise statistics in optical-fiber transmissions should be used in the MAP decoding algorithm. 相似文献
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Design methods for irregular repeat-accumulate codes 总被引:3,自引:0,他引:3
Roumy A. Guemghar S. Caire G. Verdu S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2004,50(8):1711-1727
We optimize the random-like ensemble of irregular repeat-accumulate (IRA) codes for binary-input symmetric channels in the large block-length limit. Our optimization technique is based on approximating the evolution of the densities (DE) of the messages exchanged by the belief-propagation (BP) message-passing decoder by a one-dimensional dynamical system. In this way, the code ensemble optimization can be solved by linear programming. We propose four such DE approximation methods, and compare the performance of the obtained code ensembles over the binary-symmetric channel (BSC) and the binary-antipodal input additive white Gaussian noise channel (BIAWGNC). Our results clearly identify the best among the proposed methods and show that the IRA codes obtained by these methods are competitive with respect to the best known irregular low-density parity-check (LDPC) codes. In view of this and the very simple encoding structure of IRA codes, they emerge as attractive design choices. 相似文献
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Structured IRA Codes: Performance Analysis and Construction 总被引:2,自引:0,他引:2
In this letter, we present design techniques for structured irregular repeat-accumulate (S-IRA) codes with low error-rate floors. These S-IRA codes need not be quasi-cyclic, permitting flexibility in code dimension, length, and rate. We present a simple ensemble estimate of the level of the error-rate floor of finite-length IRA codes on the additive white Gaussian noise channel. This performance estimate provides guidance on the choice of IRA code column weights which yield low floors. We also present two design algorithms for S-IRA codes accompanied by software- and hardware-based performance results which demonstrate their low floors. Lastly, we present two design algorithms for multirate S-IRA code families implementable by a single encoder/decoder 相似文献
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Mao-Ching Chiu 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2010,56(1):152-167
Using nonbinary low-density parity-check (LDPC) codes with random-coset mapping, Bennatan and Burshtein constructed bandwidth-efficient modulation codes with remarkable performance under belief propagation (BP) decoding. However, due to the random nature of LDPC codes, most of the good LDPC codes found in the literature do not have a simple encoding structure. Thus, the encoding complexity of those LDPC codes can be as high as O(N 2), where N is the codeword length. To reduce the encoding complexity, in this paper, nonbinary irregular repeat-accumulate (IRA) codes with time-varying characteristic and random-coset mapping are proposed for bandwidth-efficient modulation schemes. The time-varying characteristic and random-coset mapping result in both permutation-invariance and symmetry properties, respectively, in the densities of decoder messages. The permutation-invariance and symmetry properties of the proposed codes enable the approximations of densities of decoder messages using Gaussian distributions. Under the Gaussian approximation, extrinsic information transfer (EXIT) charts for nonbinary IRA codes are developed and several codes of different spectral efficiencies are designed based on EXIT charts. In addition, by proper selection of nonuniform signal constellations, the constructed codes are inherently capable of obtaining shaping gains, even without separate shaping codes. Simulation results indicate that the proposed codes not only have simple encoding schemes, but also have remarkable performance that is even better than that constructed using nonbinary LDPC codes. 相似文献
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Sung Ik Park Kyeongcheol Yang 《Electronics letters》2002,38(10):467-468
Two classes of codes, called extended Hamming accumulate codes and modified nonsystematic irregular repeat accumulate (IRA) codes, are introduced. Simulation results show that the performance of modified nonsystematic IRA codes are slightly superior to turbo codes of comparable complexity on an additive white Gaussian noise channel 相似文献
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This paper investigates the evolution of kurtosis of the input Gaussian amplified spontaneous emission (ASE) noise in a nonlinear fiber with negligible dispersion. The nonlinear Schrodinger equation (NLSE) describing propagation in optical fibers is simplified such that the fiber represents a zero memory nonlinear (ZMNL) system, and this approximation allows the development of analytical formulas for the statistical moments of the output noise. It is possible to calculate moments of all integer orders and the explicit expressions for the first four moments are given. The investigations show that the ASE noise does not preserve its Gaussian character when Kerr nonlinearity is significant. This observation proves that the common assumption of the Gaussian output ASE is not necessarily valid. Numerical simulations are provided to support the derivation. Kurtosis deviating significantly from the value typical for Gaussian noise is also an indicator that BER calculation in the coherent systems based on the assumption that ASE is Gaussian is likely to be inaccurate. 相似文献
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Joint source-channel turbo coding for binary Markov sources 总被引:1,自引:0,他引:1
We investigate the construction of joint source-channel (JSC) turbo codes for the reliable communication of binary Markov sources over additive white Gaussian noise and Rayleigh fading channels. To exploit the source Markovian redundancy, the first constituent turbo decoder is designed according to a modified version of Berrou's original decoding algorithm that employs the Gaussian assumption for the extrinsic information. Due to interleaving, the second constituent decoder is unable to adopt the same decoding method; so its extrinsic information is appropriately adjusted via a weighted correction term. The turbo encoder is also optimized according to the Markovian source statistics and by allowing different or asymmetric constituent encoders. Simulation results demonstrate substantial gains over the original (unoptimized) Turbo codes, hence significantly reducing the performance gap to the Shannon limit. Finally, we show that our JSC coding system considerably outperforms tandem coding schemes for bit error rates smaller than 10/sup -4/, while enjoying a lower system complexity. 相似文献