共查询到19条相似文献,搜索用时 156 毫秒
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LDPC码的改进译码算法 总被引:2,自引:0,他引:2
由于短帧长LDPC码存在很多环路,其译码性能不具有最优性.本文首先推导了有环路LDPC码的概率译码算法,然后在传统的概率译码算法引入了修正系数,从而减小了环路对译码性能的影响.仿真结果表明,采用改进的译码算法可以提高译码性能. 相似文献
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考虑多进制LDPC码的符号特性,以及对其残留错误和删除的分析,本文采用多进制LDPC码作为内码,相同Galois域下的高码率RS码作为外码来构造多进制乘积码;并提出了一种低复杂度的迭代译码方案,减少信息传输的各类错误。在译码时,只对前一次迭代中译码失败的码字执行译码,并对译码正确码字所对应的比特初始概率信息进行修正,增强下一次迭代多进制LDPC译码符号先验信息的准确性,减少内码译码后的判决错误,从而充分利用外码的纠错能力。仿真结果显示,多进制乘积码相较于二进制LDPC乘积码有较大的编码增益,并通过迭代进一步改善了性能,高效纠正了信道中的随机错误和突发删除。对于包含2%突发删除的高斯信道,在误比特率为10-6时,迭代一次有0.4 dB左右的增益。 相似文献
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由于低密度奇偶校验码(LDPC)具有逼近香农(Shannon)极限的优良性能和可实现高速编译码的潜力,使之成为信道编码领域最受瞩目的研究热点之一。主要研究对象是LDPC码的译码算法。先后介绍了LDPC码的基本概念和原理、编译码的结构原理和基于可靠度的迭代大数逻辑译码算法(RBI-MLGD)流程。译码算法是LDPC码的关键,译码复杂度的高低直接影响着系统的实现。通过Visual C++6.0编写该译码算法程序,并对该码字在8比特和4比特的量化参数下进行了算法仿真,结合Matlab 7.1对获得的数据进行画图,得到了针对该码字在RBI-MLGD算法下的译码效果。 相似文献
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有限平面LDPC码是一类重要的有结构的LDPC码,在利用和积算法(SPA)等迭代译码方法进行译码时表现出卓越的纠错性能。众所周知,次优的迭代译码不是最大似然译码,因而如何对迭代译码的性能进行理论分析一直是LDPC码的核心问题之一。近几年来,Tanner图上的停止集(stopping set)和停止距离(stopping distance)由于其在迭代译码性能分析中的重要作用而引起人们的重视。该文通过分析有限平面LDPC码的停止集和停止距离,从理论上证明了有限平面LDPC码的最小停止集一定是最小重量码字的支撑,从而对有限平面LDPC码在迭代译码下的良好性能给出了理论解释。 相似文献
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基于联合判决消息传递机制的LDPC码译码算法研究 总被引:1,自引:0,他引:1
采用消息传递算法(Message passing algorithm)对LDPC码进行译码时,变量消息的振荡会引起错误的发生.本文以(600.300)非规则LDPC码仿真实验为例分析了不同译码效果下判决消息均值的分布特点,并结合环的特点,分析了译码产生错误判决的原因.研究了"纠删"型消息传递机制和联合判决迭代停止准则,针对判决消息出现振荡情况,提出以"纠删"方式处理变量消息的更新,并结合变量节点判决消息均值分布趋势与伴随式结果确定迭代终止条件.在此基础上,提出一种新的LDPC码译码算法.仿真分析表明,新的译码算法能够在减少迭代次数和降低译码复杂度的同时,有效提高译码的纠错性能. 相似文献
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基于串行消息传递机制的QC-LDPC码快速译码算法研究 总被引:1,自引:0,他引:1
针对准循环LDPC(QC-LDPC)码基于洪水消息传递机制译码算法的不足,该文提出了一种快速的分组串行译码算法。该算法通过将LDPC码的校验节点(或变量节点)按一定规则划分成若干个子集,在每一轮迭代过程中,依次对各个子集中的校验节点(或变量节点)并行地进行消息更新,提高了译码速度。同时根据分组规则,提出了一种有效的分组方法,并通过分析发现基于循环置换阵的准循环LDPC码非常适合采用这种分组译码算法进行译码。通过对不同消息传递机制下准循环LDPC码译码算法性能的仿真比较,验证了在复杂度不增加的情况下,该译码算法在继承了串行译码算法性能优异和迭代收敛快等优点的同时,极大地提高了准循环LDPC码的译码速度。分析表明,分组串行译码算法译码速度至少为串行译码算法的p倍(p为准循环LDPC码校验矩阵中循环置换阵的行数或列数)。 相似文献
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本文主要研究了低密度校验码(LDPC码)的编译码方法及其硬件实现。在讨论几种主要的LDPC码的编译码方法的基础上,对LDPC译码错误产生原因进行了分析,提出了一种改进的置信传播译码算法——最小和算法,该算法在几乎没有增加运算复杂度的情况下,明显地提高了译码性能。同时,本文基于几何思想的LDPC码为例,提出了并串结合的FPGA实现方法,给出了仿真结果。 相似文献
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低密度奇偶校验码(LDPC)的性能取决于多种因素,包括度分布对、码字的长度以及环的分布。环的存在会影响LDPC码的译码门限和误码平层,尤其是长度比较小的环对LDPC码的性能影响很大。因此,有必要在构造LDPC码时消去长度比较小的环。文中提供了一种有效的消环算法,降低了LDPC码的误码平层。 相似文献
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针对RS码与LDPC码的串行级联结构,提出了一种基于自适应置信传播(ABP)的联合迭代译码方法.译码时,LDPC码置信传播译码器输出的软信息作为RS码ABP译码器的输入;经过一定迭代译码后,RS码译码器输出的软信息又作为LDPC译码器的输入.软输入软输出的RS译码器与LDPC译码器之间经过多次信息传递,译码性能有很大提高.码长中等的LDPC码采用这种级联方案,可以有效克服短环的影响,消除错误平层.仿真结果显示:AWGN信道下这种基于ABP的RS码与LDPC码的联合迭代译码方案可以获得约0.8 dB的增益. 相似文献
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Although Low-Density Parity-Check (LDPC) codes perform admirably for large block sizes — being mostly resilient to low levels of channel SNR and errors in channel equalization — real time operation and low computational effort require small and medium sized codes, which tend to be affected by these two factors. For these small to medium codes, a method for designing efficient regular codes is presented and a new technique for reducing the dependency of correct channel equalization, without much change in the inner workings or architecture of existing LDPC decoders is proposed. This goal is achieved by an improved intrinsic Log-Likelihood Ratio (LLR) estimator in the LDPC decoder — the ILE-Decoder, which only uses LDPC decoder-side information gathered during standard LDPC decoding. This information is used to improve the channel parameters estimation, thus improving the reliability of the code correction, while reducing the number of required iterations for a successful decoding. Methods for fast encoding and decoding of LDPC codes are presented, highlighting the importance of assuring low encoding/decoding latency with maintaining high throughput. The assumptions and rules that govern the estimation process via subcarrier corrected-bit accounting are presented, and the Bayesian inference estimation process is detailed. This scheme is suitable for application to multicarrier communications, such as OFDM. Simulation results in a PLC-like environment that confirm the good performance of the proposed LDPC coder/decoder are presented. 相似文献
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Feldman J. Malkin T. Servedio R. A. Stein C. Wainwright M. J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2007,53(1):82-89
We show that for low-density parity-check (LDPC) codes whose Tanner graphs have sufficient expansion, the linear programming (LP) decoder of Feldman, Karger, and Wainwright can correct a constant fraction of errors. A random graph will have sufficient expansion with high probability, and recent work shows that such graphs can be constructed efficiently. A key element of our method is the use of a dual witness: a zero-valued dual solution to the decoding linear program whose existence proves decoding success. We show that as long as no more than a certain constant fraction of the bits are flipped by the channel, we can find a dual witness. This new method can be used for proving bounds on the performance of any LP decoder, even in a probabilistic setting. Our result implies that the word error rate of the LP decoder decreases exponentially in the code length under the binary-symmetric channel (BSC). This is the first such error bound for LDPC codes using an analysis based on "pseudocodewords." Recent work by Koetter and Vontobel shows that LP decoding and min-sum decoding of LDPC codes are closely related by the "graph cover" structure of their pseudocodewords; in their terminology, our result implies that that there exist families of LDPC codes where the minimum BSC pseudoweight grows linearly in the block length 相似文献
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Daskalakis C. Dimakis A.G. Karp R.M. Wainwright M.J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(8):3565-3578
We initiate the probabilistic analysis of linear programming (LP) decoding of low-density parity-check (LDPC) codes. Specifically, we show that for a random LDPC code ensemble, the linear programming decoder of Feldman succeeds in correcting a constant fraction of errors with high probability. The fraction of correctable errors guaranteed by our analysis surpasses previous nonasymptotic results for LDPC codes, and in particular, exceeds the best previous finite-length result on LP decoding by a factor greater than ten. This improvement stems in part from our analysis of probabilistic bit-flipping channels, as opposed to adversarial channels. At the core of our analysis is a novel combinatorial characterization of LP decoding success, based on the notion of a flow on the Tanner graph of the code. An interesting by-product of our analysis is to establish the existence of ldquoprobabilistic expansionrdquo in random bipartite graphs, in which one requires only that almost every (as opposed to every) set of a certain size expands, for sets much larger than in the classical worst case setting. 相似文献