共查询到19条相似文献，搜索用时 156 毫秒
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低密度校验码(LDPC)具有编码增益高、译码速度快、性能接近Shannon限的优点。LDPC码应用于OFDM,能有效地提高多径环境下OFDM的性能。本文首先简单介绍LDPC码以及对数域的似然比译码算法。之后把LDPC应用于中国数字电视TDS-OFDM系统上,仿真了TDS-OFDM系统中,LDPC在AWGN和Rayleigh信道下的性能,结果表明LDPC码有效地提高了系统性能。 相似文献
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x对于二进制LDPC码,多进制LDPC码具有纠错能力更高、抗突发错误能力更强的独特优势,适宜高速率传输,为了解决多进制LDPC译码算法复杂度较高,不利于硬件实现的问题,本文重点对多进制LDPC码的构造、译码、码长及码率等方面进行仿真研究,以期为多进制LDPC码的实用化发展提供设计参考。仿真结果表明:当多进制LDPC码采用BP、FFT-BP和Log-FFT-BP三种不同译码算法时,随着码长增大和码率的下降,编码增益和性能曲线与香农限的距离都会随之而增大,并在牺牲一定的信噪比的情况下,Log-FFT-BP算法能够使多进制LDPC码的硬件复杂度得到较大的改善。 相似文献
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LDPC码是一种非常实用的信道编码,利用LDPC码在OFDM子载波之间实现联合编码,可以有效对抗多径移动信道中深度衰落对载波信道某些特定频率的影响,提高系统的性能。 相似文献
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OFDM技术凭借出色的性能广泛应用于现代通信系统中,LDPC码是已知的最接近Shannon极限的编码.本文利用一种改进的LDPC编码,结合OFDM技术构造出LDPC_OFDM系统模型,利用Simulink工具在AWGN信道下进行了仿真,结果表明基于LDPC编码方式的OFDM系统性能好于卷积编码方式的OFDM系统性能. 相似文献
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Tornado码二部图构造是一个非常重要的问题。基于PEG算法构造LDPC码二部图时显现的各种优点,本文提出了一种改进的PEG构图算法。仿真结果表明,改进的算法比原PEG算法有更快的执行速度,并且基于此算法构造的Tornado码也比原始的Tornado码有更好的性能。 相似文献
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Tubor码,由于性能接近香农理论限,在低信噪比的应用环境下比其他编码好,因而在第三代移动通信系统多种方案中,考虑将Tubor码作为无线信道的编码标准之一。论文介绍了Tubor码的结构和编解码方法,及其在移动通信系统中的应用。 相似文献
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Mehmet Ozen 《Journal of The Franklin Institute》2007,344(5):790-799
We investigate the structure of codes over Galois rings with respect to the Rosenbloom-Tsfasman (shortly RT) metric. We define a standard form generator matrix and show how we can determine the minimum distance of a code by taking advantage of its standard form. We compute the RT-weights of a linear code given with a generator matrix in standard form. We define maximum distance rank (shortly MDR) codes with respect to this metric and give the weights of the codewords of an MDR code. Finally, we give a decoding technique for codes over Galois rings with respect to the RT metric. 相似文献
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阐述了巴克码组的定义和7位巴克码识别器的组成框图。在MAX PLUS2软件平台上,给出了利用现场可编程门阵列器件设计7位巴克码识别器电路,为了便于对设计的7位巴克码识别器进行检测,该电路还设计了一个周期为31位长的模拟7位巴克码产生器,并进行了编译和波形仿真。综合后下载到可编程器件EPF10K10LC84-4中,测试结果表明,达到了预期的设计要求。 相似文献
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Cheng-Chun Chang 《Journal of The Franklin Institute》2010,347(7):1368-1373
Low-density generator matrix (LDGM) codes have recently drawn researchers’ attention thanks to their satisfying performance while requiring only moderate encoding/decoding complexities as well as to their applicability to network codes. In this paper, we aim to propose a fast simulation method useful to investigate the performance of LDGM code. Supported by the confidence interval analysis, the presented method is, for example, 108 times quicker than the Monte-Carlo computer simulation for bit-error-rate (BER) in 10−10 region. 相似文献
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Ibrahim Develi 《Journal of The Franklin Institute》2005,342(1):69-84
This paper considers the problem of detecting the optimal spreading codes (OSC) in a given code set for a direct sequence-code division multiple access system that employs despreading sequences weighted by adjustable chip waveforms. Due to computational complexity required to detect the OSC in a code set, a simple and efficient strategy is introduced. Analysis and numerical results show that the proposed strategy can successfully distinguish the spreading codes being most suitable references for a given code set in which the candidate spreading codes have equal crosscorrelation properties. 相似文献
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One of the main challenges of coding theory is to construct linear codes with the best possible parameters. Various algebraic and combinatorial methods along with computer searches are used to construct codes with better parameters. Given the computational complexity of determining the minimum distance of a code, exhaustive searches are not feasible for all but small parameter sets. Therefore, codes with certain algebraic structures are preferred for both theoretical and practical reasons. In this work we focus on the class of constacyclic codes to first generate all constacyclic codes exhaustively over small finite fields of order up to 9 to create a database of best constacyclic codes. We will then use this database as a building block for a search algorithm for new quasi-twisted codes. Our search on constacyclic codes has revealed 16 new codes, i.e. codes with better parameters than currently best-known linear codes. Given that constacyclic codes are well known, this is a surprising result. Moreover, using the standard constructions of puncturing, shortening or extending a given code, we also derived 55 additional new codes from these constacyclic codes. Hence, we achieved improvements on 71 entries in the database of best-known codes. We use a search strategy that is comprehensive, i.e. it computes every constacyclic code for a given length and shift constant, and it avoids redundantly examining constacyclic codes that are equivalent to either cyclic codes or other constacyclic codes. 相似文献
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The communication systems and disk or tape memory can sometimes cause clusters of errors, namely burst errors. There have been many designs in order to detect and even correct such errors. Recently, a new class of codes called m-spotty byte error correcting codes has found applications in high speed memory systems that employ random access memory chips wide Input/Output data, especially at 8, 16, or 32 bits. The MacWilliams identity provides the relationship between the weight distribution of a code and that of its dual code. Also, an interesting new metric called Rosenbloom–Tsfasman metric has been studied as an alternative metric for linear codes recently. In this paper, we combine these two interesting topics and introduce the m-spotty Rosenbloom–Tsfasman weights and the m-spotty Rosenbloom–Tsfasman weight enumerator of a binary code. Moreover, we prove a MacWilliams identity for the m-spotty Rosenbloom–Tsfasman weight enumerators. 相似文献