低密度奇偶检验码编码与译码的研究-通信与信息系统专业论文.docxVIP

摘要 摘要 I万方数据 I 万方数据 摘要 低密度奇偶校验(LDPC)码是一种具有稀疏奇偶检验矩阵的线性分组码，它在与基 于置信传播(BP)迭代译码算法相结合的条件下具有逼近 Shannon 限的性能。该码的译 码复杂度与码长成线性关系，使长编码分组的应用成为可能。此外，编码方面也找到 了与码长成线性关系的好码构造法。 本文首先介绍 LDPC 码的几种译码算法，然后介绍了它的编码结构，编、译码方 法是研究 LDPC 码在各种信道应用中的实现前提和基础；还给出了 LDPC 码在 Rayleigh 信道下的计算机模拟结果；最后完成了 LDPC 码与高阶调制相结合的性能分 析，并利用 π 旋转 LDPC 码设计了一种多带正交频分复用(MB-OFDM)超宽带的实现 方案。 本课题主要工作及创新点为：构造了一种准规则结构的 LDPC 码，分析了它在二 进制对称信道下的短码性能，这种码的码率改变灵活、长码构造简单，但直接实现编 码器的复杂度与码的长度平方成正比，还有待于进一步改进；将非规则 LDPC 码与高 阶调制相结合，并跟 Turbo 码进行比较，表明它具有较优异的误码率性能，并且这种 优异的性能是在复杂度不太高的情况下实现的；利用 π 旋转 LDPC 码设计了一种 MB-OFDM 的实现方案，通过仿真计算分析了 π 旋转 LDPC 码与并行级联卷积码的性 能差异。 关键词：检验矩阵；LDPC 码；置信传播；UWB；高阶调制； Abst Abstract II万方数据 II 万方数据 Abstract Low-density parity-check (LDPC) codes which is a class of linear block codes, specified by a sparse parity-check matrix. It may approach the Shannon limit when uses the belief propagation (BP) iterative decoding algorithm, which makes the decoding complexity is linear to the codes length, so that the application of long block codes becomes true. Besides, good codes which coding complexity is linear to the length have searched. LDPC codes can improve the transmitted reliability in narrowband circumstance. As the preconditions of study the performance of LDPC codes in various channels, firstly, decoding algorithms and encoding structures are introduced in this paper. Then gives their computer simulated results on Rayleigh channel. Finally, the performance of combining LDPC codes to multilevel modulation is analysed, a MB-OFDM scheme is also achieved by π rotation LDPC codes in this paper. In this topic, a new constructed method of quasi-regular LDPC codes is proposed and the short codes performances are analyzed on BSC channel. The characteristics of the new method has flexible code rate and liable to construct long codes. But the encoding complexity is in proportion to the square of the codes length. So, this method should be improved. Irregular LDPC codes and multilevel modulation are combined, and the performances betwe