毕业设计论文华侨大学.docVIP

摘　要 LDPC码的优异性能及其在信息可靠传输中的良好应用前景(例如光通信、卫星通信、深空通信、移动通信等)，已引起世界各国学术界和IT业界的高度重视，成为当今信道编译码领域最瞩目的研究热点。在现代数字通信系统中，为保证各种数据能够可靠、有效的传输，往往要利用纠错编码技术。近年来，随着无线数字通信发展及各种高速率， 突发性强的新业务的出现，研究并利用好纠错编码技术就越来越显得必要。LDPC码是Gallager最早于1963年提出的一种具有稀疏校验矩阵的分组码。之后，在Turbo码巨大成功的带动下，Mackay等人重新研究了它，并发现LDPC码具有逼近香农限的特性，同时具有低译码复杂度，因此必将在CDMA系统中得到广泛的应用。 本文首先在讨论了LDPC码的基本概念及编码算法基础上，重点对硬判决译码算法（比特翻转译码、加权比特翻转译码）、软判决译码算法（概率域和积译码、Log域和积译码、最小和译码）进行了详细地分析和一些基础的比较。 最后主要介绍了BF、BP译码算法的LDPC码仿真和分析。 关键词：CDMA系统；LDPC码；信道译码 ABSTRACT LDPC codes have good performance and reliable transmission of information in the good prospect of application (such as optical communications, satellite communications, deep space communication, mobile communication), has attracted great attention of academic circle and IT industry, become a hot research topic in the field of attention most channel coding. In modern digital communication system, in order to ensure the reliable transmission of data, effective, often make use of error correction coding technology. In recent years, with the development of wireless digital communication and high speed, strong burst of new business, study and use the error correction coding technology becomes more and more necessary. LDPC code is a Gallager first proposed in 1963 block codes with sparse parity check matrix. After the huge success, in the Turbo code under the drive, Mackay et al. To study it, and it is found that the LDPC code has the approximation property of the Shannon limit, also has low decoding complexity, so it will be widely applied in CDMA system. This paper first discusses the basic concept of LDPC code and the coding algorithm, key decoding to the hard decision algorithm (bit flipping decoding, weighted bit flipping decoding), soft decision decoding algorithm (probabilistic domain, Log domain and sum-product decoding, min-sum decoding) is analyzed and some basic. Finally introduces the LDPC code simulation and analysis of BF, BP decoding algorithm. Keywords: CDMA; LDPC code; decoding 目