系统地阐述了低密度校验码基于图模型的编译码思想，介绍了密度进化理论，对影响低密度校验码纠错性能的两个主要因素——度序列设计和围长设计进行了深入分析，详细介绍并设计了LDPC的编解码-Systematic exposition of the LDPC graph model based codecs idea, introduces the density evolution theory, the two main factors that affect the performance of LDPC error correction- the degree of sequence design and girth design depth analysis, detailed and designed LDPC codec