关键词: 准循环低密度奇偶校验码，列差矩阵，围长，搜索算法

Abstract: A parity-check matrix H with large girth has important significance to improve the performance of LDPC codes. And the key to the encoder implementation is the algebraic code structure. This paper proposed a novel code construction algorithm with low complexity based on the Column-Difference Scarch(CDS) Algorithm, which can design regular Quasi Cyclic LDPC codes with large girth and arbitrary code rate. It has linear encoding complexity and is friendly to hardware implementation. The experimental results show that CDS-LDPC codes with different code rates perform better than Tanner codes and Array codes,which increase 0. 79--3. 28dB than another two classical QC-LDPC codes,and also outperform the counterparts of random codes. In addition,CDS-LDPC codes have more flexibility on the design of code length and rate.

Key words: Quasi-cyclic LDPC codes, Column-difference matrix, Girth, Search algorithm