中文摘要：

该文提出了一种基于置换矩阵（permutation matrix）的非规则低密度奇偶校验（LDPC）码构造方法。首先,提出了基于改进eIRA（IeIRA）算法的全局矩阵;接着,通过对全局矩阵M进行矩阵置换,生成LDPC码的校验矩阵日;研究了校验矩阵H中短圈（short cycle）长度与置换矩阵循环移位系数的关系,通过选择循环移位系数,以达到改善误比特率性能的目的。仿真结果表明,该文提出的构造方法在保证线性编码复杂度的前提下,增大了码字的最小距离,减少了小停止集合（stopping set）的数量,降低了误比特率的差错平台（error floor）（达到10^-9）。

英文摘要：

A class of structured irregular Low-Density Parity-Check （LDPC） codes with high performance and low complexity is proposed in this paper. First, a global matrix M with a triangular plus dual-diagonal form based on Improved eIRA （IeIRA） method is designed. Then, each ‘1＇ in the global matrix Mis reptaced with a permutation matrix; each ‘0＇ is replaced with a null matrix to generate the parity check matrix H. Finally, the relationship between the length of short cyclic in the parity matrix H and the cyclic shift coefficient is given. Based on the relationship, error floor of BER is lowed by selecting proper cyclic shift coefficient of each permutation matrix. Simulation shows that the proposed method can reduce the number of small stopping set, increase the minimum distance of LDPC codes, and achieve very low error floor with linear encoding complexity.