Abstract: This paper proposes a coset-based Quasi-Cyclic Low Density Parity Check(QC LDPC) construction method and similar SFT-LDPC code construction method in order to guarantee the girth under high bitrate. It gives two necessary conditions of girth at least 6 when the size of cyclic permutation matrix is a composite number. This construction method with various lengths, rates and girth at least 6 can be flexiblely constructed. Simulation results show that the code constructed by this method is comparable to random ones in error correction performance over additive white Gaussian noise channel.

Key words: Quasi-Cyclic(QC), girth, coset

摘要： 为了保证在高码率下码的围长，提出一种基于子群陪集的拟循环LDPC码构造方法和类似SFT-LDPC码构造方法，给出当循环置换矩阵的大小为非素数时满足围长大于等于6的2个充分条件。通过该方法可以灵活地选择构造参数，满足不同的码长、码率的要求，且围长大于等于6。仿真结果表明，在加性高斯白噪声信道下该方法得到的码和随机构造的码有相似的纠错性能。

关键词: 拟循环, 围长, 陪集

CLC Number: 

• TP393