Abstract: Combinatoric design is a potentially powerful tool for constructing good LDPC codes.In this paper，a new approach to construct regular quasi-cyclic Low-Density Parity-Check（LDPC） codes based on the difference sets is proposed.The constructed LDPC codes is free of 4-cycles and with high flexibility in the choose of the code rate.Because of their quasi-cyclic structure，the encoding can be implemented with simple feedback shift register.Simulations show that the constructed quasi-cyclic LDPC codes with Sum-product iterative decoding perform well under BPSK modulation over an Additive White Gaussian Noise（AWGN） channel.

摘要： 组合设计是构造好的低密度校验码的潜在有力工具，提出了利用差集来构造准循环低密度校验码（QC-LDPC）的新方法。该方法构造的QC-LDPC码，最小环长至少为6，码率的选择也具有很大的灵活性。由于其准循环结构，可以用简单线性移位寄存器完成编码。计算机仿真结果表明该方法构造的QC-LDPC码，在加性高斯白噪声信道中BPSK调制下用和积迭代译码性能很好。