可见光通信中一种大围长可快速编码的QC-LDPC码构造方法

Construction of QC-LDPC Code with Large Girth and Fast Encoding in Visible Light Communications

摘要:

为了改善可见光通信(VLC)系统的性能,针对准循环低密度奇偶校验(QC-LDPC)码码字间最小距离不够大而导致纠错性能下降的问题,提出一种新颖的QC-LDPC码构造方法。该方法将最大公约数(GCD)算法和Lucas序列相结合构造QC-LDPC码的信息位；同时,为了降低编码复杂度,校验位采用了准双对角线的形式,在保证大围长的同时实现QC-LDPC码的快速编码。然后用所提出的构造方法构造了码率为0.5的GL-QC-LDPC(2650,1325)码,并运用所搭建的VLC系统仿真模型进行了仿真性能分析。仿真结果表明,在误码率为10-6时,该GL-QC-LDPC(2650,1325)码与基于阵列码(AC)构造的AC-QC-LDPC(2652,1326)码、直接使用GCD算法与修饰技术构造的GM-QC-LDPC(2650,1325)码,以及基于群可分设计(GDD)的GDD-QC-LDPC(2652,1326)码相比,其净编码增益(NCG)分别提高了0.10,0.14和0.25dB。

Abstract:

In order to improve the performance of visible light communication (VLC) systems, a novel construction method of quasi-cyclic low-density parity-check(QC-LDPC) codes is proposed to solve the problem that the minimum distance between code words of QC-LDPC codes is not large enough, which leads to the degradation of the error correction performance. In the proposed construction method, the information bit of QC-LDPC codes is constructed by combining the greatest common divisor (GCD) algorithm with Lucas sequence. At the same time, in order to reduce the encoding complexity, the check bit is designed in the form of the quasi-double diagonal, which can ensure the large girth length and realize the fast encoding of QC-LDPC codes. Then the GL-QC-LDPC (2650,1325) code with a code rate of 0.5 is constructed with the proposed construction method, and the simulation performance is analyzed in the established VLC system simulation model. Simulation results show that at the bit error rate(BER) of 10-6, the net coding gain(NCG) of the GL-QC-LDPC(2650,1325) code constructed by this method is respectively 0.10,0.14 and 0.25dB more than those of AC-QC-LDPC(2652,1326) code based on the array codes(AC), GM-QC-LDPC (2650,1325) code constructed directly using the GCD algorithm and the modification technology and GDD-QC-LDPC (2652,1326) code based on group divisible designs (GDD).