中文摘要：

基于修饰技术提出了一种改进的准循环低密度奇偶校验（QC-LDPC）码的构造方法。该方法构造的QC-LDPC码具有较低的编码复杂度,其校验矩阵围长至少为6,避免了四环的出现,具有良好的围长特性。仿真分析表明：通过该构造方法构造的码率为93.7%的QC-LDPC（3969,3717）码在降低其编码复杂度的情况下,拥有与其对应的未应用修饰技术的QC-LDPC（3969,3719）码相媲美的纠错性能;并且在相同条件下,QC-LDPC（3969,3717）码的纠错性能要好于利用随机构造方法构造的PEG-LDPC（3969,3720）码,以及ITU-T G.975中已广泛用于光通信系统中的RS（255,239）码和LDPC（32640,30592）码,更适合于光通信系统。

英文摘要：

An improved construction method of quasi-cyclic low-density parity-check（QCLDPC）codes,based on the making technology is presented.The QC-LDPC codes constructed by this improved construction method have lower encoding complexity,and their parity-check matrices can effectively avoid the girth-4phenomena and have the advantages such as better girthlength properties and more flexible adjustment in the code-length code-rate.The simulation results show that the error-correction performance of the QC-LDPC（3969,3717）with the coderate of 93.7%constructed by this improved construction method is as good as the error-correction performance of the QC-LDPC（3969,3719）code which is constructed without the making technology.Furthermore,at the same simulation conditions,the error-correction performance of the QC-LDPC（3969,3717）is better than that of the PEG-LDPC（3969,3720）code constructed by the random construction method,the classic RS（255,239）code which is widely used in optical communication systems and the LDPC（32640,30592）code in ITU-T G.975.1.Therefore,it is more suitable for optical communication systems.