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提出了一种新的准循环低密度奇偶校验(QC-LDPC)码的构造方法,给出了用该方法构造无环四QC-LDPC码的充分条件。并针对光通信系统的传输特点,用此方法构造了适用于高速长距离光通信系统的QC-LDPC(4 221,3 956)码。仿真结果分析表明:在码率为93.7%、误码率BER为10-6时,与广泛用于光通信系统中的经典RS(255,239)码相比,其净编码增益(NCG)提高了约1.8dB;比SCG-LDPC(3 969,3 720)码的NCG提高了约0.2dB,距离香农极限约1.4dB,且远低于PEG-LDPC(4 221,3 956)码的错误平层,这正满足光通信系统中低错误平层的要求。
A new method for constructing quasi-cyclic low-density parity-check (QC-LDPC) codes is proposed, and sufficient conditions for constructing acyclic quadratic QC-LDPC codes using this method are given. According to the transmission characteristics of optical communication system, a QC-LDPC (4 221,3 956) code suitable for high-speed long-distance optical communication system is constructed by this method. The simulation results show that the net coding gain (NCG) is improved by about 93.7% and the bit error rate (BER) is 10-6, compared with the classical RS (255,239) codes widely used in optical communication systems 1.8dB; the NCG of SCG-LDPC (3 969,3 720) codes is increased by about 0.2dB, the error is about 1.4dB away from the Shannon limit and far lower than that of PEG-LDPC (4 221,3 956) This is meeting the requirements of low-error leveling in optical communication systems.