基于低密度奇偶校验码的MPPM比特符号映射及系统性能研究

Study on Bit-Symbol Mapping Method of MPPM and System Performance Based on Low Density Parity Check Codes

建立了基于低密度奇偶校验(LDPC)码和多脉冲位置调制(MPPM)的无线光通信系统模型,给出了相应系统模型下的解码算法,研究了(m,2)MPPM的比特符号映射方式,提出了用改进的遗传算法(GA)搜索的优化映射方法,最后在大气湍流信道下进行了仿真。仿真结果表明基于LDPC码和MPPM的无线光通信系统性能明显优于未编码的MPPM系统,结合LDPC码和多光束发射技术可以提高系统抗强大气湍流影响的能力;通过GA优化的映射方法在不增加系统复杂性的情况下能进一步提高系统的纠错性能,可以获得更大的编码增益。

Wireless optical communication system based on low density parity check（LDPC） codes and multi-pulse position modulation（MPPM） is established,and the decoding algorithm is introduced according to the system model.Bit-symbol mapping method of（m,2） MPPM is studied,and a novel bit-symbol mapping method is presented based on modified genetic algorithm（GA）,which is simulated under turbulence channel.The simulation results show that LDPC codes have excellent error correction capabilities with MPPM,and the wireless optical communication based on multiple-beam propagating technique and LDPC codes can operate under a strong atmospheric turbulence.Bit-symbol mapping method optimized by GA can get more coding gain without increasing complication.