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针对无线光通信脉冲位置调制(PPM)与信道编码的结合应用,提出了一种多级编码调制方案,利用多级编码的多级标签结构,将PPM符号所对应的分组比特分拆到不同子码通道的码字中,同时结合PPM的信号集分割和极大似然检测解调方法,推导了方案的多阶段解调译码算法。在弱湍流大气条件下的仿真分析表明,PPM多级编码调制相对单级编码调制在误码率10-6下获得0.85dB以上的增益,且可实现对不同重要程度信息段的不等差错保护。在分量码码型给定的条件下,按纠错能力逐级配置分量码并采用所推导的多阶段解调译码,可为系统提供更好差错性能,优于直接的并行译码方法。
Aiming at the combined application of wireless optical pulse position modulation (PPM) and channel coding, a multilevel coding modulation scheme is proposed. By using multilevel tagging architecture with multilevel coding, the bits of the packet corresponding to PPM symbols are split into different sub Code channel code word, combined with PPM signal set division and maximum likelihood detection demodulation method, the program multi-stage demodulation decoding algorithm is derived. The simulation results show that, compared with single-stage coding modulation, PPM multi-stage coding modulation gains more than 0.85dB at bit error rate 10-6, and it can realize the unequal error protection for different importance information sections . Under the condition that the component code pattern is given, the component codes are arranged step by step according to the error correction ability and the deduced multi-stage demodulation decoding is adopted, which provides better error performance for the system and is superior to the direct parallel decoding method.