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针对大气光通信脉冲位置调制(PPM)调制方式与普通纠错编码结合有效性差的问题,在分析大气无线光通信信道特性和PPM符号形式的基础上,提出了具有良好抗衰落性能和高功率利用率的Turbo乘积码(TPC)-PPM编码调制机制。研究了该机制下比特交织离散连续错误能力,并导出了适合软输入输出(SISO)迭代译码的PPM软解调置信度度量计算方法。弱湍流下的仿真分析表明,TPC-PPM与匹配的RS码3-PPM编码调制相比提高增益3dB以上,码字与调制阶数无需特别设置,并可在不产生附加开销条件下,通过编码与调制间交织传输设计提升性能,为信道纠错码与高效数字调制结合应用于大气无线光通信系统提供了良好解决方案。
Aiming at the poor combination of pulse position modulation (PPM) of atmospheric optical communication and ordinary error correction coding, based on the analysis of atmospheric wireless optical communication channel characteristics and PPM symbolic form, this paper proposes a novel anti-fading performance and high power utilization Rate Turbo Product Code (TPC) - PPM coding modulation mechanism. The discrete continuous error of bit interleaving under this scheme is studied, and the calculation method of PPM soft-demodulation confidence measure is derived which is suitable for soft input-output (SISO) iterative decoding. The simulation analysis under weak turbulence shows that the TPC-PPM increases the gain by more than 3dB compared with the matched RS code 3-PPM coding modulation. The codeword and the modulation order need not be specially set, and can be encoded without coding overhead Inter-modulation transmission and modulation design to enhance performance, combined with channel error correction code and efficient digital modulation used in atmospheric wireless optical communication system provides a good solution.