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在分析了大气对光信号的影响之后,利用脉冲位置调制(PPM)的正交性构造了一种适合于强度调制/直接检测式光通信的正交空时编码,并将其引入分层空时编码的首层以增加第一层信息符号的分集度;其次采用分组干扰抑制的方法消除其它层对信号的干扰,利用空时分组码(STBC)和分层空时编码的译码方法并结合最大似然判决准则恢复出原始信号。最后,利用仿真实验进一步验证了该方法的可行性。结果表明:在自由空间光通信中,混合空时编码方案的性能明显优于传统BLAST码方案的性能。
After analyzing the influence of atmospheric on optical signals, an orthogonally space-time coding suitable for intensity modulation / direct detection optical communication is constructed by the orthogonality of pulse position modulation (PPM) and introduced into the layered space The first layer of coding is used to increase the diversity of the first layer of information symbols. Secondly, the method of packet interference suppression is used to eliminate the interference of signals from other layers. By using space-time block coding (STBC) and layered space-time coding, Combined with the maximum likelihood decision criteria to restore the original signal. Finally, the feasibility of this method is further verified by simulation experiments. The results show that in free space optical communication, the performance of hybrid space-time coding scheme is obviously better than that of the traditional BLAST code scheme.