空间光通信PPM信号的软解调及其性能

Soft Demodulation & Performance of PPM in Free-space Optical Communications

PPM调制由于其较高的功率利用率而在空间光通信系统中得到了广泛的应用,PPM信号的接收部分对整个通信系统的性能起很大作用。我们对光PPM信号的解调进行分析,提出了PPM信号的软解调而不对脉冲位置作先期判决,并对软解调及其性能进行分析,最后利用计算机对用APD接收且存在热噪声下的空间光通信PPM信号的解调进行了模拟仿真。仿真结果说明软解调由于充分利用了光电探测器计数软信息而降低了误码率。

Owing to its higher power efficiency, PPM modulation was widely applied in the free-space optical communications system. The demodulation of the PPM signal was important to FSO system. The demodulation of the PPM was discussed and the preference of soft demodulating PPM signal to hard demodulating was expressed, which was carried out by deciding the PPM pulse position. The performance of modulation was also discussed and simulated in the situation of presence of additive Gaussian thermal noise using a Gauss-modeled avalanche photodiode receiver. The results of the simulation show that the BER of the soft demodulation is lower because of its full utilization of the soft information of the APD.