脉冲展宽下水下激光PPM信号解调方法的研究

Study on demodulation methods for underwater laser stretched pulse PPM signal

在水下激光脉位调制(PPM)通信中,脉冲的时域展宽容易导致时隙串扰,进而严重影响通信质量。针对这一问题,对光PPM取样信号最大似然时隙(MLC)解调和最大累加计数样值(MAS)解调进行了改进。并根据激光脉冲水下传输后其能量分布的特点,在MAS解调的基础上,提出最大变权重累加计数(MVA)解调。计算机仿真结果表明,相比MAS解调,MVA解调时能明显改善时隙串扰情况下的PPM信号解调性能,并且对水下光信道的随机性有较好的自适应能力,证明了MVA解调方法的有效性,对水下激光无线通信的应用具有重要的实际意义。

In underwater laser PPM（pulse position modulation） communication,the pulse time-domain extension can easily lead to inter-slot interference,which may seriously affect the quality of communication.In terms of the problem,methods for sampling signal demodulation such as MLC（maximum likelihood searching for chips） and MAS（maximum accumulating count searching for samples） are improved.Based on the MAS demodulation mentioned above,MVA（maximum variable-weight accumulating count） demodulation method is proposed according to the energy distribution of the laser pulse after propagating underwater.Compared with MAS method,the simulation results illustrate that MVA demodulation has greatly improved PPM signal demodulation performance under inter-slot interference condition.Furthermore,it has good self-adaptivety to the randomness of underwater optical channel and proves the availability of MVA demodulation method,which is of much practical significance to underwater wireless laser communication.