一定背景噪声下的水下光PPM信道容量分析

根据水下光信道的特点，在分析光PPM信号接收模型的基础上，从信息论出发，研究了在一定背景噪声下，采用软判决解调时，脉冲时域展宽、单位脉冲能量、单位时帧传信时隙数等信道参数对光PPM信道容量的影响。模拟计算结果表明：信道容量和信息传输速率均随脉冲宽度的增大而减小，随脉冲能量的增大而增大，随传信时隙数增大而表现出先增大后减小，最后趋于零的趋势，存在最佳传信时隙数，使信道容量和信息传输速率分别达到最大，为设计水下光无线通信系统提供一定的理论依据。

Analysis of Underwater Optical PPM Channel Capacity Under Certain Background Noise

The characteristics of underwater laser channel are introduced and the receiving model of laser PPM signal is analyzed.Then beginning with information theory,the effects of channel parameters such as pulse time-domain extension,unit pulse power,and the number of time-slots transmitting information per unit symbol interval on the channel capacity of laser PPM have been studied by adopting soft decision demodulation in certain background noise.The simulation indicates that both the channel capacity and information transmission rate decrease with pulse width broadening,increase with power enhancing.And still the two parameters present a trend that they first increase then decrease and finally approach to zero when the transmission time-slot number becomes larger.So there is an optimal time-slot number that makes the channel capacity and information transmission rate reach a maximum respectively and provides theoretical basis for the design of underwater laser communication system.