Gamma Gamma强海洋湍流和瞄准误差下水下无线光通信系统的性能研究

采用外差式差分相移键控(Differential phase-shift keying,DPSK)调制的水下无线光通信(Underwater wireless optical communication,UWOC)系统经过Gamma Gamma强海洋湍流信道传输,当接收端与发送端之间存在瞄准误差并采用孔径接收方式时,分析了湍流效应和瞄准误差对接收光强的抖动影响,推导了UWOC系统的平均误码率(Bit error rate,BER)和中断概率(Outage probability,OP)的解析表达式。数值模拟研究了不同的瞄准误差、束宽、接收孔径和海洋湍流参数对平均BER和OP性能的影响。结果表明,在相同的束宽和信道环境下,瞄准误差越大,系统性能越差;光束束宽与孔径半径之比越大,接收孔径直径越大,系统性能越好;另外,选择较小的温度和盐度波动对海洋湍流贡献的比值ω和均方温度耗散率χT,以及较大的湍流动能耗散率ε和动力粘度u的海洋湍流环境也有利于获得较好的系统性能。

Performance of underwater wireless optical communication system in Gamma Gamma strong oceanic turbulence with pointing error

The impact of Gamma Gamma strong oceanic turbulence and pointing error on the average bit error rate(BER) and outage probability of a heterodyne differential phase-shift keying(DPSK) underwater wireless optical communication(UWOC) system with an aperture receiver was investigated. The optical intensity fluctuation due to the combined effects of oceanic turbulence and pointing error was derived. The close-form expressions for the average BER and outage probability were derived. Then the average BER performance and the outage probability performance versus signal to noise ratio(SNR) of the considered UWOC system were investigated with different point errors, source beam widths, receiver aperture sizes and oceanic turbulence parameters. The results indicate that the larger the aiming error is, the worse the system performance is, under the same beam width and channel environment. Choosing a larger radio of source beam width to aperture radius or a bigger aperture receiver can help to improve the system performance. In addition, the system shows a better performance over the strong oceanic turbulence with a smaller ratio of temperature to salinity contributions to the refractive index spectrum ω and the rate of dissipation of mean-squared temperature χ_T or a larger rate of dissipation of kinetic energy per unit mass of fluid ε and the kinetic viscosity u. This work will provide reference for the construction and performance estimation of UWOC system on strong oceanic turbulence when taking pointing error into consideration.