Performance Analysis Of Laser Underwater Wireless Optical Communication System Under Ocean Turbulence

Compared with the traditional radio frequency and acoustic wave technology,underwater wireless optical communication technology has attracted much attention because of its high speed,low delay,large capacity,and strong security.Due to the loss of Gaussian beam in ocean link,turbulence effect and aiming error caused by optical transceiver,the performance of underwater wireless optical communication system will deteriorate seriously.Therefore,it is of great significance to study the performance of underwater wireless optical communication system under the combined effects of ocean link loss,ocean optical turbulence and aiming error.The research contents of this subject are as follows:(1)Thesis summarizes the advantages and research significance of underwater wireless optical communication,and briefly describes the development process of underwater wireless optical communication,research trends and development trend at home and abroad.The theoretical basis of seawater composition,link attenuation,ocean turbulence and aiming error are introduced,and the development trend and research significance of underwater wireless optical communication under combined effect are introduced.At the same time,several common theoretical models of ocean turbulence channel and the conditional bit error rate expression of corresponding modulation techniques are given.(2)The effect of ocean turbulence on the performance of underwater wireless optical communication system is studied.The analytical expression theoretical model of average bit error rate and outage probability of underwater wireless optical communication system based on differential phase shift keying modulation and subject to gamma gamma turbulence distribution is established by generalized hypergeometric method.The factors affecting the communication performance of underwater wireless optical communication system under the effect of ocean turbulence are simulated and analyzed.(3)The combined effects of ocean link loss,ocean turbulence and aiming error on the performance of underwater wireless optical communication system are studied.The statistical distribution theoretical model of joint channel under gamma turbulence distribution is established.Based on the generalized hypergeometric function,the analytical expression theoretical model of average bit error rate and outage probability of underwater wireless optical communication system with direct detection differential phase-shift keying modulation under joint effect is established.Simulation analysis is carried out and the factors affecting the performance of underwater wireless optical communication system under the joint effect are summarized.(4)The analytical expressions of average bit error rate and outage probability of underwater wireless optical communication system based on differential phase-shift keying modulation under ocean turbulence effect and joint effect are numerically simulated and compared.The results show that the average bit error rate and outage probability of the system under the combined effect are significantly higher than that under the ocean turbulence effect,which shows that the influence of aiming error in underwater wireless optical communication system can not be ignored.Under different ocean turbulence intensity,the simulation legends with different parameter values are described,and the effects of light wave scintillation scale parameters,normalized beam width,receiving aperture diameter and ocean optical turbulence parameters on the performance of underwater wireless optical communication system are analyzed.The results of control variable method show that the increase of aiming error leads to the decrease of system performance.The system performance can be improved by increasing the normalized beam width and receiving aperture diameter;Larger temperature salt gradient ratio and turbulent temperature dissipation rate will reduce the system performance,while larger turbulent energy dissipation rate and kinematic viscosity can effectively improve the system performance.