Performance Analysis Of FSO Communication System Under Atmospheric Turbulence

Free space optical(FSO)communication is a novel wireless communication technology,which has aroused widely attention for its good secrecy,spectrum free,large communication capacity and convenient installation,etc.These merits make FSO systems very promising in many scenarios,e.g.the last mile problem,emergency communication,and so on.However,FSO communication is based on light as the carrier,and transmits the signal in the open space,so it is susceptible to the weather and other factors.The atmospheric turbulence is one of the most important factor that affects the performance of wireless optical communication system.And the effects of scintillation and phase shift caused by atmospheric turbulence will seriously affect the performance of free space optical links.Therefore,it is necessary to study the mechanism and the inhibition method of atmospheric turbulence.In general,the most widely fading model is Log-normal distribution and Gamma-Gamma,which are used in weak turbulence conditions and moderate-strong atmospheric conditions.However,they do not work well under all weak-moderate-strong atmospheric conditions if the system device is not changed.In order to increase the coverage of the communication system,we analyses the outage performance of the FSO system under different atmospheric turbulence conditions and different receiver sizes based on EW fading model.Specific contents are as follows:(1)We analyzed the outage performance of the simple end-to-end communication model for conventional RF link and FSO link is analyzed.Specifically,The Rayleigh fading model is generally adopted for RF link.However,we analyzed Log-normal distribution under weak turbulence conditions,and Gamma-Gamma fading is analyzed under moderate-strong atmospheric conditions.Then,We derive their outage probabilities based on the CDF which are calculated from the pdf of the fading models.Based on this,the communication performance of RF link and FSO link is compared and analyzed.(2)In order to solve the imitation of Lognormal and Gamma-Gamma channel fading model,we propose a FSO communication system based on EW fading.The influence of the FSO communication system under different turbulence intensity on the mixed FSO communication system applying the numerical simulation of the outage probability of the EW distribution is analyzed.Moreover,we derive approximate expression of the outage probability under high SNR,and analyze the diversity of the system.