Performance Analysis Of FSO Communication System Model Based On Relay Collaboration

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 addition,according to the propagation characteristic of the light,FSO communication system is not suitable for long distance communication.In order to increase the communication distance and coverage of the communication system,we consider the relay cooperation technology and analyses the outage performance of the mixed RF/FSO relay system and all-optical relay FSO/FSO system under different atmospheric turbulence conditions and different receiver sizes based on EW fading model.Specific contents are as follows:(1)In order to solve the imitation of Lognormal and Gamma-Gamma channel fading model,we propose a relay cooperative RF/FSO communication system based on Rayleigh-EW.The influence of the mixed RF/FSO communication system under different turbulence intensity on the mixed RF/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.(2)In order to increase the communication distance and coverage of the communication system,a symmetric relay cooperative FSO / FSO free space optical communication system is proposed.The system applies variable gain all-optical relay and subcarrier modulation technique,and its outage performance under EW atmospheric turbulence channel is studied emphatically.In particular,firstly,the cumulative distribution function(CDF)of the end-to-end SNR is deduced based on the exponential fading distribution,and then the outage probability expression of the system is obtained.Also,the approximate performance and diversity under the high SNR range are analyzed.Finally,we analyze the outage probability of the mixed RF/FSO and FSO/FSO relay system by simulation.