Research On The Effect Of Beckmann Pointing Error Distribution On The Performance Of MIMO Free Space Optical Communication

Free space optical(FSO)communication systems provide many advantages over radio frequency(RF)system,including high data rates,license-free spectrum,less power and mass requirements,immunity to interference and multi-path fading.Furthermore,the deployment of FSO systems is easier and quicker than fiber optic cables.These features make FSO communication a promising solution for the “last mile” problem.However,FSO link suffers highly from the atmospheric turbulence.In order to satisfy the requirements for transmission data and quality,multiple-input multiple-output(MIMO)technology is effective solution to mitigate turbulence-induced fading.The use of MIMO technique can significantly improve the performance of FSO system,but the existence of pointing errors can aggravate the fluctuation of channel gain and affect the communication performance of the system.Therefore,it is necessary to comprehensively consider the effects of atmospheric turbulence and pointing errors in the actual study of MIMO FSO system.In view of this situation,this paper mainly studies the following contents:Firstly,based on Gamma-Gamma(GG)turbulence model and Beckmann pointing error distribution model,the theoretical model for communication performance of singleinput single-output(SISO)FSO communication system is established.From the point of view of high signal-to-noise ratio(SNR),the probability density function of channel gain under combined effects of GG atmosphere turbulence and Beckmann pointing error is given.Based on this function,the closed expressions of outage probability and average bit error rate(BER)are obtained.The joint effects of GG atmospheric turbulence and Beckmann pointing errors on outage probability and average BER are analyzed.Secondly,the theoretical model of communication performance of MIMO FSO communication system is established.The closed expressions of outage probability and average BER for maximal ratio combining(MRC)and equal gain combining(EGC)schemes are given respectively.Based on these expressions,the outage probability and average BER of the system for MRC and EGC schemes are compared and analyzed.Thirdly,through a 11.6 km urban horizontal laser link simulation experiment,the intensity data under different pointing errors are measured,the probability density distribution of channel gain is given,and compared with the established theoretical model.The work of this paper is about the application basic research of the influence of GG atmospheric turbulence and Beckmann pointing errors on the performance of FSO communication system.Compared with the traditional pointing error distribution models,the adopted Beckmann pointing error distribution model adds different jitters and nonzero boresight factors,which can more comprehensively reflect the impact of pointing error on the performance of FSO communication system,and is more in line with the actual situation of FSO communication system.