Performance Analysis Of Free Space Optical Communication System Over The Aggregated Double Generalized Gamma Fading Channels

Free space optical(FSO)communication,which uses laser beams as carrier,has attracted significant attention as one of the most promising wireless communication technologies because of its wide bandwidth,license-free spectrum,robustness to electromagnetic interference,high speed,low cost,and high security.However,the performance of FSO link is vulnerable to the existence of the atmospheric turbulence(AT)-induced fading,misalignment between the transmitter and receiver(i.e.,pointing error,PE),and path loss caused by varying weather conditions when laser beams transmitted through atmosphere environment,resulting in random fluctuation of optical power and the system performance degradation.Moreover,selecting a photodetector with excellent performance at the receiver is also critical to the performance of FSO system.In this work,the performances of FSO communication system over the aggregated double generalized gamma(Double GG)fading channels for both plane and spherical waves are investigated.Besides,a lot of technologies such as relay-assisted,low-density parity-check(LDPC)codes and avalanche photodiode detector(APD)have been adopted to improve the system performance.The main contents are as follows:(1)On the basis of the multi-hop parallel relay-assisted(MPRA)FSO communication system over the aggregated Double GG fading channel,considering both PE and path loss,the theoretical expressions of the average bit error rate(ABER)and outage probability(OP)performances are firstly derived,and Monte Carlo simulations are also offered to verify the validity of the proposed models.Besides,for both plane and spherical waves,the different influences due to the variances of turbulence strengths,structure parameters,jitter and weather conditions have been studied.(2)On the basis of the LDPC-coded multi-hop FSO communication system over the aggregated Double GG fading channel,the analytical expressions of the end-to-end ABER performances are firstly derived considering both PE and path loss for plane and spherical waves,which have been verified by Monte Carlo simulation.Subsequently,for these two transmission beams,the different influences due to the different values of turbulence strengths,structure parameters,jitter and weather conditions have been researched.Specifically,LDPC codes are used in the simulations to enhance the proposed system performance,which is the most important.(3)On the basis of the APD-based FSO communication system over the aggregated Double GG fading channel,the analytical expressions of the end-to-end ABER performances are firstly derived for plane and spherical waves.Subsequently,for these two transmission beams,the different influences due to the variances of turbulence strengths,receiver noise temperatures,average APD gains,modulation and average photon counts per PPM have been investigated.This work is beneficial for the FSO system design.