Research On The Direct Link BER And Multiuser Throughout Based On MRC Under GG Fading Channel

Free Space Optical(FSO) communication has received extensive research as it is a access technique with cost-effective and high bandwidth. However, the FSO link is suffer from reliability and availability which are caused by atmosphere turbulence. The atmosphere turbulence leads to scintillation degrades the systems performance severely. So, how to mitigate the impairment has received increasing attention in FSO. Similar to Radio frequency(RF) system, the Maximal Ratio combing(MRC) is investigated in this paper. The main contents are as follows:1) The FSO communication systems based on MRC using binary phase shift keying(BPSK) subcarrier intensity modulation(SIM) over Gamma-Gamma fading channels have been studied. Under identically or not identically distributed branches, the analytical expressions for the bit error rate(BER) function of signal-to-noise ratio(SNR) are derived by expressing the modified Bessel function of second kind with Meijer G-function for dual- and triple-branch systems, respectively. Monte Carlo simulation is also provided to confirm the accuracy of the proposed model.2) A point-to-multipoint system consisting of an optical transmitter(known as the central node) equipped with apertures, and users communicating over free-space optical channels is considered. Based on greedy scheduling(GS), selective multiuser diversity scheduling(SMDS), the proportional fair scheduling(PFS), we simulated the throughput of our system. Furthermore,we first introduce MRC in multiuser system,and simulation the throughput with MRC with different scheduling.The results provided insight for the FSO system design.