M-ary phase-shift keying-based single-input-multiple-output free space optical communication system with pointing errors over a gamma–gamma fading channel

The performance of free space optical (FSO) communication systems is severely affected due to a number of reasons, such as atmospheric impairments, fading due to turbulence, and misalignment between transmitter and receiver sections. In this paper, we have analyzed the atmospheric turbulence and pointing error effect on M-ary phase-shift keying modulation (M-PSK)-based FSO system link performance over a gamma-gamma fading channel. In our analysis, the effect of a weak-to-strong atmospheric turbulence channel condition and pointing errors are taken into consideration. To deal with the performance degradation, a single-input-multiple-output (SIMO) link along with maximal ratio combining (MRC) diversity scheme is employed. The closed-form expressions for the estimation of average bit error rate (BER), outage probability, and spectral efficiency are derived in terms of the Meijer G-function. The analytical results are presented to indicate the effect of turbulence and pointing errors on BER. The outage probability and spectral efficiency of the proposed SIMO-FSO system with MRC technique improved significantly. The accuracy of all the analytical results is verified by Monte Carlo simulation.