Performance analysis of non-identically distributed FSO systems with dual- and triple-branch based on MRC over Gamma-Gamma fading channels

In this work, the performance of free-space optical (FSO) communication system based on maximal ratio combining using binary phase shift keying subcarrier intensity modulation over Gamma-Gamma fading channels has been studied systematically. Under identically or non-identically distributed branches, the analytical expressions for the bit error rate function of signal-to-noise are derived by expressing the modified Bessel function of second kind with Meijer G-function for dual- and triple-branch systems, respectively. In terms of H-fox function, the new expressions have more general forms and are more efficient for computation. It is found that the dual- and triple-branch systems significantly outperform the direct link system under weak, moderate and strong turbulence conditions. Monte Carlo simulation is also provided to confirm the accuracy of the proposed model.