ABER of an FSO Link in Gamma-Gamma Turbulence with SSK and SEC

In this paper, we have analyzed the average bit error rate (ABER) performance of a multiple-input-multiple-output (MIMO) free-space optical (FSO) communication link employing both transmitter and receiver diversity techniques. For the proposed MIMO FSO system, we have considered spatial shift keying (SSK), a specific case of spatial modulation (SM), as the diversity technique used at the transmitter end. On the other hand, switch and examine combining (SEC) is utilized as a spatial diversity technique at the receiver terminal of the system. A mathematical framework has been constructed to get the resultant closed-form expression of the performance metric. Specifically, a tight upper bound for the average BER of the given system is derived. It is noticed that under any receiver diversity order the amount of ABER gets improved after crosses the certain SNR level, and the impact of resultant metric also depends on the nature of atmospheric turbulence and the optimal switching threshold of the receiver diversity scheme. The outcome mathematical expression is presented in terms of Meijer’s G function and all numerical results are validated by Monte Carlo (MC) simulations.