A New Optimization Problem in FSO Communication System

Abstract

According to the physical phenomena of atmospheric channels and wave propagation, the performance of wireless communication system can be optimized by simply adjusting its natural parameters. This way is economically more favorable than consuming more power or using additional processing techniques. In this letter for the first time, an optimization problem is developed on the performance of a free-space optical multi-input multi-output (FSO-MIMO) communication system. In addition, it is the first time that the optimization of the FSO system is developed under saturated atmospheric turbulence. In order to get closer to the actual results, the effect of pointing error is taken into considerations. Assuming multiple phase-shift keying and differential phase-shift keying modulation schemes, new closed-form expressions are derived for bit error rate (BER) and outage probability ( $P_{\text {out}}$ ) of the proposed structure. Furthermore, an optimization problem is developed taking into account the equivalent beam waist as variable parameter, and BER as objective function, there is no constraint in this system. Obtained results can be a useful outcome for FSO-MIMO system designers in order to mitigate the effects of pointing error as well as atmospheric turbulence, and thus, achieve optimum performance.