Performance of free-space optical MIMO system in S-distributed turbulence

In this paper the performance of a 2 × 2 multiple-input-multiple-output (MIMO) free-space optical (FSO) communication system is investigated in S-distributed atmospheric turbulence. The S-distribution subsumes an additional scattered-but-coupled to line of sight component of the propagating optical energy, and thus characterizes the wide variety of turbulence conditions. In the considered 2 × 2 system we assume that each transmit aperture is calibrated to communicate with the respective receive aperture and thus there is no cross-reception. The outage and error performances are analyzed in the receiver side of the system when the decision at the receiver is based on the signal which has the higher signal-to-noise ratio (SNR). In particular, the outage probability and bit error rate (BER) closed form expressions are derived. Furthermore, we numerically investigate the ergodic capacity also.