Performance of FSO Communication Systems Employing Alamouti-Type Space-Time Encoding over Málaga Channels with Pointing Errors

In this work, spatial diversity techniques have been proposed for free-space optical (FSO) communication systems to combat the deteriorating effects, such as atmospheric turbulence effects and pointing errors, and the performance of FSO communication systems with Alamouti encoding scheme over Málaga ( M) turbulence channel is investigated. We first derive the probability distribution function (PDF) of end-to-end channel gain under atmospheric turbulence and pointing error circumstances. Then, by capitalizing on this PDF, closed-form expressions of the average bit error rate (BER) and the outage probability (OP) for the proposed system are obtained. Additionally, to provide more insights, the asymptotic expressions for the average BER and the OP are also derived. In the analysis, intensity modulation/direct detection and heterodyne detection techniques are considered so that the obtained results can cover both cases. Furthermore, analytic results are successfully validated through Monte Carlo simulations. Our results highlight the gains in performance that can be achieved when Alamouti encoding scheme is employed in FSO communication systems.