Outage analysis of DF based SIMO-RF/FSO system with selection combining at relay

In this paper, the authors have analyzed the performance of an asymmetric dual-hop mixed radio frequency/free space optical (RF/FSO) communication system using decode-and-forward (DF) relaying. Each branch in SIMO-RF link is assumed to experience independent and identically distributed (i.i.d.) Nakagami-m fading, whereas Gamma-Gamma distribution with misalignment error is considered for irradiance of FSO link. Selection combining (SC) diversity scheme at relay is investigated in this work. More specifically, for the SC method, we derive closed-form expressions of the cumulative distribution function (CDF) and probability density function (PDF) of end-to-end signal-to-noise ratio (SNR). Utilizing the derived statistics, we obtain the outage probability (OP) expression for the considered system. We have also analyzed the considered system for high SNR conditions. All the analytical results are validated through simulations.