Investigating and analyzing the performance of dual-hop hybrid FSO/RF systems

In this work, we investigate the performance of dual-hop hybrid free-space optical/radio frequency (FSO/RF) systems with decode-and-forward relaying, where the FSO link experiences Gamma–Gamma turbulence with pointing errors, while the RF link undergoes Nakagami-m fading. Two scenarios are considered, in the first scenario, a hard-switching (HS) scheme is used for the hybrid system, in which one of the links is active at a time, with high priority for the FSO link, whereas in the second scenario, both the FSO and RF links are active simultaneously and a selection combining (SC) scheme is used at the receiver end. We derive exact analytical expressions for the outage probability and average bit error rate (ABER) in terms of multivariate Fox H functions, and develop Monte Carlo simulations for validation. In the numerical results, we compare the performance of the two scenarios with the dual-hop FSO system. This comparison shows a respectable improvement in the system's performance when the hybrid transmission technique is exploited over the dual-hop system. Moreover, the hybrid system with the SC scheme shows superior performance when compared to the system with the HS scheme in terms of the ABER.