Unified Performance Analysis of Hybrid FSO/RF System With Diversity Combining

Hybrid free space optical (FSO)/radio frequency (RF) systems have been proved to be reliable for high-data-rate wireless backhauls. In this article, we present a unified performance analysis of the hybrid FSO/RF transmission system which transmits identical data in both links and implements two popular diversity combining schemes, namely, selection combining (SC) and maximal ratio combining (MRC), in the receiver. Specially, for the FSO link, the Gamma-Gamma turbulence with pointing errors under heterodyne detection (HD) and intensity modulation/direction detection (IM/DD) is considered in our analysis while the general κ-μ shadowed fading which unifies popular RF fading models is employed for the analysis of the RF link. As a result, unified closed-form expressions of outage probabilities and average bit error rates for different modulation schemes are derived. A preliminary extension of the RF link to multi-input-multi-output (MIMO) transmission is also analyzed. Analytical and Monte Carlo simulation results are provided to characterize the performance of the hybrid FSO/RF link which is compared to the single FSO link and the single RF link. The agreement between the analytical and simulation results confirms the unification of various FSO channels and RF fading scenarios into a single closed-form expression.