A framework on the performance analysis of dual-hop mixed FSO-RF cooperative systems

Free space optical (FSO) communication systems provide line-of-sight wireless connectivity in the unlicensed optical spectrum and achieve higher data rates in comparison to their radio frequency (RF) counterparts. FSO systems are particularly attractive for the last mile access problem by establishing a connectivity bridge between optical fiber-based backbone and RF access networks. To address this practical deployment scenario, there has been an increasing attention on the so-called mixed (dual-hop) FSO-RF systems where FSO transmission is utilized at one hop followed by RF transmission at the other one. In this paper, we investigate the performance of mixed FSO-RF transmission systems where the FSO link is modeled by the double generalized Gamma distribution with generalized pointing error impairments and the RF link experiences the extended generalized-K shadowed fading. For both amplify-and-forward and decode-and-forward relaying, we derive closed-form expressions for outage probability, bit error probability, and ergodic capacity in terms of bivariate Fox-H function. Monte Carlo simulation results are provided to verify the accuracy of derived expressions. We further provide an asymptotic analysis and discuss the achievable diversity orders of mixed FSO-RF systems.