Outage performance of mixed RF-FSO systems over DGG and nakagami-m channels

Abstract

In mixed RF (radio frequency)-FSO (free space optical) systems, the FSO link is used for backhauling while RF is used for wireless access. In many practical deployment scenarios especially in urban environments, more than one FSO hop is required to avoid blockage and facilitate the line-of-sight connectivity. In this letter, we study the performance of a triple-hop RF-FSO-FSO link. We assume that the RF link is subject to Nakagami-m fading while FSO links are subject to double generalized Gamma (DGG) turbulence in addition to pointing errors. We first derive an exact closed-form expression for outage probability (OP) in terms of bivariate Fox-H function. Then, we carry out an asymptotical analysis to derive achievable diversity gains. We further present simulations to verify the accuracy of the derived expressions and investigate the effect of several system and channel parameters on the performance.