Generalized Performance Analysis of Mixed RF/FSO Cooperative Systems

Free space optical (FSO) links provide an efficient point-to-point wireless transmission solution. They are particularly useful for filling the connectivity gap between the radio frequency (RF) access network and the fiber optic-based backbone network. To address this combined use, there has been a growing interest in so-called mixed RF/FSO systems where RF transmission is used at one hop and FSO transmission at the other in a dual-hop configuration. In this paper, we investigate the performance of mixed RF/FSO systems along with a direct RF link where the FSO link and RF links, respectively, experience double generalized gamma turbulence with pointing error and Nakagami-m fading. Moreover, the effect of cochannel interference is considered at both relay and destination. Under the assumption of amplify-and-forward relaying and selection combining at the destination, we derive closed form expressions for outage probability and bit error probability in terms of Meijer's-G and two-variate Fox-H functions. Our analysis provides a generalized framework for several existing results, since our adopted turbulence and fading statistical models are the most general ones. Based on the high signal-to-noise-ratio analysis, we further provide a diversity gain analysis and discuss the bottlenecks in the mixed RF/FSO systems.