Capacity analysis for Rayleigh/gamma-gamma mixed RF/FSO relayed transmission

In this paper, we have investigated capacity of a dual-hop mixed radio-frequency (RF)/ free-space optical (FSO) communication link equipped with a fixed-gain amplify-and-forward (AF) relay employing average power scaling (APS). The atmospheric turbulence induced fading in the FSO part of the link is modelled with gamma-gamma distribution while it is considered that the RF link experiences Rayleigh fading. Novel and simple analytical methods have been deduced for obtaining concise closed-form expressions for channel capacity under different rate/ power adaptation policies. The proposed mathematical analyses are confirmed by comparing the derived expressions with Monte Carlo simulation results.