Relay selection in mixed RF/FSO system over generalized channel fading

In this paper, a relay selection-based amplify-and-forward (AF) with mixed radio frequency/free space optical (RF/FSO) system is proposed. We have considered two relay selection schemes namely max-select, distributed switch and stay (DSS) and compared their performance when all relays are active. The AF-based relay employs (1) full-channel state information relaying (amplification gain dependent on instantaneous signal-to-noise ratio of source-relay link) (2) semi-blind relaying (fixed amplification gain) for the amplification purpose. The selected AF relay converts the received RF signal into an optical signal using the subcarrier intensity modulation scheme. The RF link is subject to a generalised eta - mu distribution, while the channel for free space optical link is modelled as gamma-gamma distributed along with pointing errors. Novel analytical expressions for the probability density function, cumulative distribution function and the moment generating function of the equivalent signal-to-noise ratio is derived. Capitalising on these channel statistics, we provide the closed form expressions of the outage probability for different relay selection schemes. Copyright (C) 2016 John Wiley & Sons, Ltd.