  In this paper, we investigate the performance analysis of dual hop relaying
system consisting of asymmetric Radio Frequency (RF)/Free Optical Space (FSO)
links. The RF channels follow a Rayleigh distribution and the optical links are
subject to Gamma-Gamma fading. We also introduce impairments to our model and
we suggest Partial Relay Selection (PRS) protocol with Amplify-and-Forward (AF)
fixed gain relaying. The benefits of employing optical communication with RF,
is to increase the system transfer rate and thus improving the system
bandwidth. Many previous research attempts assuming ideal hardware (source,
relays, etc.) without impairments. In fact, this assumption is still valid for
low-rate systems. However, these hardware impairments can no longer be
neglected for high-rate systems in order to get consistent results. Novel
analytical expressions of outage probability and ergodic capacity of our model
are derived taking into account ideal and non-ideal hardware cases.
Furthermore, we study the dependence of the outage probability and the system
capacity considering, the effect of the correlation between the outdated CSI
(Channel State Information) and the current source-relay link, the number of
relays, the rank of the selected relay and the average optical Signal to Noise
Ratio (SNR) over weak and strong atmospheric turbulence. We also demonstrate
that for a non-ideal case, the end-to-end Signal to Noise plus Distortion Ratio
(SNDR) has a certain ceiling for high SNR range. However, the SNDR grows
infinitely for the ideal case and the ceiling caused by impairments no longer
exists. Finally, numerical and simulation results are presented.
