On the Performance of AF based Mixed Triple-Hop RF/FSO/RF Communication System

In this paper, we perform a unified performance analysis of a triple-hop amplify-and-forward (AF) based mixed radio frequency/free space optical/radio frequency (RF/FSO/RF) cooperative communication system, for both types of detection, i.e., heterodyne and intensity modulation/direct detection (IM/DD). In the considered system, two variable gain AF relays connect the source and the destination using RF links, which are modeled by independent but not identically distributed (i.n.i.d.) Rayleigh fading and the FSO link, which is modeled by path loss, Malaga distributed turbulence, and pointing errors. This triple-hop RF/FSO/RF system can be employed in scenarios where the high-speed FSO link can be used to provide connectivity between two new/existing RF networks, for example, campus connectivity. For the considered system, new mathematical expressions are derived for the end-to-end signal-to-noise ratio (SNR), yielding novel analytical expressions of various performance metrics, i.e., outage probability and average bit error rate for different modulation techniques. Monte Carlo simulation results validates the proposed analysis, which depicts the effect of fading, turbulence, and pointing errors on the performance of the considered cooperative system.