Exact Capacity of Amplify-and-Forward Relayed Optical Wireless Communication Systems

In this letter, we model a dual-hop subcarrier intensity modulated amplify-and-forward (AF) relayed optical wireless communication system with the assumption that direct communication between source and destination is not feasible. The optical channels are considered to be impaired with path loss, misalignment errors, and atmospheric turbulence, and are modeled assuming independent but not necessarily identically distributed Gamma-Gamma fading statistics. We derive exact analytical expressions for the average channel capacity of the system considering both type of AF relays, i.e., variable gain and fixed gain. Further to get valuable insight, an asymptotic analysis of channel capacity is presented at high signal-to-noise ratio to find the effect of various parameters on the performance of the system.