On relay selection for cooperative free-space optical communication

In this paper, we propose two different relay selection schemes in free space optical (FSO) systems with decode-and-forward (DF) relaying. We provide closed-form outage probability expression for Selection Cooperation (SC) scheme and Monte-Carlo simulation of Opportuistic Relaying (OR) scheme for a gathered channel model which takes into account both path loss and turbulence-induced log-normal fading. Our analitical and simulation results demonstrate that the proposed SC and OR methods provide 0.5 dB and 4 dB power gains over one relay multi-hop transmission (no relay selection), respectively at a target outage probability of 10^-4 assuming the deployment of three relays in our system model. Moreover, this power gain increases with increasing number of deployed relays in OR scheme.