Average BER analysis of relay selection based decode-and-forward cooperative communication over Gamma-Gamma fading FSO links

In this paper, we consider relay selection based decode-and-forward (DF) cooperative communication over free space optical (FSO) links. A relay selection scheme is considered in which source selects a relay on the basis of highest instantaneous signal-to-noise ratio (SNR) of the source-relay links. We derive the cumulative distribution function (CDF) and probability density function (PDF) of the highest instantaneous SNR of Gamma-Gamma distributed source-relay links. The average error performance of the DF protocol with relay selection over the Gamma-Gamma fading channels is derived in terms of power series. Coding gain and diversity order of the relay selection based DF scheme are analytically obtained. It is inferred by the analysis and simulation that the performance of the DF FSO system can be significantly improved by using the simple relay selection scheme considered in this paper.