Free Space Optical Communications with Distributed Switch-and-Stay Combining

What is it about?

We study the performance of an amplify-and-forward dual-hop, switch-and-stay combining (SSC) receiver, used in free space optical communications over non-identical fading channels. One path is characterized by the generalized Málaga (or M distribution), whereas the other is influenced by the combined effects of Gamma-Gamma distributed atmospheric turbulence, pointing error and path loss. Novel closed-form expressions for the end-to-end moment generating function, probability density function, and cumulative distribution function are derived in terms of Meijer’s G function. Furthermore, the performance of the system is analyzed, and closed-form expressions are presented for the end-to-end outage probability and channel capacity.

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Why is it important?

SSC has gained interest in recent years due to its simplicity of implementation as only selected branch needs to be monitored and processed. Selection of a branch is based on the threshold value of SNR and no cophasing or channel state information is required, this has become practically feasible with the use of adaptive and intelligent systems. Recently, distributed schemes have surpassed the performance of stand-alone SSC techniques. FSO appears very promising for backhaul transmission amongst infrastructure elements in cellular networks and is very less affected by different fading conditions as compared to RF due to its LoS transmission property. This motivated us to implement DSSC over FSO network as none of the previous work addressed the same for Málaga and Gamma-Gamma distributed fading channels.