Outage and Error Rate Analysis of Network-Coded Coherent TWR-FSO Systems

This letter investigates a two-way relay assisted coherent free space optical system when the optical beam is subjected to gamma-gamma atmospheric turbulence and misalignment errors (pointing errors). A half-duplex relaying system consisting of two terminal nodes and a bidirectional relay is considered. The relay is based on decode-and-forward protocol and employs linear network coding to establish communication between the two terminal nodes in two time slots. Coherent detection with M-ary phase shift keying is employed. Closed form expressions for system outage and error performance for both binary and nonbinary cases are derived in terms of the well known Meijer´s G-function and are mathematically analyzed.