On Secrecy Performance of Multiuser FSO Networks with Opportunistic User Scheduling

This paper focuses on the impact of opportunistic scheduling schemes on the secrecy performance of a multiuser free-space optical network (MU-FSON). Considering a presence of a single passive eavesdropper, the best user with the highest signal-to-noise value is selected by the legitimate receiver among multiple users to communicate over an FSO link. The FSO links are assumed to follow the Málaga-M fading model with pointing errors. Initially, we derive a theoretical model of an MU-FSON considering the best user selection scheme. Then, the system outage probability and the system intercept probability are derived as the secrecy performance metrics of the considered MU-FSON. Our derived analytical expressions present an efficient tool to investigate the impact of some system and channel parameters on the secrecy performance, namely the number of users in the legal transmission process, atmospheric turbulence severity, and pointing errors of the FSO link. Numerical results are presented to validate the derived expressions and the accuracy of the obtained numerical results is confirmed by Monte-Carlo simulations.