Outage Performance of Multiuser Mixed RF/Parallel Relay-assisted FSO Systems

In this work, we study the outage performance of multiuser mixed radio frequency (RF)/parallel relay-assisted free-space optical (FSO) systems with decode-and-forward (DF) relaying over strong turbulence conditions, where the FSO link experiences Gamma-Gamma turbulence with pointing errors and path loss, and the RF link experiences Nakagami-m fading. A closed-form expression for the outage probability is derived. The results show that both multiuser diversity and parallel relays introduce an improvement in the outage performance of the considered system, where the system performance is dominated by the FSO link at the low values of the average signal-to-noise ratio (SNR) of the FSO link, whereas, the RF link is dominated at larger values. The perfect match of the numerical and Monte Carlo simulation results confirms the accuracy of the derived expression.