Opportunistic Scheduling in Underlay Cognitive Radio based MIMO-RF/FSO Networks

This work proposes an optimal metric for opportunistic scheduling of secondary user transmitters (SU-TXs) in underlay cognitive radio based multiple-input multiple-output radio frequency/free space optical (MIMO-RF/FSO) decode-and-forward system with fixed and proportional interference power constraints. To analyze the performance of the proposed system, the closed-form expressions are derived for the exact and asymptotic outage probabilities considering orthogonal space-time block coded transmission over Nakagami-$m$ fading RF links. Further, the FSO link between the relay and destination eNodeB is modeled as the Generalized M'{a}laga $(\mathcal{M})$ turbulence channel with pointing errors. Finally, simulation results are presented to develop several interesting insights into the end-to-end system performance and the selection probabilities of SU-TXs. It is also shown that the proposed system outperforms the ones existing in the current literature.