Performance of multiuser scheduling in free space optical systems over atmospheric turbulence channels

In this study, the authors consider a multiuser multiple-input multiple-output (MU-MIMO) free space optical (FSO) communication system and investigate the performance of various scheduling protocols which provide different degrees of tradeoff between throughput and fairness. In the MU-MIMO FSO system under consideration, the central node and each user node are equipped with multiple transmit and receive apertures and equal gain combining is employed at the receiver side. Round robin, opportunistic round Robin, select-max and mth best user selection scheduling protocols are employed. The authors derive closed-form outage probability expressions for each scheduling protocol over log-normal turbulence channels assuming non-equidistant placement of users. The authors further present Monte Carlo simulations to confirm the accuracy of derived expressions.