Joint uplink user scheduling and power allocation in cognitive MIMO system

In this paper, we investigate the problem of the multi-user uplink scheduling in cognitive radio cellular network. The objective is to maximize the system throughput, while protecting the QoS of primary user (PU) from being affected by cognitive user (CU). Here, PU´s QoS is represented by its rate outage probability and it also reflects on the interference temperature (IT). It is equivalent to say that CUs can increase transmit power to enhance the system performance as long as PU´s outage probability does not exceed the predefined threshold. We assume that the cognitive base station (CBS) is equipped with M antennas and all CUs has one antenna that means CBS can at most allow M CUs to access simultaneously. We focus on user scheduling schemes for this uplink of multiple user single-input multiple-output (MU-SIMO) system in cognitive radio network (CRN). Meanwhile, we formulate the water-filling power allocation problem at that condition. The first scheduling algorithm is proposed to maximize the system throughput through utilizing the multi-user diversity and spatial multiplexing gain. Due to the first algorithm which does not take the fairness among CUs into account, so we propose the second scheduling algorithm with considering fairness among CUs. It provides a satisfactory tradeoff between maximizing the system performance and achieving fairness among CUs. Finally, these proposed algorithms are validated through extensive simulations.