Network Sum-Rate Maximization via Joint Relay Selection and Power Allocation in Energy-Harvesting NOMA Multicast Cognitive Radio Networks

This paper studies the problem of joint relay selection and power allocation (J-RS-PA) for energy-harvesting (EH) non-orthogonal multiple-access (NOMA) multicast cognitive radio networks. Particularly, primary and secondary transmitters communicate with their receivers over EH amplify-and-forward relays, with the aim of maximizing the network sum-rate, while satisfying quality-of-service (QoS) constraints. The formulated J-RS-PA problem happens to be non-convex and computationally-intensive. Alternatively, it is solved optimally via a low-complexity solution procedure, which optimally solves the power allocation problem over each relay, and then selects the relay that maximizes the network sum-rate. Simulation results are presented to evaluate the proposed solution procedure, which is shown to efficiently yield the optimal network sum-rate solution, in agreement with the J-RS-PA scheme (solved via a global optimization package), but with lower computational-complexity, while satisfying the QoS requirements at the primary and secondary receivers.