Joint subcarrier assignment and weighted-sum energy-efficient power allocation in multi-carrier uplink NOMA relay networks

In this paper, the problem of joint subcarrier assignment and weighted-sum energy-efficient power allocation (J-SA-WSEE-PA) in multi-carrier uplink NOMA relay networks is considered. Specifically, the aim is to assign subcarriers to network users, while maximizing the weighted-sum energy-efficiency, subject to quality-of-service (QoS) constraints. The J-SA-WSEE-PA problem is shown to be non-convex, and thus is computationally-expensive. In turn, it is split into two sub-problems: (1) WSEE maximizing power allocation per subcarrier, and (2) matching-theoretic subcarrier assignment. For the first sub-problem, a low-complexity iterative solution procedure is devised to optimally solve the WSEE-maximizing power allocation problem per subcarrier. As for the second sub-problem, two linear time-complexity stable matching algorithms based on the hospitals–residents matching problem are proposed to assign subcarriers to network users. Simulation results are presented to validate the devised solution procedure and the proposed stable matching algorithms, where it has been shown that they yield comparable network sum energy-efficiency to the J-SA-WSEE-PA scheme, while satisfying QoS constraints, and with lower computational complexity.