Joint Relay Selection and Energy-Efficient Power Allocation in Downlink Multi-Cell NOMA Networks

This paper considers joint relay selection and maxmin energy-efficient power allocation (J-RS-MMEE-PA) in downlink multi-cell non-orthogonal multiple-access (NOMA) networks. Particularly, the aim is to perform relay selection for each user within each cell, so as to achieve max-min energy-efficiency, while satisfying quality-of-service (QoS) constraints. However, the J-RS-MMEE-PA problem happens to be non-convex (i.e. computationally-intensive). In turn, a solution procedure for maxmin energy-efficient power allocation is devised to determine the energy-efficiency per potential relay, while meeting the target minimum rate per user. After that, the relay selection problem is modeled as a student-project allocation with preferences over projects matching problem, where a polynomial-time complexity stable matching algorithm is proposed to pair users with relays within each cell. Simulation results are presented to validate the proposed stable matching algorithm, where it is demonstrated that it efficiently yields comparable energy-efficiency per user to the J-RS-MMEE-PA scheme, while satisfying QoS constraints.