Time and power allocation for non-orthogonal multiple access relaying networks

Power domain non-orthogonal multiple access (NOMA), which multiplexes multiple users in power domain to achieve high spectrum efficiency, is a promising technology for the fifth-generation (5G) wireless networks and beyond. In this work, we study time and power allocation for two-hop NOMA relaying with decode-and-forward (DF) protocol, to satisfy two NOMA users' different quality of service (QoS) requirements. The performance metrics of outage probability and ergodic capacity are used to evaluate two NOMA users, respectively. The closedform expression for outage probability is also derived. Furthermore, to obtain optimal time allocation factor to achieve the minimum outage probability, we formulate it as one optimization problem and develop a golden section search (GSS)-based algorithm to solve it. Also, the tradeoff between time and power allocation is further analysed to improve the system performance. Numerical and simulation results show that the proposed time and power allocation DF-NOMA behaves better than the traditional equal-time slot cooperative NOMA.