Statistical QoS Guarantee for Power-Efficient Downlink NOMA with Statistical CSI

This paper investigates statistical quality of service (QoS) guarantee in a downlink non-orthogonal multiple access (NOMA) system with statistical channel state information (CSI). The statistical QoS requirements are based on the theory of effective capacity (EC). To be more specific, we employ joint power and rate allocation to satisfy EC constraints while minimizing the total power consumption of users. As deriving the optimal power and rate allocation through mathematical analysis is nontrivial, we alternatively propose a low-complexity algorithm that can find a feasible solution. The proposed solution is optimal under the provided optimality condition. Besides, a tight lower bound of total power is obtained through analysis. Numerical results validate our analysis.