Buffer-Aided Cooperative NOMA: An Energy-Efficient Design

Abstract

This paper investigates a buffer-aided cooperative non-orthogonal multiple access scheme for simultaneous wireless information and power transfer systems, where the near users are equipped with data and energy buffers. To improve the overall energy efficiency, the transmission mode of the considered system adaptively chooses the base station or near-user transmission mode. Given the target quality of service and limited resources, the long-term power consumption minimization is formulated by a mixed integer non-linear programming problem, where the model selection, user scheduling, and power consumption are jointly optimized. To efficiently tackle such a challenging problem, we transform the original problem into an instantaneous non-convex problem by employing the Lyapunov optimization framework. Then, using the successive convex approximation algorithms, we approximate the instantaneous non-convex problem as a linear programming problem, where the Karush–Kuhn–Tucker solution of the power allocation can be obtained. The optimality and complexity of the proposed scheme are theoretically analyzed. The simulation results show that the proposed scheme can achieve a near-optimal performance and significantly improves the energy efficiency compared with the conventional transmission schemes.