Moving towards non-orthogonal multiple access in next-generation wireless access networks

Existing wireless networks have predominantly adopted orthogonal multiple access (OMA) such as OFDMA as the underlying multiple access technology. To further improve spectrum efficiency in next-generation wireless networks, however, a promising direction is to shift to non-orthogonal multiple access (NOMA). To address the new technical challenges brought forth by NOMA, in this paper we investigate the problem of scheduling multiple NOMA users in the same resource block previously dedicated to a single user in OFDMA. Unlike related work that relies on the ideal link capacity model for profiling the performance gain of NOMA, we start by implementing a more practical NOMA simulator to investigate problems such as modulation/coding scheme (MCS) selection, power allocation, and error propagation along with transmission scheduling. We formulate an optimization problem for transmission scheduling with the goal of providing proportional fairness to the set of users served by a base station. We then propose a method to integrate physical-layer simulation into a meta-heuristic search algorithm for solving the joint optimization problem. Evaluation results show that the proposed scheduling algorithm can effectively solve the problem in the target scenario and NOMA can achieve significant performance benefits over OMA, thus motivating further investigation along this direction.