Opportunistic Temporal Fair Scheduling for Non-Orthogonal Multiple Access

Non-orthogonal multiple access (NOMA) is one of the key enabling techniques for the next generation of mobile networks. Opportunistic scheduling is necessary to fully exploit the multiplexing gains in NOMA systems. In this paper, scheduling for NOMA systems under temporal fairness constraints is considered. The objective is to maximize the system utility (e.g. throughput) subject to constraints on the average active time for each user. It is shown that threshold based scheduling strategies (TBS) achieve optimal performance in terms of system utility. Furthermore, it is shown that any optimal strategy is equivalent to a TBS. An iterative algorithm based on the Robbins-Monro method is introduced which constructs the optimal TBS by finding optimal thresholds for a given system utility metric. Numerical simulations are provided to evaluate the proposed approach.