Power Control, User Scheduling and Resource Allocation for Downlink NOMA Systems with Imperfect Channel State Information

Non-orthogonal multiple access (NOMA) is a promising radio access technique for the next generation (5G) cellular communication. The optimal power control, user scheduling, and resource allocation scheme to maximize the overall network throughput of downlink NOMA systems is investigated in this paper. A practical imperfect channel state information (CSI) model is adopted in our investigation where only the distances of the involved links are known at the base station. In such a scenario, the closed-form optimal power control strategy is first derived for a NOMA user pair. Perfect CSI model is also investigated for comparison. We then extend our results into the multi-user scenario and propose an optimal user scheduling solution based on the Hungarian algorithm. Then logarithmic utility function is adopted to maximize the utility gain of system throughput and the closed-form expression of optimal bandwidth allocation is derived. Simulation results show that our proposal can effectively improve the network throughput as compared against the orthogonal multiple access.