Considerations on downlink non-orthogonal multiple access (NOMA) combined with closed-loop SU-MIMO

As a promising downlink multiple access scheme for further cellular enhancements toward 5G, non-orthogonal multiple access (NOMA) improves both cell average and cell-edge user throughput compared to orthogonal multiple access (OMA) in the cellular downlink. When NOMA is combined with multi-antenna technology in practice, some aspects are of great interest, such as error propagation (EP) of successive interference cancellation (SIC) receiver and user velocity. This paper investigates the system-level throughput of NOMA with closed-loop single-user multiple-input multiple-output (SU-MIMO) in the cellular downlink and clarifies the potential gains over OMA with SU-MIMO taking into account these practical aspects. Two EP models are presented into the NOMA with closed-loop (CL) SU-MIMO. Their impacts on performance of NOMA with CL SU-MIMO are investigated by system-level simulations with practical assumptions. Furthermore, impact of user velocity on performance gain of NOMA with CL SU-MIMO is also evaluated. Simulation results show that even with the worst case EP model, NOMA with CL SU-MIMO can still provide large performance gains for both low and high mobility scenarios.