On the Performance of SISO, SIMO and MISO-NOMA Systems under Perfect and Imperfect SIC

This paper improves a two-user downlink non-orthogonal multiple access (NOMA) system by using multi-antennas at both the transmitter and the receiver. Three NOMA scenarios: a single-input single-output (SISO), a single-input multi-output (SIMO) and a multi-input single-output (MISO) are considered and compared. Assuming that the two users were over Rayleigh fading channels, the expressions of achievable capacity and outage probability (OP) on closed-form are derived and compared. To gain further insights into these scenarios, perfect and imperfect successive interference cancellation (SIC) are considered. The results of these three scenarios are presented and discussed, and it found that the improvement of the diversity order at the transmitter or the receiver enhances the performance of NOMA systems.