Performance and design of SIC receiver for downlink NOMA with open-loop SU-MIMO

This paper investigates the performance and design of successive interference cancellation (SIC) receiver for downlink non-orthogonal multiple access (NOMA) combined with 2-by-2 open-loop single-user (SU)-MIMO. Compared to NOMA with 1-by-2 SIMO (Single Input Multiple Output), for NOMA with 2-by-2 SU-MIMO we have to deal with both inter-user and interstream interference at the receiver of each user. Therefore, we introduce different weight generation schemes for both before SIC and after SIC according to the transmission rank combination between the user equipment (UEs), while taking into account inter-user interference. In addition, we compare the performance of different SIC receivers; specifically, codeword level SIC (CWIC), symbol level SIC (SLIC), and ideal SIC. Assuming LTE (Long Term Evolution) Transmission Mode 3 (TM3), link-level simulations are conducted under different allocated transmit powers, rank combinations, and modulation and coding schemes (MCS). The link-level simulation results showed that the CWIC receiver achieves higher performance compared to SLIC and achieves almost the same performance compared to ideal SIC when the power ratio of cell-center UE is below 0.35, and the MCS of cell-center UE and cell-edge UE are 16QAM (R = 0.49) and QPSK (R = 0.49), respectively.