INTERFERENCE MITIGATION IN MULTIPLE INPUT MULTIPLE OUTPUT NON-ORTHOGONAL MULTIPLE ACCESS (MIMO-NOMA)SYSTEMS

Abstract

The maximization of the number of admissible users served, under a total transmitting power constraint and minimum ergodic user-rate constraints, is explored, for the downlink single-cell multiple input single output (MISO) NOMA, MISO orthogonal multiple access (OMA), single-carrier MIMONOMA, multi-carrier MIMO-NOMA, and MIMO-OMA systems. Successive interference cancellation (SIC) and interference alignment (IA) are used to mitigate the interference in the NOMA systems. For each of the previously mentioned systems, a closed-form lower bound for the achievable rate is obtained. A power allocation scheme is derived, and a user admission algorithm that obtains the maximum number of admissible users is proposed. Finally, a comparison between three user ordering strategies in the single-carrier MIMONOMA systems is provided. The results show that the proposed algorithms e ciently compute the number of admissible users and provide significant gains compared to the OMA schemes.