Achieve High Spectral Efficiency for 5G: Multi-User MIMO versus NOMA

Multi-User Multiple-Input Multiple-Output (MU-MIMO) and Non-Orthogonal Multiple Access (NOMA) belong to the key physical layer technologies under the context of 5th Generation (5G) New Radio (NR) communication. Both MU- MIMO and NOMA exhibit capability to significantly enhance the spectral efficiency from different aspects. In this paper, we investigate and compare MU-MIMO and NOMA in link level with respect to some practical issues, e.g. imperfect channel estimation, imperfect sectorization. Numerical results reveal that the coexistence of MU-MIMO and NOMA provide the degrees of freedom to allow the system to selectively focus on spectral efficiency per user or the number of supported users, and effectively be associated with scheduled traffic and contention-based traffic, respectively.