A Novel Code-Aided Non-Orthogonal Multiple Access Technique in Downlink MIMO System

Conventional downlink non-orthogonal multiple access (NOMA) exploits the power domain for multiple access and applies successive interference cancellation (SIC) to mitigate intra-cluster interference. It requires sophisticated user terminals (UTs) clustering, moreover, imperfect SIC results in error propagation that severely degrades system performance. In this paper, a novel code-aided multiuser multiple-input multiple-output NOMA (MIMO-NOMA) framework for downlink transmission is developed. We propose a simple grouping algorithm that separate all UTs in a cell into several clusters, with cluster number less than or equal to the BS antenna array size. ZF-based multiuser beamforming is then employed to remove the inter-cluster interference. Computer simulation results verify that the proposed method outperforms the conventional schemes.