LDMA-NOMA Beamforming in Near-Field Communication Systems

In this paper, a novel LDMA-NOMA hybrid beamforming scheme is proposed for near-field communication systems, which improves the performance of both location-division multiple access (LDMA) and non-orthogonal multiple access (NOMA), simultaneously. The key innovation of the proposed scheme is the flexible utilization of user resolution information: LDMA is applied to users with better resolution, while NOMA is used for those users with poor resolution. For each NOMA user, the most suitable beam will be selected by optimizing the system performance and beam efficiency. A unique feature of our scheme is its effectiveness even under limited beam resources. The performance of the scheme is analyzed and the closed-form results are obtained. Simulation results validate the theoretical results and demonstrate superior performance compared to that of the conventional schemes.