Efficient joint power allocation for mitigating intracluster interference in clustered NOMA system

In recent years, the growing demand for massive connectivity has focused researchers' attention on next-generation radio access techniques. Nonorthogonal multiple access (NOMA) is a candidate for supporting massive connectivity. However, NOMA systems generate severe intracluster interference, which affects user groups (clusters) with low channel gain differences because of user clustering and the low power disparity between users. Therefore, multiuser NOMA clustering and power management policies must be adopted. We propose schemes for multiuser clustering and joint power allocation. We analytically formulate power allocation for a given signal-to-interference-plus-noise ratio considering users in the cluster with different and similar locations (channel gains) in the cell. The formulation is then applied to NOMA clusters. Finally, we evaluate the optimal cluster size according to the number of users. The proposed schemes outperform other approaches in terms of total cluster throughput and user throughput with the highest channel gain.