Optimal User Clustering and Power Allocation in NOMA Systems

Non-orthogonal multiple access (NOMA) is one of the proposed techniques which improve transfer speeds. There are two primary types of NOMA: code domain and power domain. This study focuses on the power domain. The benefit of power-domain NOMA depends on how the users are clustered and the power levels of users in the same cluster. This study aims to propose the model using the two-user pairing method and three users together, combining the threshold signal-to-noise ratio (SNR) levels to decide on two or three pairings to ensure the quality of service (QoS) for users. Besides, this model consider the optimal power allocation (PA) for each user in the cluster to the maximum sum rate with QoS constraints. Simulation results show the benefits of optimizing user clustering and power allocation with QoS constraints.