Adaptive Multi-User Clustering and Power Allocation for Hybrid OMA-NOMA System with Imperfect SIC.

Non-orthogonal multiple access (NOMA) faces challenges from imperfect successive interference cancellation (SIC) impacting the achievable rates of the users. Addressing this, our hybrid OMA-NOMA system introduces a lower bound on power allocation factors, ensuring each user in a multi-user NOMA cluster achieves at least its corresponding orthogonal multiple access (OMA) rate. We propose a clustering criterion based on minimum signal-to-interference-plus-noise ratio difference for NOMA clusters, to outperform an equivalent OMA system. Adaptive multi-user clustering and power allocation algorithms are proposed, demonstrating superior rates than state-of-the-art through extensive Monte Carlo simulations.