Fairness‐Aware Comparison of <scp>PD</scp> ‐ <scp>NOMA</scp> and <scp>OMA</scp> Under Max‐Min, Proportional, and Round‐Robin Scheduling

ABSTRACT This letter presents a comparative analysis of power‐domain non‐orthogonal multiple access (PD‐NOMA) and orthogonal multiple access (OMA) under max–min fairness (MMF), proportional fair (PF), and Round Robin (RR) scheduling, with an emphasis on preserving fairness across both systems. Motivated by the lack of consistent evaluation methods for multiuser scenarios, we develop a unified fairness‐aware framework that enforces identical user‐rate distributions and resource constraints in PD‐NOMA and OMA. Fairness preservation is guaranteed by the proposed rate‐matching methodology applied to both schemes under identical transmit‐power budgets. A stochastic single‐carrier downlink model over Rayleigh fading is used to evaluate systems with up to 20 users. The results demonstrate that PD‐NOMA consistently outperforms OMA in sum‐rate across all scheduling policies, with the gain increasing with the number of users and with median SNR and approaching an asymptotic limit at high SNR and large user counts. Beyond three users, the incremental gain becomes negligible relative to the added system complexity, indicating that multiplexing two or three users provides the most practical performance–complexity trade‐off, while larger group sizes may still be relevant in connectivity‐centric scenarios.