QoS-Aware Sum-Rate Maximization and Parametric Analysis in FAS-RSMA

This paper investigates a FAS-RSMA downlink under QoS-constrained sum-rate maximization. A traditional single-antenna base station serves FAS-equipped receivers that select the port with the largest instantaneous channel power gain under Jakes spatial correlation. The number of ports N and normalized aperture W jointly shape the effective gains, RSMA feasibility, and system outage. To handle the resulting non-convex problem, a boundary-based reduction is adopted. A parametric analysis over the (N, W) configuration space is then performed, revealing near-optimal FAS designs that preserve most of the maximum average sum-rate while avoiding unnecessary receiver complexity and aperture growth under practical implementation constraints for compact receiver architectures.