Successive Port Selection for FAS-Assisted MU-MISO Downlink With Linear Precoding

Abstract

This letter investigates a receiver-side fluid antenna system (FAS)-assisted multiuser multi-input single-output downlink system under severe inter-user spatial correlation. We derive closed-form analytical achievable sum rate expressions based on linear precoding, which explicitly decompose the per-user effective channel gain into channel gain and spatial orthogonality. We then use these metrics to develop a successive port selection algorithm. Numerical results show that SPS outperforms heuristic baselines, closely approaches exhaustive search, and converges within a few sweeps. Moderate aperture sizes and port counts suffice to capture most of the observed selection gain.