Finite-Blocklength Analysis of RSMA-Aided Fluid Antenna Systems

Abstract

This letter investigates a fluid antenna system (FAS)-assisted downlink rate-splitting multiple access (RSMA) scheme in the finite blocklength regime. A single traditional antenna system (TAS) base station serves FAS-equipped central and cell-edge users, each with $N$ reconfigurable ports. Spatial correlation among ports is modelled via a spatial block structure, enabling analytically tractable performance characterization. Analytical expressions for the average block error rate under correlated fading are derived and validated through Monte Carlo simulations. The proposed scheme is benchmarked against conventional TAS and FAS-assisted non-orthogonal multiple access baselines. Additionally, the Age of Information (AoI) metric is analyzed to quantify information freshness. Results demonstrate that FAS-assisted RSMA achieves improved reliability and reduced AoI, particularly in highly correlated, low-latency regimes, for time-sensitive system design.