QoS-Aware Joint 1-Bit RIS Element Activation and Fluid-Antenna Port Selection

Overview & Synopsis

This letter jointly optimizes fluid-antenna port selection, fixed-cardinality reconfigurable intelligent surface (RIS) element activation, and 1-bit reflection phases through an exact angular event sweep that extends full-activation divide-and-sort geometry to subset selection. We establish deterministic gain bounds and activation monotonicity, derive exact single-element outage expressions and high signal-to-noise ratio (SNR) asymptotics for independent RIS branches with correlated receiving ports, and prove diversity order equal to the RIS element count for fixed positive-definite RIS covariance. With perfect instantaneous channel state information, a quality-of-service aware policy activates the minimum number of elements required to meet a target SNR while preserving full-activation outage probability. An explicit overhead condition identifies when reduced activation improves net energy efficiency. Correlated-channel benchmarks illustrate subset-selection gains, aperture effects, and overhead-dependent energy-efficiency tradeoffs.