A Joint Port Selection and Symbol-Level Precoding Scheme for Fluid Antenna-Enhanced Multi-user Communication Systems

This paper studies symbol-level precoding (SLP) in downlink multi-user multiple-input single-output (MU-MISO) systems equipped with transmitter-side fluid antenna systems (Tx-FAS). We formulate a joint optimization problem for SLP design and Tx-FAS port selection to maximize the communication quality of the worst-served user under transmit power constraints. Due to the introduction of discrete port selection variables, the resulting problem is a mixed-integer and non-convex optimization, which is challenging to solve directly. To address this challenge, a genetic algorithm (GA) is developed, incorporating de-duplication-driven crossover and mutation strategies to improve population diversity and mitigate premature convergence. Simulation results demonstrate that the proposed Tx-FAS-assisted SLP scheme outperforms state-of-the-art methods, and our analysis reveals its theoretical potential and offers insights into the joint design of FAS and SLP.