Fluid Antennas Assisted RIS-NOMA Communication Networks

2026-05-08

AI Summary

This work addresses the throughput limitation of non-orthogonal multiple access (NOMA) systems in high signal-to-noise ratio regimes by proposing a novel network architecture that integrates fluid antenna systems (FAS) with reconfigurable intelligent surfaces (RIS), termed FAS-RIS-NOMA. The system sum rate is maximized through joint optimization of fluid antenna port selection, RIS placement, and RIS phase-shift matrix design. To tackle this non-convex coupled optimization problem, an alternating optimization framework is developed, combining exhaustive search, particle swarm optimization, and a hybrid approach of semidefinite relaxation with successive convex approximation. Numerical results demonstrate that the proposed scheme significantly outperforms conventional antenna-based orthogonal multiple access systems, with performance gains further enhanced by increasing the number of RIS elements and the size of the fluid antenna, thereby substantially improving spectral efficiency and overall system capacity.

Abstract

This paper introduces a fluid antenna system (FAS) into reconfigurable intelligent surface (RIS) assisted non-orthogonal multiple access (NOMA) communication networks, where the non-orthogonal users are equipped with planar fluid antennas. Specifically, we formulate a sum rate maximization problem for FAS-RIS-NOMA networks, which jointly optimizes the fluid ports, the RIS deployment, and the phase shift matrix. To solve the resulting non-convex optimization problem involving highly coupled variables, an iterative algorithm based on alternating optimization is employed to decompose the original problem into three subproblems. Exhaustive search is employed for optimizing the fluid ports, particle swarm optimization is used for the RIS deployment, and semidefinite relaxation with successive convex approximation is adopted for optimizing the phase shift matrix. Finally, the simulation results show that: 1) compared with traditional antenna systems and orthogonal multiple access, the FAS-RIS-NOMA networks achieve higher system throughput under high signal-to-noise ratio conditions; and 2) by increasing the number of RIS elements and enlarging the FAS size, the sum rate of FAS-RIS-NOMA networks can be significantly enhanced.

Problem

• Fluid Antenna System
• Reconfigurable Intelligent Surface
• Non-Orthogonal Multiple Access
• Sum Rate Maximization

Innovation

• Fluid Antenna System
• Reconfigurable Intelligent Surface
• Non-Orthogonal Multiple Access
• Sum Rate Maximization
• Alternating Optimization