Antenna Positioning and Beamforming Design for Fluid-Antenna Enabled Multi-user Downlink Communications

TL;DR

This work tackles power-efficient downlink transmission in a MISO system where users deploy fluid antennas (FAs). It introduces a field-response based channel model and jointly optimizes FA positions and BS beamforming under SINR and movement constraints using an alternating optimization framework augmented by a penalty method and successive convex approximation. The proposed AO-based algorithm solves a sequence of tractable subproblems, yielding a suboptimal yet effective solution that outperforms fixed-position antenna baselines in simulations. The results demonstrate that FA repositioning can unlock gains in multi-user downlink scenarios, suggesting practical benefits for 6G-era networks.

Abstract

This paper investigates a multiple input single output (MISO) downlink communication system in which users are equipped with fluid antennas (FAs). First, we adopt a field-response based channel model to characterize the downlink channel with respect to FAs' positions. Then, we aim to minimize the total transmit power by jointly optimizing the FAs' positions and beamforming matrix. To solve the resulting non-convex problem, we employ an alternating optimization (AO) algorithm based on penalty method and successive convex approximation (SCA) to obtain a sub-optimal solution. Numerical results demonstrate that the FA-assisted communication system performs better than conventional fixed position antennas system.

Figures (4)

• Figure 1: The FA-assisted multi-user downlink communication system.
• Figure 2: Transmit power versus the minimum required SINR
• Figure 3: Transmit power versus the number of users.
• Figure 4: Transmit power versus the normalized region size for FA.