Downlink Multiuser Communications Relying on Flexible Intelligent Metasurfaces

TL;DR

This paper proposes a flexible intelligent metasurface (FIM) at a base station to optimize downlink power and improve multiuser communication by jointly adjusting beamforming and surface shape, achieving significant power savings.

Contribution

It introduces a novel joint optimization framework for FIM surface shape and beamforming in multiuser downlink systems, with an efficient alternating optimization algorithm.

Findings

FIM reduces transmit power by about 3 dB compared to rigid arrays.

Joint optimization improves power efficiency under SINR constraints.

Simulation results validate the effectiveness of the proposed method.

Abstract

A flexible intelligent metasurface (FIM) is composed of an array of low-cost radiating elements, each of which can independently radiate electromagnetic signals and flexibly adjust its position through a 3D surface-morphing process. In our system, an FIM is deployed at a base station (BS) that transmits to multiple single-antenna users. We formulate an optimization problem for minimizing the total downlink transmit power at the BS by jointly optimizing the transmit beamforming and the FIM's surface shape, subject to an individual signal-to-interference-plus-noise ratio (SINR) constraint for each user as well as to a constraint on the maximum morphing range of the FIM. To address this problem, an efficient alternating optimization method is proposed to iteratively update the FIM's surface shape and the transmit beamformer to gradually reduce the transmit power. Finally, our simulation results show that at a given data rate the FIM reduces the transmit power by about $3$ dB compared to conventional rigid 2D arrays.