Reconfigurable Intelligent Surface Aided Power Control for Physical-Layer Broadcasting

TL;DR

This paper investigates power control in RIS-assisted wireless systems, proposing joint optimization of beamforming and phase shifts to minimize BS transmit power, with results showing near-optimal power efficiency.

Contribution

It introduces a joint design framework for transmit beamforming and RIS phase shifts in physical-layer broadcasting, providing lower bounds and demonstrating significant power savings.

Findings

Average transmit power is close to the theoretical lower bound.

RIS significantly reduces BS transmit power compared to conventional schemes.

The proposed optimization approach effectively minimizes power consumption.

Abstract

Reconfigurable intelligent surface (RIS), a recently introduced technology for future wireless com-munication systems, enhances the spectral and energy efficiency by intelligently adjusting the propaga-tion conditions between a base station (BS) and mobile equipments (MEs). An RIS consists of manylow-cost passive reflecting elements to improve the quality of the received signal. In this paper, westudy the problem of power control at the BS for the RIS aided physical-layer broadcasting. Our goalis to minimize the transmit power at the BS by jointly designing the transmit beamforming at the BSand the phase shifts of the passive elements at the RIS. Furthermore, to help validate the proposedoptimization methods, we derive lower bounds to quantify the average transmit power at the BS as afunction of the number of MEs, the number of RIS elements, and the number of antennas at the BS.The simulation results demonstrated that the average transmit power at the BS is close to the lowerbound in an RIS aided system, and is significantly lower than the average transmit power in conventionalschemes without the RIS.