STAR-RIS-UAV Aided Coordinated Multipoint Cellular System for Multi-user Networks

TL;DR

This paper proposes a STAR-RIS-UAV aided multi-user wireless system that enhances sum rate and flexibility by optimizing beamforming and transmission/reflection coefficients using a novel iterative method, outperforming conventional RIS systems.

Contribution

It introduces a new STAR-RIS-UAV system with a simultaneous optimization approach for both energy splitting and mode switching protocols, improving system performance.

Findings

STAR-RIS-UAV system achieves higher sum rate than conventional RIS.

The iterative optimization method effectively enhances system performance.

Flexible STAR-RIS design significantly boosts network capacity.

Abstract

Different with conventional reconfigurable intelligent surface (RIS), simultaneous transmitting and reflecting RIS (STAR-RIS) can reflect and transmit the signals to the receiver. In this paper, to serve more ground users and increase the deployment flexibility, we investigate an unmanned aerial vehicle equipped with a STAR-RIS (STAR-RIS-UAV) aided wireless communications for multi-user networks. Energy splitting (ES) and mode switching (MS) protocols are considered to control the reflection and transmission coefficients of STAR-RIS elements. To maximize the sum rate of the STAR-RIS-UAV aided coordinated multipoint cellular system for multi-user networks, the corresponding beamforming vectors as well as transmitted and reflected coefficients matrices are optimized. Specifically, instead of adopting the alternating optimization, we design an iteration method to optimize all variables for both ES and MS protocols at the same time. Simulation results reveal that STAR-RIS-UAV aided wireless communication system has a much higher sum rate than the system with conventional RIS or without RIS. Furthermore, the proposed structure is more flexible than a fixed STAR-RIS and could greatly promote the sum rate.