Intelligent Reflecting Surfaces and Classical Relays: Coexistence and Co-Design

TL;DR

This paper explores the joint design of intelligent reflecting surfaces and classical relays in a multiuser downlink system, proposing an optimization algorithm to maximize sum-rate and analyzing the coexistence tradeoffs.

Contribution

It introduces a novel co-design framework for IRS and relay systems with an AO algorithm for sum-rate maximization.

Findings

The coexistence system outperforms traditional setups.

The proposed algorithm effectively handles the nonconvex optimization.

Tradeoffs between IRS passive and relay active components are analyzed.

Abstract

This paper investigates a multiuser downlink communication system with coexisting intelligent reflecting surface (IRS) and classical half-duplex decode-and-forward (DF) relay. In this system, the IRS and the DF relay interact with each other and assist transmission simultaneously. In particular, active beamforming at the base station (BS) and at the DF relay, and passive beamforming at the IRS, are jointly designed to maximize the sum-rate of all users. The sum-rate maximization problem is nonconvex due to the coupled beamforming vectors. We propose an alternating optimization (AO) based algorithm to tackle this complex co-design problem. Numerical validation and discussion on the superiority of the coexistence system and the tradeoffs therein are presented.