Coordinated Passive Beamforming for Distributed Intelligent Reflecting Surfaces Network

TL;DR

This paper introduces a distributed IRS network architecture for 6G, jointly optimizing power and phase shifts to maximize sum-rates, overcoming non-convex challenges with an alternating fractional programming approach.

Contribution

It proposes a novel distributed IRS network model and develops a coordinated passive beamforming method with closed-form solutions, addressing the channel rank deficiency issue.

Findings

Enhanced sum-rate performance demonstrated through simulations

Efficient alternating optimization algorithm developed

Closed-form expressions for passive beamforming derived

Abstract

Intelligent reflecting surface (IRS) is a proposing technology in 6G to enhance the performance of wireless networks by smartly reconfiguring the propagation environment with a large number of passive reflecting elements. However, current works mainly focus on single IRS-empowered wireless networks, where the channel rank deficiency problem has emerged. In this paper, we propose a distributed IRS-empowered communication network architecture, where multiple source-destination pairs communicate through multiple distributed IRSs. We further contribute to maximize the achievable sum-rates in this network via jointly optimizing the transmit power vector at the sources and the phase shift matrix with passive beamforming at all distributed IRSs. Unfortunately, this problem turns out to be non-convex and highly intractable, for which an alternating approach is developed via solving the resulting fractional programming problems alternatively. In particular, the closed-form expressions are proposed for coordinated passive beamforming at IRSs. The numerical results will demonstrate the algorithmic advantages and desirable performances of the distributed IRS-empowered communication network.