Towards Smart Wireless Communications via Intelligent Reflecting Surfaces: A Contemporary Survey

TL;DR

This survey reviews the development and application of intelligent reflecting surfaces (IRS) in wireless networks, highlighting their potential to actively control signal propagation and improve performance in future 5G and beyond systems.

Contribution

It provides a comprehensive overview of IRS concepts, applications, optimization techniques, and practical challenges, offering insights into future research directions.

Findings

IRS can actively control wireless signal reflections.

Joint optimization of IRS phase control and transmission improves network performance.

IRS-enabled networks show significant potential for beyond 5G communications.

Abstract

This paper presents a literature review on recent applications and design aspects of the intelligent reflecting surface (IRS) in the future wireless networks. Conventionally, the network optimization has been limited to transmission control at two endpoints, i.e., end users and network controller. The fading wireless channel is uncontrollable and becomes one of the main limiting factors for performance improvement. The IRS is composed of a large array of scattering elements, which can be individually configured to generate additional phase shifts to the signal reflections. Hence, it can actively control the signal propagation properties in favor of signal reception, and thus realize the notion of a smart radio environment. As such, the IRS's phase control, combined with the conventional transmission control, can potentially bring performance gain compared to wireless networks without IRS. In this survey, we first introduce basic concepts of the IRS and the realizations of its reconfigurability. Then, we focus on applications of the IRS in wireless communications. We overview different performance metrics and analytical approaches to characterize the performance improvement of IRS-assisted wireless networks. To exploit the performance gain, we discuss the joint optimization of the IRS's phase control and the transceivers' transmission control in different network design problems, e.g.,~rate maximization and power minimization problems. Furthermore, we extend the discussion of IRS-assisted wireless networks to some emerging use cases. Finally, we highlight important practical challenges and future research directions for realizing IRS-assisted wireless networks in beyond 5G communications.