Reconfigurable Intelligent Surfaces: Potentials, Applications, and Challenges for 6G Wireless Networks

TL;DR

Reconfigurable intelligent surfaces (RISs) are a promising technology for 6G wireless networks, offering energy-efficient, cost-effective ways to enhance signal propagation, but face practical challenges in deployment, reconfiguration, and channel estimation.

Contribution

This paper provides a comprehensive tutorial overview of RISs in 6G, discussing performance benefits, practical implementation challenges, and future research directions.

Findings

RISs can significantly improve 6G network performance.

Channel estimation accuracy is crucial for RIS effectiveness.

RIS size impacts system performance and deployment considerations.

Abstract

Reconfigurable intelligent surfaces (RISs), with the potential to realize a smart radio environment, have emerged as an energy-efficient and a cost-effective technology to support the services and demands foreseen for coming decades. By leveraging a large number of low-cost passive reflecting elements, RISs introduce a phase-shift in the impinging signal to create a favorable propagation channel between the transmitter and the receiver.~\textcolor{black}{In this article, we provide a tutorial overview of RISs for sixth-generation (6G) wireless networks. Specifically, we present a comprehensive discussion on performance gains that can be achieved by integrating RISs with emerging communication technologies. We address the practical implementation of RIS-assisted networks and expose the crucial challenges, including the RIS reconfiguration, deployment and size optimization, and channel estimation. Furthermore, we explore the integration of RIS and non-orthogonal multiple access (NOMA) under imperfect channel state information (CSI). Our numerical results illustrate the importance of better channel estimation in RIS-assisted networks and indicate the various factors that impact the size of RIS. Finally, we present promising future research directions for realizing RIS-assisted networks in 6G communication.