Reconfigurable Intelligent Surfaces for 6G Systems: Principles, Applications, and Research Directions

TL;DR

This paper reviews reconfigurable intelligent surfaces (RISs) as a transformative technology for 6G wireless systems, discussing their principles, applications, challenges, and future research directions.

Contribution

It provides a comprehensive overview of RIS technology, addressing fundamental questions and outlining eight promising research directions for future exploration.

Findings

RISs can significantly improve spectrum and energy efficiency.

Eight key research directions are identified for RIS development.

RISs are crucial for future 6G wireless systems.

Abstract

Reconfigurable intelligent surfaces (RISs) or intelligent reflecting surfaces (IRSs), are regarded as one of the most promising and revolutionizing techniques for enhancing the spectrum and/or energy efficiency of wireless systems. These devices are capable of reconfiguring the wireless propagation environment by carefully tuning the phase shifts of a large number of low-cost passive reflecting elements. In this article, we aim for answering four fundmental questions: 1) Why do we need RISs? 2) What is an RIS? 3) What are RIS's applications? 4) What are the relevant challenges and future research directions? In response, eight promising research directions are pointed out.