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

TLDR

Reconfigurable intelligent surfaces can dramatically improve spectrum and energy efficiency by actively tuning the phase shifts of many passive reflecting elements to reshape the wireless propagation environment. This article addresses four core questions—why RISs are needed, what they are, their applications, and the challenges and future research directions. The authors identify eight promising research directions for RIS technology.

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 to answer 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.