Reconfigurable Intelligent Surfaces for 6G Systems: Principles, Applications, and Research Directions
Cunhua Pana b, Hong Renc d, Kezhi Wange f, Jonas Florentin Kolba b, Maged Elkashlana b, Ming Chenc d, Marco Di Renzog h i j, Yang Haoa b, Jiangzhou Wangk l, Arnold Lee Swindlehurstm n, Xiaohu Youc d, Lajos Hanzoo p
- aQueen Mary University of London, England
- bQMUL - Queen Mary University of London (Mile End Road, London E1 4NS - United Kingdom)
- cSoutheast University, England
- dSEU - Southeast University = Dongnan Daxue (2 Sipailou Street, Xuanwu District, Nanjing, Jiangsu, 210096 - China)
- eNorthumbria University, England
- fNorthumbria University [Newcastle] (Newcastle City Campus, 2 Ellison Pl, Newcastle upon Tyne NE1 8ST, United Kingdom - United Kingdom)
- gUnivetsité Paris-Saclay, France
- hCNRS - Centre National de la Recherche Scientifique (France)
- iL2S - Laboratoire des signaux et systèmes (Plateau de Moulon 3 rue Joliot Curie 91192 GIF SUR YVETTE CEDEX - France)
- jUniversité Paris-Saclay (Bâtiment Bréguet, 3 Rue Joliot Curie 2e ét, 91190 Gif-sur-Yvette - France)
- kUniversity of Kent, England
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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.