Reconfigurable Intelligent Surfaces for 6G:Nine Fundamental Issues and One Critical Problem  

作　　者：Zijian Zhang Linglong Dai 

机构地区：[1]Department of Electronic Engineering,Tsinghua University,and also with Beijing National Research Center for Information Science and Technology(BNRist),Beijing 100084,China

出　　处：《Tsinghua Science and Technology》2023年第5期929-939,共11页清华大学学报（自然科学版（英文版）

基　　金：supported by the National Key Research and Development Program of China(No.2020YFB1805005);the National Natural Science Foundation of China(No.62031019);the European Commission through the H2020-MSCA-ITN META WIRELESS Research Project(No.956256)。

摘　　要：Thanks to the recent advances in metamaterials,Reconfigurable Intelligent Surface(RIS)has emergedas a promising technology for future 6G wireless communications.Benefiting from its high array gain,low cost,and low power consumption,RISs are expected to greatly enlarge signal coverage,improve system capacity,andincrease energy efficiency.In this article,we systematically overview the emerging RIS technology with the focuson its key basics,nine fundamental issues,and one critical problem.Specifically,we first explain the RIS basics,including its working principles,hardware structures,and potential benefits for communications.Based on thesebasics,nine fundamental issues of RISs,such as“What’s the differences between RISs and massive MIMO?”and“Is RIS really intelligent?”,are explicitly addressed to elaborate its technical features,distinguish it from existingtechnologies,and clarify some misunderstandings in the literature.Then,one critical problem of RISs is revealedthat,due to the“multiplicative fading”effect,existing passive RISs can hardly achieve visible performance gains inmany communication scenarios with strong direct links.To address this critical problem,a potential solution calledactive RISs is introduced,and its effectiveness is demonstrated by numerical simulations.

关 键 词：Reconfigurable Intelligent Surface(RIS) sixth generation mobile system(6G) wireless communications 

分 类 号：TN9[电子电信—信息与通信工程]