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 pow...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.展开更多
The reconfigurable intelligent surface(RIS)is an emerging technology,which will hopefully bring a new revolution in wireless communications.The RIS technology can be deployed in an indoor/outdoor environment to dynami...The reconfigurable intelligent surface(RIS)is an emerging technology,which will hopefully bring a new revolution in wireless communications.The RIS technology can be deployed in an indoor/outdoor environment to dynamically manipulate the propagation environment.The RIS consists of a large number of independently controllable passive elements,and these elements are involved in realizing high passive beamforming gain.Different from the conventional active phased antenna array,there is no dedicated radio-frequency(RF)chain installed at the RIS to perform complex signal processing operations.Therefore,it does not incur additional noise while retransmitting the incident wave,which is substantially a unique feature from the conventional wireless communication systems.Taking advantage of its working principle,RIS has been deployed in various practical scenarios.In this tutorial,at first we will review the latest advances in RIS,including the application scenarios such as the system and channel model,the information theoretic analysis,the physical realization and design,key signal processing techniques such as precoding and channel estimation,and prototyping.Finally,we discuss interesting future research problems for the RIS-aided communications.展开更多
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)。
文摘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.
文摘The reconfigurable intelligent surface(RIS)is an emerging technology,which will hopefully bring a new revolution in wireless communications.The RIS technology can be deployed in an indoor/outdoor environment to dynamically manipulate the propagation environment.The RIS consists of a large number of independently controllable passive elements,and these elements are involved in realizing high passive beamforming gain.Different from the conventional active phased antenna array,there is no dedicated radio-frequency(RF)chain installed at the RIS to perform complex signal processing operations.Therefore,it does not incur additional noise while retransmitting the incident wave,which is substantially a unique feature from the conventional wireless communication systems.Taking advantage of its working principle,RIS has been deployed in various practical scenarios.In this tutorial,at first we will review the latest advances in RIS,including the application scenarios such as the system and channel model,the information theoretic analysis,the physical realization and design,key signal processing techniques such as precoding and channel estimation,and prototyping.Finally,we discuss interesting future research problems for the RIS-aided communications.
