Reconfigurable Intelligent Surface Relay: Lessons of the Past and Strategies for Its Success

Reconfigurable intelligent surface (RIS) as a type of relay has recently gained enormous attention from both academia and industry. In this article, we focus on the engineering perspective of RIS relay with the purpose of taking lessons from previous standardizations and deployments that can be used for strategies of its future success. The discussion begins with a brief review of two technologies of 4G LTE, relay in 3GPP Release 10 and full-dimension multiple-input multiple-output, which had quite different outcomes in their practical deployments. Then a multi-stage approach is proposed for RIS in three major activities: 3GPP standardizations from Rel-18 to Rel-19 and to Rel-20, the hardware and control of RIS devices, and channel modeling of RIS-aided communications. In each of these activities, detailed strategies are suggested to comprehensively cover the key areas of RIS study and development in different stages.