Reconfigurable Intelligent Surfaces for 6G Mobile Networks: An Industry R&D Perspective

The reconfigurable intelligent surface (RIS) technology is a potential solution to enhance network capacity and coverage without significant investment in additional infrastructure in 6G networks. This work highlights the interest of the mobile communication industry in RIS, and discusses the development of liquid crystal-based RIS for improved energy efficiency and coverage in the millimeter-wave band. Furthermore, the paper discusses perspectives and insights from an industry R&D point of view, addressing relevant use cases, technical requirements, implementation challenges, and practical considerations for RIS deployment optimization in the context of 6G networks. A hardware design of an RIS with liquid crystal at 28 GHz is presented. A propagation model for RIS as a new part of the system architecture is discussed with the approaches of semi-empirical models, geometric models and their combination through the application of artificial intelligence / machine learning. Finally, a channel model for deployment optimization and dimensioning is presented with the findings that rather large RIS is favorable for coverage improvement as well as a greater attenuation at higher frequencies combined with a smaller RIS size.