Dear Colleagues,

Intelligent surfaces are a promising technology to tame scattering in sub-6GHz communications and overcome various issues in transmissions on millimeter waves and THz communications. Both the current fifth generation (5G) and the next sixth generation (6G) of cellular networks may significantly benefit from intelligent surfaces, not only for communication purposes, but also to improve localization accuracy and for sensing purposes. This holistic view requires a paradigm shift from the traditional use of radio waves for communication in cellular systems, posing new research challenges and stimulating the investigation of new applications. Engineering solutions should be developed for many issues, spanning from the estimation of channels including the surfaces to the impact of constraints imposed by the partial reconfigurability of surfaces on the network performance, from the techniques to be used for location to the accuracy of sensing. Additionally, on the side of opportunities, more studies on applications of intelligent surfaces beyond communications are needed, and directions for the design of future surfaces should be better identified. Considering the complexity of the entailed problems, novel techniques shall be developed, also benefiting from the flourishing interest in machine learning, which may particularly suited to cope with high-dimensionality channels and fast time-varying environments. The intelligence of 5G networks, provided by cloud and edge computing, further expands the possibility of elaborating the data collected by intelligent surfaces for high-level operations, including big data analysis and inference. This Special Issue aims at giving an extensive coverage of this recent research area, to shed new light on a key technology for future cellular networks.

Prof. Dr. Jang Hyun Baek
Prof. Dr. Stefano Tomasin
Dr. George C. Alexandropoulos
Prof. Dr. Liu Liu
Guest Editors

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• 5G/6G
• intelligent surfaces
• reconfigurable intelligent surfaces
• machine learning
• localization
• sensing