Perceptive, Resilient, and Efficient Networks: Programming the Wireless Environment with Reconfigurable Intelligent Surfaces

Wireless communications are nowadays shifting to higher operation frequencies, with the aim to meet the ever-increasing demand for bandwidth. While reconfigurable intelligent surfaces (RISs) are usually envisioned to restore the line of sight (LOS) of blocked links and to efficiently counteract the increased path loss, their functionalities can extend far beyond these basic operations. Owing to their large surface and the multitude of scatterers, RISs can be exploited to perform advanced wavefront engineering, essentially transforming the incident beam into a nontrivial reflected beam that is able to address the challenges of high frequencies more efficiently than conventional beamforming. In this article, it is demonstrated how advanced wavefront engineering with RISs enables beam profiles that are able to focus, bend, and self-heal, thus offering functionalities beyond the current state of the art. Their potential as enablers of perceptive, resilient, and efficient networks is discussed, and a localization technique based on a hybrid beamforming/beam-focusing scheme is demonstrated.