Near-Field Localization with Reconfigurable Intelligent Surfaces

Beyond the confines of fifth-generation cellular networks (5G), new paradigms and opportunities emerge into realms of wide bandwidths, high frequencies, massive antenna arrays and reconfigurable intelligent surfaces. These features expedite communication and unlock unprecedented capabilities for precise wireless positioning and sensing. A notable leap in innovation comes in the form of smart radio environments (SRE), where reconfigurable intelligent surfaces (RISs) play a pivotal role thanks to their capability of optimizing the wireless channel. These surfaces empower the control of signals at the electromagnetic (EM) level, ushering in an era of remarkably accurate positioning. The seminar aims to provide insights into integrating RISs in cellular networks for improved positioning performance. This technical seminar explores near-field positioning and tracking in RIS-assisted SRE. The seminar starts with a theoretical analysis of the ultimate limits on localization accuracy in a RIS-aided scenario and considers the impact of various RIS phase profiles on performance. Then, the seminar illustrates several near-field algorithms that exploit RISs for user localization and tracking. Finally, the seminar covers a framework addressing the joint design of reflection coefficients for multiple RISs and precoding strategies for base stations. This framework optimizes self-tracking for the position and velocity of multi-antenna user equipment in far- and near-field regions. Future perspectives on RIS-aided localization will also be presented.