Localization and communication in smart radio environments

In recent years, the concept of the Smart Radio Environment (SRE) has emerged as a transformative approach in wireless communications. This innovative paradigm shifts the perception of the wireless environment from an uncontrollable entity to an active, programmable component. By enabling dynamic programming of the propagation environment, the SRE paradigm aims to revolutionize the field. Aligned with this vision, the focus of this thesis is on advanced “smart” methods exploiting the possibility to sense and modify radio propagation environments to enable advanced communication, localization, and mapping applications. One of these key technologies employed in SRE is Reconfigurable Intelligent Surfaces (RISs), which are adaptable surfaces that can be programmed to manipulate the propagation of radio waves. Another promising technology discussed is the frequency-selective metasurfaces, which are engineered to interact selectively with different frequency components of a signal. The chapters also delve into self-conjugating metasurfaces (SCMs) that exploit the retrodirectivity property, appealing to reduce the beamforming time in MIMO systems while reducing the system complexity. Experimental validations are presented, including tests on two RIS prototypes operating at different frequencies. A key contribution is the first successful demonstration of radio simultaneous localization and mapping (SLAM) algorithms at 300 GHz. Additionally, the thesis investigates ultra-wideband localization for automated docking in harsh environments. The manuscript continues with the description of the algorithms exploiting the technologies investigated above. Regarding the use of frequency-selective surfaces, algorithms that leverage OFDM signals and FMCW signals to enhance localization accuracy using frequency-selective metasurfaces are shown. Then, algorithms that exploit SCM have been developed. These address communication, beam tracking, channel access, and localization purposes. Finally, radio SLAM algorithms are designed for simultaneous localization and mapping in high-frequency environments.