Localization by Modulated Reconfigurable Intelligent Surfaces

A multi-user localization system that uses modulated reconfigurable intelligent surfaces (RIS) is proposed. In this system, a base-station (BS) sends an unmodulated carrier, multiple RISs reflect the carrier after applying a phase shift which encodes an <inline-formula> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula>-sequence, and time-difference-of-arrival is calculated at the receivers to estimate its location. The proposed scheme is simulated in a specific street-canyon setting where it is shown to achieve sub-meter accuracy. Finally, possible improvements are discussed.