Assessing the Potential of Space-Time-Coding Metasurfaces for Sensing and Localization

Intelligent metasurfaces are one of the favorite technologies for integrating sixth-generation (6G) networks, especially the reconfigurable intelligent surface (RIS), which has been extensively researched in various applications. Although many applications and studies of electromagnetic manipulation under the linear RIS topology were performed, applying coding sequences to the element switching enables the space-frequency scattering feature, referred to as Space-Time-Coding metasurface (STCM) topology. This type of topology causes impairments to the established communication methods by generating undesirable interference both in frequency and space, which is worsened when using wideband signals. Nevertheless, it can potentially bring forward useful features for sensing and localization. This work exploits STCM sensing capabilities in target detection, localization, and classification using narrowband downlink pilot signals at the base station (BS). The results of this novel approach reveal the ability to retrieve scattering points (SP) localization within the sub-centimeter and sub-decimeter accuracy depending on the SPs positions in space. We also analyze the associated detection and classification probabilities, which show reliable performance for both in the whole analyzed environment, especially when using the STCM information. We conclude that this method presents a promising approach for future integrated sensing and communications (ISAC) protocols by providing a tool to perform sensing and localization services using legacy communication signals.