Reconfigurable Intelligent Surface-Assisted Localization: Technologies, Challenges, and the Road Ahead

Owing to the breakthrough of artificial meta-materials, the emergence and evolution of reconfigurable intelligent surface (RIS) have drawn a novel blueprint for the development of the sixth-generation (6G) wireless networks, through the creation of smart radio environment to meet the requirement of ubiquitous connectivity. Meanwhile, the vision for the 6G illuminates the integration of sensing and communication, bringing out a demand for both high-quality communication and high-precision localization. Therefore, regarding the future wireless localization, the potential of RIS to tag the signals provides additional degrees of freedom. To this end, to fulfil the increasing demands for positioning, RIS has drawn a growing amount of research both from academia and industry. In this paper, we first introduce the emerging investigations and development of RIS, and we give a concise summary of the localization principles. Then we explain the potential of RIS in localization, and provide a comprehensive survey of the current state of research on RIS-assisted localization. Finally, we discuss the most significant research challenges to tackle for RIS-aided localization in the future.