Joint Pilot-Based Localization and Channel Estimation in RIS-Aided Communication Systems

In this letter, we investigate the use of reconfigurable intelligent surfaces (RISs) to jointly estimate the position and channel of a user equipment (UE) using uplink pilot signals. We consider a setup with a user and a base station (BS), where the direct path between the BS and the UE is blocked and virtual line-of-sight (LOS) links are created over two reconfigurable intelligent surfaces (RISs). We investigate the benefits of exploiting the channel geometry to estimate the user’s position and the user-RIS channels jointly in terms of estimation performance and pilot overhead. To this end, we consider the Cramér-Rao Lower Bound for channel estimation and UE localization. Our numerical results show that exploiting the LOS structure of the channels improves the channel estimation performance by several orders of magnitude and reduces the channel estimation performance by reducing the number of unknown parameters.