Anti CSI-Based Sensing During Communication: Performance Modeling and Comparison of Using RIS and Private Precoding

This letter presents a comparative study of leveraging reconfigurable intelligent surface (RIS) or private precoding (PP) to counteract potential malicious sensing using channel state information (CSI) by a user device (UD) during communication. RIS and PP recently have emerged as two distinct approaches to address the growing concern of environment information leakage from CSI. Although both have demonstrated effectiveness, their theoretical performance and, more importantly, a comprehensive understanding of their comparative abilities in supporting a UD communication meanwhile anti its sensing remain underexplored. In this letter, we model the CSI-based sensing and communication performance of a UD controlled by RIS and PP in multi-antenna system contexts, respectively. Towards enhancing communication while restricting the sensing accuracy, we derive the exact optimal PP performance case and RIS performance bounds over feasible configurations. By analyzing the derived results, we draw insights into the characteristics of RIS and PP in influencing environment privacy and the UD communication, answering when RIS or PP is preferable. The theoretical results are verified in simulations.