RIS-Aided Positioning Under Adverse Conditions: Interference from an Unauthorized RIS

Artikel i vetenskaplig tidskrift, 2026

Positioning technology, which aims to determine the geometric state of a device in a global coordinate system, is a key component in integrated sensing and communication systems. In addition to traditional active anchor-based positioning systems, reconfigurable intelligent surfaces (RISs) have shown great potential for enhancing system performance. However, their ability to manipulate electromagnetic waves and ease of deployment pose potential risks, as unauthorized RIS may be intentionally introduced to jeopardize the positioning service. Such an unauthorized RIS can introduce unexpected interference into the legitimate positioning system, distorting the transmitted signals, and leading to degraded positioning accuracy. In this work, we investigate the scenario of RIS-aided positioning in the presence of interference from an unauthorized RIS. Theoretical lower bounds are derived to analyze the impact of unauthorized RIS on channel parameter estimation and positioning accuracy. Several codebook design strategies for unauthorized RIS are evaluated, and various system arrangements are discussed. Simulation results show that unauthorized RIS paths with high power or delay values close to those of legitimate RIS paths significantly degrade positioning accuracy. Furthermore, an unauthorized RIS generates more effective interference when using directional beamforming codebooks compared with a random phase codebook.