Practical Design and Orchestration of Frequency-Shifting RIS for NLoS mmWave Sensing

mmWave radar sensing is essential for Integrated Sensing and Communication (ISAC) but is limited by the need for LoS in environments with obstacles. However, existing NLoS solutions, including those leveraging reconfigurable intelligent surfaces (RIS) are computationally demanding, unable to generalize to new surroundings or require tight synchronization/coordination that prevent practical deployments. We propose PRISM, a framework that brings the diversity of a RIS to monostatic radars to enhance target resolution in NLoS, all without requiring real-time coordination. PRISM uses spatial modulation at the RIS to encode targets’ angular information through frequency shifts by creating a time-variant channel for improved detection at the radar. Key contributions include a wideband spatial modulation framework, a genetic algorithm to efficiently solve for the RIS configuration to enable such angle-dependent frequency shifts, and a narrowband approximation method to reduce the computational overhead.

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