Optimized IRS Positioning for Phase-Tuned Wireless Physiological Motion Detection

This paper explores the impact of physical positioning of Intelligent Reflective Surfaces (IRS) on enhancing physiological motion detection in non-line-of-sight (NLOS) millimeter-wave (mmWave) integrated sensing and communication (ISAC) systems. Operating at 28 GHz with an Orthogonal Frequency Division Multiplexing (OFDM) scheme, the proposed system incorporates a static IRS whose physical placement is systematically adjusted to optimize signal propagation and phase alignment. Experimental results reveal that precise IRS positioning significantly improves detection accuracy, with peak-to-peak (P2P) phase shifts increasing by 57 % in the perpendicular configuration and 56 % in the parallel configuration, corresponding to optimal signal reflections. These findings demonstrate the potential of physically repositioning IRS to achieve superior sensitivity and robustness in wireless physiological sensing, paving the way for advanced positioning algorithms and applications in complex multipath environments.