Rapid Diagnostics of Reconfigurable Intelligent Surfaces Using Space‐Time‐Coding Modulation

Abstract Reconfigurable intelligent surfaces (RISs) have emerged as a key technology for shaping smart wireless environments in next‐generation wireless communication systems. To support the large‐scale deployment of RISs, a reliable and efficient diagnostic method is essential for maintaining optimal performance. In this work, a robust and effective approach for RIS diagnostics is proposed using a space‐time coding strategy with orthogonal codes. The proposed method encodes the reflected signals from individual RIS elements into distinct code channels, enabling the recovery of channel power at the receiving terminals for fault identification. Theoretical analysis shows that normally functioning elements generate high power in their respective code channels, whereas faulty elements exhibit significantly lower power. This distinction enables rapid and accurate diagnostics of the elements’ operational states through simple signal processing techniques. Simulation results validate the effectiveness of the proposed method, even under high fault ratios and varying receiving angles. Proof‐of‐principle experiments on two RIS prototypes are conducted, implementing two coding strategies: direct and segmented. Experimental results in a realistic scenario confirm the reliability of the diagnostic method, demonstrating its potential for large‐scale RIS deployment in future wireless communication systems and radar applications.