Reconfigurable Intelligent Surface Control for a Moving Receiver

Abstract: Reconfigurable intelligent surfaces (RISs) are emerging as key enablers of reliable industrial automation in the millimeter-wave (mmWave) band, particularly in environments with frequent line-of-sight (LoS) blockage. While prior works have largely focused on theoretical aspects, real-time validation under user mobility remains underexplored. In this work, we propose and experimentally evaluate a self-adaptive beamforming algorithm that enables RIS reconfiguration based on a low-rate feedback link from the mobile user equipment (UE) to the RIS controller. The algorithm maintains received signal power above a predefined threshold without requiring UE position knowledge. Using a hexagonal RIS with 127 elements operating at 23.8 GHz, we validate our approach in a semi-anechoic environment over a 60 cm*100 cm observation area. The results demonstrate up to 24 dB gain in received power compared to the baseline with inactive RIS elements, highlighting the practical benefits of adaptive RIS control in mobile non-line-of-sight (NLoS) scenarios.