Reconfigurable Intelligent Surface for Industrial Automation: mmWave Propagation Measurement, Simulation, and Control Algorithm Requirements

Reconfigurable intelligent surfaces (RISs) enable reliable low-latency millimeter wave (mmWave) communication links in cases of a blocked line-of-sight (LoS) between the base station (BS) and the user equipment (UE), i.e. a RIS mounted on a wall or the ceiling provides a bypass for the radio communication link. We present an active RIS with 127 patch antenna elements arranged in a hexagonal grid for a center frequency of 23.8 GHz. Each RIS element uses an orthogonal polarization transformation to enable amplification using a field-effect transistor (FET). The source and drain voltages of each FET is controlled using two bits. We assume that the coordinates of the UE in an industrial control scenario are known to the RIS. We measure the received power on a 2D grid of 60 cm by 100 cm with the RIS working in reflective and active mode. The results show that the RIS can successfully focus the radio signal at the desired target points. The half-power beam width is characterized in axial and radial directions with respect to the RIS position, obtaining a practical RIS configuration update criterion for a mobile UE. These results clearly show that RISs are prominent solutions for enabling reliable wireless communication in indoor industrial scenarios.