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

Reconfigurable intelligent surfaces (RISs) can pro-
vide a reliable and low-latency millimeter wave (mmWave)
communication link in cases of a blocked line-of-sight (LoS)
between the base station (BS) and the user equipment (UE).
In such cases, the RIS mounted on a wall or ceiling can act as a
bypass for the radio communication link. We present an active
RIS with 127 patch antenna elements arranged in a hexagonal
grid. The RIS operates at a center frequency of 23.8 GHz and
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 are controlled using
two bits. We consider that the RIS control unit is aware of
the UE coordinates within the measurement area, relevant to
the industrial control scenarios. We measure the received power
on a 2D grid of 60 cm 90 cm using an xy-positioning table,
with the RIS working in reflective and active mode. The results
demonstrate the ability of the RIS to effectively focus the radio
signal on the desired target points. We characterize the half-
power beam width in azimuth and radial directions with respect
to the RIS position, enabling us to obtain 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.