Self-Tuning RIS Controller for Vehicular Communications: a Hardware Perspective

Reconfigurable intelligent surfaces (RIS) can reflect an incoming signal toward a target location to enhance the received signal quality. In most studies, it is assumed that the base station (BS) provides configuration data to an RIS controller. However, for a passive RIS with a high number of elements, this data transmission from the BS can introduce significant delays. This challenge is especially pronounced in vehicular communications, where reflection coefficients must be updated even for a few millimeters of movement. To overcome this limitation, we propose a self-tuning RIS controller that independently calculates the reflection coefficients with minimal input from the BS. Our RIS controller leverages the user’s location information to compute the reflection coefficients in three steps: channel gain calculation, steering vector calculation, and optimal phase control. A pipelined architecture is developed to support these steps in real-time. The proposed VLSI architecture is implemented on an Artix-7 XC7A100TCSG324-1 FPGA to calculate reflection coefficients for a vehicle moving at a 100 kmh speed.