Simple Link-Budget Estimation Formulas for Channels Including Anomalous Reflectors

Reconfigurable intelligent surfaces (RIS) are a promising tool for optimization of propagation channels for advanced  wireless communication systems. These tools are especially relevant for high-frequency (millimeter-band) links where directive antennas are used. RIS panels act as high-gain passive repeaters, whose reflected waves interfere with the waves reflected from the illuminated spots at  supporting walls, creating a complex field pattern in the far zone. In this work, we develop a simple link-budget model for non-line-of-sight channels via reflections from a finite size metasurface designed as a perfect anomalous reflector. The developed model takes into account diffraction at  the RIS panel edges as well as interference with reflections from supporting structures. We take into account realistic losses and confirm the validity of results by numerical simulations.