Simple Link-Budget Estimation Formulas for Channels Including Anomalous Reflectors

Reconfigurable intelligent surfaces (RISs) are a promising tool for the 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 consider a particular scenario of RISs for anomalous reflection and develop a simple link-budget model for nonline-of-sight (NLOS) channels via reflections from finite-size metasurfaces (MSs) designed as anomalous reflectors or splitters. 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.