Efficient Computation of Scattered Fields from Reconfigurable Intelligent Surfaces for Propagation Modeling

We propose a method to efficiently compute the scattered electric field of a reconfigurable intelligent surface (RIS) for multiple configurations. In contrast to most existing methods that assume that each unit cell scatters an incident wave individually instead of collectively, our method accounts for the mutual coupling of unit cells. This allows us to estimate the scattered fields in the main scattering direction of an RIS, at an accuracy that is comparable to full-wave analysis. Furthermore, combined with ray-tracing, the computed scattered fields can be used to model wave propagation in realistic, multipath radio environments with RISs. Hence, our method efficiently addresses three critical considerations for the analysis of RIS-enabled links: mutual coupling between unit cells of an RIS, mutlipath effects in the channel due to the RIS acting as a diffuse scatterer, and the variability of the RIS scattering properties that requires extensive computational effort to account for.