A Generalized Model for RIS-Assisted Communications: On the Effect of Scattered Electromagnetic Wave

Reconfigurable intelligent surface (RIS) has been envisioned as a promising technique for future wireless networks. In order to capture the actual scattered characteristics of RIS, several RIS scattered models have been proposed by researchers. Nevertheless, these models neglect vital factors that influence the scattered properties of RIS. In this letter, we aim to investigate the scattered characteristics of RIS more comprehensively and propose a more generalized RIS scattered model based on the wave optics theory. The impacts of electromagnetic (EM) wave incident/reflected elevation and azimuth angles, the distances from the RIS to the transmitter (TX)/receiver (Rx), and the size/shape/radiation pattern of RIS are explicitly formulated. Simulation results illustrate how these factors, especially the EM wave incident/reflected angles and the geometry configuration of RIS, exert a significant impact on the scattered characteristics of RIS. Our findings indicate that these critical factors should be taken into consideration for more comprehensive theoretical analysis and more sophisticated system designs.