Optimal Phasors for Wideband RIS Transmissions

Configuring reconfigurable intelligent surfaces (RISs) based on a practical RIS model is a fundamental problem in RIS-assisted wireless transmission. In this work, we propose a concept named optimal phasor (OP), a latent quantity that can considerably help the practical model-based RIS configuration. Under such a concept, we can design versatile algorithms that are applicable to different RIS models. As an example, we formulate the optimization problem of frequency selectivity reduction and develop an OP-based algorithm, allowing us to reach a remarkable performance based on the practical one-bit RIS model.