ABSTRACT
Appropriate modeling of a RIS is crucial to the performance analysis and designs of RIS hardware and system implementation. In this chapter, channel models for generic mobile communications, e.g., base station to mobile, are discussed first where mainstream large-scale fading and small-scale fading models are overviewed. Then, spatial channel models, which are key to MIMO technology, are elaborated, together with the typical antenna models and configurations. Based on the fundamental models for mobile communications channels, large-scale and small-scale channel models for RIS, which consist of base station to a RIS, and a RIS to mobile, are discussed. Besides the wireless communications channels, electromagnetic field modeling for metasurface structures is also briefly reviewed, which can be used to characterize the metamaterial devices.
