The improvements in received signal power brought about by a reflective intelligent surface (RIS) might be overstated if background propagation mechanisms such as reflections, scattering, and diffraction are ignored. This paper addresses this issue for non-line-of-sight indoor settings, contrasting the energy conveyed by an RIS with the energy already reaching the receiver through environmental reflections. And, to prevent artifacts, such naturally occurring reflections are not modeled via approximate methods, but rather through a rigorous physics-based formulation. It is found that the environment contributes a level of energy commensurate with that of an ideal RIS of considerable size; to have substantial impact, an actual RIS would have to generously exceed this size.

翻译：若忽略反射、散射和衍射等背景传播机制，反射智能表面（RIS）带来的接收信号功率改善可能被高估。本文针对非视距室内场景，将RIS传递的能量与环境中通过反射已到达接收端的能量进行对比。为避免人为假象，此类自然反射并非采用近似方法建模，而是基于严格的物理公式。研究发现，环境贡献的能量水平与理想RIS相当，且该理想RIS需具备较大尺寸；若要产生显著影响，实际RIS的尺寸必须远超此基准。