A Comparison Study of Non-specular Diffuse Scattering Models at Terahertz Frequencies

At terahertz (THz) frequencies, dimensions of optically thin building materials (e.g., sand-lime brick, gypsum plaster) are comparable to or even larger than the wavelength. Such materials, normally neglected and assumed smooth evidently become rough now. A smooth material will reflect the incident ray specularly in a single direction, whilst a rough material will scatter it into various directions. Perhaps, for very rough materials the specular reflection loses its privileged position, and the non-specular diffusely scattered rays dominate the reflection behaviour. Likewise, a widely known fact that the surface roughness alters the scattered field far more than its electrical properties, emphasizes that these unique features lead to new multipath scattering models to characterize the THz channel. Effective Roughness (ER) and Beckmann-Kirchhoff (B-K) models address the problem of diffuse scattering by means of approximate models. This paper compares the aforementioned models considering the impact of diffuse scattering on total received power by employing ray-tracing tool in an indoor office environment. For this study, particular attention is diverted to the non-line-of-sight (NLoS) scenario due to its imminence in terms of coverage and performance.