Scattering from Rough Surfaces in 100+ GHz Wireless Mobile Networks: From Theory to Experiments

The use of frequencies above 100 GHz has received increasing attention due to the large amount of available bandwidth. Given the high chance of signal blockage, reflected paths play a key role in 100+ GHz networks. Interestingly, at these frequencies, the signal wavelength becomes comparable to the height perturbation in common natural surfaces. Hence, the reflection pattern deviates from mirror-like smooth reflection and exhibits rough scattering patterns that consist of non-specular components. This paper presents an in-depth analysis and experimental demonstration of "rough" surface scattering and its implications for wireless networking, namely in coverage, mobility resilience, and channel reciprocity. Furthermore, we present a novel framework for estimating the surface roughness level from the unique spectral and spatial signatures seen in the reflection spectra. We perform extensive modeling, simulation, and over-the-air experiments using a broadband sub-THz wireless system employing typical indoor/outdoor surfaces such as tile, brick, redstone, and granite.