Comparison of Different Diffuse Scattering Models on Random Rough Surface Based on Common Outdoor Materials at 28 GHz Band

The millimeter-wave (mmWave) band was introduced in 5G wireless systems, offering high data rates but facing challenges due to high attenuation and sensitivity to obstacles. Diffuse scattering (DS) becomes increasingly significant in this band, as the surface roughness and irregularities of interacting objects are comparable to the wavelength. To model DS, two approaches have been proposed: the effective roughness (ER) model and the Beckmann–Kirchhoff (BK) model, which differ significantly in their assumptions and formulations. This study aims to bridge the gap between the two by analyzing their scattering characteristics and parameter relationships at 28 GHz across varying root-mean-square (rms) heights and correlation lengths. Since the BK model is analytically derived from Kirchhoff approximation and is more physically accurate, it was used as a reference for tuning the scatter lobe width parameter of the ER model. Given that outdoor urban environments are key 5G deployment scenarios, rough surface parameters were derived from typical materials, such as concrete, roof shingles, and roads. The results indicate that the scattering lobe width increases with smaller rms heights and larger correlation lengths. These findings are expected to support the development of accurate outdoor channel models in the mmWave band.