A Universal Attenuation Model of Terahertz Wave in Space-Air-Ground Channel Medium

Providing continuous bandwidth over several tens of GHz, the Terahertz (THz) band (0.1-10 THz) supports space-air-ground integrated network (SAGIN) in 6G and beyond wireless networks. However, it is still mystery how THz waves interact with the channel medium in SAGIN. In this paper, the absorption and scattering effect in THz space-air-ground channels are modeled as a collision process between THz photons and medium particles, based on which a universal space-air-ground attenuation model is proposed for THz waves. The proposed model incorporates the attenuation effects induced by particles including condensed particles, molecules, and free electrons. The propagation loss of THz waves in the atmosphere and the outer space are numerically assessed. Numerical results indicate that the attenuation effects except free space loss are all negligible at the altitude higher than 50 km while they need to be considered in the atmosphere lower than 50 km.