A Long‐Term Experimental Investigation on the Impact of Rainfall on Short 6G D‐Band Links

Abstract

The D band, extending from 130 to 175 GHz, is currently being considered a potential candidate to enable 6G communications (Zhang et al., 2019) (Saad et al., 2020). Thanks to its large bandwidth, it is expected to support the continuous increase in traffic and provide ultra-fast data rates (up to 100 Gb/s), in compliance with the upcoming network requirements . On the other hand, the detrimental effects that the atmosphere induces on electromagnetic (EM) waves quickly increase as we shift to the higher portion of the spectrum. The influence of gas (water vapor and oxygen), suspended water droplets (fog), and hydrometeors (e.g., hail, snow, and rain) play a significant role in causing impairments to EM propagation at higher bands (Paraboni et al., 2002). Among these, rainfall causes the strongest deterioration to the signal as the raindrop dimensions are comparable in size to the wavelength, specifically inducing scattering and absorption of the incident EM wave. Hence, it is necessary to investigate the effects of rain on the propagating EM waves, even more so because, at higher frequencies, the estimation of the impact of precipitation becomes complex due to the dependence of the specific attenuation on the shape and dimension of raindrops. This goal can be achieved by means of theoretical studies, such as those presented in Pérez-Pena et al. ( 2021) and Pimienta-del-Valle et al. ( 2022), where the information on the microphysical properties of rainfall is used to accurately estimate the induced attenuation in the 80-200 GHz band. On the other hand, it is also vital to conduct propagation experiments, which represent the first key step for the development of propagation models aimed at predicting the statistics of the rain attenuation affecting terrestrial links. Some previous experiments focused on characterizing the indoor channels at D band (Chen & Cao, 2013) , while (Ishii et al., 2016) investigated the impact of rain attenuation on links at D band, but only on a short-term basis (2 months) and considering quite a limited precipitation intensity (11 mm/hr maximum). To the best of our knowledge, no long term outdoor propagation experiment at D band has been conducted yet.Originating from the collaboration between Politecnico di Milano and the Huawei European Microwave Centre in Milan, this research activity aims at filling this gap by investigating the effect of the atmosphere on two D-band terrestrial links. The experimental setup in Milan, Italy, consists of a 325 m D-band link operating with a carrier frequency equal to 156 GHz used to investigate the effect of rain attenuation, starting from the received power.