Sub6GHz Non-Line-of-Sight Effects in Mobile Communications: A New Perspective for Rainfall Monitoring

Sub6GHz non-line-of-sight signals are a potential opportunistic source of rainfall information that promises to improve the current urgent need regarding near-surface rainfall detection, but the complex mechanisms in which these signals are impacted by rainfall have hindered further development in this area. In this study, we focus on four types of microwave propagation processes to explore the theoretical basis for Sub6GHz signal sensitivity to rainfall. We also investigate how these signals change during rainy conditions using a cell phone signal recording experiment. The results demonstrate that the indirect effect of rainfall-induced changes in the interfacial water film may significantly affect the Sub6GHz signal, making it an opportunity to reflect rainfall information. Finally, we offer a comprehensive overview of the potential challenges, benefits, and drawbacks of low-frequency non-line-of-sight links in the context of rainfall inversion.