Terahertz channel power and BER performance in rain.

Terahertz (THz) communications have emerged as a promising technology for 6G networks due to their potential for achieving terabit-per-second data rates. However, the impact of rainfall on THz channel characteristics remains incompletely understood, particularly regarding power attenuation mechanisms and bit error rate (BER) performance. This paper presents a systematic measurement-based and theoretical investigation of line-of-sight (LoS) THz channel behavior under rainfall conditions, methodically examining both power attenuation mechanisms and bit error rate (BER) performance. Our experimental campaign, conducted at frequencies of 220-230 GHz over a 54-meter outdoor channel, is complemented by analytical frameworks incorporating ITU-R and Mie scattering models. The study reveals that while rain induces significant power attenuation, multipath scattering effects remain minimal, with Rician K-factors maintaining high values. Notably, we observe substantial variations in power loss under constant rain rates attributed to dynamic changes in raindrop size distribution. Comparative analysis demonstrates superior BER performance of quadrature amplitude modulation (QAM) in rainfall conditions while revealing increased environmental sensitivity at higher frequencies. These findings underscore the necessity for adaptive modulation schemes and strategic frequency planning in future THz communication systems.