Measurement-based Evaluation of Path Loss and Propagation Mechanisms in the 300 GHz band

Advanced cyberspace and physical space integration is being pursued with B5G/6G, and technology studies for ultrahigh capacity beyond 5G are underway. The terahertz band, which enables ultrawideband transmission, is thus attracting much attention. However, this band has large path losses, so it is necessary to consider the feasibility of using it as an access line for mobile communication systems, and it is essential to understand its radiowave propagation characteristics. Among the terahertz bands with frequency over 100 GHz, the 300 GHz band (252-296 GHz), which ITU has agreed to be used for land mobile services with a bandwidth of 44 GHz, is expected to be utilized. However, there are few reports on propagation characteristics in this frequency band and few applicable radiowave propagation models. In this paper, we report the path loss characteristics obtained from radiowave propagation experiments at 300 GHz in indoor and outdoor environments. Additionally, we report the propagation mechanism of the 300 GHz band as revealed by arrival wave distributions obtained by angle of arrival measurements. Our findings indicate that diffraction contributes minimally to both indoor and outdoor environments, while reflected and scattered waves dominate the propagation characteristics. We also showed that use of a site-specific model, such as the P.1411 model that considers curved corners in outdoor environments, is effective for modeling the steep changes in the transition region in indoor and outdoor environments.