# Path Loss Measurement of Outdoor Wireless Channel in D-band
## 1 Introduction
NYU Wireless also evaluated indoor channels (including offices, conference rooms, classrooms, large hallways, open-plan cubicles, elevators, and a factory building) at 140 GHz using this system in conjunction [12; 13; 14; 15]. In an urban microcell setting, the team also ran directionally resolved outdoor wideband measurement operations at 140 GHz [16]. In 2018, Aalto University reported a microcell directional channel at 140 GHz for a large indoor shopping mall environment, arguing that the spatiotemporal characteristics of the strong path are remarkably consistent between the 28 and 140 GHz channels, and they discovered that the channel's large-scale parameters are comparable at both frequencies [17]. Georgia Institute of Technology conducted a comprehensive analysis of the physical parameters of the terahertz indoor channel, including LOS path loss, power delay angle profile, temporal and spatial characteristics, and correlation between terahertz multipath characteristics [18]. The University of Southern California (USC) conducted a typical office line-of-sight measurement experiment in the frequency range of 140-220 GHz and estimated the path loss exponent and standard deviation of the shading factor of the CI model using the measurement data [19]. USC has also made some progress recently with longer distances and outdoor settings, but only within 100 m [20]. The University of Ghent designed a VNA-based D-band channel sounder with a 60 GHz bandwidth for characterizing the entire D-band radio channel at distances of up to 5 m. The authors present indoor and outdoor propagation measurements and develop D-band channel models for network performance evaluation [21; 22; 23]. Shanghai Jiao Tong University (SJTU) developed a 140 GHz VNA-based channel measurement system. They conducted directionally resolved channel measurements in a typical indoor meeting room with Tx/Rx distances ranging from 1.8 to 7.3 m, and in an office room with Tx/Rx distances ranging from 3.75 to 20 m. The team analyzed the temporal and angular distribution of MPCs, as well as the correlation between channel parameters and their distribution [24; 25]. Meanwhile, some agencies have measured the channel characteristics of D-band, but to our knowledge, few outdoor long-distance D-band channel characterization based on measurements have been reported [12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29]. This paper presents the measurements of the D-band outdoor long-distance channels, explores the applicability of the FI and CI models at long distances in the D-band, and also fits the path loss index and shadow fading. The results show that the path loss of the D-band in outdoor long-distance transmissions is greater than that in free space, indicating that the propagation condition is worse than that in free space. Furthermore, in the CI model, the path loss exponent is greater than 2 and increases with frequency, while in the FI model, the path loss exponent has no apparent frequency dependence. This paper presents prospective and referential outdoor measurement results for D-band channels with large outdoor radio propagation distances up to 800 m.