# Path Loss Measurement of Outdoor Wireless Channel in D-band
## 1 Introduction  
With the advent of the era of Internet of Everything, more and more things, people, and data are connected via the Internet, which has lead to increasing demand for more authorized wireless spectrum or shared spectrum resource access. The millimeter-wave (MMW) spectrum source is a critical device for a variety of application systems, such as symbiotic sensing and communications, molecular imaging, atmospheric remote sensing and detection, and scaled radar range systems. As a part of MMW resources, the D-band spectrum with its broad bandwidth has become a research hotspot in recent years. Not only do we see a growing attention to D-band as a potential spectrum resource, but there is also a fast-growing number of related channel measurement experiments. D-band radios operating at 110-170 GHz offer benefits, such as high capacities and high antenna gains with a small footprint [1, 2, 3, 4]. The narrower transmit beam makes it more accurate when viewing smaller targets, and also reduces the risk of signal eavesdropping and inter-user interference [5, 6, 7, 8, 9, 10]. Moreover, it can be seen from Figure 1 that under the standard environment, the atmospheric attenuation does not exceed 2 dB/km in the D-band, which is acceptable for power control and can meet the 5G communication indicators to have an excellent potential in future 5G and 6G communication [11]. However, the poor transmissivity and large propagation attenuation of MMW bring challenges to the research and utilization of MMW. For a better design of outdoor wireless pico-cellular communication systems, the characteristics of propagation channels, especially regarding path loss, need to be modeled and explored in detail. D-band channel characteristics are summarized in Table 1.  
As shown in Table 1, New York University has done a lot of work on D-band channel measurements. In 2021, NYU Wireless provided a measurement system with dual-mode switching between the real-time spread spectrum and sliding correlation mode. The researchers measured and examined the reflection and scattering characteristics of wave propagation at 140 GHz. Furthermore, in order to simulate ground-to-satellite and ground-to-unmanned aerial vehicle communications at 140 GHz, they measured rooftop surrogate \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Frequency** & **Antennas** & **Environment** \\ \hline \multirow{4}{*}{New York University} & \multirow{4}{*}{142 GHz} & \multirow{4}{*}{\begin{tabular}{c} 27 dBi narrow-beam horn \\ antennas (TX and RX) \\ \end{tabular} } & \multicolumn{2}{c}{1–40 m Indoor offices, conference rooms, classrooms, long hallways, open-plan cubicles, elevators, and the factory building [12; 13; 14; 15]; 25–117 m} \\  & & & Outdoor Urban Microcell (UMi) area [16] \\ \hline \multirow{2}{*}{Aalto University} & \multirow{2}{*}{140 GHz} & \multirow{2}{*}{\begin{tabular}{c} 19 dBi horn (RX) and 2 dBi bicone \\ (TX) antennas \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} 3–65 m Indoor shopping mall [17] \\ \end{tabular} } \\  & & & \\ \hline \multirow{2}{*}{\begin{tabular}{c} Georgia Institute of \\ Technology \\ \end{tabular} } & \multirow{2}{*}{140 GHz} & \multirow{2}{*}{\begin{tabular}{c} 22–23 dBi horn antennas (TX and \\ RX) \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} 1-5 m Outdoor [21]; \\ 0.5–8.5 m Indoor office and laboratory [22; 23] \\ \end{tabular} } \\ \cline{1-1} \cline{3-3}  & & & & 1.8–20 m Indoor meeting room and office \\ \hline \multirow{2}{*}{\begin{tabular}{c} SJTU \\ This work \\ \end{tabular} } & \multirow{2}{*}{138–165 GHz} & \multirow{2}{*}{\
\begin{tabular}{c} 25 dBi narrow-beam horn \\ antennas (TX and RX) \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} 100–800 m Outdoor street \\ \end{tabular} } \\  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Reference Review of Exploring Channel Characteristics. Figure 1: Free-space path atmospheric attenuation. satellite and backhaul.