# Smartphone-Based Experimental Analysis of Rainfall Effects on LTE Signal Indicators
## 3 Experimental Setup and Data Collection
### Data Collection  
The data collection is carried out across three locations in Sydney, Australia, each presenting distinct propagation environments. The experiment is conducted during the frequent rainfall season from November 2023 to March 2024 [33]. Table 2 summarizes the data collection conditions and results. The first experiment's location is on the third floor of a townhouse, where the mobile phone is put on the red desk shown in Figure 2a. The second experiment's location is in the yard of the same townhouse, with the phone tied to a tree inside a plastic bag, as illustrated in Figure 2b. The third location is inside a typical house with the collecting mobile phone placed on a table. These diverse environments facilitate the investigations of how indoor and outdoor conditions affect mobile signal-based rainfall sensing. They also help assess the robustness of our method in varying scenarios with different mobile network configurations. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Dataset** & **Sample Interval (s)** & **Indoor/Outdoor** & **Collection Time** &
\begin{tabular}{c} **Number of** \\ **Samples** \\ \end{tabular} \\ \hline
1 & 5 & Indoor &
\begin{tabular}{c} 24 October 2023–20 \\ March 2024 \\ \end{tabular} & 1,813,140 \\ \hline
2 & 5 & Outdoor &
\begin{tabular}{c} 22 March 2024–25 \\ June 2024 \\ \end{tabular} & 798,717 \\ \hline
3 & 30 & Indoor &
\begin{tabular}{c} 28 March 2024–5 \\ April 2024 \\ \end{tabular} & 20,319 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Datasets for signal measurements at different locations. Figure 2: Signal data collection locations: (**a**) Signal data collection location 1. (**b**) Signal data collection location 2. The signal data collection location, weather station location, and the location of cells that the mobile terminal is most frequently connected to are shown in Figure 3. The longitude and latitude coordinates for the signal collection sites and weather stations are recorded, while the cell locations can be identified using Opencellid [34], based on the cell ID, MCC, MNC, and LAC (TAC). The distances between the weather stations and the signal data collection locations are small enough to ensure that rainfall intensity in the surrounding area is accurately captured. In this work, the signal data are collected where an LoS path between the cell and the smartphone is not guaranteed. This differs from most existing papers investigating the relationship between signal data and weather based on the LoS propagation path between BS and a mobile terminal. In these studies, maintaining an LoS path is generally considered, but in practice, this can be quite challenging. Here, we adopt visual inspection and ray-tracing simulation to confirm that there is no direct path between the cell and the data collection location. The experimental location 1, as noted in Table 2, is selected as an example. The surrounding environment for data collection is shown in Figure 4. We could not see the BS. A ray-tracing simulation is performed in MATLAB R2024a with map and building files of experimental locations, as obtained from OpenStreetMap [35]. The simulation allows us to visualize the microwave propagation between the cell and the user terminal. The red marker represents the BS while the blue marker represents UE in Figure 4,c. By configuring the simulation to ignore reflected paths, we can check for the existence of an LoS between the BS and the user terminal. As shown in Figure 4, there is no LoS path between the BS (indicated in red) and signal data location 1 (indicated in blue). Furthermore, when the simulation is configured to account for additional reflected paths, we can observe the effects of path loss and signal degradation. Figure 4 illustrates one reflected path in experimental location 1, when the maximum number of reflections is set to two. One of the raw signal data snippets is shown in Table 3, after removing columns with invalid values or data that are irrelevant here. The table displays the key signal power metrics, as detailed in Section 2.