## 4 Results and Discussion
As seen in Figure 2d,f, lower values were obtained because, in the UMTS, LTE and 5G networks, the spread spectrum technic was used to establish a voice call with a lower spectral density. The mean values for Sub-Scenario 1a for different locations and days were 0.558 V/m, 0.653 V/m and 0.949 V/m, as shown in Table 3. From the results, we can conclude that RF energy accumulated in the car during ongoing voice calls in GSM, and the auto connect (5G/LTE/3G/2G) mode has the potential to be used as a source in energy-harvesting systems for low-power IoT devices. Figure 2: _Cont._  
Figure 3 shows the measured electric field in the car during ongoing video calls (Scenario 2 from Table 1) in each sub-scenario at two locations (Location 1 and Location 2) for weekdays and weekends. As can be seen from the presented results in Figure 3, an ongoing video call was not able to be realized via the GSM and 5G network at Location 2 \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Scenario** & **Sub-Scenario** & **Mean** & **Minimum** & **Median** & **Maximum** \\ \hline \multirow{8}{*}{Scenario 1: voice call} & Sub-Scenario 1a, Location 1, Weekend & 0.559 & 0.116 & 0.436 & 21.846 \\  & Sub-Scenario 1a, Location 1, Weekday & 0.653 & 0.128 & 0.519 & 18.390 \\  & Sub-Scenario 1a Location 2, Weekday & 0.949 & 0.111 & 0.219 & 20.867 \\ \cline{2-6}  & Sub-Scenario 1b, Location 1, Weekend & 0.428 & 0.127 & 0.407 & 3.461 \\  & Sub-Scenario 1b, Location 1, Weekday & 0.515 & 0.120 & 0.488 & 1.801 \\  & Sub-Scenario 1b Location 2, Weekday & 0.316 & 0.126 & 0.2886 & 1.217 \\ \cline{2-6}  & Sub-Scenario 1c, Location 1, Weekend & 0.627 & 0.116 & 0.479 & 4.930 \\  & Sub-Scenario 1c, Location 1, Weekday & 0.559 & 0.126 & 0.504 & 3.279 \\  & Sub-Scenario 1c Location 2, Weekday & 0.275 & 0.120 & 0.242 & 2.307 \\ \hline \multirow{8}{*}{Scenario 2: video call} & Sub-Scenario 2a, Location 1, Weekend & 0.573 & 0.116 & 0.439 & 7.846 \\  & Sub-Scenario 2a, Location 1, Weekday & 0.613 & 0.130 & 0.553 & 6.324 \\ \cline{2-6}  & Sub-Scenario 2b, Location 1, Weekend & 0.452 & 0.125 & 0.443 & 1.306 \\  & Sub-Scenario 2b, Location 1, Weekday & 0.597 & 0.126 & 0.581 & 2.653 \\  & Sub-Scenario 2b Location 2, Weekday & 0.818 & 0.126 & 0.429 & 5.426 \\ \cline{2-6}  & Sub-Scenario 2c, Location 1, Weekend & 1.196 & 0.111 & 0.635 & 11.061 \\  & Sub-Scenario 2c, Location 1, Weekday & 1.062 & 0.207 & 0.673 & 8.671 \\  & Sub-Scenario 2c Location 2, Weekday & 0.636 & 0.132 & 0.254 & 6.395 \\ \cline{2-6}  & Sub-Scenario 2d Location 1, Weekend & 1.392 & 0.128 & 0.525 & 22.355 \\  & Sub-Scenario 2d Location 1, Weekday & 1.120 & 0.133 & 0.532 & 20.505 \\ \hline \multirow{8}{*}{Scenario 3: data usage (Mobile Hot Spot) *} & Sub-Scenario 3a, Location 1, Weekend & 0.627 & 0.111 & 0.470 & 9.077 \\  & Sub-Scenario 3a, Location 1, Weekday & 0.709 & 0.126 & 0.489 & 7.585 \\ \cline{1-1}  & Sub-Scenario 3a Location 2, Weekday & 0.727 & 0.133 & 0.403 & 5.751 \\ \cline{1-1}  & Sub-Scenario 3b, Location 1, Weekend & 1.288 & 0.143 & 0.739 & 9.530 \\ \cline{1-1}  & Sub-Scenario 3b, Location 1, Weekday & 0.924 & 0.131 & 0.607 & 7.552 \\ \cline{1-1}  & Sub-Scenario 3c, Location 1, Weekend & 1.209 & 0.147 & 0.667 & 14.266 \\ \cline{1-1}  & Sub-Scenario 3c, Location 1, Weekday & 1.058 & 0.145 & 0.673 & 19.225 \\ \hline \hline \end{tabular}
* UT is configured as a Mobile Hot Spot, and a laptop is connected to it.  
\end{table} 
Table 3: Descriptive statistics. Figure 2: Boxplot charts and time variation of electric field for Scenario 1 (voice call) of the electric field measured in each sub-scenario at two locations (Location 1 and Location 2) for weekdays and weekends: (**a,b**) Sub-Scenario 1a: voice call set up via GSM network; (**c,d**) Sub-Scenario 1b: voice call set up via UMTS network; and (**e,f**) Sub-Scenario 1c: voice call set up via 5G/LTE/3G/2G (auto connect) network. (underground parking).