## 4 Results and Discussion
Comparing the results depicted in Figure 3a-h, we can see that the highest measured value of the electric field appeared during the video calls via the 5G network (Sub-Scenario 2d, see Table 3). These results were obtained because, in LTE and 5G, the uplink power control depended upon main factors such as several resource blocks, the modulation and coding scheme, path loss, UE maximum power, etc. Comparing the results depicted in Figure 3f,h with those in Figure 2d,f, it can be seen that, during ongoing video calls, the measured E-field increased due to the increased UE transmit power. We assume that the higher values of the electromagnetic fields were caused by the higher video image quality, which led to the transmission of a larger volume of data via the LTE and 5G networks and the allocation of more resource blocks. In LTE and 5G, the UE transmit power was increased in direct proportion to the number of allocated resource blocks. The mean values for Sub-Scenario 2d were 1.392 V/m and 1.120 V/m, as shown in Table 3. The generated electromagnetic fields during a video call in a car are suitable for the design of RF energy-harvesting systems for IoT devices and sensors. Figure 3: \(Cont\). Figure 4 shows the measured electric field in the car during data transmission (Scenario 3 from Table 1) in each sub-scenario at two locations (Location 1 and Location 2) for weekdays and weekends. In Scenario 3, we configured UT as a mobile hotspot. After that, we connected a laptop to the mobile hotspot. During the measurements in all sub-scenarios, we activated a video with 4k resolution on YouTube on the laptop. Figure 3: Boxplot charts and time variation of electric field for Scenario 2 (video 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 2a: video call set up via GSM network; (**c,d**) Sub-Scenario 2b: video call set up via UMTS network; (**e,f**) Sub-Scenario 2c: video call set up via LTE network; and (**g,h**) Sub-Scenario 2d: video call set up via 5G network. Figure 4: Boxplot charts and time variation of electric field for Scenario 3 (data transmission) 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 3a: data transmission via UMTS network; (**c,d**) Sub-Scenario 3b: data transmission via LTE network; and (**e,f**) Sub-Scenario 3c: data transmission via 5G network. The results depicted in Figure 4 show that the electric field that accumulated in the car during data transmission exhibited slight variations depending on the day of the week in Location 1. The highest values of the electric field (14.266 V/m and 19.225 V/m, see Table 3) again were obtained during data transmission via the 5G network, i.e., for Sub-Scenario 3c. The obtained mean values in this sub-scenario were 1.209 V/m and 1.058 V/m. The mean values obtained were close to those of a video call (scenario 2) and were suitable for the design of RF energy-harvesting systems. In 5G, when a large data packet needs to be transmitted, UE can be indicated to activate a bandwidth part with a wide bandwidth comprising several continuous physical resource blocks. Comparing the results depicted in Figure 4a-f, we can see that the lower measured value of the electric field appeared during data transmission via the LTE network. As is known, in LTE, UE cannot transmit more than its maximum UE power, which is 23 dBm. Control measurements of the electromagnetic field outside and inside the car were performed. The control measurements aimed to determine the RF energy in the vehicle when there was no source of an electromagnetic field in the cabin. In all control measurements, only the RF energy inside and outside the vehicle cabin, which was created by wireless cellular networks, wireless local area networks, etc., was evaluated. During the control measurements, the user terminal was switched off.