# An Experimental Tethered UAV-Based Communication System with Continuous Power Supply
## 7 Saving the iptables rules' configuration:
#### 3.2.5 Power System Analysis and Design  
* **Analysis of UAV energy consumption**: Table 5 shows that for a payload of 1.3 kg, the power consumption is approximately 16 V and 16.37 A. However, these values may vary depending on the weight carried, weather conditions, and other elements that influence system performance. Therefore, evaluating how power consumption varies as a function of the weight being transported is essential for selecting the right components for efficient UAV operation. For this purpose, initial tests were performed using a 1500 mAh, 4S, and 120C spec battery, as shown in Figure 14.  
Two different weights were selected for the tests on energy consumption: (i) a reduced weight of 1155 g, which includes the UAV and the battery necessary for its operation, to analyze the system behavior under minimum load conditions, and (ii) a weight of 2100 g, which includes the UAV, the battery and 945 g weights, to observe the UAV performance under more realistic conditions, i.e., with a higher weight that simulates the system operating scenario. This approach enabled the collection of voltage and current consumption data in various scenarios, the results of which are presented in Table 8.  
From the electrical parameters obtained using a battery as a power supply, it was estimated that this prototype's reasonable power consumption is 16 V and 20 A. This value corresponds to the consumption under an approximate weight required for the uninterrupted UAV-enabled communication system. Knowing the current needed for the system, the theoretical operating time of the UAV using an 1500 mAh battery was calculated using Equation (1). This formula considers that the battery's rated capacity is consumed uniformly, without interruptions and loss of efficiency. The result obtained, 0.075 h, is approximately equivalent to 4.5 min of autonomy under ideal conditions. \begin{table}
\begin{tabular}{c c} \hline
**Feature** & **Detail** \\ \hline
**Reception sensitivity** & \(-117\) dBm \\ \hline
**Communication** & Full-duplex bidirectional via UART TDM interface \\ \hline
**Dimensions** & \(28\times 53\times 10.7\) mm \\ \hline
**Maximum output power** & 100 mW \\ \hline
**Power supply voltage** & 5 V DC (via USB or JST-GH) \\ \hline
**Weight** & 13.6 g \\ \hline \end{tabular}
\end{table} 
Table 7: SiK V3 telemetry radio [37]. Figure 14: The 1500 mAh battery, 4S, and 120C. \begin{table}
\begin{tabular}{c c c} \hline
**Weight [g]** & **Voltage [V]** & **Current [A]** \\ \hline
**1155** & 15.4 & 8.9 \\ \hline
**2100** & 15 & 20 \\ \hline \end{tabular}
\end{table} 
Table 8: Electrical consumption parameters of the UAV obtained using a battery. \[T=\frac{1500\,\mathrm{mAh}}{20\,\mathrm{A}} \tag{1}\]  
\[T=0.075\,\mathrm{\ h} \tag{2}\]  
An additional test was performed with the UAV, which included the Raspberry Pi, its power supply battery, and 1500 mAh, 4S, 120C battery to supply power to the UAV, as shown in Figure 15. During the experiment, the QGroundControl software version 4.4.2, available for download at [38], was used to monitor the voltage and current parameters of the UAV. These parameters varied as a function of horizontal and vertical velocity and height. With a total weight of 1.47 kg, it was observed that at higher altitudes, the current increased and the voltage decreased. This behavior is because, as the UAV ascends, it needs to generate more lift to counteract the force of gravity, which leads to an increase in energy consumption. This increase in energy demand translates into higher current consumption, as the motors must work harder to maintain the UAV's flight. The results obtained are presented in Figure 1  
With the PlotJuggler application, downloaded from its official repository on GitHub [39], and using the log file in _.ulg_ format generated by the flight controller during the UAV operation, the graph representing the variation of voltage and current was obtained.