# Cellular and Virtualization Technologies for UAVs:
## 4 Testbed Experimentation
### Indoor Flight Validation  
Indoor flight tests have been carried out to validate the payload as an operation onboard system (no outdoor flight has been done due to regulatory restrictions). These results serve as a proof of concept demonstrating the functionality of the proposed testbed. For this purpose, indoor tests have been carried in the 5 TONIC laboratory. On the other hand, the K8s controller, Video-consumer, and UAV-controller elements (see Figure 2) are located at UC3M. In this way, an inter-site experiment is performed to demonstrate that the BRLoS management operations run correctly. As it can be appreciated in Figure 2(a),b, the communication prototype (RPi + Qualtec PCIe) has been on-boarded as an UAV payload, using a compact battery to power up the prototype. The overall dimensions of this prototype are 6 \(\times\) 11 \(\times\) 4 centimeters, with a total weight of 200 g including the battery. It is essential to consider lightweight and compact equipment since the power required by the UAVs to carry all its load can significantly impact the life-time of the UAV main engines battery.  
It is essential to consider that Multi-UAV operations entail certain risks, not only in colliding with aerial traffic (i.e., other UAVs, human-crewed aircraft in the proximity of airports), and accidents including people and vehicles on the ground in populated areas. Authors in [54] proposed a complete risk assessment model for UAV operation in urban environments with three main risk categories (people, vehicles, and human-crewed aircraft). The mission planner generally contemplates the operations and factors involving the most significant risk. However, unbounded exploration can lead to undesirable scenarios. To solve that issue, authors in [55] propose a framework that evaluates the risk of the potential actions. In case of actions deemed too risky, they are replaced with another action of lower risk.  
C2 information has been transmitted from the UAV-controller to the RPi (UAV payload) using the Ansible automation platform explained in Section 3.2. Once the payload has received the trajectory, it replicates the instructions to the UAV using its WiFi interface (also explained in Section 3.2). This traffic is represented in Figure 5(a),b. Figure 5(a) shows a traffic peak corresponding to the trajectory transfer. On the other hand, Figure 5(b) displays the transmitted and received traffic between the RPi and the UAV. The two traffic peaks that can be appreciated correspond to the take-off and landing procedures.  
On the other hand, the testbed virtualization platform has been used to test multimedia services viability. A docker container deployed on the RPi (Video TX container in Figure 2) transmits a 2 Mb/s UDP traffic flow to a docker container deployed on the video-consumer. This stream emulates an HD video transmission (HD 720p [56]), a target rate that most HD cameras are able to generate. All this traffic has been sent using the VPN tunnel describedin previous sections, since it provides an extra security layer to the information being transmitted (i.e., preventing third-party attacks that could compromise the video feed in real scenarios). Figure 6c reveals that the video-consumer has correctly received the flow.  
Finally, the traffic transmitted and received for the correct management of the virtualization platform is shown in Figure 6d. This traffic should not be neglected as it shares the same channel as other critical communications such as C2, and its presence can disrupt other traffic if it requires a high amount of bandwidth for its proper functionality. However, it is relatively small in comparison to the available bandwidth of the channel, with an average of 2.71 Kb/s for transmitted management traffic and 6.52 Kb/s for received management traffic (representing less than 1% of the available throughput), so it is unlikely that this traffic will interfere with C2 communications and other applications embedded in the UAV payload.