# The Use of Drones in Spain: Towards a Platform for Controlling UAVs in Urban Environments
## 5 Experiment and Results  
Having designed and developed the system system, it was necessary to test all its functionalities in a real environment, in addition to evaluating other aspects such as the scope, response time and the performance of different types of commercial UAVs. This section details, the experiments performed for validation.  
The proposed system was tested and evaluated in the city of Salamanca, Spain. It is a small town of 39.34 km2. Infrastructure was deployed in this city, consisting of 36 points with 4 Wi-Fi antennas at each point. The antennas used were Ubiquitin NanoStation M2 antennas, which have a unit price of 80E. Different existing tools were used to determine the coverage areas and the best positions for placing the antennas. With the chosen model, an average range of 10 km for each antenna placed with direct view was achieved (obviously, parameters can affect connectivity). Instead of a WiFi antenna, other models can be used as access points, even if they come from another manufacturer. Deployment in a city with these characteristics has not been evaluated on another model as it requires a high initial investment and could be part of future work.  
Once the infrastructure was deployed, the area in which the different tests were to be carried out was defined. In this regard, all take-offs had to be carried out in a secure area and the UAVs had to reach a safe height, which for the city of Salamanca was established at 900 m above sea level, approximately 100 m away from the pilot or the control station that operates the UAV. To monitor air traffic, UAV traffic controller software was constantly running in a cloud environment that allows storing all UAV connections to the platform as well as all telemetry was generated during that connection.  
The tests were carried out with 8 UAVs of 3 different commercial models, at randomly selected points, which were distributed throughout the city. The time it takes the system to display information in the air traffic controller software is negligible (average of 185 ms relative to the time of representation in the pilot control software). Similarly, the time it took to modify the behavior of the UAVs was also negligible and, therefore, could not affect safety, for example when avoiding collisions between them. In this case, the average time that passed between the flight order being sent and the UAV executing it was 211 ms. Therefore, the reaction time, from the moment a behavior occurs that must be independently rectified by the platform until the UAV actually performs it, is approximately 396 ms.  
Therefore, even though the system is distributed throughout the city, the average reaction time that the platform invests in solving incidents autonomously can be said to be much shorter than the average reaction time that pilots would manually invest.  
With respect to the number of UAVs that can be connected to the platform without affecting the performance of the overall system, the maximum has not yet been determined, although it is a high number of UAVs given the low bandwidth to be dedicated to telemetry sending: 40 bytes on average per message and 6 messages exchanged per second. That is, each UAV consumes 240 B/s (not counting the sending of the video, optional) and the TX/RX rate in Nanostation M2 is 130/130 Mbps. Thus, we could use thousands of UAVs theoretically.