Propagation modelling of C band directional UAV ground control links

Unmanned Aerial Vehicles (UAVs), commonly known as drones, have been widely used in specific military applications since the last century. In the recent years, technological developments regarding main aspects of these vehicles such as batteries, electronics and lightweight materials, have made UAVs more feasible to commercial applications. One of the most remarkable fields where the drones are being applied is for telecommunication applications. Several studies propose systems where the UAVs are used as communication relays. These systems, known as Drone Small Cells (DSCs), act as aerial base stations to support communication networks in high demand situations or when the current ground infrastructures have been damaged. The work done in this Thesis belongs to a project whose main goal is to implement a DSC system. The system proposed in this project will provide a wireless access point to the clients using a communication relay mounted in an aerial vehicle. The link that connects the terminals of the clients to the UAV is performed with a simple connection that uses omnidirectional antennas. However, the most critical part of this design, is the link between the UAV and the ground station which will connect the system to the backbone network. This link will use antennas with high directivity in order to deploy the aerial access point at longer distances. In this way, this Master Thesis focuses on the characterization of the link channel with more complexity. This Master Thesis has developed a propagation model intended for air-to-ground communication links. The path loss between a ground station and a UAV can be analysed by means of the implemented propagation model. The measurement equipment has been set and calibrated in advance in order to present the desired path loss information. Based on empirical data obtained in three different LOS scenarios, a comparison is proposed to some well-known state of art models. However, none of the analysed models describes the path loss properly for this type of environment. Therefore, a new propagation model has been developed by a linear approach which considers a correction factor according to the UAV's height. As the model is based on a set of empirical measurements, it can only be applied in environments with a certain of features. These characteristics are a distance range between 0 and 600 m, a drone antenna height between 7 and 35 m and a carrier frequency of 5580 MHz. The performance and accuracy of the proposed model have been analysed considering a fourth set of measurements deployed with a different drone antenna height