Antennas and Propagation for UAV-Assisted Wireless Networks Towards Next Generation Mobile Systems

Unmanned Aerial Vehicles (UAV), also known as "drones", are attracting increasing attention as enablers for many technical applications and services, and this trend is likely to continue in the near future. UAVs are expected to be used extensively in civil and military applications where aerial surveillance and assistance in emergency situations are key factors. UAVs can be more useful and flexible in reaction to specific events, like natural disasters and terrorist attacks since they are faster to deploy, easier to reconfigure and assumed to have better communication means due to their improved position in the sky, improved visibility over ground, and reduced hindrance for propagation. In this regard, UAV enabled communications emerge as one of the most promising solutions for setting-up the next-generation mobile networks, with a special focus on the extension of coverage and capacity of mobile radio networks for 5G applications and beyond. However, air-to-ground (A2G) propagation conditions are likely to be different and more challenging than those experienced by traditional piloted aircraft. For this reason, knowledge of this specific propagation channel – together with the UAV antenna design and placement - is paramount for defining an efficient communication system and for evaluating its performance. This PhD thesis tackles this challenge, and it aims at further investigating the narrowband properties of the air-to-ground propagation channel by means of GPU accelerated ray launching simulations for 5G communications and beyond. As a conclusion, this PhD thesis might bring deep insights into the air-to-ground channel characteristics and UAV antenna design, which can be helpful for designing UAV communication networks and evaluating or optimising their performances in a fast and reliable manner, with no need for exhausting – multiple - in-field measurement campaigns.