Physical Layer Aspects of Uncrewed Aerial Vehicle (UAV)-to-Ground Communications

Abstract

With the projected capabilities of 6G networks aiming to deliver a peak data rate of 1 Tbps and extend connectivity to millions of devices within square kilometers by 2030, the inclusion of aerial connectivity emerges as a pivotal trend and enabling technology within 6G networking. This integration of non-terrestrial networks (NTN) brings forth new airborne vehicles complementing existing ground networks. Among these vehicles, uncrewed aerial vehicles (UAVs) have garnered considerable attention from both academia and industry due to their affordability and versatility across diverse scenarios and applications.

Given the critical need for precise characterization of the UAV-to-ground channels, this thesis focuses on investigating the physical layer aspects of the UAV-to-ground channels. These novel fading channel models take into account multipath as well as shadowing. This dissertation studies the various capacities of UAV-to-ground channels. Specifically, it evaluates the effective capacity and ergodic capacity under various power adaptation techniques. These capacity metrics serve as fundamental measures, allowing an assessment of the transmission's achievable rates. Moreover, this dissertation analyzes the physical layer security metrics of these novel channel models, which offers insights into the security robustness of the UAV-to-ground communication system.

Furthermore, this dissertation examines system reliability by deriving the error probability in the presence of phase noise. Introducing phase noise into the assessment of receiver performance makes the analysis more practical and enhances the potential for designing an improved system. Moreover, the dissertation extends its evaluation by considering multiple antenna receivers, specifically selection combining (SC) and maximal ratio combining (MRC). These techniques aim to alleviate channel fading effects and enhance diversity for improved system performance. The analysis encompasses key metrics such as outage probability, average channel capacity, outage capacity, average bit error rate (ABER), and average symbol error rate (ASER). By assessing these metrics for different receiver configurations, this study comprehensively examines the efficacy of SC and MRC in mitigating channel fading effects, thus enhancing system reliability and achieving superior performance under various channel conditions.

Additionally, this thesis offers a thorough examination of the characteristics and performance metrics of interference-limited wireless communication systems functioning across UAV-to-ground fading channels. Moreover, it introduces cascaded shadowed UAV-to-ground fading channels and conducts a rigorous statistical analysis to unveil their intricate dynamics. Furthermore, it presents an analytical framework for assessing energy detection-based spectrum sensing receivers operating in these challenging environments. Through mathematical derivations and simulations, this work provides valuable insights and methodologies for enhancing the reliability and performance of wireless communication systems in UAV-to-ground scenarios. The expressions derived in this thesis are then verified by comparing them against the results obtained through Monte Carlo simulations.