Performance Analysis Of Unmanned Aerial Vehicles-enabled Wireless Networks

Beyond their inevitable role as users of the mobile communication systems,Unmanned Aerial Vehicles(UAVs)can be leveraged to complement ground,terrestrial networks by providing connectivity to hotspots and to areas in which infrastructure is scarce.In addition,equipped with self-navigation and strong automation,UAVs can have extensive applications to environmental and natural monitoring,patrolling and disaster recovery,search and rescue,goods delivery and air combat,owing to their excellent agility and autonomy.As a result,an increasing demand arises for ubiquitous connectivity and reliable commu-nication for safe control and data exchange between the autonomous UAVs,and between the UAVs and ground stations.Due to the fact that the UAVs operate in 3D spaces with strong maneuverability,and 3D random trajectories and wireless propagation environment can pose significant challenges to the study on the coverage and capacity of UAV communication networks.On the other hand,UAVs are increasingly posing threats to information security and privacy.UAVs can be potentially used to eavesdrop,jam,and spoof wireless transmissions between legitimate terrestrial transceivers.It is of practical inter-est to understand the robustness of terrestrial wireless communications under exposure to new threats from aerial adversaries,such as aerial eavesdroppers.In this thesis,we study the coverage and capacity performance,including secure coverage and secrecy capacity performance,of UAV-enabled wireless networks with autonomous UAVs flying 3D random trajectories.Based on stochastic geometry and the theory of convergence in measure,several traceable models are proposed to analyze the coverage and capacity of the UAV-enabled wireless networks in terms of ergodic capacity,outage probability,secrecy outage prob-ability,outage capacity,ergodic secrecy capacity,and outage secrecy capacity.The research content and detailed contributions of this paper are summarized as follows.(1)Capacity analysis of UAV networks under random trajectories.To ana-lyzes the link capacity between autonomous Unmanned Aerial Vehicles(UAVs)with random three-dimensional(3D)trajectories,we propose a novel mathmati-cal framework to derive the closed-form bounds for the capacity between UAVs,and between UAVs and ground stations.Another important aspect is that we extrapolate the idea to dense UAV networks,and analyze the impact of network densification and imperfect channel state information on the capacity.Corrob-orated by simulations,our analysis is accurate and can be used to evaluate the impact of the system parameters on the capacity of the UAV networks.(2)Connectivity analysis of uncoordinated UAV swarms.To analyze the connectivity of a swarm of uncoordinated UAVs,both in the absence and the presence of ground interference,where,distinctively different from existing studies,the UAVs fly independent and random 3D flight trajectories with prac-tical smooth turns.New closed-form bounds are derived for(a)the outage probability of individual UAVs to the rest of the swarm,and(b)the broadcast connectivity of each UAV which evaluates the reliability of broadcast across the swarm.The qualifying conditions of the bounds in terms of 3D cover-age of the UAVs,and the impact of the ground interference on the outage of UAVs are identified.Corroborated by simulations,our analysis is accurate and particularly useful for evaluating the connectivities of a dense uncoordinated UAV swarm with practical 3D trajectories.Interesting insights are shed on the connectivity and coverage of uncoordinated UAV swarms.(3)Secure connectivity analysis in UAV networks.To characterize and evaluate the trust relationships among UAVs in UAV networks,we propose a novel trust model for UAV networks that is based on the behavior and mobility pattern of UAVs and the characteristics of inter-UAV channels.Based on the trust model,the secure link in UAV networks can be formulated that exists only when there are both a physical link and a trust link between two UAVs.We derive accurate analytical expressions of both physical and secure connectivity probabilities using stochastic geometry with or without considering Doppler shift.Extensive simulations show that compared to physical connection proba-bility with or without malicious attacks,the proposed trust model can guarantee secure communication and reliable connectivity between UAVs and enhance network performance when the UAV networks face malicious attacks and other security risks.(4)Secrecy capacity analysis against aerial eavesdroppers.To understand the increasingly severe threat of UAVs to the confidentiality of terrestrial radio links,we analyze the ergodic and?-outage secrecy capacities of the links in the presence of multiple cooperative aerial eavesdroppers flying autonomously in 3D spaces.The analysis is extended to study the impact of the oscillator phase noises and finite memories of the aerial eavesdroppers on the secrecy performance of the ground link.Validated by simulations,an important finding is that the cut-off density only depends on the range of the link in the case of SC eavesdropping,while it depends on the flight region of the eavesdroppers in the case of MRC eavesdropping.In summary,this paper focuses on the capacity and coverage analysis of the UAV communication networks,and theoretically analyzes the performance parameters such as ergodic capacity,outage probability,secrecy outage proba-bility,outage capacity,ergodic secrecy capacity,and outage secrecy capacity.The impact of the unique characteristics of the UAV communication networks on capacity and coverage performance is also investigated.The study and analyses in this thesis can provide theoretical insights for the deployment and implementation of the practical UAV communication networks.