Reliable Communications and Energy Efficient Relay in Aerial Wireless Sensor Networks

An Aerial Wireless Sensor Network (AWSN) composed of bird-sized Unmanned Aerial Vehicles (UAVs) equipped with sensors and wireless radio, enables low cost high granularity three-dimensional sensing of the physical world. A swarm of UAVs as airborne relay has great potential to extend the coverage of wireless sensor networks (WSN). This thesis considers the problems of reliable communications, localisation and energy efficient packet load scheduling in AWSNs.We construct two applied scenarios where a swarm of UAVs is employed to fly over a target area, establishing a multi-hop aerial wireless relaying transmission link between the source and destination. In the first scenario (SCE-I), the flying trajectories of UAVs are independent of each other. In the second scenario (SCE-II), the flight trajectory of UAVs is predetermined to achieve efficient network coverage. The first contribution of this thesis is that we investigate the use of a hybrid antenna to accomplish efficient neighbour discovery and reliable communication in SCE-I of AWSNs. We propose the design of a hybrid antenna, which combines the complimentary features of an isotropic omnidirectional radio and beamforming antennas. The second contribution of this thesis is that we propose an actor localisation strategy, which uses the Valence Shell Electron Pair Repulsion (VSEPR) theory of chemistry and the hybrid antenna in SCE-II. VSEPR theory is used to determine the flight geometries. These geometries are adapted to real life conditions by using hybrid antenna. The third contribution of this thesis is the design of energy-efficient scheduling in SCE-II of AWSNs. We propose an energy-efficient relaying scheme to overcome the lossy channels and extend the lifetime of cooperative UAVs substantially. We develop a practical suboptimal solution by decoupling the processes of energy balancing and modulation selection. Although this thesis primarily focuses on the AWSNs with bird-sized UAVs, the scheduling problem could be generally investigated in a wide variety of aerial sensing scenarios such as birds or bats monitoring. As the fourth contribution of this thesis, we address the problem of scheduling for data collection from the aerial sensors, specifically applied to bats tracking