Stochastic geometric analysis of multiple unmanned aerial vehicle-assisted communications over internet of things

Due to the advantages of large area coverage, low capital cost and fast deployment, unmanned aerial vehicles (UAVs) are believed to play a key role in the emerging Internet of Things (IoT). In this paper, we first develop an effective analytical approach to characterize the properties of UAV-assisted communications over a large number of IoT devices by introducing average channel access delay for packets that can be successfully transmitted. Specifically, an IoT device is said to establish a full transmission to a UAV, only if its time duration covered by the UAV is greater than the specified average channel access delay. Then, we present a stochastic geometry based mathematical framework to analyze the coverage probability and average achievable rate for a multi-UAV assisted downlink network. Different from previous works: 1) we consider a flexible multi-UAV deployment strategy connecting IoT devices to the Internet via sky-haul links to the satellite, where the altitudes of the UAVs can be adjusted to fulfill the requirements of various IoT applications and 2) we derive analytical expressions, in particular integral form, for the coverage probability and average achievable rate. Our results indicate that the developed framework is very helpful for network designers to efficiently determine the optimal network parameters at which the optimum IoT system performances can be achieved.