  This paper explores an emerging wireless Internet-of-things (IoT)
architecture based on unmanned aerial vehicles (UAVs). We consider a network
where a fleet of UAVs at a fixed altitude flies on planned trajectories and IoT
devices on the ground are scheduled to transmit their data to the UAVs when the
latter are nearby. In such a system, the UAVs' motion triggers the uplink
transmissions of the IoT devices. As a result, network performance is
determined by the geometric and dynamic characteristics of the system. We
propose a joint stationary model for UAVs and IoT devices and then evaluate the
interference, the coverage probability, and the data rate of the typical UAV.
To assess the harvesting capability of the proposed architecture, we derive a
formula for the amount of data uploaded from each IoT device to a UAV. We also
establish a linear relationship between the UAV coverage and the harvesting
capability of the network, which provides insights into the design of the
proposed harvesting scheme. In addition, we use our analytical results to
numerically show that there exists a trade-off between the uploaded data and
the size of the IoT scheduling window. Specifically, for a given UAV and IoT
geometry, there exists an optimal scheduling window that maximizes the
harvesting capability of the proposed network.
