  With the advancements achieved in drones' flexibility, low cost, and high
efficiency, they obtain huge application opportunities in various industries,
such as aerial delivery and future communication networks. However, the
increasing transportation needs and expansion of network capacity demands for
UAVs will cause aerial traffic conflicts in the future. To address this issue,
in this paper, we explore the idea of multi-purpose UAVs, which act as aerial
wireless communication data relays and means of aerial transportation
simultaneously to deliver data and packages at the same time. While UAVs
deliver the packages from warehouses to residential areas, we design their
trajectories which enable them to collect data from multiple Internet of Things
(IoT) clusters and forward the collected data to terrestrial base stations
(TBSs). To select the serving nearby IoT clusters, UAVs rank them based on
their priorities and distances. From the perspectives of data and package
delivery, respectively, we propose two algorithms that design the optimal UAVs
trajectory to maximize the transmitted data or minimize the round trip time.
Specifically, we use tools from stochastic geometry to model the locations of
IoT clusters and TBSs. Given the nature of random locations, the proposed
algorithm applies to general cases. Our numerical results show that
multi-purpose UAVs are practical and have great potential to enhance the
energy/time-efficiency of future networks.
