  On-board battery consumption, cellular disconnectivity, and frequent handoff
are key challenges for unmanned aerial vehicle (UAV) based delivery missions,
a.k.a., cargo-UAV. Indeed, with the introduction of UAV technology into cargo
shipping and logistics, designing energy-efficient paths becomes a serious
issue for the next retail industry transformation. Typically, the latter has to
guarantee uninterrupted or slightly interrupted cellular connectivity for the
UAV's command and control through a small number of handoffs. In this paper, we
formulate the trajectory planning as a multi-objective problem aiming to
minimize both the UAV's energy consumption and the handoff rate, constrained by
the UAV battery size and disconnectivity rate. Due to the problem's complexity,
we propose a dynamic programming based solution. Through simulations, we
demonstrate the efficiency of our approach in providing optimized UAV
trajectories. Also, the impact of several parameters, such as the cargo-UAV
altitude, disconnectivity rate, and type of environment, are investigated. The
obtained results allow to draw recommendations and guidelines for cargo-UAV
operations.
