  This paper studies a rechargeable unmanned aerial vehicle (UAV) assisted
wireless network, where a UAV is dispatched to disseminate information to a
group of ground terminals (GTs) and returns to a recharging station (RS) before
the on-board battery is depleted. The central aim is to design a UAV trajectory
with the minimum total time duration, including the flight and recharging time,
by optimizing the flying velocity, transmit power and hovering positions
jointly. A flow-based mathematical programming formulation is proposed to
provide optimal for joint optimization of flying and recharging time.
Furthermore, to attack the curse of dimensionality for optimal decision making,
a two-step method is proposed. In the first step, the UAV hovering positions is
fixed and initialize a feasible trajectory design by solving a travelling
salesman problem with energy constraints (TSPE) problem. In the second step,
for the given initial trajectory, the time consumption for each sub-tour is
minimized by optimizing the flying velocity, transmit power and hovering
positions jointly. Numerical results show that the proposed method outperforms
state of art techniques and reduces the aggregate time duration in an efficient
way.
