  Motivated by the fact that current mathematical methods for the trajectory
design of an unmanned aerial vehicle (UAV) considering no-fly-zones (NFZs)
cannot perfectly avoid NFZs throughout the entire continuous trajectory, this
study introduces a new constraint that ensures the complete avoidance of NFZs.
Moreover, we provide mathematical proof demonstrating that a UAV operating
within the proposed constraints will never violate NFZs. Under the proposed
constraint on NFZs, we aim to optimize the scheduling, transmit power, length
of the time slot, and the trajectory of the UAV to maximize the minimum
throughput among ground nodes without violating NFZs. To find the optimal UAV
strategy from the non-convex optimization problem formulated here, we use
various optimization techniques, in this case quadratic transform, successive
convex approximation, and the block coordinate descent algorithm. Simulation
results confirm that the proposed constraint prevents NFZs from being violated
over the entire trajectory in any scenario. Furthermore, the proposed scheme
shows significantly higher throughput than the baseline scheme using the
traditional NFZ constraint by achieving a zero outage probability due to NFZ
violations.
