Coarse Trajectory Design for Energy Minimization in UAV-enabled Wireless Communications with Latency Constraints

In this paper, we design the UAV trajectory to
minimize the total energy consumption while satisfying the
requested timeout (RT) requirement and energy budget, which is
accomplished via jointly optimizing the path and UAV’s velocities
along subsequent hops. The corresponding optimization problem
is difficult to solve due to its non-convexity and combinatorial nature.
To overcome this difficulty, we solve the original problem via
two consecutive steps. Firstly, we propose two algorithms, namely
heuristic search, and dynamic programming (DP) to obtain a
feasible set of paths without violating the GU’s RT requirements
based on the traveling salesman problem with time window
(TSPTW). Then, they are compared with exhaustive search and
traveling salesman problem (TSP) used as reference methods.
While the exhaustive algorithm achieves the best performance at
a high computation cost, the heuristic algorithm exhibits poorer
performance with low complexity. As a result, the DP is proposed
as a practical trade-off between the exhaustive and heuristic
algorithms. Specifically, the DP algorithm results in near-optimal
performance at a much lower complexity. Secondly, for given
feasible paths, we propose an energy minimization problem via
a joint optimization of the UAV’s velocities along subsequent
hops. Finally, numerical results are presented to demonstrate
the effectiveness of our proposed algorithms. The results show
that the DP-based algorithm approaches the exhaustive search’s
performance with a significantly reduced complexity. It is also
shown that the proposed solutions outperform the state-of-theart
benchmarks in terms of both energy consumption and outage
performance.