Time-Efficient Data Download for Emergency UAV: Joint Optimization of On-Board Computation and Communication Under Energy Constraint

Reducing data download time helps in improving the time efficiency of unmanned aerial vehicle (UAV) for emergency services. While download time can be shortened either by increasing the data download rate, or by reducing the data size via on-board computation, the optimal trade-off between the two parts is still an open question. In this letter, the joint optimization of on-board computation and communication is studied to minimize the download time under realistic energy constraint. To decouple computation from communication, we first derive the exact expressions for the optimal computation frequency and transmit power based on a given computation strategy. As the resulting univariate optimization problem is an implicit one, we develop a Dinkelbach-like algorithm that iterates between solving a simplified explicit parametric problem to find a candidate strategy, and updating the parameter to approach the optima. The proposed scheme reduces at least 33.3% download time compared with conventional strategies, and the advantage becomes more significant under stringent energy constraint.