Covert communication towards a flying warden in UAV-assisted MEC system

Due to the high flexibility of Unmanned Aerial Vehicles (UAVs), equipping Mobile Edge Computing (MEC) servers on UAVs can effectively and rapidly handle the high computing requirements of computation-intensive tasks. However, the Line-of-Sight (LoS) transmission between the UAV and ground users makes the offloading information be easily monitored. Therefore, this paper proposes a covert communication scheme against a flying warden in UAV-assisted MEC system. In the proposed scheme, the UAV server assists ground users in completing the computation of offloading tasks. To reduce the possibility of the flying warden detecting the transmission behavior of ground users to the UAV server, a ground jamming device sends jamming signals to the flying warden. The minimum computing capacity of the system is maximized by jointly optimizing ground users’ resources and the UAV server's trajectory under the constraint of system covertness. Due to the multivariable coupling, the optimization problem is non-convex. The optimization problem is first transformed into a tractable form, and then the optimizing solution is iteratively obtained using Successive Convex Approximation (SCA) and Block Coordinate Descent (BCD) algorithms. Numerical results show that, compared to the benchmark schemes, the proposed scheme effectively enhances the computing capacity of the system while meeting the system's covertness requirements.