# Joint Optimization of a UAV's Trajectory and Transmit Power for Covert Communications

## TL;DR

This paper develops an iterative optimization algorithm for UAV covert communications, jointly optimizing trajectory and transmit power to maximize covert data rate while ensuring covertness and reliability.

## Contribution

It introduces a novel joint optimization framework for UAV trajectory and power control in covert communications, employing successive convex approximation for efficient solution.

## Key findings

- Significant improvement in covert communication performance over benchmark schemes.
- Effective handling of location uncertainties at Bob and Willie.
- Successful formulation and solution of a complex non-convex optimization problem.

## Abstract

This work considers covert communications in the context of unmanned aerial vehicle (UAV) networks, aiming to hide a UAV for transmitting critical information out of a scenario that is monitored and where communication is not allowed. Specifically, the UAV as a transmitter intends to transmit information to a legitimate receiver (Bob) covertly in order to avoid being detected by a warden (Willie) with location uncertainties at Bob and/or Willie. In order to enhance the considered covert communication performance, we prefer to jointly optimize the UAV's trajectory and transmit power in terms of maximizing the average covert transmission rate from the UAV to Bob subject to transmission outage constraint and covertness constraint. The formulated optimization problem is difficult to tackle directly due to the intractable constraints. As such, we first employ conservative approximation to transform a constraint into a deterministic form and then apply the first-order restrictive approximation to transform the optimization problem into a convex form. By applying the successive convex approximation (SCA) technique, an efficient iterative algorithm is developed to solve the optimization problem. Our examination shows that the developed joint trajectory and transmit power optimization scheme achieves significantly better covert communication performance as compared to a benchmark scheme.