UAV-Assisted Downlink Satellite Covert Communication

TL;DR

This paper explores how UAVs can assist low-Earth orbit satellites in covert communication with ground users by optimizing UAV placement, power, and satellite transmission to maximize covert rates while avoiding detection.

Contribution

It introduces a novel joint optimization framework for UAV-assisted satellite covert communication, including a new detection error probability bound and solution algorithms.

Findings

The derived detection error probability bound is tight.

The proposed algorithms effectively optimize system parameters.

Numerical results show significant covert rate improvements.

Abstract

This paper investigates the use of an unmanned aerial vehicle (UAV) to assist covert communication between a low-Earth orbit (LEO) satellite and a ground user under the surveillance of a passive warden. The UAV simultaneously serves its own ground network and acts as a friendly jammer to enhance the covertness of satellite transmissions. We derive a closed-form lower bound on the warden's average minimum detection error probability which is then used to define the covert constraint. Building on this, we formulate an optimization problem to jointly design the UAV's 3D placement, its power allocation, and the satellite's transmit power to maximize the system's covert rate. To solve the resulting non-convex problem, we propose an algorithm based on the block coordinate descent (BCD) and successive convex approximation (SCA) techniques, and further develop a Dinkelbach's algorithm for a special case. Numerical results validate the tightness of the derived bound and demonstrate the effectiveness of the proposed algorithms in configuring optimal system parameters.