Security of UAV Relay Networks based on Covert Communication in the Presence of an Eavesdropping UAV

This paper proposes the use of a trusted decoder and forward (DF) Unmanned Aerial Vehicle (UAV) relay to establish a covert communication between a terrestrial transmitter (Alice) and a receiver (Bob), which is located in a remote area outside the allowable transmitting radius of Alice. The terrestrial transmitter uses the Maximum Ratio Transmission (MRT) technique and several antennas to send the covert signal, and also the UAV relay operates in a Full-Duplex frequency band so that in addition to relaying Alice’s signal message to Bob, it also sends disturbance signals to increase the covert transmission detection error by the eavesdropping UAV. In this paper, the source-based jamming scheme (SBJ) is used to avoid the need of using an external jammer in the network. First, the covert transmission conditions in the mentioned network have been investigated and the optimal detection thresholds of the eavesdropping UAV have been obtained with respect to the terrestrial transmitter and the UAV relay. In the simulations, the effects of using multiple antennas at the transmitter as well as the location of the eavesdropping UAV have been investigated to indicate the effectiveness of the proposed covert communication relay scheme with the help of a UAV relay.