Covert Communications for Cognitive Satellite Terrestrial Networks

This work investigates a cognitive satellite-terrestrial covert communication network, where a satellite serves as the primary transmitter to communicate with a primary user (PU) covertly under the surveillance of an unauthorized warden and a terrestrial base station (BS) serves as the secondary transmitter to communicate with a secondary user. Considering imperfect channel state information (CSI) of warden, we jointly design both satellite's transmit power and BS's transmit beamforming to maximize the PU's covert rate while satisfying the terrestrial network's information rate requirement, satellite network's covertness and both satellite's and BS's power constraints. The successive convex approximation method is employed to obtain the optimal BS beamforming. In addition, the imperfect CSI is tackled by the
$S$
-procedure technique. Simulation results reveal that compared to other benchmark schemes the proposed optimization algorithm performs better in terms of the covert rate.