Resource Allocations for Secure Cognitive Satellite Terrestrial Networks

Cognitive satellite-terrestrial networks (STNs) have been recognized as the promising architecture for addressing spectrum scarcity in the next generation communication networks. In this letter, we investigate the secure transmission schemes in the cognitive STNs where the interference from terrestrial base station (BS) is introduced to enhance security of the satellite link. Our objectives are to minimize the transmit power by jointly optimizing the cooperative beamforming and artificial noise (AN) while guaranteeing the secrecy rate constraint for satellite link, the information rate constraint for terrestrial link and the total transmit power constraint. Both scenarios of the perfect and imperfect channel cases are respectively considered. These constraints make the optimization problems formulated non-convex and challenging, which are efficiently solved via certain transformations to be formulated more tractable versions, respectively. Numerical results are provided to corroborate the proposed schemes.