Power-Efficient Secure Beamforming in Cognitive Satellite-Terrestrial Networks

This paper proposes a power-efficient secure beamforming (BF) algorithm for cognitive satellite-terrestrial wireless networks, where the satellite network termed as the primary network under the intercept of an eavesdropper shares the spectrum of the primary network with the terrestrial secondary network. Specifically, we propose a optimal BF scheme with the objective of minimizing the transmit power of the terrestrial base station (BS), while meeting the secrecy rate constraint of the primary user and the communication rate constraint of the secondary user. Then, we use constraint transformation and semidefinite relaxation (SDR) method to convert the nonconvex optimization problem into the convex optimization problem. Thus, the optimal BF weight vector can be solved by semidefinite program (SDP) method. Finally, the results of computer simulation verify the effectiveness and superiority of the proposed BF algorithm.