Electrical & Computer Engineering, Department of


Date of this Version



2011 45th Annual Conference on Information Sciences and Systems (CISS), doi: 10.1109/CISS.2011.5766188


Copyright IEEE (2011). Used by permission.


In this paper, a cognitive relay channel is considered, and amplify-and-forward (AF) relay beam forming designs in the presence of an eavesdropper and a primary user are studied. Our objective is to optimize the performance of the cognitive relay beamforming system while limiting the interference in the direction of the primary receiver and keeping the transmitted signal secret from the eavesdropper. We show that under both total and individual power constraints, the problem becomes a quasiconvex optimization problem which can be solved by interior point methods. We also propose two sub-optimal null space beamforming schemes which are obtained in a more computationally efficient way.