In this paper, we propose a cooperative approach to improve the security ofboth primary and secondary systems in cognitive radio multicast communications.During their access to the frequency spectrum licensed to the primary users,the secondary unlicensed users assist the primary system in fortifying securityby sending a jamming noise to the eavesdroppers, while simultaneously protectthemselves from eavesdropping. The main objective of this work is to maximizethe secrecy rate of the secondary system, while adhering to all individualprimary users' secrecy rate constraints. In the case of passive eavesdroppersand imperfect channel state information knowledge at the transceivers, theutility function of interest is nonconcave and involved constraints arenonconvex, and thus, the optimal solutions are troublesome. To address thisproblem, we propose an iterative algorithm to arrive at a local optimum of theconsidered problem. The proposed iterative algorithm is guaranteed to achieve aKarush-Kuhn-Tucker solution.
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