Abstract: Cognitive radio (CR) technology is one of the strong candidate technologies to solve the spectrum scarcity problems.We proposed a time-bandwidth allocation scheme for physical layer security in cognitive radio networks,in which the primary users (PUs) communicate with the help of the secondary users (SUs).As feedback,PUs share the bandwidth with SUs for the communication of the secondary network.Particularly,we selected two SUs,a relay SU and a jammer SU,to maximize the physical secrecy capacity of the PUs on the premise of meeting the lowest transmission rate requirement of the SUs.The optimal bandwidth allocation factor,time allocation factor and the cooperative power allocation of the SUs were given in this paper.Numerical results show that the proposed scheme can improve the secrecy capacity of the PUs significantly.

Key words: Cooperative cognitive radio networks,Physical security,Time allocation,Bandwidth allocation