1M.Sc. student, Department of Electrical Engineering, Shahrood University of Technology, Iran.
2Assistant Professor, Department of Electrical Engineering, Shahrood University of Technology, Iran
In this paper, we consider a cooperative cognitive radio network in which there is an OFDM primary link and multiple single carrier secondary links.The primary link is required to maintain its secrecy rate above a predeﬁned threshold. If the secrecy rate requirement is not satisﬁed, the secondary system help primary link to maintain its secrecy rate requirement. In doing so, the secondary transmitters work as decode and forward (DF) relays and hence, as a reward, gains access to network resources to transmit its own information. Our objective is to maximize the data rate of secondary system while satisfying the primary secrecy rate constraint and individual transmit power constraints for primary link and secondary system. We solve our proposed optimization problem using dual Lagrange approach to ﬁnd the set of cooperating secondary link, subcarrier assignments, and transmit power over each subcarrier. Using simulations, we evaluate our proposed scheme in various situations.