Cooperative networking towards secure communications for CRNs

In this paper, we investigate cooperative networking in cognitive radio networks (CRNs), which targets to help the primary users (PUs) for secure communications and provide transmission opportunities to secondary users (SUs). Two cooperation schemes: relay-jammer (R-J) scheme and cluster-beamforming (C-B) scheme, are proposed. In R-J cooperation scheme, two individual SUs, a relay and a friendly jammer, are leveraged by the PU to improve communication secrecy via cooperation; In return, the PU allocates a fraction of access time for SUs´ transmission. To achieve the maximum secrecy rate, joint time and power allocation is considered. In C-B cooperation scheme, the PU cooperates with a cluster of SUs, which enhance the secrecy of primary link via collaborative beamforming and gain spectrum access opportunities as a reward. With the objective of maximizing the secrecy rate, the optimal weights and time allocation are studied. Numerical results validate the proposed schemes and demonstrate that the PU can significantly enhances the secrecy through cooperation with the cooperating SUs by allocating time and transmission power optimally.