Worst-Case Jamming for Secure Communications in Multi-antenna Cooperative Cognitive Radio Networks with Energy Harvesting

To further improve the spectrum efficiency, Multi-Antenna Cooperative Cognitive Radio Networks (MCCRNs) have been proposed. In MCCRNs, secondary users (SUs) may cooperatively relay the primary signals for the primary users (PUs) while concurrently accessing the spectrum provided by PUs. To achieve secrecy transmissions in MCCRNs, in this paper, we propose a novel cooperative jamming scheme to protect both the primary and the secondary traffic from being eavesdropped. Specifically, in our scheme, a certain SU is employed as the helper to harvest energy transmitted by the source and then uses the harvested energy to generate an artificial noise to jam the eavesdropper without interfering the legitimate receivers. Our goal is to minimize the signal to interference plus noise ratio (SINR) at the eavesdropper subject to the QoS constraints of the primary traffic and the secondary traffic. In this paper, we consider a practical case where the channel state information of the eavesdropper (ECSI) is imperfect. We formulate the considered minimization problem into a two-stage robust optimization problem based on the worst-case ECSI. By using the semi-definite programming (SDP), the optimal solutions of the transmit covariance matrices can be obtained. Simulation results demonstrate that the SINR of the eavesdropper is remarkably deteriorated using our cooperative jamming scheme.