Achieving secure communications in multi-antenna cooperative cognitive radio networks using cooperative jamming

Multi-antenna based cooperative cognitive radio networks (MCCRNs) have been proposed recently to further improve the spectrum efficiency. Secure communications may be impeded by the eavesdropper in MCCRNs. In this paper, we use physical layer methods to prevent the eavesdropping attack. A cooperative jamming scheme is proposed, in which SUs are employed as helpers to send jamming signals. We optimise the design of beamformers and power allocation vectors to maximise secrecy capacity. To further improve the secrecy capacity, we design an effective cooperation strategy of helpers using coalition formation game. Based on the merge-and-split rules, a coalition formation algorithm is proposed.