Secure Transmission in Cognitive MIMO Networks Using Cooperative Jammer With Outdated CSI

In this paper, we investigate the secrecy performance of an underlay spectrum sharing cognitive MIMO networks with the help of a cooperative jammer (Charlie), in which the secondary transmitter (Alice) aims to communicate with secondary receiver (Bob) in the presence of an eavesdropper (Eve). In order to analyze the impact of the imperfect channel state information (CSI), the CSI of the links between secondary network and primary network, Alice and Bob, Charlie and Eve are considered to be outdated, respectively. We propose the transmit antenna selection-maximal-ratio combining/zero forcing beamforming scheme (TAS-MRC/ZFB) to improve the secrecy performance of the considered networks. Furthermore, the exact and the asymptotic closed-form expressions of secrecy outage probability are provided to analyze the impacts of the outdated CSI and the proposed TAS-MRC/ZFB on the considered networks. The results reveal that the outdated CSI between secondary network and primary network has a significant impact on secrecy performance of the considered networks in the low signal-to-noise ratio (SNR) region, the outdated CSI between Charlie and Eve will significantly deteriorate the secrecy performance of the considered networks in high SNR region. Finally, Monte Carlo simulations are carried out to verify our analysis.