Secure relay beamforming with correlated channel models in dual-hop wireless communication networks

In this article, the authors focus on a correlated channel model for secure relay beamforming in the relayeavesdropper network. In this network, a single-antenna sourcedestination pair transmits secure information with the help of a amplify-and-forward (AF) relay equipped with multiple antennas. The relay cannot obtain the instantaneous channel state information (CSI) of the eavesdropper. The relay only have the knowledge of correlation information between the legitimate and eavesdropping channels. Depending on this information, we derived the conditional distribution of the eavesdropping channel. Three beamformers at the relay are studied: the zero-forcing (ZF) beamformer, the generalized match-forward (GMF) beamformer and the general-rank beamformer (GRBF). The authors found that the ZF beamformer is invalid in this system, and the GMF beamformer is the optimal rank-1 beamformer, and the GRBF is the iteratively optimal beamformer. Numerical results are presented to illustrate three beamformers' performance, and the impacts of different parameters, especially the channel correlation, on the system performance are analyzed.