Ensuring Secrecy in MIMO Wiretap Channels with Imperfect CSIT: A Beamforming Approach

In this paper, we investigate transmit beamforming schemes based on artificial interference for physical layer security in a multi-antenna wiretap channel. We consider the case where no information regarding the eavesdropper is present, and we use the signal-to-interference-plus-noise-ratio of a single transmitted data stream as our performance metric. Using a second-order perturbation analysis, we quantify the degradation in performance due to imperfect CSI of the main channel at the transmitter. We then present a robust beamforming scheme that approaches the performance obtained in the perfect CSI case. Numerical simulations verify our analytical performance predictions, and illustrate the benefits of the robust beamforming scheme.