Optimal Beamforming Design for Secure Transmission with Channel Covariance Uncertainty

Physical layer security has attracted substantial research interests in recent years. The introduction of cooperative jamming (CJ) into physical layer security can improve transmission security through generating jamming signals with the assistance of external helpers. In this paper, we study robust beamforming design for multiple-input single-output (MISO) wiretap channels under CJ by exploiting imperfect channel state information (CSI), in which the source employs transmit beamforming for delivering information to the destination and the helper generates Gaussian noise to confuse the eavesdropper. We assume that all the wireless channels from the source/helper to the destination/eavesdropper are subject to quadratic channel uncertainty. Our objective is to minimize the total transmit power at both the source and the helper subject to the minimum signal-to-interference-plus-noise ratio (SINR) constraint at the destination and the maximum SINR constraint at the eavesdropper. Relying on the techniques of semidefinite relaxation (SDR) and S-procedure, we obtain the optimal robust beamforming solution. Simulation results show the effectiveness of our proposed scheme.