Date Added: Feb 2012
In this paper, the authors consider the secure transmission in fast Rayleigh fading channels with full knowledge of the main channel and only the statistics of the eavesdropper's channel state information at the transmitter. For the multiple-input, single-output, single-antenna eavesdropper systems, they generalize Goel and Negi's celebrated Artificial-Noise (AN) assisted beamforming, which just selects the directions to transmit AN heuristically. Their scheme may inject AN to the direction of the message, which outperforms Goel and Negi's scheme where AN is only injected in the directions orthogonal to the main channel. The ergodic secrecy rate of the proposed AN scheme can be represented by a highly simplified power allocation problem.