Optimal Cooperative Relaying and Jamming for Secure Communication

This letter considers joint cooperative beamforming and jamming schemes in a cooperative relay network where distributed relay nodes perform cooperative beamforming. The problem of interest is to keep the eavesdropper´s signal to interference and noise ratio (SINR) as low as possible while maintaining the legitimate receiver´s SINR requirement. Applying semidefinite relaxation (SDR) technique, it is shown that a rank-one optimal solution always exists if perfect channel information is available. An optimal relay beamforming scheme has also been proposed for the scenario where only the second-order statistics of the eavesdropper´s channel is available.