Robust Beamforming and Jamming for Secure AF Relay Networks with Multiple Eavesdroppers

In this paper, we study the secrecy transmission in multi-antenna relay networks with multiple eavesdroppers. The relay employs the amplify-and-forward relaying protocol and simultaneously sends the artificial noise to interfere the eavesdroppers. It is assumed that only imperfect channel state information on the main and eavesdropping channels is available at the relay. We exploit the robust beam forming and jamming to maximize the worst-case secrecy rate under a total relay power budget. Because of the infinitely nonconvex constraints, the problem is difficult to solve. Therefore, we approximate the problem into several tractable semi definite programs by semi definite relaxation, S-procedure, and the successive convex approximation techniques. Simulation results show the effectiveness of the proposed scheme.