Abstract
In this letter, we investigate the secrecy design in a wireless-powered amplify-and-forward relay network, where the relay is energy constrained and powered by the signal from the transmitter. Specifically, by adopting the power splitting (PS) scheme at the relay, we investigate the worst-case secrecy rate maximization by jointly designing the relay beamforming matrix, artificial noise covariance, and the PS ratio. However, the formulated problem is highly nonconvex due to the secrecy rate function and the dynamic relay power constraint. By exploiting the hidden convexity, we transform the original problem to a solvable reformulation via the successive convex approximation and constrained concave-convex procedure, which can provide a high-level approximated beamforming solution. Then, an iterative algorithm is proposed to obtain the solution. Numerical results showed the effectiveness of the proposed robust scheme.