Secure Beamforming and Ergodic Secrecy Rate Analysis for Amplify-and-Forward Relay Networks With Wireless Powered Jammer

In this correspondence, we consider an amplify-and-forward relay network in which relayed information is overheard by an eavesdropper. In order to confound the eavesdropper, a wireless-powered jammer is also considered which harvests energy from a multiple-antenna source. We proposed a new secure beamforming scheme in which beamforming vector is a linear combination of the energy beamforming (EB) and information beamforming (IB) vectors. In particular, we present a new closed-form solution for the proposed beamforming vector which is shown to achieve a near-optimal secrecy capacity for asymptotic regime of a large number of antennas at the source. Moreover, it is also demonstrated that the proposed beamforming vector achieves significantly higher secrecy rate as compared to the trivial EB and IB vectors. A tight closed-form approximation for the ergodic secrecy rate is also derived for a large number of antennas. Finally, numerical examples and simulations are provided which validate our analytical results.