Secrecy Outage Minimization for Wireless-Powered Relay Networks With Destination-Assisted Cooperative Jamming

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To solve security vulnerability and energy scarcity problems in relay, we propose two secure relaying protocols, power splitting-based relaying (PSR) and time switching-based relaying (TSR), in a wireless-powered relay network with destination-assisted cooperative jamming. In these protocols, the relay adaptively controls the amount of energy harvested from the received signals using PS or TS policy, considering information leakage to the eavesdropper. We first prove the convexity of the secrecy outage probability with respect to the PS ratio ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho $ </tex-math></inline-formula> ) and TS ratio ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> ), and then derive the closed-form expressions of the optimal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> for minimizing secrecy outage under the signal-to-noise ratio (SNR) assumption. Numerical results reveal that the proposed PSR and TSR protocols using the derived <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> can achieve near-optimal performance in terms of secrecy outage. It is observed that the optimal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> do not depend on the eavesdropping channels in a high SNR regime such that the near-optimal secrecy outage can be achieved practically without knowledge of the eavesdropper location. Furthermore, intensive simulations reveal that it is advantageous to allocate more power to energy harvesting for PSR, whereas more time to signal processing for TSR to minimize secrecy outage.