Full-duplex wireless-powered jammer aided secure communication for cognitive radio networks

A novel full-duplex (FD) wireless-powered cooperative jammer (CJ) aided transmit scheme is proposed to enhance the security for cognitive radio networks (CRNs). The CJ operates in an FD mode, so that it can harvest energy from the signals that transmitted from the secondary transmitter (ST), and send jamming noise (JN) to confuse the potential malicious eavesdroppers in the meantime. We aim to maximize the achievable secrecy rate of the secondary system by jointly designing the transmit covariance matrix at the ST and the JN covariance matrix at the CJ, while subject to the transmit power constraints at the ST and the CJ, and the interference constraint at the primary user (PU). Specifically, we formulate the secrecy rate maximization problem based on the perfect channel state information (CSI). As a solution, we propose a two-stage optimization algorithm to solve the non-convex problem. More particularly, we extend our proposed scheme to the imperfect CSI case. To tackle the robust secrecy rate maximization problem, we exploit the two-stage optimization algorithm with the extended S-procedure and rank-one relaxation. Simulation results have validated that our proposed scheme outperforms, in terms of secrecy rate, the isotropic JN scheme and the scheme without aided by CJ for the perfect CSI scenario. In addition, the robust scheme achieves higher secrecy rate gains as compared to the non-robust scheme for the imperfect CSI case. (C) 2018 Published by Elsevier B.V.