Secure Communications for Wireless-Powered Cooperative NOMA Systems Under Imperfect CSI and Imperfect SIC

In this paper, we investigate the robust relay and jammer selection for secure communications in wireless-powered cooperative non-orthogonal multiple access (NOMA) networks under imperfect channel state information (CSI) and imperfect successive interference cancellation (SIC). The proposed secrecy communication scheme consists of two transmission phases. In the first transmission phase, a relay is selected from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> candidates to assist in the transmission from the base station (BS) to a pair of NOMA users. A wireless-powered jammer is selected from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> candidates based on the criterion of maximizing the generated interference to the eavesdropper (Eve), and the selected jammer harvests energy from the transmitted signals of the BS. In the second transmission phase, the selected relay serves NOMA users, and the selected wireless-powered jammer emits artificial noise (AN) to confuse the Eve. To assess the transmission security and reliability of the proposed scheme, closed-form expressions for the connection outage probability (COP), secrecy outage probability (SOP), effective secrecy throughput (EST), and secrecy diversity order for a pair of NOMA users are derived under imperfect CSI and imperfect SIC, revealing that our robust relay and jammer selection scheme improves the transmission performance of NOMA users. Numerical results verify the correctness of our theoretical analysis and demonstrate the performance superiority of the proposed scheme to existing schemes.