This paper investigates a secure wireless-powered sensor network (WPSN) with the aid of a cooperative jammer (CJ). A power\nstation (PS) wirelessly charges for a user equipment (UE) and the CJ to securely transmit information to an access point (AP) in\nthe presence of multiple eavesdroppers. Also, the CJ are deployed, which can introduce more interference to degrade the\nperformance of the malicious eavesdroppers. In order to improve the secure performance, we formulate an optimization\nproblem for maximizing the secrecy rate at the AP to jointly design the secure beamformer and the energy time allocation. Since\nthe formulated problem is not convex, we first propose a global optimal solution which employs the semidefinite programming\n(SDP) relaxation. Also, the tightness of the SDP relaxed solution is evaluated. In addition, we investigate a worst-case scenario,\nwhere the energy time allocation is achieved in a closed form. Finally, numerical results are presented to confirm effectiveness of\nthe proposed scheme in comparison to the benchmark scheme.
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