In this paper, we consider the issue of the secure transmissions for the cognitive radio-based Internet of Medical Things (IoMT)\nwith wireless energy harvesting. In these systems, a primary transmitter (PT) will transmit its sensitive medical information to a\nprimary receiver (PR) by a multi-antenna-based secondary transmitter (ST), where we consider that a potential eavesdropper may\nlisten to the PTâ??s sensitive information. Meanwhile, the STalso transmits its own information concurrently by utilizing spectrum\nsharing. We aim to propose a novel scheme for jointly designing the optimal parameters, i.e., energy harvesting (EH) time ratio\nand secure beamforming vectors, for maximizing the primary secrecy transmission rate while guaranteeing secondary transmission\nrequirement. For solving the nonconvex optimization problem, we transfer the problem into convex optimization form\nby adopting the semidefinite relaxation (SDR) method and Charnesâ??Cooper transformation technique. Then, the optimal secure\nbeamforming vectors and energy harvesting duration can be obtained easily by utilizing the CVX tools. According to the\nsimulation results of secrecy transmission rate, i.e., secrecy capacity, we can observe that the proposed protocol for the considered\nsystem model can effectively promote the primary secrecy transmission rate when compared with traditional zero-forcing (ZF)\nscheme, while ensuring the transmission rate of the secondary system.
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