Abstract
The integration of non-orthogonal multiple access (NOMA) in cognitive radio (CR) networks has demonstrated how to enhance spectrum efficiency and achieve massive connectivity for future mobile networks. However, security is still a challenging issue due to the wireless transmission environment and the broadcast nature of NOMA. Thus, in this paper, we investigate a beamforming design with artificial noise (AN) to improve the security of a multi-user downlink, multiple-input single-output (MISO) NOMA-CR network with simultaneous wireless information and power transfer (SWIPT). To further support power-limited, battery-driven devices, energy-harvesting (EH) users are involved in the proposed network. Specifically, we investigate the optimal AN, power-splitting ratios, and transmission beamforming vectors for secondary users and EH users in order to minimize the transmission power of the secondary network, subject to the following constraints: a minimum signal-to-interference-plus-noise ratio at the secondary users, minimum harvested energy by secondary users and EH users, maximum power at the secondary transmitter, and maximum permissible interference with licensed users. The proposed solution for the challenging non-convex optimization problem is based on the semidefinite relaxation method. Numerical results show that the proposed scheme outperforms the conventional scheme without AN, the zero-forcing-based scheme and the space-division multiple-access-based method.
Highlights
The rapid development of wireless communications requires advanced communications techniques that can provide massive connectivity, high spectral efficiency, high energy efficiency, and low latency in support of the fast proliferation of the Internet of Things (IoT), mobile devices, and so on
We focus on power-domain non-orthogonal multiple access (NOMA), which can be further combined with other communications technologies (multiple-input single-output (MISO), multiple-input multiple-output (MIMO), cooperative communications) to reach a better yield [11,12,13,14,15,16]
MISO-NOMA-cognitive radio (CR) aided by simultaneous wireless information and power transfer (SWIPT) with EH users, in comparison with an space-division multiple-access (SDMA) approach and with a scheme without artificial noise (AN)
Summary
The rapid development of wireless communications requires advanced communications techniques that can provide massive connectivity, high spectral efficiency, high energy efficiency, and low latency in support of the fast proliferation of the Internet of Things (IoT), mobile devices, and so on. NOMA has surged as another powerful technology to enhance spectrum efficiency while providing high transmission rates and high user densities for future mobile communications [9,10]. Energy-efficient techniques have been investigated for future wireless networks in support of environmental concerns and battery-limited devices, such as sensors and wearables [17]. In this sense, achieving high energy efficiency and recycling energy are the main goals of energy-efficient techniques, where simultaneous wireless information and power transfer (SWIPT). This metric is calculated by the difference between the legitimate and eavesdropper’s channel capacities
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