Abstract
By the integration of cooperative cognitive radio (CR) and nonorthogonal multiple access (NOMA), cooperative CR NOMA networks can improve the spectrum efficiency of wireless networks significantly. Due to the openness and exposure of wireless signals, secure communication is an important issue for cooperative CR NOMA networks. In this paper, we investigate the physical layer security design for cooperative CR NOMA networks. Our objective is to achieve maximum secrecy rate of the secondary user by designing optimal beamformers and artificial noise covariance matrix at the multiantenna secondary transmitter under the quality-of-service at the primary user and the transmit power constraint at the secondary transmitter. We consider the practical case that the channel state information (CSI) of the eavesdropper is imperfect, and we model the imperfect CSI by the worst-case model. We show that the robust secrecy rate maximization problem can be transformed to a series of semidefinite programmings based on S-procedure and rank-one relaxation. We also propose an effective method to recover the optimal rank-one solution. Simulations are provided to show the effectiveness of our proposed robust secure algorithm with comparison to the nonrobust secure design and traditional orthogonal multiple access schemes.
Highlights
Cooperative cognitive radio (CR) is a promising technique for easing the strain on the spectrum resources, where the secondary user (SU) works as a relaying station and assists the primary user (PU) to transmit the signals, and as a return, the SU can use the spectrum occupied by the PU to serve its own cognitive user [1,2,3,4,5]
We focus on secure beamforming and artificial noise (AN) covariance matrix design problem for a cooperative CR Nonorthogonal multiple access (NOMA) network, where the channel state information (CSI) of the eavesdropper is considered to be imperfect
We investigate AF relaying in the cooperative CR NOMA network, where the multiantenna secondary transmitter (ST) helps relaying the information from the primary transmitter (PT) to the PU and serves its own SU, while an eavesdropper located near the SU intends to overhear the signal intended for the SU
Summary
Cooperative cognitive radio (CR) is a promising technique for easing the strain on the spectrum resources, where the secondary user (SU) works as a relaying station and assists the primary user (PU) to transmit the signals, and as a return, the SU can use the spectrum occupied by the PU to serve its own cognitive user [1,2,3,4,5]. Physical layer security has been proposed in [21,22,23,24,25,26,27] for cooperative CR NOMA networks, where the security performance of communication networks can be greatly improved by the cooperation of the relay node (i.e., SU). E authors in [21] studied the physical layer security in a Security and Communication Networks cooperative CR NOMA network where all the nodes had a single antenna and the SU employed amplify-and-forward (AF) relaying to forward the PU’s signal, aiming to analyze the security performance of the PU and throughput of the SU. In the study by She et al [23], the authors investigated the optimization of power allocation and transmit covariance matrix to improve the security energy efficiency of the SU for a DF-relaying cooperative CR NOMA network. In the study by She et al [23], the authors investigated the optimization of power allocation and transmit covariance matrix to improve the security energy efficiency of the SU for a DF-relaying cooperative CR NOMA network. e works [25,26,27] focused on the DFrelaying cooperative CR NOMA network in order to analyze the security performance of the network
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