In this paper, we develop a non-orthogonal multiple access (NOMA)-based cooperative network against multiple eavesdroppers, in which the source delivers confidential information using rate-splitting approach to the destination under the help/protection of the full-duplex relay. Specifically, by splitting the symbol into two sub-symbols at the source, the channel gain differences created by the relay can be exploited between two sub-symbols to use spectral resource more efficiently with NOMA proposal. On the other hand, by enabling the full-duplex technique in the first phase, the relay not only forwards the confidential information to the destination but also keeps radiating artificial noises to confuse multiple potential eavesdroppers. Different decoding schemes based on the successive interference cancellation (SIC) are proposed for the destination, relay, and eavesdroppers. Closed-form expressions of the ergodic secrecy rates are derived, which perfectly match the computer simulation results for our proposed network.
In this paper, we develop a non-orthogonal multiple access (NOMA)-based cooperative network against multiple eavesdroppers, in which the source delivers confidential information using rate-splitting approach to the destination under the help/protection of the full-duplex relay. Specifically, by splitting the symbol into two sub-symbols at the source, the channel gain differences created by the relay can be exploited between two sub-symbols to use spectral resource more efficiently with NOMA proposal. On the other hand, by enabling the full-duplex technique in the first phase, the relay not only forwards the confidential information to the destination but also keeps radiating artificial noises to confuse multiple potential eavesdroppers. Different decoding schemes based on the successive interference cancellation (SIC) are proposed for the destination, relay, and eavesdroppers. Closed-form expressions of the ergodic secrecy rates are derived, which perfectly match the computer simulation results for our proposed network.
In this paper, we develop a secure non-orthogonal multiple access (NOMA)-based two-way relay network, in which two users wish to exchange their NOMA signals via a trusted relay in the presence of an eavesdropper. To ensure secure communications, the relay not only forwards confidential information to the legitimate users but also keeps emitting jamming signals all the time to confuse any potential eavesdropper. Specifically, we equip the relay and each user with the full-duplex technique in the multiple-access phase to combat the eavesdropping and improve the data transmission efficiency, respectively. Different decoding schemes based on the successive interference cancellation (SIC) are proposed for the legitimate users, relay, and eavesdropper. Closed-form expressions for the achievable ergodic secrecy rates of all data symbols are derived, validated by the excellent fitting to the computer simulation results for our proposed network.
In this paper, we develop a non-orthogonal multiple access (NOMA)-based two-way relay network with secrecy considerations, in which two users wish to exchange their NOMA signals via a trusted relay in the presence of single and multiple eavesdroppers. To ensure secure communications, the relay not only forwards confidential information to the legitimate users but also keeps emitting jamming signals all the time to degrade the performance of any potential eavesdropper. Moreover, we equip the relay and each user with the full-duplex technique in the multiple-access phase to combat the eavesdropping and improve the data transmission efficiency, respectively. We propose different decoding schemes based on the successive interference cancellation for the legitimate users, relay, and eavesdroppers. Closed-form expressions for the achievable ergodic secrecy rates of all data symbols under both single- and multiple-eavesdropper cases are derived, validated by the excellent fitting to the computer simulation results for our proposed network.
Non-orthogonal multiple access (NOMA) has been envisioned as a promising multiple access technique to improve spectral efficiency and provide massive connectivity in future wireless networks. However, the inherited security issues with NOMA should be carefully addressed to further exploit its potential benefits in NOMA enabled wireless networks. As such, we consider a cooperative NOMA network, where a source uses the NOMA to simultaneously communicate with a multi-antenna near-user and a far-user. While directly communicating with the near-user, the source employs multiple full-duplex (FD) decode-and forward (DF) relays to establish communication with the far-user in the presence of a passive eavesdropper. To address the eavesdropping in this cooperative NOMA network, we propose a new two-phase FD-based artificial noise (AN) scheme with different relay selection techniques. In the first phase, the selected FD relay emits AN to confuse the eavesdropper while receiving the superimposed signal from the source. In the second phase, the selected relay performs exclusive OR (XOR) operation on both the message intended to the far-user and the AN before broadcasting the resulting mixed signal. By utilizing null-space beamforming, self-interference cancellation techniques and DF-XOR cooperative protocol, the AN in the proposed scheme can be efficiently eliminated at the near-user and far-user as well as at the selected relay. However, the AN cannot be suppressed at the eavesdropper which serves the purpose of AN through degrading the decoding capability of the eavesdropper. We evaluate the performance of the proposed scheme in terms of security-reliability trade-off (SRT). For the AN-aided scheme with max-min and partial relay selection techniques, we theoretically derive the exact and asymptotic closed-form expressions of the outage probability and intercept probability. Numerical results have been provided to validate the derivations. In addition, the results reveal that the SRT of the near-user and far-user can be improved by increasing the number of antennas at the near-user and the number of relays.
Non-orthogonal multiple access (NOMA) and wireless energy harvesting are two promising technologies for improving spectral efficiency and energy efficiency, respectively. In this paper, we study the physical layer security of a wireless-powered full-duplex (FD) relay-aided cooperative NOMA system. In particular, the source is wiretapped by an eavesdropper, and the FD relay assists the transmission from the source to a near user and a far user with self-energy recycling. To enhance the security performance of the system, we propose an artificial noise (AN)-aided cooperative transmission scheme, in which the relay emits a jamming signal to confuse the eavesdropper while receiving the signal from the source. For the proposed scheme, the ergodic secrecy sum rate (ESSR) is derived to characterize the secrecy performance and a lower bound of ESSR is obtained. Finally, numerical results verify the accuracy of the theoretical analysis of the proposed AN-aided secure transmission scheme. The superiority of the proposed scheme is also demonstrated since this scheme can achieve better secrecy performance, compared to the conventional cooperative NOMA scheme.
In a downlink non-orthogonal multiple access (NOMA) system, the reliable transmission of cell-edge users cannot be guaranteed due to severe channel fading. On the other hand, the presence of eavesdroppers can severely threaten the secure transmission due to the open nature of wireless channel. Thus, a two-user NOMA system assisted by a multi-antenna decode-and-forward relay is considered in this paper, and a two-stage jamming scheme, full-duplex-jamming (FDJam), is proposed to ensure the secure transmission of NOMA users. In the FDJam scheme, using full-duplex, the relay transmits the jamming signal to the eavesdropper while receiving confidential messages in the first stage, and the base station generates the jamming signal in the second stage. Furthermore, we eliminate the self-interference and the jamming signal at the relay and the legitimate node, respectively, through relay beamforming. To measure the secrecy performance, analytical expressions for secrecy outage probability (SOP) are derived for both the cell-center and cell-edge users, and the asymptotic SOP analysis at high transmit power is presented as well. Moreover, two benchmark schemes, half-duplex-jamming and full-duplex-no-jamming, are also considered. Simulation results are presented to show the accuracy of the analytical expressions and the effectiveness of the proposed scheme.
In this paper, we investigate an artificial-noise (AN) aided secure transmission for non-orthogonal multiple access (NOMA) full-duplex (FD) relay network. We propose a novel joint NOMA and AN-aided full-duplex relay (NOMA-ANFDR) scheme to enhance the physical security. In this scheme, the optimal power allocation between the information and the AN signal is determined such that the capacity of the two end-to-end (i.e., two source-relay-destination pairs) channel are maximized to ensure the highest quality of cooperative transmission. To fully examine the benefits of the NOMA-ANFDR scheme, we derive a new closed-form expression for the secrecy outage probability.We show that the NOMA-ANFDR scheme significantly outperforms the joint NOMA and AN in half-duplex relay (NOMA-ANHDR) scheme as well as the NOMA-HDR scheme in terms of minimum secrecy outage probability and effect secrecy throughout. This result indicates that adopting the joint of FD and AN technique at relays can effectively enhance the physical layer secrecy performance in the NOMA cooperative network.