In 5G wireless communication networks, Non-Orthogonal Multiple Access (NOMA) has attracted much attention in recent years. This paper investigates physical layer security of a NOMA system with Full Duplex Relay (FDR) and Half Duplex Relay (HDR). This system consists of one eavesdropper and two legal NOMA users where a dedicated FDR (or HDR) assists far user. In order to characterize the secrecy performance of the considered scenario, new exact expressions are derived for the Secrecy Outage Probability (SOP) of both FDR and HDR systems. Monte Carlo simulations are provided to verify the derived analytical results. Simulations demonstrate that, the NOMA-FDR system attains better performance compared to the NOMA-HDR system for both users. Also, we find that far user has always poor secrecy against near user.
In 5G wireless communication networks, Non-Orthogonal Multiple Access (NOMA) has attracted much attention in recent years. This paper investigates physical layer security of a NOMA system with Full Duplex Relay (FDR) and Half Duplex Relay (HDR). This system consists of one eavesdropper and two legal NOMA users where a dedicated FDR (or HDR) assists far user. In order to characterize the secrecy performance of the considered scenario, new exact expressions are derived for the Secrecy Outage Probability (SOP) of both FDR and HDR systems. Monte Carlo simulations are provided to verify the derived analytical results. Simulations demonstrate that, the NOMA-FDR system attains better performance compared to the NOMA-HDR system for both users. Also, we find that far user has always poor secrecy against near user.
In 5G and beyond wireless communication net-works, non-orthogonal multiple access (NOMA) and Full-Duplex (FD) techniques are considered as promising key techniques. However, the secrecy in NOMA systems has proven to be quite challenging, especially in the presence of multiple eavesdroppers. For this purpose and using the potential of cooperative and FD communication, we investigate the secrecy performance of dual-hop FD Amplify-and-Forward NOMA system. Based on the channel state information of the first hop, partial relay selection (PRS) is performed to determine the best relay. The secrecy outage behaviour of the considered system is studied through deriving closed-form expressions of the secrecy outage probability (SOP) metric for both strong and weak NOMA users under the presence of multiple eavesdroppers in colluding and non-colluding wiretapping scenarios. Numerical results are also provided to verify the derived analytical results.
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 non-orthogonal multiple access (NOMA) systems, serving multiple users in shared resource blocks can allow untrusted users to overhear the messages of other users. In this context, we study a network consisting of a base station (BS), a near user and a far user, where the latter attempts to overhear the message of the former. The near user is a full-duplex (FD) node that can also act as a relay. Two operating scenarios are considered: 1) friendly jammer (FJ), where the FD node broadcasts noise for degrading the channel between the BS and the far user, while receiving data from the BS; and 2) friendly jammer relay (FJR), where, in addition to degrading the channel between the BS and the far user, the FD node relays the message of the far user. We investigate the secrecy performance of the network by characterizing the secrecy outage probability (SOP) in both scenarios. We obtain the exact SOP of the FJ case, and an approximation for the SOP of the FJR scenario, both expressed in closed-form. Numerical results confirm the accuracy of the analytical results. For a given BS power budget and power allocation to the users, it is demonstrated that the jamming and relaying powers are prominent factors to make the NOMA-FJR scheme superior to NOMA-FJ, as well as to conventional and cooperative NOMA schemes.
This paper investigates the application of a cooperative non-orthogonal multiple access (NOMA) network with two down-link users in Nakagami-m fading scenario. The near user acts as a decode-and-forward full-duplex relay for the far user. An eavesdropper is also present in the network, which tries to access messages intended for legitimate users. In full-duplex mode, the near user will send jamming signals and receive desired signals during the first phase. During the second phase, the base station sends jamming signals. Analytical expressions for the secrecy outage probabilities and the overall system secrecy outage probability (SOP) are derived. Also, the optimal power allocation coefficient that minimizes the overall SOP is determined using the simulated annealing (SA) algorithm. We establish that using optimal power allocation coefficients can reduce the overall outage probability significantly as compared to the random selection of the power allocation factor.
In this letter, we consider a non-orthogonal multiple access (NOMA) network with a half-duplex (HD) decode-and-forward (DF) relay to improve physical layer security (PLS) of two users. Two legitimate users of U1 and U2 are far from the multi-antenna base station (BS). Thus, a relay with multi-antenna is used to enhance communication and obtain diversity gain. In the first stage, the BS transmits the superimposed signal to the relay via NOMA. Meanwhile, U1 generates the jamming signal to the eavesdropper (Eve). In the second stage, the relay forwards the signal to two users while the BS transmits the jamming signal to disrupt the eavesdropping. It is assumed that the Eve has strong eavesdropping ability. Thus, we need to introduce jamming to guarantee security. Furthermore, we use U1 instead of a full-duplex (FD) relay to send the jamming signal in the first stage to avoid self-interference. To measure the secrecy performance, a closed-form expression of secrecy outage probability (SOP) is derived for the two users. Simulation results are provided to verify the correctness of the proposed scheme.
Non-orthogonal multiple access (NOMA) is an important technology for the forthcoming 5G and beyond. However, its privacy often suffers from adversarial eavesdropping, especially for the users with higher transmit power. In this paper, we propose a jamming-aided secure transmission scheme for cooperative NOMA networks with a full-duplex (FD) relay. In this scheme, two pairs of users perform secure transmission with the help of a decode-forward (DF) relay, which forwards information and generates artificial jamming to counteract eavesdropping. The precoding vectors are designed to zero-force the artificial jamming at legal receivers. Then, the channel statistics are calculated, based on which the expressions of secrecy outage probability (SOP) are derived. Simulation results show the accuracy of our analysis, and demonstrate that the proposed scheme can effectively reduce the SOP and improve the effective secrecy throughput via artificial jamming and FD relaying.