The close relationship between multiple access technologies and efficient spectrum utilization makes power- domain non-orthogonal multiple access (NOMA) an attractive solution that enables the support of high data rates, user fairness and low-latency communications in 5G and next generation networks. However, user pairing and successive interference cancelation applied in NOMA facilitates eavesdropping on the far user’s signal by the near user establishing security as a main issue in NOMA systems. Due to their numerous advantages, the means of physical layer security (PLS) are extremely suitable to combat internal NOMA eavesdropping. Up to the present only a few studies exist which examine different PLS approaches against eavesdropping on the far user by the near user. Among them are a joint beamforming and power allocation algorithm, an angle conversion method that alters the original signal constellation before transmission, and a directional modulation approach. In this paper, the available PLS methods against eavesdropping on the far user by the near user are investigated and the main advantages and drawbacks of these methods are compared.
The close relationship between multiple access technologies and efficient spectrum utilization makes power- domain non-orthogonal multiple access (NOMA) an attractive solution that enables the support of high data rates, user fairness and low-latency communications in 5G and next generation networks. However, user pairing and successive interference cancelation applied in NOMA facilitates eavesdropping on the far user’s signal by the near user establishing security as a main issue in NOMA systems. Due to their numerous advantages, the means of physical layer security (PLS) are extremely suitable to combat internal NOMA eavesdropping. Up to the present only a few studies exist which examine different PLS approaches against eavesdropping on the far user by the near user. Among them are a joint beamforming and power allocation algorithm, an angle conversion method that alters the original signal constellation before transmission, and a directional modulation approach. In this paper, the available PLS methods against eavesdropping on the far user by the near user are investigated and the main advantages and drawbacks of these methods are compared.
Non-orthogonal multiple access (NOMA) is an important multiple access mode in 5G. Nevertheless, eavesdropping may appear between the users in NOMA. In this case, physical layer security schemes can be introduced to combat eavesdropping. Different from the existing schemes, eavesdropping suppression in NOMA should be based on several rules: (i) successive interference cancellation (SIC) should be normally operated; (ii) each user can not attain others' privacy information; (iii) each adopted scheme had better not to depend on the spatial disparity between channels (since the channels may have the strong spatial similarity). Therefore, we propose a novel scheme to adapt to these rules. In our scheme, the original signals of users are separately transformed into the transmitted signals by a well-designed angle conversion method, and the principles of these variations for diverse users are different. Furthermore, an auxiliary mechanism with full-duplex technology is devised to guarantee the users to safely learn the principles, respectively. Through this scheme, each user can deduce other users' transmitted signals for SIC, while the original signals are difficult to be determined from transmitted signals. Hence, our scheme can effectively improve security.
Non-orthogonal multiple access systems will face serious physical layer security (PLS) problems in the present of internal eavesdropper. However, in the existing schemes, it's difficult to always guarantee the positive secrecy rate of the system. To this end, we consider the PLS against internal eavesdropping in two-users scenario and the beamforming design and optimal power allocation problems are given. The developed analytical results demonstrate that the proposed scheme can absolutely achieve positive secrecy rate if provided sufficient power. Simulation results show that the performance of proposed scheme is better than the existing solutions.
Nonorthogonal multiple access (NOMA) has been viewed as a potential candidate for the upcoming generation of wireless communication systems. Comparing to traditional orthogonal multiple access (OMA), multiplexing users in the same time-frequency resource block can increase the number of served users and improve the efficiency of the systems in terms of spectral efficiency. Nevertheless, from a security viewpoint, when multiple users are utilizing the same time-frequency resource, there may be concerns regarding keeping information confidential. In this context, physical layer security (PLS) has been introduced as a supplement of protection to conventional encryption techniques by making use of the random nature of wireless transmission media for ensuring communication secrecy. The recent years have seen significant interests in PLS being applied to NOMA networks. Numerous scenarios have been investigated to assess the security of NOMA systems, including when active and passive eavesdroppers are present, as well as when these systems, are combined with relay and reconfigurable intelligent surfaces (RISs). Additionally, the security of the ambient backscatter (AmB)-NOMA systems are other issues that have lately drawn a lot of attention. In this article, a thorough analysis of the PLS-assisted NOMA systems research state-of-the-art is presented. In this regard, we begin by outlining the foundations of NOMA and PLS, respectively. Following that, we discuss the PLS performances for NOMA systems in four categories depending on the type of the eavesdropper, the existence of relay, RIS, and AmB systems in different conditions. Finally, a thorough explanation of the most recent PLS-assisted NOMA systems is given.
Non-orthogonal multiple access (NOMA) has been widely considered as a promising technology to enable high-efficient wireless transmissions in future 5G communication systems. In this chapter, we investigate single-input single-output (SISO) NOMA systems from the perspective of physical layer security. There into, two different SISO NOMA systems are studied in sequence so as to explore security issues in NOMA. First, we attempt the physical layer security technique in a SISO NOMA system which consists of a transmitter, multiple legitimate users and an eavesdropper who aims to wiretap the messages intended for all legitimate users. The objective is to maximise sum of secrecy rates subject to an individual quality of service constraint for each legitimate user, respectively. The investigations in this system will provide a preliminary analysis of the secure performance of SISO NOMA systems. Second, on the basis of the SISO NOMA system previously studied, a multi-antenna jammer is additionally equipped to enhance secure transmissions of the system. The joint optimisation of power allocation and beamforming design is considered. The efforts in this second system aim to propose an effective solution for realising secure transmissions for each legitimate user.
Non-orthogonal multiple access (NOMA) is emerging as a popular radio access technique to serve multiple users under the same resource block to improve spectral efficiency in 5G and 6G communication. But the resource sharing in NOMA causes concerns on data security. Since power domain NOMA exploits the difference in channel properties for bandwidth-efficient communication, it is feasible to ensure data confidentiality in NOMA communication through physical layer security techniques. In this work, we propose to ensure resistance against internal eavesdropping in NOMA communication through a secret key derived from channel randomness. A unique secret key is derived from the channel of each NOMA user; which is used to randomize the data of the respective user before superposition coding (SC) to prevent internal eavesdropping. The simulation results show that the proposed system provides very good security against internal eavesdropping in NOMA.
The key idea of non-orthogonal multiple access (NOMA) is to serve multiple users in the same resource block to improve the spectral efficiency. Whereas due to the resource sharing, a security flaw of NOMA emerges in the presence of internal untrusted users, especially untrusted near users who are closer to the base station and can easily access the confidential information for paired far users. To mitigate the flaw, in this paper, we investigate the reliable and secure transmission of NOMA systems with untrusted near users, and propose joint beamforming and power allocation (JBP) scheme for the scenario. Meanwhile, from security point of view, we extend to a worse-case scenario where both untrusted near users and external eavesdroppers exist, and propose joint artificial noise aided beamforming and power allocation (JANBP) scheme to achieve a reliable and secure transmission for the scenario. The exact and asymptotic closed-form expressions of secrecy outage probability (SOP) for the two scenarios are derived to evaluate the secrecy performance achieved by the proposed schemes, respectively. The analysis and simulation results show the superiority of the proposed JBP and JANBP schemes in terms of combating internal and external eavesdropping, and also indicate the two schemes can achieve the same SOP at high SNR.