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Physical layer security scheme based on channel estimation error compensation in non-orthogonal multiple access systems

Chaosheng Qiu, Xu Datong

Published Feb 1, 2026• 0 citations

Abstract

Non-orthogonal multiple access (NOMA) has been regarded as a key enabling technology for sixth-generation (6G) communications, since resource utilization was significantly enhanced by allowing multiple users to share the same time-frequency and spatial resources. However, in power-domain NOMA systems, user privacy information may be eavesdropped due to the application of successive interference cancellation, which introduces potential security vulnerabilities. To address this issue, various physical layer security schemes have been proposed in the literature, while their performance was highly dependent on sufficiently accurate channel state information (CSI). When channel estimation accuracy was insufficient, the achievable security performance often failed to meet expectations. To overcome this limitation, a physical layer security scheme based on channel estimation error compensation was proposed under imperfect CSI conditions. First, channel estimation errors were compensated through an additional low-complexity estimation process. Then, the transceiver was redesigned based on the more accurate CSI obtained after error compensation. Simulation results demonstrated that the proposed scheme significantly improved the secrecy rate and transmission reliability under different levels of channel estimation errors and signal-to-noise ratio. This scheme now provides a feasible solution to the physical layer security problem in scenarios where channel estimation errors exist.

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Non-orthogonal multiple access (NOMA) has been regarded as a key enabling technology for sixth-generation (6G) communications, since resource utilization was significantly enhanced by allowing multiple users to share the same time-frequency and spatial resources. However, in power-domain NOMA systems, user privacy information may be eavesdropped due to the application of successive interference cancellation, which introduces potential security vulnerabilities. To address this issue, various physical layer security schemes have been proposed in the literature, while their performance was highly dependent on sufficiently accurate channel state information (CSI). When channel estimation accuracy was insufficient, the achievable security performance often failed to meet expectations. To overcome this limitation, a physical layer security scheme based on channel estimation error compensation was proposed under imperfect CSI conditions. First, channel estimation errors were compensated through an additional low-complexity estimation process. Then, the transceiver was redesigned based on the more accurate CSI obtained after error compensation. Simulation results demonstrated that the proposed scheme significantly improved the secrecy rate and transmission reliability under different levels of channel estimation errors and signal-to-noise ratio. This scheme now provides a feasible solution to the physical layer security problem in scenarios where channel estimation errors exist.

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.

This article clarifies pivotal security issues in the context of non-orthogonal multiple access (NOMA) technology and presents potential methodologies to address them at the physical layer. Specifically, we first clarify the channel conditions for an external eavesdropper to use successive interference cancellation (SIC) for cancelling interference, which has recently been considered in the literature of physical layer security for NOMA. We then explicitly demonstrate the advantages and drawbacks of using NOMA to achieve wireless communication security; that is, NOMA improves the security of a strong user, but reduces the security of a weak user. Finally, we discuss a strategy to protect the confidentiality of a weak user's information from a strong user, while still allowing the latter to seek SIC for harnessing the benefits of NOMA. Research challenges and future works along the aforementioned three different aspects of security issues in NOMA are presented in this article.

Non-Orthogonal Multiple Access (NOMA) is a potential candidate for 6th Generation (6G) cellular commu-nication. It outperforms the conventional Orthogonal Multiple Access (OMA) schemes in terms of connectivity, spectral efficiency and latency. In spite of these advantages, NOMA faces information security challenges. In this paper, two phases of NOMA are considered which are the direct transmission phase and the cooperative phase. In the direct transmission phase, all users receive the superimposed signal while in the cooperative phase the user with a higher channel condition helps the user with the weaker channel condition. In the proposed work, the secrecy rate of users with weaker channel conditions is considered for maximisation under total power and Quality-of-Service (QoS) constraints. Our results show an improvement in the secrecy rate.

This paper presents a novel physical layer security (PLS) scheme for non-orthogonal multiple access (NOMA) systems that jointly enhances secrecy and bit error rate (BER). The proposed approach leverages power hopping (PH), wherein users’ power coefficients are dynamically allocated to obscure both the decoding order and actual power allocation from potential eavesdroppers. This uncertainty significantly reduces the feasibility of successful interception. Analytical expressions for the BER and secrecy outage probability (SOP) are derived under diverse channel conditions and eavesdropping scenarios. The theoretical findings, validated through Monte Carlo simulations, confirm that the proposed scheme robustly preserves the secrecy of legitimate users regardless of the eavesdropper’s channel quality. Moreover, the approach yields substantial improvements in both BER and SOP, particularly for the near user.

Non-orthogonal multiple access (NOMA) can be combined with physical layer security technology to greatly improve spectral efficiency while tackling security issues for the Internet of Things (IoT) networks. This paper investigates the security performance in a fifth-generation (5G) downlink NOMA system with an untrusted user in the presence of imperfect successive interference cancellation (SIC). Analytical expressions of secrecy outage probability (SOP) and connection outage probability (COP) are derived as performance metrics to evaluate the secrecy of the proposed system. In order to further improve the secrecy performance, we propose an optimal power allocation scheme based on two users' different quality of service (QoS) requirements and obtain a closed-form solution of the optimal parameter. Through numerical simulations and exhaustive search algorithm, we validate the correctness of the derived analytical results. It is proved that the proposed power allocation scheme can achieve the optimal secrecy performance.

Spectrum sharing and successive interference cancellation (SIC) techniques used in power-domain non-orthogonal multiple access (NOMA) systems impose secrecy challenges because untrusted users can decode the information of trusted ones. In this context, physical layer security (PLS) appears as an alternative to address the possible risks. In this paper, the secrecy performance of a power-domain NOMA network that employs improper Gaussian signals (IGS) is explored for the first time. The system model considers the downlink where a base station (BS) employs IGS to transmit information to a couple of users. It is assumed that the user closest to the BS is the trusted user and the user furthest away is the untrusted user. The network security is evaluated in terms of the secrecy outage probability (SOP) considering imperfect SIC at the receivers. Expressions to evaluate the achievable rate for each user are calculated and, with these results, an expression to evaluate the SOP is also obtained. Results show that IGS allow the security to be improved, i.e., the SOP can be reduced if the impropriety degree of the transmitted signals is properly selected based on the operation parameters.