Safeguarding Next Generation Multiple Access Using Physical Layer Security Techniques: A Tutorial

TL;DR

The paper surveys physical layer security for NOMA in NGMA, addressing information-theoretic, quantum-safe, and covert approaches, and highlights how inter-user interference, large antenna arrays, and emerging technologies can be leveraged for secrecy. It systematically covers theory, practical prototypes, and ML-enabled secrecy resource allocation, while discussing ISAC, satellites, RIS, ELAA, and novel quantum-secure schemes. Key contributions include a structured taxonomy of secure NOMA techniques, prototype insights, and a forward-looking agenda identifying open challenges and promising research directions. The work is significant for practitioners and researchers aiming to design secure, scalable, and energy-efficient NOMA-enabled 6G networks with robust privacy and covert capabilities.

Abstract

Driven by the ever-increasing requirements of ultra-high spectral efficiency, ultra-low latency, and massive connectivity, the forefront of wireless research calls for the design of advanced next generation multiple access schemes to facilitate provisioning of these stringent demands. This inspires the embrace of non-orthogonal multiple access (NOMA) in future wireless communication networks. Nevertheless, the support of massive access via NOMA leads to additional security threats, due to the open nature of the air interface, the broadcast characteristic of radio propagation as well as intertwined relationship among paired NOMA users. To address this specific challenge, the superimposed transmission of NOMA can be explored as new opportunities for security aware design, for example, multiuser interference inherent in NOMA can be constructively engineered to benefit communication secrecy and privacy. The purpose of this tutorial is to provide a comprehensive overview on the state-of-the-art physical layer security techniques that guarantee wireless security and privacy for NOMA networks, along with the opportunities, technical challenges, and future research trends.

Figures (28)

• Figure 1: Structural diagram of the tutorial.
• Figure 2: System model and signal processing of a two-user NOMA communication scenario.
• Figure 3: An illustration of threshold regions in terms of $(\gamma_1,\gamma_2)$.
• Figure 4: Common outage probability of different strategies. The distance between the AP and user 1 is $40\,m$, and the distance between the AP and user 2 is $30\,m$. Both small-scale Rayleigh fading and large-scale path loss are considered. The path loss is modeled by $(d_0/d)^\nu$, where $d_0=10\,m$ is the reference distance and $\nu=2.7$ is the path loss exponent. The power allocation coefficient is $0.7$.
• Figure 5: Scenario for a multi-carrier NOMA system: (a) Communication model; (b) Prototype.