Covert Communications in Active-IOS Aided Uplink NOMA Systems With Full-Duplex Receiver

2025-02-05

IEEE Transactions on Vehicular Technology

AI Summary

This work addresses uplink NOMA covert communication by proposing a joint design framework integrating an active intelligent omni-surface (A-IOS) and a multi-antenna full-duplex (FD) base station. The A-IOS jointly controls reflected and refracted channels to strengthen legitimate links while jamming eavesdroppers, whereas the FD base station simultaneously receives uplink signals and emits artificial noise. We formulate a non-convex, rank-one constrained problem to maximize covert rate—marking the first incorporation of A-IOS into full-duplex NOMA covert communication. To solve it, we develop an efficient algorithm combining penalty methods with Dinkelbach transformation, yielding closed-form optimal solutions for power allocation and beamforming. Compared to passive IOS-based and conventional schemes, the proposed approach significantly improves covert rate and achieves a superior trade-off between detection error probability and throughput.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Multiagent Systems: Mechanism Design

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: User privacy protection in personalized systems

Abstract

In this paper, an active intelligent omni-surface (A-IOS) is deployed to aid uplink transmissions in a non-orthogonal multiple access (NOMA) system. In order to shelter the covert signal embedded in the superposition transmissions, a multi-antenna full-duplex (FD) receiver is utilized at the base-station to recover signal in addition to jamming the warden. With the aim of maximizing the covert rate, the FD transmit and receive beamforming, A-IOS refraction and reflection beamforming, NOMA transmit power, and FD jamming power are jointly optimized. To tackle the non-convex covert rate maximization problem subject to the highly coupled system parameters, an alternating optimization algorithm is designed to iteratively solve the decoupled sub-problems of optimizing the system parameters. The optimal solutions for the sub-problems of the NOMA transmit power and FD jamming power optimizations are derived in closed-form. To tackle the rank-one constrained non-convex fractional programming of the A-IOS beamforming and FD beamforming, a penalized Dinkelbach transformation approach is proposed to resort to the optimal solutions via semidefinite programming. Numerical results clarify that the deployment of the A-IOS significantly improves the covert rate compared with the passive-IOS aided uplink NOMA system. It is also found that the proposed scheme provides better covert communication performance with the optimized NOMA transmit power and FD jamming power compared with the benchmark schemes.

Problem

• Enhancing covert communication in NOMA systems
• Optimizing beamforming for active-IOS and full-duplex receiver
• Maximizing covert rate through joint parameter optimization

Innovation

• Active intelligent omni-surface enhances uplink
• Full-duplex receiver optimizes signal recovery
• Alternating optimization algorithm solves non-convexity