Grover-Based PLS: AUD and Beamforming with Artificial Noise in CD-NOMA

2026-07-02

AI Summary

This work proposes a novel active user detection (AUD) scheme integrating Grover’s quantum search algorithm for sixth-generation (6G) massive connectivity and ultra-low latency scenarios, marking the first application of Grover-based search to code-domain non-orthogonal multiple access (CD-NOMA) systems. The approach achieves near maximum-likelihood performance while reducing search complexity to quadratic order. Leveraging the AUD outcomes, an artificial noise-aided beamforming mechanism is devised to dynamically align the legitimate channel with the artificial noise direction, thereby jointly mitigating both passive and active eavesdropping. Experimental results demonstrate that the proposed scheme significantly enhances average secrecy rate and effectively widens the rate gap between legitimate and eavesdropping channels compared to baseline methods based on compressive sensing and classical correlator receivers, confirming its efficacy in 6G physical-layer security.

Abstract

Sixth-Generation (6G) networks will require massive connectivity, ultra-low latency, and robust security, making reliable Active User Detection (AUD) essential for interference control and physical layer protection. This letter proposes a Grover-based physical layer security (PLS) framework for a code-domain non-orthogonal multiple access (CD-NOMA) network, where the base station employs artificial-noise (AN)-assisted beamforming and identifies the active set via Grover's quantum search algorithm. We consider two threat models: passive eavesdroppers formed by detected inactive users, and active eavesdroppers selected as the top f% most frequent transmitters among detected active users. By aligning beams and AN with the Grover-based AUD output, the proposed scheme enlarges the main-wiretap rate gap and significantly improves the average secrecy rate compared with compressive sensing and classical correlation receiver baselines, while approaching maximum-likelihood detection performance with a quadratic reduction in search complexity. The impact of the information/AN power split, the base station transmit power, and the fraction of highly active users treated as eavesdroppers on secrecy is characterized through numerical simulations, and design insights are extracted for 6G PLS under both passive and active eavesdropping.

Problem

• Active User Detection
• Physical Layer Security
• CD-NOMA
• Eavesdropping
• 6G networks

Innovation

• Grover's quantum search
• physical layer security
• active user detection
• artificial noise
• CD-NOMA