RIS-Assisted Near-Field Physical Layer Security for mmWave In-Band Full Duplex Systems
IEEE Open Journal of the Communications Society, cilt.7, ss.6557-6575, 2026 (ESCI, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 7
- Basım Tarihi: 2026
- Doi Numarası: 10.1109/ojcoms.2026.3701605
- Dergi Adı: IEEE Open Journal of the Communications Society
- Derginin Tarandığı İndeksler: Emerging Sources Citation Index (ESCI), Scopus, Compendex, INSPEC, Directory of Open Access Journals
- Sayfa Sayıları: ss.6557-6575
- Anahtar Kelimeler: Artificial noise, fairness, full-duplex, mmWave, optimization, physical layer security, power control, power efficiency, reconfigurable intelligent surface, secrecy capacity, sum rate maximization
- İstanbul Medipol Üniversitesi Adresli: Evet
Özet
To address the growing threat of eavesdropping in millimeter wave (mmWave) communications—where high-frequency signals suffer from severe propagation losses and are easily blocked—robust physical layer security (PLS) solutions are essential. Scaling reconfigurable intelligent surfaces (RISs) to very large apertures, especially at high frequencies, shifts operation from the conventional far-field to the near-field regime. In this domain, the spherical nature of wavefronts must be considered, and signal energy can be beamfocused into a finite region, creating a vulnerable zone (VZ), within which unintended receivers are exposed to elevated signal levels and an increased likelihood of successful signal interception, in contrast to locations outside the focal region where signal power diminishes sharply. Recognizing the security risks posed by the VZ, we propose a near-field RIS-assisted in-band full-duplex (IBFD) system that integrates PLS without requiring any knowledge of the eavesdropper’s location, channel state, or numbers. The design employs artificial noise (AN) and near-field beamfocusing to support simultaneous bidirectional transmission of both confidential data and AN signals, enhancing secrecy while preserving quality-of-service (QoS) for legitimate users. An intelligent RIS-assisted power control strategy is employed, where the transmit powers and RIS phase shifts are jointly configured to both enhance the secrecy rate of legitimate users and suppress information leakage to unintended receivers within the defined VZ. We formulate and solve optimization problems targeting three key objectives: minimizing total transmit power, maximizing the minimum secrecy rate (fairness), and maximizing the sum-rate, while also investigating the impact of RIS size. Closed-form expressions are derived for efficient power allocation under stringent QoS constraints. Simulation results validate the analytical findings, demonstrating that the proposed scheme achieves notable gains in weighted secrecy capacity compared to scenarios where AN is applied solely at Alice or solely at Bob, achieving an overall improvement of approximately 35% with N = 10000 over these baselines. Furthermore, the method improves energy efficiency by reducing transmit power at Alice and Bob by 31% and 15%, respectively, as the eavesdropper’s QoS constraint is relaxed from 8% to 10% of the legitimate rate.