Multi-user interleaving physical-layer secure transmission in photonics-aided W-band fiber-wireless system enabled by...

Secure and high-capacity transmission is of great importance for future photonics-aided millimeter-wave fiber-wireless systems, especially in W-band links where broadband access and multi-user connectivity are required. To enhance transmission security at the physical layer while maintaining system flexibility, this paper proposes a photonics-aided W-band fiber-wireless scheme using digital frequency conversion and multidimensional interleaved encryption. Two chaotic models are employed to encrypt user bit sequences and symbols with 4D and 2D chaotic sequences, respectively, while interleaving further enhances encryption randomness. Digital frequency conversion generates multiple sub-carriers for collaborative transmission of ciphertext and key. A 2 Gbaud 16QAM encrypted signal is successfully demonstrated in a photonics-aided W-band fiber-wireless coherent transmission system over a 2 m wireless link. Quadrature phase shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) are adopted, with digital frequency points of 2 GHz for the key, 4.5 GHz for User 1, and 7 GHz for User 2. For QPSK, the bit error rate (BER) of encrypted User 1 and User 2 are 3.39 × 10^-4 and 1.01 × 10^-3; for 16QAM, they are 3.5 × 10^-3 and 1.4 × 10^-2, respectively. The key space reaches 10¹¹², while the BER at the illegal receiver remains around 0.5. These results show that the proposed scheme supports multi-user transmission and ensures information security, indicating strong potential for future 6 G wireless communication systems.