The security and privacy of wireless communication networks constitute a critical challenge in the evolution toward 6G-enabled space-air-ground integrated networks. To address sophisticated eavesdropping threats in complex scenarios characterized by three-dimensional coverage and multi-domain collaboration, this study proposes an uplink secure transmission framework for space-air-ground integrated networks. The system model encompasses four core entities: a satellite, a legitimate relay unmanned aerial vehicle (R-UAV), a malicious eavesdropping UAV (E-UAV), and terrestrial users. The satellite is configured to receive relayed signals solely from the R-UAV, modeling harsh channel conditions or application-specific cooperative communication requirements. The E-UAV cruises within the communication airspace, attempting to opportunistically intercept the users’ uplink transmissions. For this dynamic scenario, we formulate a system secrecy rate maximization problem based on a fairness criterion. To solve this highly non-convex and coupled problem, a cooperative optimization algorithm integrating block coordinate descent, semidefinite relaxation, successive convex approximation, and a dual deep Q-network is proposed. This algorithm jointly designs the UAV’s flight trajectory, resource allocation strategy, and beamforming parameters to balance security and communication performance. Simulation results demonstrate that the proposed method offers superior flexibility and security advantages in dynamic eavesdropping environments. Furthermore, the analysis elucidates the intrinsic trade-off between the R-UAV’s onboard resources, hardware configuration, and overall system performance.
[1] 吴建军,孙黎,王东晖,等.面向6G网络的内生安全架构和关键技术思考[J].中国科学:信息科学，2024,54(12):2881-2904..
WU J J. SU L. WANG D H. et al. Thoughts on the Endogenous Security Architecture and Key Technologies for 6G Networks[J]. Chinese Science: Information Science, 2024, 54(12):2881-2904 (in Chinese).
[2] 陈山枝,孙韶辉,康绍莉,等.6G星地融合移动通信关键技术[J].中国科学:信息科学,2024,54(05):1177-1214.
CHEN S Z. SUN Z H. KANG S L. et al. Key Technologies of 6G Satellite-Ground Integrated Mobile Communication[J]. Chinese Science: Information Science, 2024, 54(05):1177-1214 (in Chinese).
[3] 张更新,廖磊瑶,何元智.面向空天地海一体化的卫星通信关键技术研究[J].电信科学,2024,40(06):11-24.DOI:CNKI:SUN:DXKX.0.2024-06-002.
ZHANG G X. LIAO L Y. HE Y Z. Research on Key Technologies for Satellite Communication Integrated across Air, Space, Ground and Sea[J]. Telecommunications Science, 2024,40(06):11-24 (in Chinese).
[4] 鲁信金,施育鑫,雷菁,等.无线通信物理层内生安全：关键技术、优势与未来挑战[J].通信学报,2024,45(S1):87-96.
LU X J. SHI Y X. LEI Q. et al. Endogenous Security in the Physical Layer of Wireless Communication: Key Technologies, Advantages and Future Challenges[J]. Journal on Communications, 2024,45(S1):87-96 (in Chinese).
[5] YAO Y. XIAO W Q. MIAO P. et al., UAV-Relay-Aided Secure Maritime Networks Coexisting with Satellite Networks: Robust Beamforming and Trajectory Optimization[J], IEEE Transactions on Wireless Communications, (2025-08-12) [2025-11-12]. https://ieeexplore.ieee.org/document/11123630. doi: 10.1109/TWC.2025.3596136.
[6] HE D X. SHA Z Y. LIU H. et al. UAV-Assisted Satellite-Terrestrial Secure Communication Using Large-Scale Antenna Array With One-Bit ADCs/DACs[J], IEEE Transactions on Communications, vol. 71, no. 1, pp. 580-594, Jan. 2023, doi: 10.1109/TCOMM.2022.3225576.
[7] WANG Q B J. WANG H. ZHAO N. et al. Aerial Bridge: A Secure Tunnel Against Eavesdropping in Terrestrial-Satellite Networks[J], IEEE Transactions on Wireless Communications, vol. 22, no. 11, pp. 8096-8113, Nov. 2023, doi: 10.1109/TWC.2023.3258599.
[8] YIN Z S. CHENG N. SONG Y C. et al. UAV-Assisted Secure Uplink Communications in Satellite-Supported IoT: Secrecy Fairness Approach[J], IEEE Internet of Things Journal, vol. 11, no. 4, pp. 6904-6915, 15 Feb.15, 2024, doi: 10.1109/JIOT.2023.3313197.
[9] LI H F. LI J. LIU M. et al. UAV-Assisted Secure Communication for Coordinated Satellite-Terrestrial Networks[J], IEEE Communications Letters, vol. 27, no. 7, pp. 1709-1713, July 2023, doi: 10.1109/LCOMM.2023.3267119.
[10] LIAO C J. XU K. ZHU H P. et al. Secure Transmission in Satellite-UAV Integrated System Against Eavesdropping and Jamming: A Two-level Stackelberg Game Model[J], China Communications, vol. 19, no. 7, pp. 53-66, July 2022, doi: 10.23919/JCC.2022.07.005.
[11] 刘畅,呼志远,刘海宁,等.低空飞行器物理层通信安全：技术发展现状、挑战与未来发展[J].移动通信,2025,49(08):34-41.
LIU C. HU Z Y. LIU H N. et al. Physical Layer Communication Security for Low-altitude Aircraft: Current Technological Developments, Challenges, and Future Prospects[J], Mobile Communication, 2025,49(08):34-41 (in Chinese).
[12] SHI J. LI X M. TIE Z Z. et al. Covert LEO Satellite Communication Aided by Generative Adversarial Network Based Cooperative UAV jamming[J], China Communications, vol. 21, no. 9, pp. 27-39, Sept. 2024, doi: 10.23919/JCC.fa.2023-0063.202409.
[13] Zhou Y. YEOH P L. WANG K Z. et al. Caching and UAV Friendly Jamming for Secure Communications With Active Eavesdropping Attacks[J], IEEE Transactions on Vehicular Technology, vol. 71, no. 10, pp. 11251-11256, Oct. 2022, doi: 10.1109/TVT.2022.3186730.
[14] HAN C. BAI L. BAI T. et al. Joint UAV Deployment and Power Allocation for Secure Space-Air-Ground Communications[J], IEEE Transactions on Communications, vol. 70, no. 10, pp. 6804-6818, Oct. 2022, doi: 10.1109/TCOMM.2022.3203471.
[15] YIN Z S. JIA M. CHENG N. et al., UAV-Assisted Physical Layer Security in Multi-Beam Satellite-Enabled Vehicle Communications[J], IEEE Transactions on Intelligent Transportation Systems, vol. 23, no. 3, pp. 2739-2751, March 2022, doi: 10.1109/TITS.2021.3090017.
[16] YE R L. PENG Y Y. Al-Hazemi F. et al. A Robust Cooperative Jamming Scheme for Secure UAV Communication via Intelligent Reflecting Surface[J], IEEE Transactions on Communications, vol. 72, no. 2, pp. 1005-1019, Feb. 2024, doi: 10.1109/TCOMM.2023.3325488.
[17] LIU Y. HUANG C. CHEN G J. et al. Deep Learning Empowered Trajectory and Passive Beamforming Design in UAV-RIS Enabled Secure Cognitive Non-Terrestrial Networks[J], IEEE Wireless Communications Letters, vol. 13, no. 1, pp. 188-192, Jan. 2024, doi: 10.1109/LWC.2023.3325066.
[18] 丁伟豪,屈正浩,申凌峰,等.基于RIS辅助的UAV物理层安全传输技术[J].无线电工程,1-12(2025-07-14) [2025-10-22]. https://link.cnki.net/urlid/13.1097.tn.20250714.1011.002.
DING W H. QU Z H. SHEN L F et al. UAV physical layer secure transmission technology assisted by RIS[J]. Radio Engineering, (in Chinese).
[19] HUANG M Y. LI G. GONG F K. et al. Robust Secure Precoding for UAV-Aided Multi-Beam Satellite NOMA Communications[J], IEEE Transactions on Vehicular Technology, vol. 73, no. 6, pp. 8069-8082, June 2024, doi: 10.1109/TVT.2024.3349686.
[20] 李美玲,任康,薛凯轩,等.UAV辅助的非理想STAR-RIS认知NOMA物理层安全性能分析[J].电讯技术,2025,65(06):874-881.
LI M L. REN K. XUE K X. et al. Analysis of the Physical Layer Security Performance of Non-Ideal STAR-RIS Cognitive NOMA with UAV Assistance[J]. Telecommunication Technology, 2025,65(06):874-881 (in Chinese).
[21] Zhang Y Y. Wang B H. Ding G R. et al. ISAC-Assisted Covert Transmission: Joint Secure Sensing and Communication[J], IEEE Journal on Selected Areas in Communications, doi: 10.1109/JSAC.2025.3637793.
[22] 胡杨林,张天魁,李博,等.无人机使能的通信感知一体化组网与技术研究综述[J].电子与信息学报，2025,47(04):859-875.
HU YL. ZHANG T K. LI B. et al. A Review of Research on Integrated Networking and Technology of Communication and Perception Enabled by Unmanned Aerial Vehicles[J]. Journal of Electronics & Information Technology, 2025,47(04):859-875 (in Chinese).
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