关键词: 空天地网络, 上行安全传输, 动态窃听, 无人机轨迹, 波束成形, 资源分配

Abstract: 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.

Key words: Space-air-ground integrated networks, uplink secure transmission, dynamic eavesdropping, UAV trajectory, beamforming, resource allocation