Abstract
—In space-air-ground integrated networks (SAGIN), the interference generated in the communication process poses a significant challenge to both information security and communication reliability. To address these issues, we first introduce the unmanned aerial vehicle carrying the reflecting intelligent surface (UAV-RIS) to enhance network performance. Then, a UAV-RIS-assisted secure space-time interference management scheme (SSTIM) is proposed for maximizing system capacity while ensuring that user information remains secure. In the proposed scheme, low-earth-orbit (LEO) satellite actively participates in the space-time coding design under strict security constraints, while the UAV-RIS provides flexible signal reflection and interference shaping, enabling secure transmission and effective suppression of multi-domain interference. The simulation results show that the UAV-RIS-SSTIM scheme improves network capacity, safeguards information, and enhances communication reliability. Index Terms—SAGIN, UAV-RIS, secure space-time interference management scheme, secure degree of freedom, secure rate