多 卫 星 的 星 地 混 合 协 作 网 物 理 层 安 全 性 能 分 析

Satellite communication has shown broad application prospects in various scenarios such as recon-naissance，broadcasting，early warning，resources exploration，topographic mapping due to its advantages of high transmission quality，long transmission distance and wide coverage. Objectives To address the security problem，Methods multiple-input-multiple-output （MIMO） technology is applied to the satellite relay sys-tem，a hybrid satellite-terrestrial relay network（HSTRN） with multiple satellites is constructed，and the physical layer security performance is studied in this paper.The relay is adopted either amplify-and-forward （AF） or decode-and-forward（DF） protocol to assist the transmission. The satellite link follows shadowed-Rician distribution，while terrestrial link and eavesdropper link follows Rayleigh distribution.The the theo-retical expressions of the system security outage probability（SOP）based on AF and DF relay are derived，as well as approximate expression and the system throughput under high signal-to-noise ratio conditions，the correctness of the theoretical analysis through computer simulation experiments is also verified. Results The results showed that，the security performance of the considered network gets better with the increase of the number of the satellites，and the decrease of the severity of the channel fading scenario；the security perfor-mance of the system based on the DF relaying is better than AF at low SNR region，while they will get in-creasingly consistent at high SNR region；the improvement of the channel fading scenario and high SNR can result in high throughput of the system. Conclusions The satellite number，security rate threshold，the chan-nel fading degree and other parameters have great impact on the security performance of AF and DF HSTRN，which can provide reference for subsequent research on the security performance of satellite com -munication physical layer.