## 4 Problem Equation
### A3C Algorithm
The scheme of A3C-based all takes into account the coverage area of the LEO satellite, the state of communication link between users and the LEO satellite, the transmission state of the GEO data relay satellite, the caching state of caches, and the computing state of the MEC server. It effectively improves the efficiency of unit resource utilization, and has more advantages than other schemes. Figure 10 shows the relationship between the unit charging price for using caching resources and the expected benefit of the unit resource. With the increase of the unit charging price for using caching resources, the expected benefit of the unit resource of the SIN increases gradually. The scheme of A3C-based all takes into account the coverage area of the LEO satellite, the state of communication link between users and the LEO satellite, the transmission state of the GEO data relay satellite, the caching state of caches, and the computing state of the MEC server, which has better resource utilization efficiency. Figure 11 shows the relationship between the unit charging price for using computing resources and the expected benefit of the unit resource. With the increase of the unit charging price for using caching resources, the expected benefit of the unit resource of the SIN increases gradually. The proposed A3C-based all scheme takes into account the coverage area of the LEO satellite, the communication link state between users and the LEO satellite, the transmission state of the GEO data relay satellite, the caching state of caches, and the computing state of the MEC server, which has better resource utilization efficiency. Figure 10: The relationship between the unit charging price for using caching resources and the expected benefit of unit resources. Figure 9: The relationship between the unit charging price for using transmission resources and the expected benefit of unit resources. ## 6 Conclusions

In this paper, in order to improve the resource management and utilization efficiency of the SIN, firstly, based on the core idea of SDN, a hierarchical and domain-controlled SIN architecture was established. The overall networking architecture and network control architecture were designed. On this basis, the transmission resources, caching resources, and computing resources of the SIN were managed in a unified way. Next, the satellite coverage and transmission model, communication link model, caching model, and computing model of the SIN were modeled and analyzed. Finally, the A3C algorithm of deep reinforcement learning was introduced to model and simulate the multi-dimensional resource allocation problem of the SIN. The simulation results show that the proposed scheme can effectively improve the expected benefits of unit resources and the utilization efficiency of the SIN resources. In this paper, LEO communication satellites and several GEO data relay satellites were taken as examples for analysis. However, the SIN is a huge system. In practical applications, the scheduling of remote-sensing satellites, navigation satellites, and other resources may have different situations, which need specific analysis. Furthermore, in a follow-up study, we will further analyze the other SIN resources such as energy resources and sensor resources. Conceptualization, X.M. and L.W. ; Methodology, X.M. and L.W. ; Software, X.M. and S.Y. ; Validation, X.M. ; Formal Analysis, X.M. ; Investigation, X.M. ; Resources, X.M. and S.Y. ; Data Curation, X.M. ; Writing-Original Draft Preparation, X.M. ; Writing-Review & Editing, X.M. ; Visualization, X.M. ; Supervision, L.W. China Equipment Named Research Funded Project with grant number 6142010010301. The authors would like to thank [PERSON] of Beijing University of Posts and Telecommunications for her guidance on the ideas for the text. The authors declare no conflict of interest. ## References

* [PERSON] (2016) [PERSON] _Topological Control Theory and Method of Space Information Network_; PLA University Science and Technology: Nanjing, China, 2016; pp. 1-5. * [PERSON] et al.