## 2 Related Work
### SDN-Based Space Information Networks  
Based on the advantages of SDN technology, some scholars and research institutes proposed its application in the SIN. The related research is still in its infancy, mainly focusing on the research of architecture and routing algorithms. Researchers at the Centre National de la Recherche Scientifique (CNRS) and Universite de Toulouse studied handover decision-making algorithms in satellite networks through SDN's programmability [19]. Joint researchers from the Polytechnic University of Catalonia and the Greek National Research Center are exploring the introduction of SDN technology into satellite networks. SDN technology is used to improve the satellite network infrastructure, so as to improve the joint service capability of ground and satellite networks and hybrid access service capability [20]. Researchers from Hughes Network Systems Inc. of the United States directly proposed  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Architecture** & **Satellite–Earth Network** & **Space-based Network** & **Space-net–Earth Network** \\ \hline \multirow{3}{*}{Typical system} & **Civil:** Inmanst, O3b, OneWb, & **Civil:** Iridium & **Civil:** SCaN, ISICOM \\  & **Illitary:** WGS, MUGS & **Military:** AEHF & **Military:** TSAT \\ \cline{2-4}  & Global distributed ground station & The system can operate independently of the ground station & The earth and the sky cooperate with each other; the ground \\ \multirow{3}{*}{Ground} & Global distributed ground station & The system can operate independently of the ground station & The earth and the sky cooperate with each other; the ground \\  & network & ground station & network does not need the global \\ \multirow{3}{*}{Inter-satellite networking} & No & Yes & Yes \\  & Equipment on satellite & Simple & Complex & Moderate \\ \cline{1-1} Difficulty of System Maintenance & Simple & Complex & Moderate \\ \cline{1-1} Technical complexity & Simple & Complex & Moderate \\ \cline{1-1} Construction cost & Low & High & Moderate \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of different space information network (SIN) architectures.  
a software-defined satellite network (SDSN) architecture, and applied it to their SPACEWAY system (a new generation of broadband satellite communication system). By establishing modules and performance objects, the extended allocation of inter-satellite packet routing addresses and the resource management control in the controller were realized [21]. Reference [22] proposes a networking architecture for on-board switching systems based on SDN. SDN on-board switching system can effectively reduce the load of traditional on-board switching systems, optimize the utilization of satellite channel resources, and improve the quality of service support capability of satellite communication networks. References [23; 24] analyzed the routing algorithm of SDN-based SIN.  
SIN includes a large number of heterogeneous nodes such as satellites, caches, mobile edge computing (MEC) servers, and so on. The allocation of the SIN resources involves the allocation of multi-dimensional resources such as transmission, caching, and computing. It is necessary to make overall considerations to achieve the maximum effective use of the SIN resources.