# Research on Task-Oriented Computation Offloading Decision in Space-Air-Ground Integrated Network
## 1 Introduction  
Space-Air-Ground Integrated Network (SAGIN) is a large-scale and complex heterogeneous network system formed by the interconnection of space-based information network, internet, and mobile communication network, which combines satellite network with terrestrial network closely. Further, it collects, transmits, and processes space information in real-time to meet the demand for communication services with global coverage. The space-Air-Ground Integrated Network is a strategic and fundamental critical infrastructure network, which can drive the development of China's emerging industries. In the field of military and civilian information applications and Internet of everything era, it plays a crucial role to deal with the demand for massive information services and will be the inevitable trend of the future development of the network [1]. The space-ground integrated network is a large complex hierarchical heterogeneous network, which mainly consists of three parts: space-based backbone network, space-based edge access network and ground-based backbone network. As shown in Figure 1, the space-based network consists of satellites and satellite constellations as well as the corresponding ground infrastructure such as ground stations and network operation control centers. These satellitesare in different orbits, and according to the altitude, the satellites can be divided into Geostationary Orbit (GEO) satellites, Medium Earth Orbit (MEO) satellites, and Low Earth Orbit (LEO) satellites [2]. Among them, the space-based backbone network is the core infrastructure of the integrated space-ground information network, using satellites of different levels at each orbital level to unite with each other to provide information transmission and processing industry for the whole space information system. Space-based edge access network contains various types of low-altitude vehicles, forming a single-layer constellation, or dual constellation of low and medium orbit, information transmission through satellite links, which can provide communication services to cover information in the beam center gateway control station and various user terminals. The ground-based network includes five theaters on the ground and various types of ground nodes (such as cell phones, submarines, etc. ), mainly consisting of cellular networks, mobile ad hoc network (MANET) [3], Worldwide Interoperability for Microwave Access (WiMAX), Wireless Local Area Network (WLAN) and other ground-based communication systems. Among them, the ground-based backbone network is the ground infrastructure of the integrated space-ground information network, connecting to the ground control station network and communication gateway stations, thus forming a kind of information transmission method for integrated scheduling of heaven and earth resources. The GEO satellites have the characteristics of high coverage, high transmission rate, and dynamic adaptation, but there are limitations of orbit fixation and high processing task delay, while the low-medium orbits have the advantages of wide distribution and  
Figure 1: Architecture of the Space–Earth Integration Network. The structure of the Space–Air–Ground Integrated Network is given from the perspective of network nodes, and the space-based backbone network is the core infrastructure of the space–ground integrated information network to meet the needs of various types of communications through the integration of space and ground networks. short distance, and the computing storage ability of ground base stations is strong. Using air, space, and ground resources to work collaboratively can achieve multi-dimensional strategic information services. However, due to the dynamic change of the Space-Air-Ground Integrated Network topology, the number of tasks to be processed is huge and the number of satellites is limited, so there are many problems such as limited computing resources abilities of network nodes, and untimely task processing, resulting in some important task processing to fail [4].