# A Computation Offloading Strategy in LEO Constellation Edge Cloud Network
## 1 Introduction  
With the development of space technology, the cost of satellite manufacturing and launch has been greatly reduced, and the second wave of low-orbit constellation construction has arrived [1]. New space companies, such as OneWeb, SpaceX, Telsat and others, are ambitious to build low-orbit mega-constellations. SpaceX has laughed 1892 satellites [2] in orbit as of November 2021. A large number of LEO satellites run in space and form the satellite internet through inter-satellite links. LEO satellites act as data routing and forwarding nodes, but most nodes cannot effectively cover users on land most of the time, resulting in a waste of satellite resources and energy [3]. Along with the commercialization of 5G technology, academia has started research on 6G technology. The 6G technology is still in the stage of demand analysis and concept demonstration, but a consensus can be reached that the 6G network will be a ubiquitous network integrating the sky and the ground, connecting everything. However, the ground network cannot achieve global coverage, and it is impossible to lay optical fibers or set up base stations in deep mountains, seas, and deserts. At present, ground networks can only cover 20% of the global land area, and they are mainly concentrated in urban areas [4]. On the other hand, the ground network is very fragile and vulnerable to damage caused by various natural disasters. The low-orbit constellation communication has the advantages of seamless global coverage, ultra-low latency, and no need for ground infrastructure. It will be an indispensable and important part of Internet of Things and has become a researchhotspot in the industry and academia. Figure 1 shows the scenario of the satellite-terrestrial integrated Internet of Things. The rapid development of the mobile internet has brought us many innovative user applications, such as voice/face recognition, 4K/8K high-definition video, VR/AR games, holographic communication [5], etc. Most of these new applications are computationally sensitive, which drives the development and deployment of edge computing in terrestrial Internet of Things. In the coming years of satellite-terrestrial integrated Internet of Things, the network will extend to space. As a way for users to access Internet of Things, LEO satellites are at the edge of the entire network. Deploying edge computing servers on LEO constellation satellites to provide users with space edge cloud computing services is a matter worth considering. First of all, LEO satellites are at the edge of the network and can provide lower response delays. Even if users can access the data center through the ground network, the current global distribution of data centers is not uniform. In the case of long distances, the edge of LEO computing services can provide users with lower propagation delay [3]. Secondly, the LEO edge cloud does not need the support of ground infrastructure. On the one hand, it can operate autonomously and has strong damage resistance; on the other hand, it will not be constrained by geography, politics, economy and other factors, such as ground deployment. It is the only means for users without ground infrastructure to obtain nearby computing resources. Finally, the advantages of LEO constellation global coverage can lift the time and space constraints of users. Users anywhere in the world can access the edge of cloud computing services at any time. In the LEO constellation edge cloud, the LEO satellite is no longer only a user access and routing switching node, but also a node capable of providing computing services. The LEO constellation is no longer just a communication carrier network or pipeline, but a space-based computing network. Using the mega-constellation network to provide users with edge cloud computing services has the following benefits. (1) It breaks through the capability limit of a single LEO satellite and can provide more powerful computing capacity.