## 1 Introduction
### Background
The realization of Extended Reality (XR), Holographic Telepresence (HT), and Connected Autonomous Vehicles (CAV) require the support of large bandwidth. The traditional satellite communication systems have fixed bandwidth which is difficult to expand [11]. In multi-beam satellite communication systems, the multi-dimensional coverage can effectively increase bandwidth, improve system capacity, and meet users' demands. Compared with terrestrial communication systems, the distribution areas of users which are covered by satellite communication systems are different day and night [12]. In multi-beam satellite communication systems, beams can be scheduled dynamically according to users' demands to ensure that users can be covered dynamically and radio resources can be used effectively. Users can be provided with time-sharing services. The European Space Agency (ESA) has promoted a project of beam hopping techniques for multi-beam satellite systems in 2004 [13], and Hughes has developed and launched the Spaceway-3 satellite system using the hopping spot beam [10]. However, most of the existing researches about beam hopping technology has been analyzed for the GEO satellite communication system. In this paper, we construct a scenario where multi-satellite and multi-beam simultaneously transmit uplink data for a single user. The multi-satellite multi-beam cooperative communication system has the following characteristics:  
1. The user can transmit packets with multiple different beams at the same time. The users have the function of joint packet transmission and processing. 2. Satellites share each other's channel status and control information through the gateway, but do not share packets. There is obvious spatial isolation between the different beams of satellites, which can provide convenience for flexible spectrum utilization schemes. The cross-satellite and cross-dimensional packet transmission scheme in the multi-satellite multi-beam cooperative communication system can effectively increase the user transmission rate. Expanding the space dimension can ensure the stability and flexibility of the link. The seamless coverage of the world can improve the global spectrum utilization. However, while providing high-speed, efficient, reliable, and stable services, there are also many technical challenges. High dynamic and multiple dimensional radio resources optimization: In the multi-satellite multi-beam cooperative communication system, the LEO is moving at high speed. The channel between satellites and users changes rapidly. The signals of different beams suffer different fading. Users are covered by different beams of different satellites, and there is obvious spatial isolation between different beams. Therefore, how to make full use of the degree of freedom in the airspace and select the optimal resource for transmission according to different SINR and QoS is an urgent problem to be solved in the multi-satellite multi-beam cooperative communication system. Time division and discontinuous packet segmentation: After the multi-satellite multi-beam resource allocation is completed, the radio resource of a beam cannot meet the user's needs, and the radio resource is non-continuous to the user. The packets are transmitted by different beams, and the size of the packets does not match the allocated radio resources. Therefore, how to segment packets into smaller packets effectively to match optimal resources for coordinated transmission is another difficult problem in the multi-satellite multi-beam cooperative communication system.