# Hierarchical Resource Management for Mega-LEO Satellite Constellation
## 6 Approaches and Algorithms
### Beam Scheduling for Beam-Hopping  
Beam-hopping technology is increasingly used in LEO broadband satellite communication systems, such as Starlink, to improve performance. Beam-hopping involves using a limited number of beams to achieve the coverage of a traditional multi-beam satellite system. This is based on time slicing technology, where beams are activated and deactivated in a sequence to cover specific areas of the satellite's service area. In a beam-hopping slot, all or part of the satellite beams are in the working state, lighting up cells in the satellite service area based on demand. This concept--\"where there is a demand, the beam goes there\"--allows beam-hopping to better adapt to unbalanced service demands compared to traditional multi-beam technology. By dynamically allocating beams based on demand, beam-hopping can optimize network resources and improve overall system performance. Beam-hopping technology uses spatial isolation among the working beams to reduce CCI. However, it does not completely solve the interference problem. Specifically, if the angle between two beams is small, the sidelobes of the beams can cause interference, affecting the signal quality. To control this interference, a beam scheduling algorithm is designed. This algorithm optimizes the activation and deactivation of beams to avoid the impact of inter-beam interference on communication quality. By carefully scheduling the beams, the algorithm can improve system throughput and ensure reliable communication. In summary, beam-hopping technology, combined with a well-designed beam scheduling algorithm, can effectively reduce CCI and improve system performance in LEO broadband satellite communication systems. The beam scheduling algorithm must take into account several constraints to ensure efficient and effective resource allocation, which involves the following areas:  
* The ephemeris of SBS. The location of an SBS, which includes its longitude, latitude, and altitude, or XYZ coordinates in the Earth-centered Earth-fixed (ECEF) coordinate system, is crucial for determining the area it can cover. The SBS's position is directly related to the grids that it can serve, and these grids are associated with specific users and services. To generate an effective beam-hopping pattern, it is necessary to calculate the number of slots required for each cell within the SBS's service area. This calculation is based on the distribution of services within the area. Once the number of slots required for each cell is determined, the slots can be allocated to each cell according to its needs. By understanding the relationship between the SBS's location and the grids it can cover, as well as the process of calculating and allocating slots for each cell, we can ensure that the beam-hopping pattern is optimized to meet the needs of users and services within the SBS's service area. * Service area planning. The service area range of the space base station, meaning the location area it contains, is determined by the scheduling of the service area of the NCC. When calculating the beam-hopping pattern, the space base station only needs to pay attention to the users and services within its service area. * User and service distribution. To generate the beam-hopping pattern, the SBS first assesses the number of slots required for each cell within its service area. Slots refer to the time intervals during which the SBS can communicate with users. The SBS then allocates the required slots to each cell, taking into account the distribution of users and services within that cell. After allocating the slots, the SBS schedules the beams according to the beam-hopping pattern. This scheduling process involves determining the sequence and timing of the beams, as well as the power and frequency of each beam. By carefully scheduling the beams, the SBS can ensure efficient and effective communication with users in its service area. * The distribution of the cells.