# Hierarchical Resource Management for Mega-LEO Satellite Constellation
## 6 Approaches and Algorithms
### Service Area Planning  
Service area planning is a crucial function of the RRSC. This process is influenced by numerous factors, including grid partition, the distribution of communication services, interference avoidance with GEO satellites, and the management of intra-system and inter-system interference. Additionally, it considers the residence time and propagation distance between SBSs and grids (or users), the available resources of SBSs, and the continuity and heritability of service areas. Given the dynamic nature of LEO satellites, particularly their rapid orbital changes and positional shifts, and considering the unique technical features and application demands of the MLSCS, several key factors will influence service area planning and resource scheduling. These factors are outlined below:  
* The high-speed movement of SBSs causes their coverage area to change constantly, which, in turn, affects the planning of their service areas. * The non-uniform distribution of users, changing user traffic, and high-speed movement of dynamic users (such as those on high-speed trains and aircraft) lead to rapid and uneven changes in service distribution. These factors pose significant challenges to the dynamic scheduling of service areas and resources. * Due to different spectrum usage policies and statuses in various regions, the available spectrum resources for SBSs are also dynamically changing. * The high-speed movement of SBSs constantly changes the constellation topology and the connection relationships between users/gateways and SBSs. This results in frequent handovers of users/gateways among different SBSs and beams. To successfully complete the service area planning and resource scheduling in the MLSCS, several key challenges must be addressed. By tackling these issues, we can ensure that our planning and scheduling efforts are effective and efficient. * How can we efficiently calculate and dynamically schedule service areas in response to changes in SBSs' positions and available resources, constellation topology, and user and service distribution? To address this challenge, we need to develop methods or algorithms that can quickly adapt to these dynamic factors and optimize service area planning. * How can we reduce user handovers among different SBSs and beams while ensuring extended connectivity time for users and reasonable scheduling of service areas and resources? To achieve this, we need to develop methods or algorithms that can optimize the placement and scheduling of SBSs and beams to minimize handovers and maximize user satisfaction. * How can we ensure real-time and reliable space-ground link connections while minimizing the costs or delays associated with handovers? To address this challenge, we could consider using advanced communication protocols, optimizing network topology, or implementing efficient handover algorithms. These solutions could help ensure that users maintain continuous and reliable connections while minimizing the disruptions, delays, and overheads caused by handovers. Given the challenges discussed above, the RRSC should follow the following principles when planning its service areas:  
* The SBS must cover the grids in its service area. These grids are small areas divided on the ground based on longitude and latitude, serving as the basic unit for satellite service area planning. The SBS's service area must be entirely within the coverage area of a larger satellite service provider; otherwise, it cannot meet the communication conditions and provide service to users within the grids. * Interference avoidance for GEO satellites is crucial. The connections between users and SBSs must be kept away from the geostationary orbit to prevent interference with GEO satellites. If a connection between a grid and an SBS passes too close to the geostationary orbit, grid users must be handed over to adjacent SBSs to maintain communication without interference. * Ensuring sufficient resources in SBSs is crucial for providing effective and reliable service to users in their service areas.