# Hierarchical Resource Management for Mega-LEO Satellite Constellation
## 5 Detailed Elaboration of Each Layer
### Functions of Radio Resource Scheduling Center  
MLSCS provides high-reliability, low-delay services to user terminals. However, the strong mobility of LEO satellites and the imbalance of resource usage worldwide cause the available spectrum and coverage area of SBSs to change dynamically. Therefore, the RRSC is primarily responsible for resource planning for the entire constellation, including global spectrum resource scheduling and service area planning for all SBSs. The primary function of the RRSC in MLSCS is to analyze spectrum usage and service evolution patterns by using machine learning. This analysis considers historical data (such as user distribution, service distribution, and interference), current usage status (including spectrum usage, interference status, real-time service distribution, and signal bursts), and national/regional spectrum usage policies. Grids can be used as the basic unit for planning SBSs' service areas, and game theory-based spectrum planning is employed to guide SBSs' frequency usage behavior. In addition to normal management, mandatory scheduling strategies are needed for service enhancement in hotspot and emergency rescue areas. To address the problem of temporal-spatial mismatch between global service and resource, a multi-satellite collaborative support strategy will be used at multiple levels, such as SBSs and beams. The specific functions of the RRSC in MLSCS are as follows (Figure 4):  
Interference avoidance: ITU regulations grant GEO satellites priority in the use of spectrum compared to LEO satellites, meaning that the spectrum used by GEO satellites is protected. In middle- and-low latitude areas, however, common line-of-sight (CoLoS) interference may occur between GEO and LEO satellites. To avoid this interference and ensure compliance with ITU regulations, the MLSCS must address two key issues. First, user beam pointing must be prohibited towards GEO satellites to prevent interference. Second, feeder link interference avoidance measures must be implemented to protect GEO satellites from interference from LEO satellites. Addressing these issues will be critical to the successful implementation of the MLSCSScheduling of feeder links: To ensure that the feeder link connection is optimized and avoids interference from GEO satellites, we first perform calculations for GEO interference avoidance. Based on these calculations, we generate a plan to guide the SBSs and gateways in completing the feeder link scheduling. This plan includes specific instructions for beam pointing of the feeder link. The beam pointings are then generated and distributed to the corresponding control units, which are responsible for real-time feeder link scheduling. Following this process, we can ensure that the feeder link connection is optimized and compliant with GEO interference avoidance requirements. Interference management: Combined with system sensing data, the RRSC system supports global interference cognition and management. Terrestrial voluntary and involuntary interference in various regions can potentially impact the performance of the MLSCS, especially with the expansion of the 5G frequency band. To address this, the RRSC collects spectrum sensing data from SBSs and user terminals worldwide equipped with spectrum sensing modules. These data help construct a comprehensive global spectrum situation. By mining the temporal-spatial laws of interference from these data, the RRSC optimizes resource planning. Additionally, multi-satellite and multi-terminal sensing data are integrated to achieve interference cognition and enhance quasi-real-time spectrum scheduling, ultimately improving the system's service quality. Global spectrum management: The mega-LEO satellite constellation system aims to provide comprehensive communication services to global users. However, spectrum availability varies across different regions, and spectrum usage policies and requirements also differ.