Mobility Management Approach for Co-Orbital Regenerated LEO Satellites

In order to achieve wide-area Internet of Things (IoT) and emergency communication, non-terrestrial network (NTN) has become a research hotspot in academia and industry in recent years. Satellites are used as access nodes or relay nodes to expand the coverage of communication services. However, current research mostly focuses on transparent satellites, which face the problems of large air interface delay and poor network flexibility. Therefore, a low earth orbit satellite (LEO) network architecture based on regenerative satellites is proposed in this paper to reduce the transmission delay and increase network flexibility, in which a centralized unit (CU)-distributed unit (DU) split architecture is adopted to reduce the requirements for on-board processing capabilities of satellites. Based on this architecture, a handover scheme between co-orbital regenerated LEO (CRLEO) satellites based on the virtual cell is proposed. By dividing the ground into different virtual cells and conducting orbital cell identifier (COI) planning for these virtual cells, UE’s seamless handover can be realized. In order to further reduce the transmission delay and on-board load, an inter-CRLEO satellite handover scheme based on the inter-DU interface is proposed. By introducing the inter-DU interface, signaling between DUs does not need to be forwarded to the $\mathbf{C U}$ satellite for processing. Simulation results show that the proposed inter-CRLEO satellite handover scheme based on the inter-DU interface can greatly reduce the number of inter-satellite link hops experienced, thereby significantly reducing the handover delay.