A Graph-Based Customizable Handover Framework for LEO Satellite Networks

Future satellite networks are expected to have thousands of low Earth orbit (LEO) satellites orbiting Earth at very high speeds. User equipment (UE) communicating directly with LEO satellites will experience frequent handovers. Managing the handover process is complicated due to the high frequency of handovers and the availability of multiple LEO satellites as handover targets. In addition, as the status of the communication link between a UE and an LEO satellite varies in accordance with the visibility period of the satellite, initiating handovers at the right time will significantly affect the quality of service (QoS) of the communication provided. To address this problem, this work proposes a graph-based customizable handover framework that considers both the handover timing and target while selecting a handover sequence that maintains QoS. A time-based graph is designed where the vertices represent the satellites' instances over a certain period of time and the edges' weights are the customizable handover criteria (i.e., data rate and delay in this work). The appropriate sequence and timing of handovers that fulfill the required QoS are obtained by finding the shortest path in the graph. Discussion and simulations, which were conducted on the Starlink Phase I constellation, show the low complexity and performance advantages of the proposed handover framework.