Abstract: With the accelerated advancement of 6G technologies, integrated space-ground networks (ISGN) are evolving from conceptual exploration toward large-scale deployment, becoming a fundamental infrastructure for achieving global seamless coverage and ubiquitous connectivity. However, due to factors such as the high mobility and dynamic characteristics of satellites, mobility management in ISGN faces significant challenges. This paper first presents the background of dynamic handover in space–terrestrial integrated networks and systematically analyzes three major challenges: handover decision challenges under dual high dynamics of satellite-ground networks and cross-domain coordination constraints, handover control challenges under signaling storms and satellite-borne resource mismatch, and handover security challenges under low-latency authentication and highly reliable security protection constraints. In response to these challenges, existing key handover technologies are comprehensively reviewed and categorized. Finally, in light of the evolutionary requirements of 6G, this paper discusses future trends toward intelligent deployability, global resource optimization, and integrated security capabilities, providing technical insights for building efficient, reliable, and autonomous space-terrestrial integrated handover systems.

Key words: Integrated Space-Ground Networks, Dynamic Handover, Cross-domain Coordination, Resource Optimization, Network Security