Mobility Enhancements in 3GPP: Toward Rel-20 and Beyond

Mobility management remains a cornerstone of network evolution, yet ever-tighter latency and reliability targets, heterogeneous deployments, and AI-driven network intelligence demand continual refinement of handover mechanisms. Tracking and understanding recent developments in mobility management is essential to support the integrated, intelligent, and ubiquitous connectivity envisioned for 6G networks. This paper delivers a 3GPP-centric review of progressive mobility enhancements from Rel-15 through Rel-20 and offers insight into the emerging roadmap for 5G-Advanced and early 6G networks. After summarizing baseline measurement procedures and event-triggered reporting, we analyze three principal handover paradigms-Baseline Handover, Conditional Handover, and the recent Lower-Layer Triggered Mobility-highlighting their respective trade-offs in signaling overhead, interruption time, and robustness. We then examine how AI/ML techniques are positioned within 3GPP to predict optimal handover parameters, adapt to dynamic radio conditions, and reduce failure rates. The paper synthesizes Rel-20 hot topics, including mobility enhancements and AI/ML-based mobility use cases, and distills key contributions from 6G standardization meetings. By aligning ongoing 3GPP efforts with performance goals, this work highlights key challenges and outlines directions for future standardization beyond Rel-20.