Mobility-Aware Timer-based Conditional Handover for LEO Satellite Networks

Low Earth orbit (LEO) satellites have emerged as a key technology of non-terrestrial networks (NTNs) in sixth-generation (6G) systems, providing global coverage and lower latency than geostationary satellites. However, the high mobility of LEO satellites results in frequent handovers (HOs) and unstable connectivity. To address these challenges, this paper proposes a dynamic timer-based conditional HO (CHO) scheme for NTN environments. The proposed method leverages the geometric relationship between user equipment (UE) and satellite beams to dynamically configure UE-specific time-domain HO thresholds. This geometry-assisted timer design estimates each UE’s time-of-stay (ToS) in the current cell and adjusts the HO triggering time accordingly. The proposed mechanism prevents unnecessary HO (UHO) execution within the cell, making it particularly suitable for NTN environments characterized by high mobility. Simulation results based on 3GPP study case 9 show that the proposed scheme significantly reduces radio link failures (RLF), unnecessary handovers (UHOs), and handover ping-pong (HOPP), while improving average downlink SINR compared to signal-based CHO. These results confirm that incorporating geometric awareness into timer configuration enables stable and efficient mobility management in highly dynamic NTN environments.