Uplink Timing Adjustment for Non-Terrestrial Network Handover

The UE performs time adjustment based on differential propagation delay calculation before the random access procedure completes. The network configures reference signals from multiple base stations, and the UE measures arrival times to determine propagation delay differences, allowing early uplink timing alignment with the target base station. This preliminary timing adjustment enables the UE to start uplink transmissions earlier without waiting for complete random access procedure confirmation.

The UE autonomously calculates differential propagation delay by measuring the arrival times of reference signals from multiple base stations and determines its own uplink transmission timing adjustment. The UE configures its own transmission time based on the calculated delay difference, enabling self-synchronized uplink transmissions to the target base station without requiring external timing commands during the handover process.

The network provides feedback by configuring reference signal parameters from multiple base stations, enabling the UE to calculate differential propagation delay. The UE uses this feedback information to determine the appropriate timing adjustment, ensuring that uplink transmissions are synchronized with the target base station's reception window, thereby avoiding interference while minimizing latency.