16.19.2.2 Timing Advance

For the serving cell, the network broadcasts coarse gNB location information. The UE shall have valid GNSS position as well as gNB location before connecting to an ATG cell. To achieve synchronisation, before and during connection to an ATG cell, the UE shall compute the RTT between UE and the gNB based on the GNSS position and the gNB location parameters, and autonomously pre-compensate the TTA for the RTT between the UE and the gNB.

In connected mode, the UE shall be able to continuously update the Timing Advance.

The UE may be configured to report Timing Advance during Random Access procedures or in connected mode. For an RRC_CONNECTED UE, event-triggered reporting of the Timing Advance is supported.