Section: 4.7.5.2 RACH-less handover
Content: During the mobile IAB-DU migration procedure, RACH-less handover can be configured for a UE that is migrated from the source logical mobile IAB-DU to the target logical mobile IAB-DU. The RACH-less handover procedure applies the following functionality: The UE uses the same timing advance at the cell of the target logical mobile IAB-DU as signalled by the cell of the source logical mobile IAB-DU. The handover command for the UE contains a beam identifier for the beam to be used by the UE at the target logical mobile-IAB cell. The beam may be determined based on a UE measurement report and/or based on implementation, e.g., using the target cell's knowledge about the beam(s) used by the UE at the co-located source cell. The handover command may include a pre-allocated UL grant. Alternatively, an UL grant is dynamically signalled by the target logical IAB-DU cell. The UE transmits the RRCReconfigurationComplete message using the pre-allocated or dynamically signalled UL grant. The UE's successful UL data reception on the target logical mobile-IAB cell terminates the RACH-less handover execution.