5.11.4 HNB to RNC CELL_FACH, CELL_PCH and URA_PCH mobility

25.4673GPPRelease 17Stage 2TSUTRAN architecture for 3G Home Node B (HNB)

The CELL_FACH, CELL_PCH and URA_PCH mobility message flow is described in Figure 5.11.4-1 below.

Figure 5.11.4-1: HNB to RNC CELL_FACH/CELL_PCH and URA_PCH mobility

1. At initial RRC Connection Setup, the HNB assigns to the UE a U-RNTI value based on the S-RNTI-prefix previously assigned to the HNB by the HNB-GW.

2. Subsequently, when the UE performs Cell or URA Reselection to the target RNC, it sends an RRC: Cell Update message (in case of CELL_FACH or CELL_PCH) or an RRC: URA Update message (in case of URA_PCH) containing the U-RNTI value previously assigned by the HNB.

3. Based on the RNC-ID part of such U-RNTI, the RNC detects that the UE is reselecting from one of its neighbour HNB-GWs.

NOTE: The RNC may determine whether or not the source HNB supports CELL_FACH/CELL_PCH/URA_PCH mobility. If the source HNB does not support CELL_FACH/CELL_PCH/URA_PCH mobility, the RNC may release the RRC connection.

4. The RNC forwards the received RRC Cell/URA update message via a RNSAP Uplink Signalling Transfer Indication message to the selected HNB-GW.

5. The HNB-GW, based on the S-RNTI-prefix included in the received U-RNTI and, if applicable, on the macro cell ID received from the RNC, selects the Source HNB.

6. The HNB-GW forwards the Uplink Signalling Transfer Indication RNSAP message to the source HNB.

7. The source HNB now executes the SRNS Relocation/enhanced SRNS Relocation towards the target RNC to transfer the UE context.

8. The RNC sends to the UE an RRC: Cell Update Confirm message (in case of CELL_FACH or CELL_PCH) or an RRC: URA Update Confirm message (in case of URA_PCH) to terminate the mobility procedure. If the SRNS relocation procedure is not used, the RRC: Cell Update Confirm message (in case of CELL_FACH or CELL_PCH) or the RRC: URA Update Confirm message (in case of URA_PCH) is sent by the serving HNB.