5.11.5 RNC to HNB 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 5.11.5-1 below.

Figure 5.11.5-1: RNC to HNB CELL_FACH/CELL_PCH and URA_PCH mobility

1. At initial RRC Connection Setup, the source HNB assigns to the UE a U-RNTI based on its RNC-ID and a set of locally defined bits.

2. Subsequently, the UE performs Cell or URA Reselection to a HNB supporting CELL_FACH/CELL_PCH/URA_PCH.

3. Based on the received U-RNTI, the target HNB detects the UE is reselecting from a neighbour RNC.

If, based on the received U-RNTI, the Target HNB cannot detect from which node the UE is coming from,

3a. it may establish an Iurh interface with the source RNC;

3b.alternatively, it may terminate the mobility procedure, re-establish the RRC connection for the UE and skip the subsequent steps.

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

5. The HNB-GW finds the proper source RNC based on the RNC-ID.

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

7. The source RNC may now execute the SRNS Relocation/Enhanced SRNS Relocation towards the target HNB to transfer the UE context or initialise the UE context in the target HNB via RNSAP Common Transport Channel Resources Initialisation procedure.

8. The HNB 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 (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.