C.3 Disambiguation at the HNB-GW

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

This solution allows the HNB-GW to identify the target HNB based on the source Cell ID and the measurements including OTD which are reported by the UE during the handover as shown in Figure C.3-1. The procedure includes two parts:

– Construction and Update of HNB Timing Information (OTD) Database at the HNB-GW.

– Target Cell Disambiguation at the HNB-GW during handover to a HNB connected to this HNB-GW.

Figure C.3-1: ΔOTD based disambiguation at the HNB-GW.

C.3.1 Construction and Update of ΔOTD Database at the HNB-GW

ΔOTD = (OTDHNB – OTD MNB) represents a HNB’s timing with respect to a macro cell (MNB) as measured by the UE where ΔOTDcell is the timing of a UE with respect to a given cell [25]. The HNB-GW keeps a database of the ΔOTD values for HNBs under its control and their neighbour MNB cells. The HNB-GW also keeps the mapping of a MNB’s Cell ID and its PSC.

The HNB-GW updates the ΔOTD database by using the information provided by the UEs during handovers to MNB cells. During these hand-outs, a HNB includes the MEASUREMENT REPORT message (MRM) in the RRC transparent container which is sent in the RANAP Relocation Required message and set the Target Cell Id IE to the ID of the macro cell with respect to which the OTD is computed.

C.3.2 Target Cell Disambiguation for Handover to the HNB

The procedure can be implemented as follows:

1. UE is triggered to send an RRC Measurement Report (including OTD for both source and target cells) to the SRNC by the rules set by the UTRAN.

2. The source RAN triggers relocation of the UE session by sending the RANAP RELOCATION REQUIRED message to the Core Network:

– The time difference information of the target HNB cell and the source Macro cell is contained in the RRC Container IE as defined in TS 25.331 [25].

– Source Cell ID is transmitted in the Source RNC to Target RNC Transparent Container.

– Target Cell ID IE may be set to a special value since the actual Cell ID is not known.

3. HNB-GW determines that PSC disambiguation is needed when target cell ID does not identify a HNB under its control. The HNB GW selects the target HNB using the received information (including the source Cell ID and MRM) and the ΔOTD database.

4. The remainder of the relocation procedure continues normally as documented in 3GPP TS 25.413 [9] and 3GPP TS 23.060 [10].

Additionally, after the successful inbound handover, the HNB GW can update the ΔOTD information between the target HNB cell and the source MNB cell using the received information.