5.9a Inbound Mobility to HNB

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

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.9.1a General

The following sub-sections describe the mechanism for handling the inbound mobility to HNB via the Iu and Iuh interfaces. This mechanism is also applicable to the handover between HNBs under the same HNB-GW.

5.9.2a Connected Mode Inbound Mobility for CSG UEs to CSG HNBs or to Hybrid Cells

The following figure and accompanying steps describe the inbound mobility procedure for CSG UEs from Rel-9 onwards when the Source RAN supplies to the Core Network a CSG id associated with the target HNB. The following is assumed:

– UE is CSG capable from Rel-9 onwards and SIB-reading capable.

– UE is able to provide in the RRC measurement report the cell identity and the CSG-Id (if requested) of the target HNB.

– The Source RAN is able to determine the Cell Access Mode of the target HNB.

NOTE: It is assumed that the network knows whether the target cell is a hybrid cell, e.g. by PSC range for hybrid cells.

– The Source RAN is able to determine the necessary information of the target HNB for which mobility is possible.

NOTE: It is assumed that the network knows the PLMN ID, LAC, RAC and RNC ID of such possible target cell, e.g. a possible implementation may be based on PSC ranges or based on location information of the macro-cell.

– The Core network is CSG capable from Rel-9 onwards and is able to perform access control or membership verification for relocated CSG UE.

– The HNB-GW is able to route the incoming relocation to the appropriate target HNB using the target cell identity provided in RANAP RELOCATION REQUEST (i.e. Target Cell Id is unique for a HNB in a given HNB-GW).

Figure 5.9.2a-1: Connected Mode inbound mobility for CSG UEs to CSG HNB or Hybrid Cell.

1. The UE is triggered to send an RRC Measurement Report by the rules set by the UTRAN. The Measurement Report includes the Cell Identity, CSG id (if requested) of the target HNB as in TS 25.331 [25]. If the target cell is a shared CSG/hybrid cell, the measurement report also includes the subset of the broadcast PLMN identities that pass PLMN ID check and for which the Permitted CSG list of the UE includes an entry comprising the cell’s CSG ID and the respective PLMN identity.

2. The Source RAN node makes a decision to relocate the UE session.

3. The source RAN triggers relocation of the UE session by sending the RANAP RELOCATION REQUIRED message to the Core Network. The target RNC-Id, CSG id, Target Cell Id and – for relocation to a hybrid cell – Cell Access Mode information along with relocation information are included by the source RAN in the RANAP RELOCATION REQUIRED message.

4. If the target cell is a CSG HNB, the Core Network performs access control on the basis of the CSG ID associated with the target cell and the selected PLMN ID, as reported to the Core Network (TS 25.413 [9]). Otherwise (if the target is a Hybrid Cell), the Core Network performs membership verification and fills the CSG Membership Status IE in step 5 to reflect the UE’s membership to the target cell. If the Core Network determines that this relocation is for an emergency call then it will allow inbound mobility to CSG cells even if the access control fails and, in case of access control failure, the Core Network sets the CSG Membership Status IE to the value “non-member” in step 5.

5. The HNB-GW receives a RANAP RELOCATION REQUEST message from the Core Network, including the CSG id, Target Cell Id and – for relocation to a hybrid cell – CSG Membership Status. For cases where the access control failed for relocation of one or more RABs with a particular ARP value (see TS 23.060 [10]) to a hybrid or to a CSG cell the CSG Membership Status IE shall be included and set to “non-member”.

6. The steps for HNB-GW Triggered UE Registration are executed between the HNB-GW and the HNB. The HNB-GW/HNB validates the CSG id received in the RANAP RELOCATION REQUEST message. If the CSG HNB determines that this relocation is for one or more RABs with a particular ARP value (see TS 23.060 [10]) and CSG ID validation fails and/or UE is non member then it will accept only those RABs with a particular ARP value (see TS 23.060 [10]) and fail the others.

7. The remainder of the relocation procedure continues normally as documented in TS 25.413 [9], TS 23.060 [10]

NOTE: Steps 2 to 7, as appropriate, are repeated for the second CN domain when present with the following exceptions. The relocation of the 2^nd domain shall not trigger an additional registration. The 2^nd RANAP Relocation Request shall be carried as RUA Direct Transfer. There is only one Context Id assigned to the UE regardless of the number of domains relocated from the source RAN.

5.9.3a Connected Mode Inbound Mobility for non-CSG UEs to CSG HNBs or to Hybrid Cells

The following figure and accompanying steps describe the inbound mobility procedure for non-CSG UEs, when the Source RAN is able to identify the target HNB. The following is assumed:

– UE is non-CSG capable not able to read SIBs for CSG inbound mobility purposes.

– The HNB-GW is able to perform access control or membership verification for the UE

– The HNB-GW is able to route the incoming relocation to the appropriate target HNB.

Figure 5.9.3a-1: Connected Mode inbound mobility for non-CSG UEs to CSG HNB or Hybrid Cell.

1. The UE is triggered to send an RRC Measurement Report by the rules set by the UTRAN as in TS 25.331[25].

2. The Source RAN node makes a decision to relocate the UE session.

3. The source RAN triggers relocation of the UE session by sending the RANAP RELOCATION REQUIRED message to the Core Network. The target RNC-Id and Target Cell Id are included by the source RAN in the RANAP RELOCATION REQUIRED message. The source RAN shall not include target CSG ID and the Cell Access Mode in the RELOCATION REQUIRED message.

4. The Core Network shall not perform any access control or membership verification for the UE and it shall not include target CSG ID and CSG Membership Status in the RELOCATION REQUEST message.

5. The HNB-GW receives a RANAP RELOCATION REQUEST message not including the target CSG ID and the CSG Membership Status. The HNB-GW shall perform access control (in case of CSG cells) or membership verification (in case of Hybrid cells) for the UE. If the relocation is towards a hybrid cell the HNB-GW may include the CSG Membership Status in the RUA Connect message. If the HNB-GW determines that this relocation is for one or more RABs with a particular ARP value (see TS 23.060 [10]) then it will allow inbound mobility to CSG cells even if the access control fails and, in case of access control failure, the HNB-GW sets the CSG Membership Status IE to the value “non-member” in the RUA Connect message.

6. The steps for HNB-GW Triggered UE Registration are executed between the HNB-GW and the HNB. If the CSG HNB determines that this relocation is for one or more RABs with a particular ARP value (see TS 23.060 [10]) and the UE is non member then it will accept only those RABs with a particular ARP value (see TS 23.060 [10]) and ensure that the others are not continued in the target cell.

7. The remainder of the relocation procedure continues normally as documented in TS 25.413 [9], TS 23.060 [10].

5.9.4a Connected Mode Inbound Mobility to open access HNBs

The following figure and accompanying steps describe the inbound mobility procedure when the Source RAN is able to identify the target HNB. The following is assumed:

● The HNB-GW is able to route the incoming relocation to the appropriate target HNB.

Figure 5.9.4a-1: Connected Mode inbound mobility to open access HNBs.

1. The UE is triggered to send an RRC Measurement Report by the rules set by the UTRAN as in TS 25.331[25].

2. The Source RAN node makes a decision to relocate the UE session.

4. The Core Network shall not perform any access control or membership verification for the UE and it shall not include target CSG ID and CSG Membership Status in the RELOCATION REQUEST message.

5. The HNB-GW receives a RANAP RELOCATION REQUEST message not including the target CSG ID and the CSG Membership Status.

6. The steps for HNB-GW Triggered UE Registration are executed between the HNB-GW and the HNB.

7. The remainder of the relocation procedure continues normally as documented in TS 25.413 [9], TS 23.060 [10]