4 Overall architecture

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

4.1 General

The overall UMTS architecture and UTRAN architectures are described in TS 25.401 [4] and TS 25.410 [5]. For clarity and ease of understanding, at appropriate places references to TR-069 [7] and associated methods are described briefly although they are beyond the scope of this specification.

The reference model shown in Figure 4.1-1 below contains the network elements that make up the HNB access network. There is a one-to-many relationship between a HNB-GW and the HNB(s) it serves.

Figure 4.1-1: HNB access network reference model.

The HNB-GW appears to the CN as an RNC and serves as a concentrator of HNB connections. The Iu interface between the CN and the HNB-GW serves the same purpose as the interface between the CN and a RNC. The HNB GW is uniquely identified towards the CN on a particular Iu interface by the RNC ID. One HNB serves only one cell.

The HNB-GW appears to other RNCs as an RNC and serves as a concentrator of HNB connections. The HNB GW is uniquely identified towards the RNC on a particular Iur interface by the RNC ID.

The Local Gateway (L-GW) may be present only when the HNB operates in LIPA mode or when the HNB operates in SIPTO@LN mode. When present, it is co-located with the HNB, in which case the HNB has a Gn/S5 interface towards the SGSN/SGW which does not use the HNB-GW, and a Gi interface towards the residential/IP network.

If the L-GW is present within the HNB, the HNB shall use for Gn/S5 connectivity the same secure interface established by the HNB for Iuh signalling as specified in TS 33.320 [16].

If the HNB-GW is supporting Fixed Broadband Access network interworking function, the HNB-GW uses a S15 interface towards PCRF for CS sessions as specified in TS 23.139 [36].

The HNB may be assigned the same inner IP address for the Gn/S5 interfaces as for the Iuh interface, or a different IP address.

NOTE: If the HNB uses the same IP address for Gn/S5 and the Iuh interface, they should be assigned distinct ranges of TEIDs in order to be able to discriminate downlink GTP-U packets.

NOTE: The Security gateway is a logically separated entity and may be implemented either as a separate physical element or integrated into, for example, a HNB-GW.

The HNB access network includes the functional entities as shown in Figure 4.1-1 and detailed below.

The HNB access network supports Iurh connectivity between HNBs and connectivity between HNBs and RNCs via the HNB-GW.

This version of specification supports three different Iurh connectivity options:

– Option1: Direct Iurh interface connectivity between the two involved HNBs.
In this case the HNB-GW is not involved at all in Iurh RNL signalling.

– Option 2: Iurh interface connectivity between HNBs with the HNB-GW serving as an Iurh proxy.
In this case the HNB-GW, acting as an Iurh-proxy, appears to a HNB as the peer HNB.
For this connectivity option the role of the HNB-GW is transparent with regard to RNSAP signalling. Conveying respective signalling messages via the HNB-GW is performed by routing based on information provided by the RNSAP User Adaptation (RNA) layer, see TS 25.471 [19].

– Option 3: Iurh interface connectivity between HNBs and the HNB-GW utilised for transporting RNL signalling between those HNBs and RNCs via the HNB-GW.

NOTE: If Option 2 and Option 3 coexist, they share the same SCTP association.

Iurh connectivity between one pair of HNBs shall either support direct Iurh connectivity or Iurh connectivity via the HNB-GW, not both at the same time.

With respect to HNB-HNB mobility, there is no requirement for a HNB to support direct Iurh connectivity and Iurh connectivity via the HNB-GW at the same time in the current release of the specification.

4.1.1 HNB Management System (HMS)

The HMS:

– is based on the TR-069 family of standards [7].

– facilitates HNB-GW discovery.

– provides configuration data to the HNB.

– performs location verification of HNB and assigns appropriate serving elements (HMS, Security Gateway and HNB-GW).

4.1.2 Security Gateway (SeGW)

The SeGW:

– terminates secure tunnelling for TR-069 [7] as well as Iuh.

– terminates secure tunnelling for Iurh and Gn/S5 for certain deployment options.

– authenticates HNBs.

– provides the HNB with access to the HMS and HNB-GW.

4.1.3 HNB Gateway (HNB-GW)

The HNB Gateway:

– terminates Iuh from HNB and appears as an RNC to the Core network.

– supports HNB registration and UE registration over Iuh.

– may terminate TNL for the Iurh interface, in case Iurh connectivity via the HNB-GW is deployed for at least one HNB or connectivity to an RNC via the HNB-GW.

– may support Fixed Broadband Access network interworking via S15 interface towards PCRF for CS sessions as specified in TS23.139 [36].

4.1.4 HNB

The HNB:

– offers the Uu Interface to the UE.

– provides RAN connectivity using the Iuh and Iurh interfaces.

– acts as RNS (details are captured in Table 4.2-1).

– supports HNB registration and UE registration over Iuh.

– In case of LIPA support or SIPTO at the Local Network with collocated L-GW support, it supports the following additional functions:

– transfer of the Gn/S5 IP address of the HNB over Iuh.

– support of basic GGSN/P-GW functions in the collocated L-GW function by support of the Gi/SGi interface corresponding to LIPA or SIPTO@LN.

– Support of use of the Correlation ID or SIPTO Correlation ID, respectively, for correlation purposes between the collocated L-GW function and the HNB.

– In case of Fixed Broadband Access network interworking support, it supports transferring of Tunnel Information over Iu/Iuh as specified in TS 23.139 [36].

4.1.5 L-GW

The L-GW function within the HNB provides:

– in Idle mode, support for sending the first packet to the SGSN/SGW and, buffering of subsequent downlink packets.

– support of internal direct user plane path towards the corresponding HNB user plane functions.

– deactivation of the Gn/S5 interface connection.

The mobility of the LIPA PDN connection is not supported in this Release of the specification. The LIPA connection is always released with handover as described in TS 23.060 [10].

The mobility of the SIPTO@LN PDN connection is not supported in this Release of the specification. The SIPTO@LN PDN connection is always released after a handover is performed, as described in TS 23.060 [10].

4.2 Functional split

The UTRAN functions in the HNB are supported by RANAP, whereas the HNB specific functions are supported by the Home Node B Application Protocol (HNBAP) between the HNB and the HNB-GW. The HNB-GW provides a concentration function for the control plane and may provide a concentration function for the user plane.

This sub-clause defines the functional split between the core network and the UMTS radio access network. The functional split is shown in Table 4.2-1 and 4.2-2.

Table 4.2-1. Functional split for UTRAN function in the HNB access.

Function	HNB	HNB-GW	CN
RAB management functions:
RAB establishment, modification and release	X	X Note 1	X
RAB characteristics mapping Iu transmission bearers	X	X
RAB characteristics mapping Uu bearers	X
RAB queuing, pre-emption and priority	X		X
Radio Resource Management functions:
Radio Resource admission control	X
Broadcast Information	X	X Note 2	X
Iu link Management functions:
Iu signalling link management	X	X	X
ATM VC management		X	X
AAL2 establish and release		X	X
AAL5 management		X	X
GTP-U Tunnels management	X	X	X
TCP Management		X	X
Buffer Management	X	X
Iu U-plane (RNL) Management:
Iu U-plane frame protocol management			X
Iu U-plane frame protocol initialization	X
Mobility management functions:
Location information reporting	X		X
Handover and Relocation
Inter RNC hard HO, Iur not used or not available	X	X	X
Serving RNS Relocation (intra/inter MSC)	X	X	X
Inter system hard HO (UMTS-GSM)	X	X	X
Inter system Change (UMTS-GSM)	X		X
Paging Triggering	X		X
Paging Optimization		X
GERAN System Information Retrieval	X		X
Security Functions:
Data confidentiality
Radio interface ciphering	X
Ciphering key management			X
User identity confidentiality	X		X
Data integrity
Integrity checking	X
Integrity key management			X
Service and Network Access functions:
CN Signalling data	X		X
Data Volume Reporting	X
UE Tracing	X		X
Location reporting	X		X
Positioning	X	X
Iu Co-ordination functions:
Paging co-ordination	X		X
NAS Node Selection Function		X
MOCN Rerouting Function		X	X
SIPTO at the Local Network with Standalone GW	X		X
Note 1: This function could be needed for TNL address translation in the HNB-GW when there is no user plane direct transport connection between HNB and CN Note 2: HNB-GW is able to perform the filtering of SABP messages i.e. determines from the SAI list to which HNB the SABP message needs to be sent and then distributes the SABP messages to the appropriate HNBs. This is an optional function in HNB-GW.

Table 4.2-2. Functional split for HNB function in the HNB access.

Function			HNB			HNB-GW			CN
HNB Registration Note 1
HNB Registration Function			X			X
HNB-GW Discovery Function			X
HNB de-registration Function			X			X
UE Registration for HNB Note 1
UE Registration Function for HNB			X			X
UE de-registration Function for HNB			X			X
Iuh user-plane Management functions
Iuh User plane transport bearer handling			X			X
Functions for multiplexing CS user plane on the Uplink			X			X
Traffic Offload Functions
LIPA			X						X
SIPTO at the Local Network with Collocated L-GW			X						X
Enhanced Interference Management
Mitigation of Interference from HNB to Macro			X
UE Access Control / Membership Verification
IDLE mode			XNote2			X			X
Connected mode (inbound relocation to HNB cells)						X			X
CSG ID validation			X			X
CSG Subscription Expiry			X			X			X
Iurh Connectivity Functions
Iurh Establishment			X			XNote 3
Exchange of Iurh Connectivity data for neighbour HNBs			X			X
Fixed Broadband Access network Interworking
CS sessions			X			X			X
PS sessions			X						X
Note 1: Protocol support for this group of functions is provided by the HNB Application Protocol. Note 2: Access control or membership verification at the HNB are optional. Note 3: If the HNB-GW is involved in Iurh Establishment for Iurh connectivity option 2, it acts only as pure relay for this signalling.