1

IEEE 802.21 MEDIA INDEPENDENT HANDOVER

DCN: 21-10-0135-00-srho

Title: Introduction of 3GPP IWLAN Architecture and SRVCC

Date Submitted: 2010-7-10

Presented at IEEE 802 July Plenary

Authors or Source(s):

Dapeng Liu, Ge Liu(China Mobile)

Abstract: Introduction of 3GPP IWLAN and SRVCC architecture which is related to single radio handover.

1

22

IEEE 802.21 presentation release statementsThis document has been prepared to assist the IEEE 802.21 Working Group. It is offered as a basis

for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.21.

The contributor is familiar with IEEE patent policy, as stated in Section 6 of the IEEE-SA Standards Board bylaws <http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and in Understanding Patent Issues During IEEE Standards Development http://standards.ieee.org/board/pat/faq.pdf> 

Agenda

•3GPP IWLAN Introduction

•3GPP SRVCC Introduction

21-09-0198-02-srho 3

3GPP IWLAN Introduction• 3GPP TS 23.327

• Mobility between 3GPP-Wireless Local Area Network (WLAN) interworking and 3GPP systems

• 3GPP TS 24.327• Mobility between 3GPP-Wireless Local Area Network (WLAN) interworking and 3GPP systems; Stage 3

4

WLAN 3GPP IP Access

3GPP Home Network

WLAN Access Network

WLANUE

Ww

HSS HLR

OfflineChargingSystem

OCSWa

Wn

Wx

D' / Gr'

Wf

Wo

Wi

Intranet / Internet

Wm

WAG Wp PDG

Wg

Wu

Dw

SLF

3GPP AAAServer

Wy

Wz

L2/L1

TransportIP

Tunnelinglayer

WLANUE

WLAN AN WAG PDG

L2/L1

TransportIP

L2/L1

TransportIP

L2/L1 L2/L1 L2/L1

TransportIP

Remote IP

L2/L1Transport

IPTransport

IP

Remote IP

Tunnelinglayer

Non-roaming reference model

Protocol stack between the WLAN UE and the Packet Data Gateway

IWLAN Architecture

5

PDG Architecture TTG Architecture

• PDG has both WAG and PGD function• PDG is introduced for WLAN access• Less impact of the current GGSN and 2/3G network

• TTG uses Gn’ interface connect to GGSN• TTG has tunnel termination function• Reuse current 2/3G network’s GGSN• May has impact to the current GGSN

WLANUE

WLANAccess

Network

WAG PDG

3GPP AAA

OCS

HSS/HLR

Packet Data

Network

WLANUE

WLANAccess

Network

TTG GGSN

3GPP AAA

OCS

HSS/HLR

Packet Data

Network

IWLAN Mobility Architecture

• Stand alone HA(Home Agent)

• UE should support DSMIPv6(Dual Stack Mobile IPv6)

6

HSS 3GPP AAA

Server

PDG/ AR

WLAN Access Network

UE HA External PDN

Wn Wp WAG

H3 H2

Wx

H1 HGi

Ww Wu

GERAN/UTRAN

Uu/Um

GGSN/ AR

Iu_ps/Gb Gn

SGSN

H3

IWLAN Mobility Architecture in deployment: HA co-located with GGSN

• 3GPP network as UE’s home network

• WLAN network as UE’s foreign network7

SGSN

WAG PDG

GGSN

HA Packet Data Network

HSS

AAA Server

GERAN

UTRAN

WLAN AN

Gn

H3

Wm

Wp

Iu-PS

Wx

Gr

Gb

Wn

Gi

UE

Wu

Ww

Uu

Um

H1

H2

Attach procedure over 2G/3G for the GGSN and HA collocated scenario

8

UE SGSN GGSN/HA HLR/HSS

2. Update Location and Insert Subscriber Data 3. Activate PDP

Context Request (APN)

5. Create PDP Context Request (APN)

AAA DHCP

6. AAA/DHCP Query/Response (PDP address)

7. Create PDP Context Response (PDP address == HoA)

8. Activate PDP Context Response

3GPP access-specific data transmission

4. GGSN selection

GTP tunnel

1. GPRS Attach Request/Accept

1. Authentication

• 1. The UE initiates the attach procedure at power on. The UE is authenticated and authorized to access the 2G/3G network according to TS 23.060 [3]. SGSN may interact with the HLR for Authentication.

• 2. The SGSN interacts with the HLR and updates the mobile node's location area as it is specified in TS 23.060 [3]. SGSN receives the Subscriber Data from HLR.

• 3. The UE initiates the PDP context activation procedure as it is specified in TS 23.060 [3] to obtain the IP address. The Access Point Name (APN) specified by the service provider may be passed as a parameter. The UE shall leave the PDP Address empty to request a dynamic PDP address.

• 4. The SGSN performs the GGSN selection as it is specified in TS 23.060 [3].

• 5. The SGSN requests the selected GGSN to set up a PDP context for the UE as it is specified in TS 23.060 [3].

• 6. If the GGSN can assign an address for the UE locally, it assigns the address and the GGSN creates a TEID for the requested PDP context. Otherwise the GGSN uses External PDN Address Allocation mechanism as it is specified in TS 23.060 [3] and in TS 29.061 [13]. The GGSN obtain a PDP address from the PDN by means of protocols such as DHCP or RADIUS and creates a TEID for the requested PDP context.

• 7. The GGSN responds back to the SGSN, indicating completion of the PDP context activation procedure as it is specified in TS 23.060 [3]. The PDP address, which is sent back to the UE, is the Home Address. In addition to the GPRS specification TS 23.060 [3], if the Home Link information is available, the GGSN shall return the HA IP address and the HNP via the PCO to the UE.

• 8. The SGSN replies back to the UE as it is specified in TS 23.060 [3]. This signals completion of the PDP context activation and the IP address allocated corresponds also to its HoA. The UE stores the information for future use.

9

10

Data routed by HA to UE's CoA via I-WLAN

UE WLAN AN

PDG 3GPP AAA Server

GGSN/HA

2. Authentication Authorization

3. HA Discovery

2. I-WLAN Attach Tunnel establishment

Mobile IP tunnel inside an IPsec tunnel

1. WLAN connection

4. H1-PDN-Attach Procedure

IPsec Tunnel

I-WLAN Attach Procedure with mobility service

• 1. The WLAN UE selects a WLAN Access Network and establishes the WLAN connection with a WLAN technology specific procedure. The UE gets allocated a local IP address and optionally WLAN Access Authentication and Authorization which may depend on the home operator policy as well as the policy of the provider of the WLAN AN according to TS 23.234 [2].

• 2. I-WLAN attachment and IPsec tunnel setup is executed according to TS 23.234 [2]. In addition to the procedure defined in TS 23.234 [2]. The PDG may return the HA address in IKEv2 configuration payload to the UE.

• 3. The method by which HA is known to the UE is defined in HA discovery clause 5.3.2 The UE must know the HA in order to perform BU/BA. This step is required only if HA address was not discovered via IKEv2 configuration payload in the previous steps.

• 4. H1 PDN-Attach procedure is performed as it is specified in clause 6.1.

• 5. The UE can send and receive packet.

11

Handover from 3GPP access to I-WLAN

12

3GPP access-specific data transmission ta transmission

Data routed by HA to UE's CoA via I-WLAN

UE SGSN PDG GGSN/HA 3GPP AAA Server

3. Authentication and Authorization

5. Binding Update

6. Binding Acknowledgement

2. HO decision

3. I-WLAN Attach, Tunnel establishment, CoA allocation

7. Mobile IP tunnel inside an IPsec tunnel

1. GTP tunnel

IPsec Tunnel

4. IKEv2 Bootstrap

8. Bearer Resource Release

• 1. The precondition of this flow is that the UE is attached to a 3GPP access and has active PDP context(s) with a GGSN/HA node. There is a GTP tunnel between the SGSN and the GGSN.

• 2. The UE needs to handover to a WLAN access network. The HO decision mechanism could be based on local policy in the UE.

• 3. I-WLAN attachment and IPsec tunnel setup is executed according to TS 23.234 [2]. In addition to the procedure defined in TS 23.234 [2] the UE may also obtain the Home Agent information via IKEv2 configuration payload if not already available in the UE.

• 4. The UE perform IKEv2/IPsec security association setup procedure with the Home Agent for DSMIPv6.

• 5. The UE sends a binding update to its home agent to update the binding cache entry at the home agent. The UE will use its IP address used in 3GPP access as its Home Address. This address will be preserved unless further indication from the 3GPP access. The UE uses the address configured from the PDG as the care-of address. The care-of address may be an IPv4 or IPv6 address.

• 6. The Home Agent responds with a binding acknowledgement if the binding update process was successful. The Home Agent also creates the binding cache entry with the new care-of address of the UE. In this message, the HA also includes the APN corresponding to the home link for the UE to store.

• 7. The successful exchange of binding update and binding acknowledgement results in a Mobile IP tunnel between the UE and the home agent over the IPsec tunnel between the UE and the PDG. Data packets are now routed by Home Agent to UE's Care-of-Address via I-WLAN.

• 8. During this procedure, bearer resources reserved for the UE are released.

13

Handover from I-WLAN to 3GPP Access

14

3GPP access-specific data transmission

Data routed by HA to UE's CoA via I-WLAN

UE SGSN PDG GGSN/HA

3GPP AAA Server

1. Mobile IP tunnel inside an IPsec tunnel

2. HO Decision. Attach to 3GPP Access

3. PDP Context Activation Service Request

8. Bearer Resource Release

7. GTP tunnel

4. AAA interactions

6. Binding Acknowledgement

5. Binding Update (Lifetime =0)

• 1. The precondition of this flow is that he UE is attached over I‑WLAN with mobility support. There is a Mobile IP tunnel between the UE and the Home Agent over an IPsec tunnel between the UE and the PDG.

• 2. The UE may need to handover to 3GPP access network because I‑WLAN is no longer able to provide the required user-to-PDN connection service or based on operator policies. The UE attaches to 3GPP access according to TS 23.060 [3].

• In  order to generate an APN to be used when activating a PDP context in the GPRS access, the UE uses the APN information received in the BA during H1 PDN attach as described in clause 1.6. If no APN is received in the Binding Acknowledgement message during H1 PDN attach, the UE shall use the pre-configured APN, if available

• 3. The UE initiates PDP context setup according to TS 23.060 [3]. The  UE provides an APN corresponding to the combined GGSN/HA used in the source access. This results in a PDP context setup with a GTP tunnel between the SGSN and the GGSN. GGSN returns a PDP address to the UE which is same as the HoA the UE used in WLAN access in step 1. In case of IPv6, the prefix associated with the PDP context is the same as the one for HoA (i.e. HNP).

• 4. The GGSN/HA interacts with the AAA server for mobility service authentication and authorization according to TS 29.061 [13].

• 5. The UE detects that the HoA and the PDP address are same, so the UE considers itself in home link. The UE sends a Binding Update to its home agent with lifetime=0, and CoA=HoA to delete the binding cache entry at the home agent.

• 6. The Home Agent responds with a Binding Acknowledgement if the binding update process (binding deletion) was successful.

• 7. With the Binding Update and binding acknowledgement exchange the HA recognizes that the UE has returned home and deletes the binding cache. There is no Mobile IP tunnel between the UE and the home agent however a GTP tunnel is established between the SGSN and the GGSN.

• 8. Bearer Resources on the I-WLAN access system are released according to TS 23.234 [2]. For that the UE detaches from I-WLAN if it has not happened before.

15

Pre-registration in IWLAN

• Motivation？• From WLAN handover to 3GPP• WLAN signal may decline too fast

• Potential solution for discussion• WiMAX to E-UTAN Single Radio Interworking

Architecture• 3GPP SFF emulate SGSN

21-09-0198-02-srho 16

WiMAX to 3GPP Pre-8 Single Radio Interworking

17

Procedures of WiMAX- 3GPP Pre-8 Interworking

18

Procedures of WiMAX- 3GPP Pre-8 Interworking

21-09-0198-02-srho 19

Potential Pre-registration Solution for IWLAN

• 3GPP SFF help to do the authentication PDP context activation before handover

• When UE decides to handover to 3GPP, UE connects to the SGSN then send BU message with lift time=0

20

UE

WAG PDG

SGSN GGSN/HA

3GPP SFF

WLAN Access Network

GERAN

Agenda

•3GPP IWLAN Introduction

•3GPP SRVCC Introduction

21-09-0198-02-srho 21

Introduction of 3GPP Single Radio Voice Call Continuity(SRVCC)

• Motivation• Limited coverage during initial stage of LTE deployment• Difficult for UE to attach to both LTE and GSM/UMTS

network at the same time

• Single Radio Voice Call Continuity(SRVCC): • Voice call continuity between IMS over PS access and CS

access for calls that are anchored in IMS when the UE is capable of transmitting/receiving on only one of those access networks at a given time. [TS 23.216]

21-09-0198-02-srho 22

SRVCC Concept• SRVCC Types

• E-UTRAN and 3GPP2 1xCS SRVCC• E-UTRAN and 3GPP UTRAN/GERAN SRVCC• UTRAN (HSPA) to 3GPP UTRAN/GERAN SRVCC

• High Level Concepts （ E-UTRAN to UTRAN/GERAN）

21-09-0198-02-srho 23

SRVCC Architecture 1• E-UTRAN and 3GPP2 1xCS SRVCC architecture

21-09-0198-02-srho 24

E-UTRAN

MME

Serving/PDN GW

SGi

1xRTT CS Access

1xRTT MSC

1xCS IWS

S102

S11 S1-MME

S1-U

A1

1xCS SRVCC UE

Bearer before HO

Bearer after HO

SIP signalling

A1

IMS

Tunnelled 1xRTT messages

1xCS SRVCC

UE

• 1x CS IWS: • 3GPP2 1x CS SRVCC interworking solution function• Emulate a 1xRTT BSS towards the 1xRTT MSC

Concept procedure

21-09-0198-02-srho 25

UE MME 1xCSIWS

1xRTTMSC

1xRTTCS accessE-UTRAN

1a. IMS Emergency Session ongoing over E-UTRAN access1b. MME indicates to E-UTRAN that CN and UE are SRVCC capable

2. MeasurementReports

3. SRVCC Handover to CDMA200 1x is required as defined in TS 23.216

4. Initiates Inter-Technology Emergency SRVCC Handover

6. Emergency voice ongoing call over the CS leg established over 1xRTT access

7. Handover execution

5. 1x traffic assignment & 3GPP2 emergency VCC procedure

8. Reconfigure Location Support

E-UTRAN and 3GPP2 1xCS

SRVCC Architecture 2

• E-UTRAN and 3GPP UTRAN/GERAN SRVCC architecture

21-09-0198-02-srho 26

UE E-UTRAN

MME

MSC ServerTarget

UTRAN/GERAN

Serving/PDNGW

IMS

UE Um/Uu Iu-cs/A

S3

Sv

S11S1-MME

S1-UE-UTRAN Uu SGi

HSSS6a

SGSN

Iu-ps/Gb

Bearer path before HO

Bearer path after HO

SIP signaling path before HO

• MSC Server is enhanced for SRVCC• Handling the Relocation Preparation procedure requested for

the voice component from MME/SGSN via Sv reference point;• Invoking the session transfer procedure from IMS to CS

Concept procedure

21-09-0198-02-srho 27

UE E-UTRAN MME MSC ServerTarget

UTRAN/GERAN

MeasurementReports

Handover to UTRAN/GERAN required

3GPP IMS

Initiates SRVCC for voice component

CS handover preparation

IMS Service Continuity ProcedureHandles PS-PS HO for

non-voice if needed

PS HO response to MME(CS resources)

To eUTRANCoordinates SRVCC and PS HO response Handover CMD

Handoverexecution

E-UTRAN and 3GPP UTRAN/GERAN

SRVCC Architecture 3

• UTRAN (HSPA) and 3GPP UTRAN/GERAN SRVCC architecture

21-09-0198-02-srho 28

UE

Target UTRAN/GERAN MSC Server

SGSN

SGSN HSS

GGSN UTRAN (HSPA) UE

IMS

Uu

Um/Uu Iu-cs/A

Iu-ps/Gb

Gn

Sv

Gr

Gn

Gi

Iu-ps

• MSC Server is enhanced for SRVCC• Handling the Relocation Preparation procedure requested for

the voice component from MME/SGSN via Sv reference point;• Invoking the session transfer procedure from IMS to CS

Concept procedure

21-09-0198-02-srho 29

UEUTRAN(HSPA)

SGSN MSC ServerTarget

UTRAN/GERAN

MeasurementReports

Handover to UTRAN/GERAN required

3GPP IMS

Initiates SRVCC for voice component

CS handover preparation

IMS Service Continuity ProcedureHandles PS-PS HO for

non-voice if needed

CS HO response to SGSNTo UTRAN(HSPA)

Coordinates SRVCC and PS HO response Handover CMD

Handoverexecution

UTRAN (HSPA) and 3GPP UTRAN/GERAN

30

Thanks!