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TR 23.885 (SA2) ★
Feasibility Study of
Single Radio Voice Call Continuity (SRVCC)
from UTRAN/GERAN to E-UTRAN/HSPA

use "3GPP‑Page" to get the Word version
for a better overview, the Table of Contents (ToC) is reproduced

V11.0.0 (Wzip) 2011/09 83 p.

Rapporteur: Mr. Barankanira, Delphin

The objective of the feasibility study is to investigate a solution for supporting Single Radio Voice Call Continuity (SRVCC) from 3GPP UTRAN/GERAN CS access to 3GPP E-UTRAN/HSPA access, for voice call initiated in LTE/HSPA access and previously handed over to UTRAN/GERAN CS access, as well as for the voice call directly initiated in UTRAN/GERAN CS access.

full Table of Contents for TR 23.885 Word version: 11.0.0

1 Scope Word-p. 7

3 Definitions and abbreviations Word-p. 8

3.1 Definitions

3.2 Abbreviations

4 Requirements and Assumptions

4.1 Assumptions

4.2 Architectural requirements

4.3 Performance requirements Word-p. 9

4.4 Reverse SRVCC deployment scenarios Word-p. 10

5 Architecture model and reference points

5.2 Reference architecture Word-p. 11

5.2.1 3GPP UTRAN/GERAN and E-UTRAN SRVCC architecture

5.2.2 3GPP UTRAN/GERAN and UTRAN (HSPA) SRVCC architecture

5.3 Functional Entities Word-p. 12

5.3.1 MSC Server enhanced for SRVCC

5.4 Reference points

6.1 Solution 1: Session transfer initiated on E-UTRAN/HSPA

6.1.1 Functional Description

6.1.2 Information flows Word-p. 13

6.1.2.1 GERAN/UTRAN Attach procedure

6.1.2.2 E-UTRAN attach procedure

6.1.2.3 Call establishment procedure in GERAN/UTRAN

6.1.2.4 SRVCC from E-UTRAN/HSPA to GERAN/UTRAN Word-p. 14

6.1.2.5 Handover procedure in GERAN/UTRAN

6.1.2.6 Call flows for SRVCC from UTRAN/GERAN to E-UTRAN

6.1.2.6.1 SRVCC handover from GERAN without DTM support to E-UTRAN

6.1.2.6.2 SRVCC handover from UTRAN or GERAN with PS handover support to E-UTRAN Word-p. 16

6.1.2.7 Call flows for SRVCC from UTRAN/GERAN to HSPA Word-p. 18

6.1.2.7.1 SRVCC handover from GERAN without DTM support to HSPA

6.1.2.7.2 SRVCC handover from UTRAN or GERAN with PS handover support to HSPA Word-p. 19

6.2 Solution 2: Session transfer initiated on E-UTRAN/HSPA Word-p. 20

6.2.1 Functional Description Word-p. 21

6.2.2 Information flows

6.2.2.1 GERAN/UTRAN Attach procedure

6.2.2.2 E-UTRAN attach procedure

6.2.2.3 Call establishment procedure in GERAN/UTRAN

6.2.2.4 SRVCC from E-UTRAN/HSPA to GERAN/UTRAN Word-p. 22

6.2.2.5 Handover procedure in GERAN/UTRAN

6.2.2.6 Call flows for SRVCC from UTRAN/GERAN to E-UTRAN Word-p. 23

6.2.2.6.1 SRVCC handover from GERAN without DTM support to E-UTRAN

6.2.2.6.2 SRVCC handover from UTRAN or GERAN with PS handover support to E-UTRAN Word-p. 24

6.3 Solution 3+5: Media anchoring in serving network with Access Transfer Control Functionality Word-p. 25

6.3.1 Architecture Reference Model

6.3.2 Functional Entities Word-p. 26

6.3.2.2 SCC AS Word-p. 27

6.3.2.4 MSC Server enhanced for reverse SRVCC

6.3.2.5 SGSN enhanced for rSRVCC

6.3.2.6 UE enhanced for rSRVCC

6.3.2.7 HSS Word-p. 28

6.3.2.8 MME/SGSN enhanced for rSRVCC

6.3.3 Message Flows

6.3.3.1 General principles

6.3.3.2 GERAN/UTRAN Attach procedure Word-p. 29

6.3.3.3 E-UTRAN attach procedure

6.3.3.3a Informing the source RAN about the possibility to perform rSRVCC

6.3.3.4 Codec and transport address related procedure Word-p. 30

6.3.3.4.1 General

6.3.3.4.2 Information in IMS registration and handover procedure

6.3.3.5 Establish a session over CS

6.3.3.5.1 STN-SR allocated by the ATCF and Transfer Info sent to ATCF

6.3.3.5.2 Registration when ATCF involved Word-p. 31

6.3.3.5.3 Origination procedures when ATCF involved

6.3.3.5.4 Termination procedures when ATCF involved Word-p. 32

6.3.3.6 CS - PS Access Transfer Overview Word-p. 33

6.3.3.6.1 Anchored in ATGW

6.3.3.6.2 Not Anchored in ATGW Word-p. 34

6.3.3.7 Access Transfer Preparation

6.3.3.7.1 Access Transfer Preparation Alternative 1

6.3.3.7.2 Access Transfer Preparation Alternative 2 Word-p. 36

6.3.3.7.3 Access Transfer Preparation Alternative 3 Word-p. 38

6.3.3.7.4 Access Transfer Preparation Alternative 4 Word-p. 40

6.3.3.7.5 Access Transfer Preparation Alternative 5 (the combination) Word-p. 43

6.3.3.8 IMS Session Continuity procedure Word-p. 45

6.3.3.8.0 General

6.3.3.8.1 Anchored in ATGW Word-p. 46

6.3.3.8.2 Not Anchored in ATGW Word-p. 47

6.3.3.9 Identification of serving PS node Word-p. 48

6.3.3.9.1 Alternative 1: CN nodes based

6.3.3.9.2 Alternative 2: UE and/or RAN provided information

6.3.3.9.3 Alternative 3: RAN provided information Word-p. 49

6.3.4 IMS registration Considerations Word-p. 50

6.3.4.1 General

6.3.4.2 ATCF controlled registration

6.3.4.3 SCC AS controlled registration Word-p. 51

6.3.4.4 rSRVCC HO Cancellation in case of UE loss of IMS registration Word-p. 52

6.4 Solution 4: Session transfer by local anchoring with Indirect Forwarding Word-p. 53

6.4.1 Functional Description

6.4.2 Architecture Reference Model Word-p. 54

6.4.3 Information flows

6.4.3.1 Initial ATTACH / TA update procedure

6.4.3.2 Call origination procedure in GERAN/UTRAN

6.4.3.3 Call termination procedure in GERAN/UTRAN Word-p. 56

6.4.3.4 SRVCC handover from UTRAN or GERAN to LTE Word-p. 57

6.5 Solution 5: IMS procedure is initiated by MSC Server to ATCF Word-p. 59

6.5.1 Architecture Reference Model

6.5.1.1 General

6.5.1.2 Concepts of reverse SRVCC Word-p. 60

6.5.2 Functional Entities Word-p. 61

6.5.2.3 S-CSCF Word-p. 62

6.5.2.4 MSC Server enhanced for reverse SRVCC

6.5.2.6 UE enhanced for reverse SRVCC

6.5.2.7 UTRAN/GERAN

6.5.3 Message Flows Word-p. 63

6.5.3.1 Home control rSRVCC

6.5.3.2 RAU/LAU/TAU procedure

6.5.3.3 GERAN/UTRAN performs handover procedure

6.5.3.4 Maintaining IMS Registration

6.5.3.5 Preparation of media transfer

6.5.3.6 Selection of the ATCF Word-p. 64

6.5.3.7 Originating sessions in CS Word-p. 65

6.5.3.7.1 Serving MSC Server is not enhanced for ICS

6.5.3.7.2 Serving MSC Server is enhanced for ICS Word-p. 66

6.5.3.7.3 Serving MSC Server is enhanced for rSRVCC

6.5.3.7.4 UE is enhanced for ICS Word-p. 67

6.5.3.8 Terminating sessions in CS Word-p. 68

6.5.3.8.1 UE is not enhanced for ICS

6.5.3.8.2 UE is enhanced for ICS Word-p. 69

6.5.3.9 CS - PS Access Transfer Word-p. 70

6.5.3.9.0 Introduction

6.5.3.9.1 IMS Session Continuity procedure

6.5.3.9.2 CS to PS handover procedure Word-p. 71

6.5.3.10 Failure to complete CS-PS Access Transfer Word-p. 72

7 Assessment of the solutions Word-p. 73

7.1 Assessment Criteria

7.2 Assessment of the solution 3+5 access transfer preparation alternatives Word-p. 74

8 Conclusion Word-p. 77

8.2 Access Transfer preparation / How to reserve bearer for VoIP

8.3 Source SGSN selection by MSC Server

8.4 Maintaining IMS registration over PS access during the CS session

A Mechanisms to re-enable E-UTRAN capability Word-p. 78

A.1 Functional description

A.2 Information flows Word-p. 79

A.2.1 Proposed signalling flow for Alternative A to re-enable E-UTRAN capabilities using broadcast indicator

A.2.2 Proposed signalling flow for Alternative B to re-enable E-UTRAN capabilities using NAS indicator Word-p. 80

A.2.3 Proposed signalling flow for Alternative C to re-enable E-UTRAN capabilities using change in RFSP/RAC of the UE Word-p. 81

B Mechanisms for GERAN/UTRAN sending Handover/Relocation Required message Word-p. 82

C Change history Word-p. 83