VoLTE Service Description and Implementation Guidelines ...

1 GSM Association Non-confidential Official Document - VoLTE Service Description and Implementation Guidelines Page 1 of 121 VoLTE Service Description and Implementation Guidelines Version 26 March 2014 This is a Non-binding Permanent Reference Document of the GSMA Security Classification: Non-confidential Access to and distribution of this document is restricted to the persons permitted by the security classification. This document is confidential to the Association and is subject to copyright protection. This document is to be used only for the purposes for which it has been supplied and information contained in it must not be disclosed or in any other way made available, in whole or in part, to persons other than those permitted under the security classification without the prior written approval of the Association.

2 Copyright Notice Copyright 2014 GSM Association Disclaimer The GSM Association ( Association ) makes no representation, warranty or undertaking (express or implied) with respect to and does not accept any responsibility for, and hereby disclaims liability for the accuracy or completeness or timeliness of the information contained in this document. The information contained in this document may be subject to change without prior notice. Antitrust Notice The information contain herein is in full compliance with the GSM Association s antitrust compliance policy. GSM Association Non-Confidential Official Document Page 2 of 121 Table of Contents 1 Introduction 6 Overview 6 Relationship to Standards 6 Scope 7 Definition of Terms 7 Document Cross-References 12 2 VoLTE Architecture 16 VoLTE Functional Node Description 17 VoLTE UE (User Equipment) 17 Evolved Universal Terrestrial Access Network (E-UTRAN) 17 Evolved Packet Core 17 IMS 18 Additional Network Functionality 19 VoLTE Interface Description 20 LTE-Uu Interface (UE eNodeB) 20 S1-MME Interface (UE MME) 20 S1AP Interface (eNodeB MME) 20 S1-U Interface (eNodeB SGW) 20 X2 Interface (eNodeB eNodeB) 20 S5 Interface (SGW PGW) 20 S6a Interface (HSS MME) 20 S9 Interface (H-PCRF V-PCRF) 20 S10 Interface (MME MME)

3 21 S11 Interface (MME SGW) 21 Gx Interface (PCRF PGW) 21 Rx Interface (PCRF P-CSCF) 21 SGi Interface (PGW P-CSCF) 21 Cx Interface (I/S-CSCF HSS) 21 Sh Interface ( VoLTE AS HSS) 21 Gm Interface (UE P-CSCF) 21 Ut Interface (UE VoLTE AS) 21 Mx Interface (x-CSCF IBCF) 22 Mw Interface (x-CSCF x-CSCF) 22 Mg Interface (xCSCF MGCF) 22 Mi Interface (xCSCF BGCF) 22 Mj Interface (BGCF MGCF) 22 ISC Interface (S-CSCF TAS) 22 Mr Interface (S-CSCF MRF) 22 Mr Interface (TAS MRF) 22 Cr Interface (TAS MRF) 22 Mb Interface (media bearer) 22 Ici Interface (IBCF IBCF) 23 GSM Association Non-Confidential Official Document Page 3 of 121 Izi Interface (TrGW TrGW) 23 Related GSMA Permanent Reference Documents 23 3 VoLTE Implementation - Single PMN 25 General 25 VoLTE Basic call Flows 25 VoLTE UE Attachment and IMS Registration 26 VoLTE UE Initiated Detach and IMS Deregistration 32 Basic VoLTE UE to VoLTE UE call Establishment originating Side 35 Basic VoLTE UE to VoLTE UE call Establishment Terminating Side 39 Basic VoLTE UE to VoLTE UE call Clearing - Initiated 43 Basic VoLTE UE to VoLTE UE call Clearing - Received 45 VoLTE -CS Interworking 47 Basic VoLTE UE to CS call Establishment originating Side 47 Basic VoLTE UE to CS call Establishment Terminating Side 50 Basic VoLTE UE to CS call Clearing - Initiated 53 Basic VoLTE UE to CS call Clearing - Received 54 Supplementary Services 55 General 55

4 ENUM/DNS 57 General 57 Number Portability 57 IP Service Routing 57 Number Resolution 57 ENUM 57 Diameter Signalling 60 General 60 Diameter Agents 60 Diameter Transport 60 Diameter Peer Discovery 60 Diameter Capability Exchange 60 Diameter Routing 61 Traffic Management and Policy 61 General 61 Policy and Charging Control 61 DiffServ 63 Mapping between QCI and DiffServ 63 Session Border Controllers 64 Emergency call 64 Lawful Intercept 64 Security 64 General 64 Security Gateway 65 IMS Media Plane Security 65 SMS over IP 65 GSM Association Non-Confidential Official Document Page 4 of 121 Support of Legacy Proprietary CS Services 65 Complementing VoLTE with 2G/3G voice 66 SRVCC 66 PS Handover 66 IMS Service Centralization and Continuity 66 Charging 66 Codecs 67 IP Version & Transport 67 Home eNodeB (HeNB)

5 67 4 VoLTE Implementation - Interconnect 69 General 69 VoLTE Interconnect 69 Basic VoLTE UE to Peer IMS call Establishment originating Side 70 Basic VoLTE UE to Peer IMS call Establishment Terminating Side 73 Basic VoLTE UE to Peer IMS call Teardown - Initiated 76 Basic VoLTE UE to Peer IMS call Teardown - Received 78 Bi-lateral Interconnect 80 Physical Configuration of Bi-lateral Interconnect 80 Usage of ENUM/DNS 80 Usage of Session Border Controllers 81 IPX-Based Interconnect 81 Configuration of IPX-based Interconnect 81 Usage of ENUM/DNS 82 Usage of Session Border Controllers 82 CS Interconnect 82 Charging 82 5 VoLTE Implementation - Roaming 83 General 83 VoLTE Roaming Basic call Flows 84 Roaming VoLTE UE Attachment and IMS Registration 84 Roaming VoLTE UE Initiated Detach and IMS Deregistration 90 Roaming VoLTE UE to VoLTE call Establishment originating Side 92 Roaming VoLTE UE to VoLTE UE call Establishment Terminating Side 96 Roaming VoLTE UE to VoLTE UE call Clearing - Initiated 100 Roaming VoLTE UE to VoLTE call Clearing - Received 102 Roaming Architecture for voice over IMS with Local break-out (RAVEL)

6 104 Optimal Media Routing 105 Diameter Signalling 105 Traffic Management and Policy 106 Session Border Controllers 106 IMS Emergency call 106 Lawful Intercept 106 Security 106 GSM Association Non-Confidential Official Document Page 5 of 121 Charging 106 6 Implementation Guidelines 107 Open Implementation Issues 107 VoLTE Device Implementation Guidelines 107 LTE/EPC Implementation Guidelines 109 VoLTE IMS Implementation Guidelines 111 Other Guidelines 116 Document Management 121 Document History 121 GSM Association Non-Confidential Official Document Page 6 of 121 1 Introduction Overview voice over LTE, or VoLTE is a GSMA profile of the standards definition for the delivery of services currently provided via Circuit Switch networks - mainly voice and SMS - over the Packet Switched only network of LTE, leveraging the core network IP Multimedia Sub-System (IMS).

7 When mobile networks deploy LTE radio access technology, conformity to the VoLTE profile provides operators with assurance of interworking between their LTE network and the devices that connect to it, as well as providing for the expected user experience of voice Multi-Media Telephony Service and SMS. In combination with Policy Control, IMS provides for the required QoS appropriate for voice Service using LTE radio access technology, thereby providing the user experience of voice calls that subscribers expect. Moreover, VoLTE is designed to fully integrate with the existing user experience that is currently implemented with circuit switched voice devices, and therefore whether the call is a circuit switched call or a VoLTE call is transparent to the end user (including when moving in and out of LTE coverage) and is dependent only on which radio access technology to which the user is attached.

8 At the same time, using new, wideband codecs can provide higher voice quality and enhance the user experience. VoLTE is in accordance with 3 GPP specifications and additional profiling is defined within GSMA Permanent Reference Documents. GSMA PRD [54] defines the UNI for IMS voice and SMS. It defines a profile that identifies a minimum mandatory set of features which are defined in 3 GPP specifications that a wireless device (UE) and network are required to implement in order to guarantee an interoperable, high quality IMS-based telephony Service over LTE. The NNI for VoLTE is defined in the IMS Roaming & Interworking Guidelines GSMA PRD [51]. VoLTE Roaming is defined in the LTE Roaming Guidelines GSMA PRD [53]. This document defines the VoLTE Service Description and Implementation Guidelines in order to provide an end-to-end VoLTE deployment.

9 Note that in this version of the document, CSFB and SRVCC are not in scope. Relationship to Standards VoLTE is based on publically available and published 3 GPP specifications as listed in Section 3 GPP Release 8, the first release supporting LTE, is taken as a basis for the VoLTE profile. It should be noted, however that not all the features mandatory in 3 GPP Release 8 are required for compliance with VoLTE . Conversely, some features required for compliance with VoLTE are based on functionality defined in 3 GPP Release 9 or higher releases. Unless otherwise stated, the latest version of the referenced specifications for the relevant 3 GPP release applies. Detailed information related to the support of specific 3 GPP functionality per release is defined within GSMA PRD [54].

10 GSM Association Non-Confidential Official Document Page 7 of 121 Scope This document is separated into 5 main sections. Section 2 VoLTE Architecture:- defines the logical architecture, functional node Description , and interfaces required for VoLTE deployment. Section 3 VoLTE Implementation Single PMN:- defines what is required to deploy VoLTE within a single MNO's domain; detailing call flows, supplementary services required, Diameter configuration aspects, traffic management and QoS aspects, security, etc. Section 4 VoLTE Implementation Interconnect:- defines what is required in addition to an Intra-PMN deployment, for interconnecting two MNO's VoLTE deployments; detailing call flows, bi-lateral interconnect, IPX interconnect, ENUM/DNS, usage of Session Border Controllers, etc.