IMS

TPC

EPC

IP Multimedia System: general aspects and migration perspectives

Dr. Leo Lehmann Federal Office of Communication, Switzerland

ITU Workshop on “Developments regarding network architectures and services”, Kampala 2 April 2012 Content IMS definition & features IMS history IMS basic architecture IMS & UMTS/ LTE networks IMS registration and session setup IMS Billing IMS centralized services IMS & NGN IMS migration scenarios Further information

IMS definition & features

The IP Multimedia Subsystem is an architectural framework for delivering Internet Protocol (IP) multimedia services

Do we really need the IMS? Not just for enabling IP services in mobile networks B U T for

Combination session establishment with QoS/ security provision (enjoy rather than suffer)

Means for appropriate charge of multimedia sessions (e.g. flat rate, time/volume based, QoS based)

combination & integration of different type of (multimedia) services (own, 3rd party) by standard interfaces

Inhering services like VoIP, Video, IM

IMS definition & features cont.

Overlay for fixed and mobile IP based networks; merging the cellular world with the internet Abstraction from underlying network Multimedia Services Fix/ mobile convergence

Interoperability with CS mobile IMS networks (MAP)

Roaming/ location awareness (IP domain) Packet Data Networks Common control platform GW SIP service enabler CS NW Based on SIP (IETF), (IETF), H.248 (ITU-T) IMS history (some highlights)

3GPP Release 5:  Introduction of SIP based IMS  Mobile Multimedia over IP (new applications)  End 2 end QoS Voice over MSC server/MGW

3GPP Release 6  IMS phase 2 (realization access independence IPCAN) IPCAN: IP conncetivity access network  Voice over IMS 3GPP Release 7 IMS TISPAN NGN Extensions eCall via IMS ICS Charging and QoS Optimizations

IMS history (cont)

3GPP Release 7  IMS centralized services  Charging and QoS Optimizations

3GPP Release 8  Common IMS  IMS Extensions for packetized switched streaming  MM broadcast/multicast services  Session mobility support

3GPP Release 9/10  home node B  M2M IMS basic architecture (3GPP 23.002)

Databases Databases Application HSS/SLF AS

MGCF P-CSCF I-CSCF S-CSCF MRF

BGCFMGCF

MGCF IMS Core MGCF

MGCF MGCF MGW SGW

IP Core CS mobile, PSTN IMS basic architecture (cont) IMS & UMTS/ LTE – EPC networks

IMS PSTN AS MGW CSCF

PDN GMSC GGSN HSS GW Core MSC/ SGSN MME Serving VLR GW

RNC

NodeB eNB

UTRAN E-UTRAN IMS & UMTS/ LTE – EPC networks (cont)

EPC Components Mobility Management Entity IMS + Internet Serving Gateway Home Subscriber Server Packet Data Network Gateway PDN HSS Functions GW AAA Mobility Management MME Serving IP over LTE GW QoS, Charging

eNB

E-UTRAN IMS registration & session setup

Public Presence Presence

Internet Databases Converged Converged Services Platforms and

xDSL AAA DHCP

MMS MMS SMS IP Network PDG/PDG HSS DNS SMS

WAG

PDG/PDG Conversational -

WAG -

IMS WiFi PDF S-CSCF I- CSCF PDG/PDG P- CSCF WAG Service Provider

PDN

SSF Data Network

BGCF Streaming

MGCF

PS Backbone

SGSN Network GGSN

CSCF: Call Session Control Function RNC HSS: Home Subscriber Server (includes HLR) MGW: Media Gate Way MGCF: Control Function MGW SGW 3G RAN PDG: Packet Data Gateway PDN: Packet Data Network RAN: Radio Access Network RNC, BSC: Radio Network Controller (3G), Base Station Controller (2G) IMS IP Multimedia Subsystem PSTN BSC SGSN: Serving GPRS Support Node PLMN GGSN: Gateway GPRS Support Node AS (provider, 2G RAN 3rd Party) access network Core network IMS registration

Registration in 2G/ 3G access UE SGSN/GGSN IMS Network (location update) through SGSN/ HLR

1. Bearer Level Registration: GPRS Attach

IP address assignment by GGSN 2. PDP Context Activation (Packet Data Protocol Context)

3. P- CSCF Discovery P-CSCF address determination through GGSN or DHCP server 4. IMS Registration

Request via P-CSCF I-CSCF to Home network. AAA and S-CSCF Assignment by home network IMS registration (cont)

IMSI/ UID

Auth. Info

Adr. S-CSCF

HSS U-Profile core nw

U_Reg Query Adr(SCSCF) (Home) UID

Adr. UE Forward (REGISTER) I-CSCF S-CSCF Adr. PCSCF

OK

UID

access nw Adr. UE Forward (REGISTER) Adr.ICSCF= f(UI) (home, visited) Adr. ICSCF

Adr. SCSCF

Adr. GGSN P-CSCF

OK

IMSI/ UID OK SGSN GGSN PDP Adr. (UE) REGISTER TEID (UI) Adr. PCSCF

Adr. SGSN PSTN voice call

HSS

6 2 3

S_CSCF 4 MGCF

ISUP 5 SIP 1

7 P-CSCF

8 5 8 PSTN/ISDN 5

8 SGSN GGSN MGW TDM

VoIP

1. Incomming PSTN call 3. S-CSCF addree, UID 6. Ressource reservation confirmation 2. Protocol transformation & 4. INVITE Session 7. MGW activation localisation 5. Forward (INVITE) 8. IP PDU transformation & transport IP media session establishment

1. Session initiation (URI HSS callee)

2. 2. HSS request for callee localization (IP domain)

3. CSCF 2 CSCF 1 3. Forward session initiation

4. Caller notification, 4. 1. Bearer establishment 4. 1.

UMTS/ 4. 1. UMTS/ SGSN GGSN GGSN SGSN 5. IP PDU streaming GPRS GPRS 5. 5. 5. 5. 5.

IMS Billing (3GPP 32.240)

OCF charging

account information

IMS GWF charging information online

P-CSCF S-CSCF AS MGCF BGCF

CTF CTF CTF CTF CTF

charging Events

CDF

CDR Billing System charging

CDR CGF offline

CDF Charging Data Function CGF Charging Gateway Function OCF Online Charging Function CTF Charging Trigger Function IMS centralized services (3GPP 23.292)

Enables IMS services when using CS devices (CS access)

Enables CS access to transport IMS voice/video services where PS access is not available for VoIP/ IP-Video (no full duplex speech/video component by PS)

IMS centralized services (cont) Service Centralization and Continuity Application Server (SCC AS): SCC AS is a home network based IMS Application that provides functionality required to enable IMS Centralized Services Acts as ICS User Agent (IUA) and provides SIP UA behavior on behalf of the UE for setup and control of for IMS sessions using CS bearers processes as CAA (CS Access Adaptation) the service control signaling received via the CS access for interworking with other IMS functional elements Directs an incoming session to an ICS User ICS provision in UE Communicates with the SCC AS for service control signaling. Establishes the Bearer Control Signaling Path to setup the media through the CS domain ICS provision in MSC Server: MSC Server processes the user-network signaling received over the CS access for interworking with IMS SIP and vice versa. It controls the MGW functions described to enable the interworking between CS access and RTP bearers. It performs the interworking to support multimedia call in ICS.

Multimedia session continuity (3GPP TR 23.893 )

Media component transfer

Different network access

Different UE

Continuation of ongoing media session

IMS & NGN (ITU-T Y.2021)

Application Platform

IMS

NGN Service Stratum

NGN Transport Stratum

The 3GPP IMS is the central service control component in NGN IMS & NGN (cont)

Applications

Service Stratum Application SupportApplication Functions andFunctions Service Support Functions

Service S. User Other NGN Control Profile Service Components Functions Functions IPTV Service Component

PSTN / ISDN Emulation Other Networks Other Service Component Networks Other IP MultimediaIP Multimedia Component &PSTN/ISDNService Component Simulation GW Legacy Terminals

Network AccessAttachment Resource and Admission

T. UserUser GW ProfileProfile Control Functions Control Functions Legacy Attachment Functions FunctionsFunctions (NACF) (RACF) Terminals

Customer Networks Core Transport Access TransportNetwork Core transport FunctionsFunctions Edge FunctionsFunctions NGN Functions Terminals End- U ser Transport Stratum Functions ETSI TISPAN IMS & NGN (cont)

The 3GPP IMS is the central service control component in NGN

3GPP functional entities NGN functional entities S-CSCF S-CSC-FE

P-CSCF P-CSC-FE

I-CSCF I-CSC-FE

MGCF MGC-FE

MRFC MRC-FE

BGCF BGC-FE Relationship EPC/ NGN-FE’s

Access network Core network ITU-T 3GPP entity Functions performed Y.2018 entity HSS responsible

NAS signalling NACF NAS signalling security NACF hPCRF AS security control NACF Rx S6a Home Gx Inter CN node signalling for mobility between 3GPP NACF S9 access networks SGi Idle mode UE reachability (including control and TBD* PDN Operator's execution of paging retransmission) gateway IP services (IMS, etc.) Tracking area list management (for UE in idle and TBD (Note 1) active mode) S10 PDN GW and serving GW selection TBD (Note 2) Mobility management entity (MME) MME selection for handovers with MME change NACF MME S8 vPCRF S1-MME SGSN selection for handovers to 2G or 3G 3GPP NACF access networks S3 S11 Gxc NACF (TAA- FE) S1-U Serving E-UTRAN gateway Authentication NACF (TAA- FE) S4 Visited Bearer management functions including dedicated HDC-FE bearer establishment 2G/3G Support for ETWS message transmission NACF SGSN Y2018(09)_FIII.2 The local mobility anchor point for inter-eNB L2HE-FE handover Mobility anchoring for inter-3GPP mobility L2HE-FE E-UTRAN idle mode downlink packet buffering and L2HE-FE initiation of network triggered service request procedure

Lawful interception EN-FE Packet routing and forwarding EN-FE Serving gateway Transport level packet marking in the uplink and the EN-FE downlink Accounting on user and QCI granularity for inter- EN-FE operator charging UL and DL charging per UE, PDN, and QCI EN-FE Originator of PMIP signalling. Proxy point for PMIP MLM-FE(P) signalling (chained PMIP) tunnel end point L3HEF IMS migration scenarios

Not at all

network without IMS

time From the beginning (Greenfield)

IMS based network

time IMS migration scenarios (cont)

Full introduction

network without IMS IMS based network

time Stepwise migration

IMS Introduction together with new broadbad services network without IMS ICS to cover CS

time Summary

IMS has left the trial stage and has become an adequate System to enhance IP sessions in mobile networks with QoS/ security provision and appropriate billing capabilities

IMS enables fix-mobile convergence and is the 3GPP-TISPAN implementation of the service control in the NGN service stratum (e.g. VoIP services via DSL and mobile access)

Large IMS deployment is feasible in the next years based on PSTN migration from CS to IP by big incumbents as well as the deployment of LTE. The IMS benefits and the practical application have been understood and identified by the operators

IMS expectations

Source: Hype Cycle according Gartner Inc. Thank You !