IMS: An Architecture for Convergent Next Generation Multimedia Services. Research and Standardisation Challenges

1
IMS An Architecture for Convergent Next
Generation Multimedia Services. Research and
Standardisation Challenges

• Dr. Sorin Georgescu
• sorin.georgescu_at_ericsson.com

2
Agenda

• IMS Architecture Overview
• Standardisation Status
• The Service Layer View
• IMS and SOA
• Research and Standardisation Challenges

3
Next Generation Networks Evolution Drivers

• Societal and Business trends
• Internet is becoming a major enabler of
  communications
• Consumers are embracing computing, mobile and
  digital technology in their everyday life
• Evolution of Business models require increased
  levels of personal mobility

• Convergence
• Converged devices (Mobile, WLAN, Internet etc.)
  ? Connectivity
• Converged services ? Ease of use
• Converged networks ? Reliability, Security,
  Reduced OPEX/CAPEX
• Converged business models ? Increased margins,
  Avoidance of twin pitfalls risk

• Access Technology Enhancements
• HSPA (High Speed Packet Access) evolved WCDMA
• OFDMA (Orthogonal Frequency Division Multiple
  Access) 3GPP LTE, WiMAX, MBWA, ADSL/VDSL,
  DVB-T/H etc.
• Spatial Processing multi-antennas Base
  Stations supporting advanced spatial processing

4
The Evolution to IMS Multimedia Applications
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Watch and Communicate service

• While out in town, Bob stopped by at the Jazz
  festival. He made a short clip and would like to
  ask his friends if they are interested to go to
  the evening performance.
• He checks the presence information of Alice and
  Dave.
• Bob opens a Chat session and sends the clip to
  his friends. He asks if they are interested to go
  to the evening performance.
• Dave is watching TV, therefore the chat session
  is diverted to his IMS enabled STB.

Communication services
Personalised content services
Group and context support
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IMS a Standard-based Architecture for NG
Services

• IMS defines an open IP-based service
  infrastructure where service intelligence is
  located in the servers and mobile devices.
• IMS as originally specified by 3GPP, was aiming
  to enable real-time multimedia services over the
  IP bearer in GSM and W-CDMA networks.
• 3GPP2 defined later the MMD for CDMA2000
  networks which is now aligned with IMS.
• TISPAN provided the specifications for DSL
  access.
• CableLabs provided the specifications for the
  cable access and now their work together with
  3GPP to incorporate PC 2.0 specifications into
  IMS release 8.
• Since release 6, interworking with WLAN is
  supported.

• If IMS is not used
• Multimedia communication at best effort
• Service orchestration can be complex
• Service roaming can be difficult to implement
• Provisioning and charging are service specific
• Compliance with LI requirements can be an issue

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IMS/TISPAN Architecture
8
Functional Overview (1)

• CSCF (Call Session Control Function) consists of
  3 separate functions P-CSCF, I-CSCF, S-CSCF
• P-CSCF (Proxy-CSCF)
• Entry point to IMS from any access network
• Performs integrity protection
• Local outbound stateful proxy for all SIP
  requests/responses, ensuring all signalling is
  sent via the home network
• Includes a Policy Decision Function (PDF) that
  authorizes bearer resources
• I-CSCF (Interrogating-CSCF)
• First contact point in home network
• Selects assigned S-CSCF
• Performs network hiding (THIG)
• S-CSCF (Serving-CSCF)
• Stateful proxy that provides session control
• Performs subscriber authentication
• Acts as SIP registrar
• Invokes the AS (Application Servers) based on
  IFC (Initial Filter Criteria)
• SLF (Subscriber Location Function)
• Look-up function used in networks where
  multiples HSS exist

• HSS (Home Subscriber Server)
• IMS subscriber records and service profile
• IMS authentication data
• MRF (Media Resource Function) consists of 2
  separate functions MRFC, MRFP
• MRFC (Media Resource Function Controller)
• Controls media resources in MRFP
• Acts as SIP B2BUA
• MRFP (Media Resource Function Processor)
• Media stream processing (transcoding etc.)
• Multimedia announcements
• Incoming streams mixing

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Functional Overview (2)

• SIP AS (Application Server)
• Hosts IMS native applications
• IM SSF (IP Multimedia Switching Service
  Function)
• Provides interworking with CAMEL, ANSI-41, INAP
  or TCAP services
• OSA SCS (Open Service Architecture Service
  Capability Server)
• Provides interworking with OSA services
• BGCF (Breakout Gateway Control Function)
• Selects the network in which PSTN breakout is to
  occur and within that network selects the MGCF
• MGCF (Media Gateway Control Function)
• Controls media channels in IMS MGW
• Performs conversion between ISUP/TCAP and IMS
  call control protocols
• IMS MGW (IMS Media Gateway)
• Terminates bearer channels from CS networks and
  PS media streams
• Owns/handles resources (echo cancellers, codes,
  etc.)

• SGW (Signaling Gateway)
• Performs conversion at transport level (SCCP,
  SCTP)
• SBC (Session Border Controller)
• PDF/SPDF (Policy Decision Function / Serving
  Policy Decision Function)
• A-RACF (Access - Resource and Admission Control
  Function)
• NASS (Network Attachment Subsystem)
• DSLAM (Digital Subscriber Line Access
  Multiplexer)

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IMS Service Routing the IFCs
IMS AS

• In comparison to IETF SIP Routing where the
  originator of SIP request may specify a preferred
  path in the Route header, in IMS the P-CSCF
  removes this path and ensures that IMS SIP
  Routing is followed.
• SIP requests in IMS architecture are always
  routed to the Home S-CSCF, in both the
  originating and terminating network.
• The S-CSCF uses subscribers Service Profile
  (downloaded during registration), to link-in the
  SIP AS which will process the SIP request.
• The Initial Filter Criteria (IFC) within the
  Subscriber Profile provide a simple service logic
  to decide which AS shall be linked-in. These
  rules are of static nature i.e. they do not
  change on a frequent basis.

HSS
Home B
IMS AS
HSS
Home A
2
7
9
5
1
8
6
S-CSCF
I-CSCF
S-CSCF
4
10
Visited B
Visited A
P-CSCF
P-CSCF
3
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IMS Service Routing Service Profile based
Routing
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Service/application identification ICSI/IARI
A Communication Service is an aggregation of one
or several media components and the service logic
managing the aggregation, represented in the
protocols used. An IMS application is an
application that uses an IMS Communication
Service(s) in order to provide a specific service
to the end-user. Only IMS applications other than
the default application associated to the
Communication Service are identified through
IARIs.

• 3GPP TS 23.228 R7 introduced the ICSI/IARI
  identifiers as a mechanism for UEs to provide a
  hint to the network on the AS they wish to be
  linked-in the signalling path.
• The introduction of ICSI/IARI in 3GPP aims to
  address to a certain extent the limitations due
  to the use of the Service Profile routing
  paradigm. The ICSI/IARI are used as parameters in
  the IFC, therefore the AS selection process
  becomes more dynamic.

• The ICSI/IARI provides a mechanism to control
  rating based on selected pricing model. For
  example, it is possible to rate differently a
  Messaging Communication Service when invoked from
  a Multimedia application then when invoked from a
  Gaming application.

ICSI IMS Communication Service ID IARI IMS
Application Reference ID CS Communication
Service
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Service Convergence in Quadruple Play
Industry consolidation and alliances Convergence
at Service Provider level.
End User experience Access to subscribed
services from any device in the bundle
Service continuity
Common provisioning, mgmt and billing
Common service and subscriber management
Fixed Mobile Convergence Converged Service
Architecture
Setup of the appropriate QoS and resources
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Agenda

• IMS Architecture Overview
• Standardisation Status
• The Service Layer View
• IMS and SOA
• Research and Standardisation Challenges

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Standardisation fora
Multimedia Telephony
IP
GSM/WCDMA Access to IMS
Broadband Access to IMS
WLAN Access to IMS
PacketCable
WiMAX Forum
DSL Forum
DOCSIS
Mobile
Enterprise
Residential
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3GPP R7 Reference Model
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TISPAN R1 Reference Model
Application Servers
Rf
/Ro
Ut
Rf
/Ro
Other types of service logic
Charging
Ut
Functions
PSTN/ISDN Emulation logic
Network
Sh
Rf
/Ro
ISC
Dh
Attachment
UPSF
Iw
SLF
Cx
IWF
Subsystem
Dx
Ib
P3
PES
e2
Mw
Mw/Mk/Mm
e2
IBCF
Ic
I/S
-
CSCF
P2
Mk
AGCF
P1
Mi
Mk
BGCF
Mw
Mr
Mj
Gq
'
Gm
Mg
SGF
P
-
CSCF
MGCF
MRFC
Ie
Other IP Networks
Gq
'
Gq
'
PSTN/ISDN
Mp
Mn
Resource and Admission Control Subsystem
MRFP
Z
T
-
MGF
Z
S/T
S/T
IP Transport (Access and Core)
I
-
BGF
MG
Z
Z
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WIs in 3GPP release 7 (02/2008)

• Coexistence between TISPAN and 3GPP
  authentication schemes study
• SAE (System Architecture Evolution)
• RAN LTE (Long Term Evolution)
• MMTel (Multimedia Telephony)
• VCC (Voice Call Continuity) between IMS VoIP and
  CS speech
• CSiCS (Circuit Switched IMS Combinational
  Service)
• SMS/MMS over IP
• FBI (Fixed Broadband access to IMS)
• IMS Emergency Calls
• PCC (Policy Control and Charging Evolution)
• E2E QoS
• AIPN (All IP Network) Feasibility Study

• Service Identification using ICSI/IARI
• Liberty Alliance and 3GPP security interworking
• Location Services for WLAN interworking
• MRFP-MRFC (Mp) Interface
• Parlay X WS
• Message broadcast
• Geocoding
• Application driven QoS
• Device Management
• Multimedia Streaming/Multicast Control
• ISIM API for Java Card

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WIs in 3GPP release 8 (tentative 03/2009)

• Architecture impacts of Service Brokering
• Enhancements for support of PacketCable 2.0
  requirements
• Multimedia Priority Service
• Personal Network Management
• Enhancements for support of machine to machine
  communication
• Enhanced Generic Access Networks
• HSPA FDD (Frequency Division Duplex)
• Enhancements to SAE/LTE Architecture
• OAMP Studies

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Agenda

• IMS Architecture Overview
• Standardisation Status
• The Service Layer View
• IMS and SOA
• Research and Standardisation Challenges

20
IMS in OMA Service Environment context
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OMA SIMPLE IM Reference Model
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Limitations of ISC Service Orchestration Model
SIP-AS
SIP-AS
SIP-AS
SIP-AS
SIP-AS
SIP-AS
Req URI A
Req URI B
S-CSCF
HSS
S-CSCF
HSS
I-CSCF
I-CSCF

• The application server decides whether to remain
  linked-in for the whole session by adding its
  address to the Record-Route SIP header.
• Application Servers are unaware of the existence
  of other AS', and whether these will be
  linked-in.
• No service or session state will be passed
  between application servers unless they use
  proprietary extensions i.e. are co-designed.
• Response messages are routed to the ASs in the
  reverse order

• If during call handling procedure an AS
  retargets the SIP request by changing the Request
  URI, subsequent filter analysis in the S-CSCF is
  stopped and the S-CSCF forwards the request
  towards the new target without linking-in the
  other AS specified by IFC.

1
2
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SCIM vs. Service Broker
Camel Services
AS
AS
OSA AS
AS
AS
AS
AS
OSA API
CAP
SCIM
OSA SCS
IM SSF
Service Broker
Service Broker
MAP
ISC
Si
ISC
Sh
ISC
Cx
HSS
S-CSCF
S-CSCF
Sh

• The Service Broker architecture has been
  introduced as WI in IMS Release 8.
• The objective is to provide a coherent and
  consistent IP multimedia service experience when
  multiple applications are invoked.
• The work is handled by 3GPP SA2 (Architecture)
  group in TR 23.810. So far, just the some high
  level deployment scenarios and some uses cases
  have been defined.
• Can be centralised, distributed or hybrid (as in
  the figure above).

• The Service Capability Interaction Manager
  (SCIM) orchestrates service delivery among
  application servers.
• Underspecified in TS 23.002, the SCIM has become
  a sort of magic box that would solve all issues
  related to service orchestration.
• Possible types of SCIM
• AS Internal SCIM (figure above)
• SIP Broker SCIM / Service Broker SCIM
• Legacy SCIM

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Parlay X Web Services
WS-I Basic Profile WSDL SOAP WS-I Secure
Profile WSDL SOAP WS-Security

• Parlay X Web Services is an abstraction of
  Parlay WS
• Parlay X WS GW acts as a Service Broker SCIM
• Enablers which only support WS-I Basic Profile
  are enhanced with additional WS functionality
  such as WS-Security, WS-Policy, WS-Addressing
• Services defined so far (17) cover call
  control, messaging (SMS, MMS), payment, location,
  geocoding and mapping, presence etc.
• Described in WSDL. Service discovery is based on
  UDDI.

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Agenda

• IMS Architecture Overview
• Standardisation Status
• The Service Layer View
• IMS and SOA
• Research and Standardisation Challenges

26
SOA Reference Model

• What is SOA
• A paradigm which defines concepts and general
  techniques for the design, encapsulation and
  instantiation of reusable business functions
  using loosely coupled service interactions
• SOA Reference Model
• Service
• Service description
• Interaction
• Contract Policy
• Visibility
• Execution Context
• Real world effect

27
SOA Orchestration
Routing based on service identity (equivalent to
PSI routing in IMS)

• SOA Characteristics
• Services have well defined Service Contracts
• Services are encapsulated
• Services share a message bus and messages
  exchanged are well documented
• Services can be discovered dynamically
• Services are loosely coupled
• Systems of services are assembled at runtime

• Service bus functions
• Supports an asynchronous message based
  communication protocol that uses a common format
  encoding scheme (SOAP/XML)
• Routes, Translates and can Store and Forward
  exchanged messages
• Supports a Discovery mechanism

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IMS-SOA Architecture

• Service Enablers
• Provide functionality which can be used by other
  end-user applications (ex. Location Service)
• Unaware of the context in which they are used.
  Only the consumer service is aware.
• Service Bus
• Handles the communication between IMS
  Application Servers and the Service Enablers and
  the communication with SOA Application Servers.
• Optimized for Server-to-Server communication
• Besides providing support for standard open
  protocols (ex. SOAP), may provide support for
  Native Interface protocols (ex. MLP, MM7, SIP
  etc.)
• Service Orchestration
• The consumer AS that invokes the Service Enabler
  implements the SCIM function. An external Service
  Broker may be used as well.
• IMS Service Enablers are invoked from SOA domain
  through the GW AS.

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Agenda

• IMS Architecture Overview
• Standardisation Status
• The Service Layer View
• IMS and SOA
• Research and Standardisation Challenges

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IMS Core Network

• Coexistence of access specific authentication
  methods
• Media Adaptation using UE capabilities discovery
• Design of efficient algorithms for real-time
  adaptation of MBMS content
• Access agnostic vs. access aware P-CSCF
• QoS awareness, access agnostic control of the QoS
• Media security

31
IMS Service Layer

• Service Orchestration paradigms. The integration
  with SOA architecture
• Enhancements to presence service to support
  device capabilities, subscription state, user
  preferences, context awareness, bearer state
• Multimodal interaction
• Payment brokerage
• Personalised/interactive advertisement
• QoS control over the Service Bus.

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Thank you for your attention!
sorin.georgescu_at_ericsson.com