IP%20Multimedia%20Subsystem%20(IMS)%20%20???

1
IP Multimedia Subsystem(IMS)???
2
Agenda

• Background
• IMS Definition
• IMS Architecture
• IMS Entities
• IMS-CS Interworking

3
Background - AMPS

• Advanced Mobile Phone System (AMPS)
• First generation (1G) cellular network
• Analog mobile phone system
• Standardized by ANSI
• Operate in the 800 MHz band
• Voice call

4
Background - GSM

• Global System for Mobile communications (GSM)
• Second generation (2G) cellular network
• Digital mobile phone system
• Most GSM networks operate in 900 MHz or 1800 MHz
  bands
• Each radio channel bandwidth is 200 kHz
• Standardized by ETSI
• Voice call, short message service

5
Background - GPRS

• General Packet Radio Service (GPRS)
• 2.5G packet oriented mobile network
• Provide data rates from 56 up to 114 kbps
• Standardized by ETSI/3GPP
• Short Message Service (SMS), Wireless Application
  Protocol (WAP), Multimedia Messaging Service
  (MMS), Internet Access

6
Background - EDGE

• Enhanced Data rates for GSM Evolution (EDGE)
• 2.75G packet oriented mobile network
• Data rate up to 236.8 kbps
• Standardized by 3GPP
• Multimedia services, Internet access

7
Background - WCDMA

• Wideband Code Division Multiple Access (WCDMA)
• Third generation (3G) cellular network
• 18852025 MHz for uplink band and 21102200 MHz
  for downlink band
• Each radio channel bandwidth is 5 MHz
• Data rate up to 384 kbps
• Standardized by 3GPP
• The world's first commercial WCDMA network, FOMA,
  was launched by NTT DoCoMo in Japan in 2001.

8
Background - HSDPA

• High Speed Downlink Packet Access (HSDPA)
• 3.5G packet oriented mobile network
• Adaptive Modulation and Coding (AMC)
• Depend on signal quality and cell usage
• QPSK in initial scheme, 16QAM in good radio
  condition.
• Data rate up to 14.4 Mbps for downlink and
  384 kbps for uplink
• Standardized by 3GPP (since release 5)

9
Background - LTE

• Long Term Evolution (LTE)
• Fourth generation (4G) cellular network?
• Orthogonal FDMA (OFDMA) for downlink and Single
  Carrier FDMA (SC-FDMA) for uplink
• Support Multiple-Input and Multiple-Output (MIMO)
  
• Improve communication performance
• Increase data throughput
• Without additional bandwidth or transmit power
• Channel bandwidth between 1.5 and 20 MHz
• All IP Network (AIPN)
• Data rate up to 326.4 Mbps for downlink and
  86.4 Mbps for uplink
• Standardized by 3GPP (since release 8)

10
IMS Definition

• 3GPP Release 5 introduced the IMS as part of 3GPP
  specifications in March 2002
• The IMS is supposed to be a standardized
  access-independent IP-based architecture that
  interworks with existing voice and data networks
  for both fixed (e.g., PSTN, Internet) and mobile
  (e.g., GSM, WCDMA) users

11
IMS in Converged Networks
12
IMS Architecture
13
IMS Entities

• Routing and Session Management
• Databases
• Services
• Interworking Functions
• Support Functions

14
Routing and Session Management

• Call Session Control Functions (CSCF)
• Proxy Call Session Control Function (P-CSCF)
• Interrogating Call Session Control Function
  (I-CSCF)
• Serving Call Session Control Function (S-CSCF)

15
P-CSCF

• The first contact point for users within the IMS
• SIP compression
• IPSec security association
• Interaction with Policy Decision Function (PDF)
• Emergency session detection

16
I-CSCF

• Obtain the name of the S-CSCF or Application
  Server (AS) from the Home Subscriber Server (HSS)
• Assign an S-CSCF based on received capabilities
  from the HSS
• Route incoming requests to an assigned S-CSCF or
  AS

17
S-CSCF

• Handle registration process
• Store service profile
• Make routing decision
• Maintain session state

18
IMS Entities

• Routing and Session Management
• Databases
• Services
• Interworking Functions
• Support Functions

19
Databases

• Home Subscriber Server (HSS)
• Subscription Locator Function (SLF)

20
HSS

• The main data storage for all subscriber and
  service-related data
• User identities
• Private and public user identities
• Registration information
• Access parameters
• Allocated S-CSCF names
• Service triggering information

21
SLF

• The resolution mechanism that enables the I-CSCF,
  the S-CSCF and the AS to find the address of the
  HSS that holds the subscriber data for a given
  user identity when multiple and separately
  addressable HSSs have been deployed by the
  network operator.

22
IMS Entities

• Routing and Session Management
• Databases
• Services
• Interworking Functions
• Support Functions

23
Services

• Multimedia Resource Function Controller (MRFC)
• Multimedia Resource Function Processor (MRFP)
• Application Server (AS)

24
MRFC

• A signalling plane node
• Provide the mechanism for bearer-related services
  such as announcement
• Handle SIP communication to/from the S-CSCF
• Control the MRFP

25
MRFP

• A media plane node
• Mix the incoming media streams for multiple
  parties
• Process the media stream source for multimedia
  announcements

26
AS

• Provide value-added multimedia services
• Process the incoming SIP sessions from the
  S-CSCF
• Originate SIP requests
• Send accounting information to the charging
  functions

27
IMS Services

• Presence
• Multimedia Chat
• Push to talk Over Cellular (POC)
• Conferencing

28
IMS Entities

• Routing and Session Management
• Databases
• Services
• Interworking Functions
• Support Functions

29
Interworking Functions

• For exchanging signalling and media between IMS
  and CS Core Network
• Breakout Gateway Control Function (BGCF)
• Media Gateway Control Function (MGCF)
• Signalling Gateway (SGW)
• IMS Media Gateway (IMS-MGW)

30
BGCF

• It chooses where a breakout to the CS domain
  occurs
• If the breakout happens in the same network, then
  the BGCF selects a MGCF to handle the session.
• If the breakout takes place in another network,
  then the BGCF forwards the session to another
  BGCF in a selected network.

31
MGCF

• Send a converted request via the Signalling
  Gateway (SGW) to the CS CN
• Control the IMS Media Gateway (IMS-MGW)
• Perform protocol conversion between SIP and ISDN
  User Part (ISUP)

32
SGW

• Perform signalling conversion at the transport
  level between the IP-based transport of
  signalling and the Signalling System No. 7 (SS7)
• i.e., between SCTP and SS7

33
IMS-MGW

• Provide the user plane link between CS domain and
  IMS domain
• Perform transcoding for the user plane traffic
• i.e., between TDM and RTP

34
IMS Entities

• Routing and Session Management
• Databases
• Services
• Interworking Functions
• Support Functions

35
Support Functions

• Policy Decision Function (PDF)
• Security Gateway (SEG)

36
PDF

• Session establishment in the IMS involves the
  end-to-end messages exchange using SIP and SDP
• The P-CSCF forwards the relevant SDP information
  to the PDF
• The PDF authorizes the IP flows of the media
  components and transfers the authorized IP QoS
  parameters to the GGSN to establish an IMS session

37
SEG

• Protect control plane traffic between security
  domains
• Enforce the security policy of a security domain
• Coincide with operator borders

38
IMS-CS Interworking
39
CS-IMS Interworking
40
Thank You