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IP Multimedia Subsystem (IMS) 江培文

IP Multimedia Subsystem (IMS) 江培文. Agenda. Background IMS Definition IMS Architecture IMS Entities IMS-CS Interworking. Background - AMPS. Advanced Mobile Phone System (AMPS) First generation (1G) cellular network Analog mobile phone system Standardized by ANSI

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IP Multimedia Subsystem (IMS) 江培文

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  1. IP Multimedia Subsystem(IMS)江培文

  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 • 1885–2025 MHz for uplink band and 2110–2200 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 standardizedaccess-independentIP-basedarchitecture that interworks with existingvoiceanddatanetworks for bothfixed(e.g., PSTN, Internet) andmobile(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 inthe same network, then the BGCF selectsaMGCFto handle the session. • If the breakout takes place inanother network, then the BGCF forwards the session toanotherBGCFin 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 usingSIPandSDP • TheP-CSCFforwards the relevant SDP information to thePDF • The PDFauthorizes the IP flows of the media components and transfers the authorized IP QoS parameters to theGGSNto 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

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