The 3G IP Multimedia Subsystem Scribd

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The 3G IP Multimedia Subsystem (IMS)Seminar Selected Topics in Communications Engineering May 21, 20130OutlineThe 3G IP Multimedia Subsystem1IntroductionIMS ServicesArchitecture of IMSProtocols used in IMSQuality of service as key differentiator of IMSInterworking example: Voice Call ContinuityService example: ConferencingSummaryIntroduction to IMSThe 3G IP Multimedia Subsystem2Review of current mobile technologies2G : GSM/EDGEEngineered with transport of voice in mindData rates in the kbps range

3G : CDMA2000, TD-SCDMA, WCDMA (UMTS)Split architecture for voice and dataData rates in the Mbps range

4G : HSPA+, LTE (LTE-Advanced), Mobile WiMAXDesigned for IP transportData rates in the Mbps and Gbps rangeIrving Barra - The 3G IP Multimedia Subsystem3Review of current mobile technologies3G coverage is growing and expected to reach that of 2G

Voice traffic is steady, whereas data traffic increases exponentially!The 3G IP Multimedia Subsystem4

Source: Ericsson Mobility Report (2012)

Traffic and user behaviorSmartphone trafficIrving Barra - The 3G IP Multimedia Subsystem5

Tablet trafficSource: Cisco Visual Networking Index (March 2013)Communications over packet networksMain concernsQuality of Service (QoS)AvailabilityAccounting

Can we offer some degree of quality over the Internet?

IMS enables a better identification of types of traffic.

Operators can adjust quality and tariffs accordingly.Irving Barra - The 3G IP Multimedia Subsystem6La primera pregunta se contestar en el captulo sobre calidad de servicio. La segunda tambin, est bien relacionada a la clasificacin del trfico (key terms: PCRF, Diffserv)6The need for IMSUser benefitsMore alternatives of communicationQuality as required per servicesMore flexibility (access-independent)

Operator benefitsReduced CAPEX and OPEXIncreased revenueQuick development of new servicesMore customer loyalty, less churnIrving Barra - The 3G IP Multimedia Subsystem7IMS RequirementsIP Multimedia Sessions

Quality of Service (QoS)

Interworking with the PSTN (Gateway)

Roaming

Service control

Rapid service creation

Multiple accessIrving Barra - The 3G IP Multimedia Subsystem8Source: Camarillo, Garca-Martn [2008]Requirements that the IMS framework had to meet during its design8IMS ServicesIrving Barra - The 3G IP Multimedia Subsystem9What is possible with IMS?Irving Barra - The 3G IP Multimedia Subsystem10

Source: AT&T Developer ProgramTraditional services over IMSVoice CallsSame look and feel for the user. Totally different interworking underneath.Enhanced user experienceHD Codecs

Voice MailUnified messagingText-to-speech

Short messages/Multimedia messagesIrving Barra - The 3G IP Multimedia Subsystem11Novel services of IMSPresence

Instant messaging

Push-to-talk

Video/picture/file sharing

Multimedia conferencing

Other third-party servicesIrving Barra - The 3G IP Multimedia Subsystem12

Architecture of IMSIrving Barra - The 3G IP Multimedia Subsystem13Review of the GSM/UMTS architectureIrving Barra - The 3G IP Multimedia Subsystem14Source: Smith, Collins [2004]

3GPP Release 99MSC, GGSN, HLR14Review of the GSM/UMTS architectureIrving Barra - The 3G IP Multimedia Subsystem15Source: Smith, Collins [2004]

3GPP Release 4Key: Layering introduced, HSS introduced (IP signaling)15Review of the GSM/UMTS architectureIrving Barra - The 3G IP Multimedia Subsystem16Source: Smith, Collins [2004]

3GPP Release 5Key: ALL-IP Architecture, MSC replaced by CSCF16Towards IMS: The mobile softswitch architectureLayered architectureApplies to voice and signalingIrving Barra - The 3G IP Multimedia Subsystem17

Source: EricssonExplain the concept and advantages of layering17

Functions and interfaces of the IMS architectureHSS and SLFCSCF (P,S,I)Application Servers (AS)BGCFSGW and MGWIrving Barra - The 3G IP Multimedia Subsystem18Source: Camarillo, Garca-Martn [2008]HSS=Home Subscriber ServerSLF=Subscriber Location FunctionP-CSCF=Proxy Call/Session Control FunctionS-CSCF=Serving Call/Session Control FunctionI-CSCF=Interrogating Call/Session Ctlr. Func.AS=Application ServersBGCF=Breakout Gateway Control FunctionSGW/MGW=Signaling/Media Gateway

Functions and interfaces of the IMS architecturePCRF and PCEFApplication FunctionP-CSCFApplication ServerIrving Barra - The 3G IP Multimedia Subsystem19Source: Camarillo, Garca-Martn [2008]PCRF=Policy and Charging Rules FunctionPCEF=Policy and Charging Enforcement FunctionThe Policy and Charging Control Architecture19

Functions and interfaces of the IMS architectureInterworking between networks with different address type.Irving Barra - The 3G IP Multimedia Subsystem20Source: Camarillo, Garca-Martn [2008]Functions and interfaces of the IMS architectureInterface to the PSTN and legacy mobile operatorsIrving Barra - The 3G IP Multimedia Subsystem21

Source: Camarillo, Garca-Martn [2008]User identification in IMSPublic user identitiesMost typical (E-Mail-like) sip:[email protected]

With telephone number sip:[email protected];user=phone

Telephone URIs URI}tel:+1-212-555-0293

Private user [email protected] Barra - The 3G IP Multimedia Subsystem22User identification in IMS3GPP Release 5Irving Barra - The 3G IP Multimedia Subsystem23

3GPP Release 6Source: Camarillo, Garca-Martn [2008]Protocols used in IMSIrving Barra - The 3G IP Multimedia Subsystem24A glimpse on SIP (Session Initiation Protocol)Signaling protocol in IMSDefines methods and responsesIrving Barra - The 3G IP Multimedia Subsystem25

Source: Camarillo, Garca-Martn [2008]A glimpse on SIP (Session Initiation Protocol)SIP ResponsesIrving Barra - The 3G IP Multimedia Subsystem26

Source: Camarillo, Garca-Martn [2008]Examples:

100 Trying180 Ringing183 Session in Progress200 OK302 Moved Temporarily407 Proxy Authentication Required503 Service Unavailable603 DeclineA glimpse on SIP (Session Initiation Protocol)IMS Services using SIP: Example of registrationIrving Barra - The 3G IP Multimedia Subsystem27Source: Camarillo, Garca-Martn [2008]

A glimpse on SIP (Session Initiation Protocol)IMS Services using SIP: Session establishment (1/3)Irving Barra - The 3G IP Multimedia Subsystem28Source: Camarillo, Garca-Martn [2008]

A glimpse on SIP (Session Initiation Protocol)IMS Services using SIP: Session establishment (2/3)Irving Barra - The 3G IP Multimedia Subsystem29Source: Camarillo, Garca-Martn [2008]

A glimpse on SIP (Session Initiation Protocol)IMS Services using SIP: Session establishment (3/3)Irving Barra - The 3G IP Multimedia Subsystem30Source: Camarillo, Garca-Martn [2008]

Description of sessions with SDPAppended to SIP messages (depends on method)Contains information of the media to be exchangedIrving Barra - The 3G IP Multimedia Subsystem31

Other protocols in IMSRTP/RTCPUses UDP as transport protocolRTP includes sequence numbers, timestamps.RTP uses even port numbers.RTCP provides feedback about the quality of the session (packet loss, delay, jitter).RTCP uses the next port number to that of RTP (odd).SRTP if encryption is required

H.248/MegacoUsed by controllers to control MGWs.Defines terminations and contexts.Physical terminations for ports, ephemeral terminations for RTP streams.Irving Barra - The 3G IP Multimedia Subsystem32Quality of Service for IMSIrving Barra - The 3G IP Multimedia Subsystem33Review of QoS methodsQoS in the InternetRSVP (Resource ReSerVation Protocol)Resources are reserved per sessionOffers two types of QoS: guaranteed and controlled loadRequires the data to travel along the path over which the reservation was made.Increased load for the routers

DiffServ (Differentiated services)Treatment given to packets according to DSCP fieldProvides either expedite forwarding (top priority) or assured forwarding (several drop priorities)Irving Barra - The 3G IP Multimedia Subsystem34Review of QoS methodsQoS in mobile networksDifferent traffic classes per PDP contextIrving Barra - The 3G IP Multimedia Subsystem35

Source: Holma, Toskala [2007]

Source: Camarillo, Garca-Martn [2008]The PDP contexts used for SIP signaling are always conversational.35Admission controlWhy do we need Admission Control?Complementary to quality of serviceAvoids oversubscription of links (preventive)When links are tightly loaded, just one more session will degrade all the others.Irving Barra - The 3G IP Multimedia Subsystem36

Policy control for QoS in IMSDecisions made by the PCRF according to information from Application Function and Subscriber Profile RepositoryPolicies enforced by the PCEF (i.e. GGSN)Irving Barra - The 3G IP Multimedia Subsystem37

Source: Camarillo, Garca-Martn [2008]Interworking example: Voice Call Continuity (VCC)

Irving Barra - The 3G IP Multimedia Subsystem38Voice Call Continuity (VCC)Smooth transitions of voice calls between IMS and regular Circuit Switched callsIMS calls can be "transferred" to or from a GSM/UMTS networkIrving Barra - The 3G IP Multimedia Subsystem39

Source: Camarillo, Garca-Martn [2008]

Architecture for VCCInterworking with GSM Intelligent NetworkCAMEL protocol used towards gsmSCFIrving Barra - The 3G IP Multimedia Subsystem40Source: Camarillo, Garca-Martn [2008]

VCC Example call scenarioIrving Barra - The 3G IP Multimedia Subsystem41Source: Camarillo, Garca-Martn [2008]VCC anchoring: CS originated call leg using CAMEL services41Service example: ConferencingIrving Barra - The 3G IP Multimedia Subsystem42Standardization of conferencingWorking groups: SIPPING, XCONIMS is based on the SIPPING framework. Uses BFCP from XCON.Makes use of the tightly-coupled model for conferencing:Irving Barra - The 3G IP Multimedia Subsystem43

Source: Camarillo, Garca-Martn [2008]

Architecture and controlSIPPING architecture for signaling (see left figure)BFCP from XCON used for floor control (see right figure)Irving Barra - The 3G IP Multimedia Subsystem44

Source: Camarillo, Garca-Martn [2008]

Conferencing sample call flowsSpecial URI for conference creation: factory URIIrving Barra - The 3G IP Multimedia Subsystem45Source: Camarillo, Garca-Martn [2008]

Conferencing sample call flowsIrving Barra - The 3G IP Multimedia Subsystem46Source: Camarillo, Garca-Martn [2008]SummaryIMS is an architectural framework which enables providing multimedia services over IP networks.IMS helps operators to reduce expenditures, while increasing profitability by enabling more effective charging.IMS can be integrated to current UMTS and LTE networks. Actually, IMS is independent of the access method.The key differentiator compared to current Internet services is the enhanced quality of service.IMS creates another layer of abstraction with respect to user mobility.The protocols SIP and SDP are fundamental for the operation of IMS.

Irving Barra - The 3G IP Multimedia Subsystem47ReferencesThe 3G IP Multimedia Subsystem IMS, Merging the Internet and the Cellular Worlds, Gonzalo Camarillo and Miguel A. Garca-Martn, 3rd Ed, 2008The IMS: IP Multimedia Concepts and Services, Miikka Poikselk and Georg Mayer, 3rd Ed, 20093G Wireless Networks, Clint Smith and Daniel Collins, 2004Carrier Grade Voice Over IP, Daniel Collins, 2nd Ed, 2004WCDMA for UMTS, Harri Holma and Antti Toskala, 4th ed, 2007Irving Barra - The 3G IP Multimedia Subsystem48