THE IMS
`IP MULTIMEDIA CONCEPTS AND
`SERVICES, THIRD EDITION
`
`
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`)WILEY
`
`Miikka Poikselk&
`Nokia Siemens Networks, Finland
`
`Georg Mayer
`Nokia, Finland
`
`A John Wiley and Sons, Ltd., Publication
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`ISBN 978-0-470-72196-4 (H/B)
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`This edition first published 2009
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`© 2009 John Wiley & Sons Ltd
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`Library of Congress Cataloging-in-Publication Data
`
`Poikselka, Miikka.
`The IMS: IP multimedia concepts and services / Miikka Poikselka, Georg Mayer. — 3rd ed.
`p. cm.
`Rev. ed. of: IMS / Miikka Poikselka... [et al.]. 2006
`Includes bibliographical references and index.
`ISBN 978-0-470-72196-4 (cloth)
`1. Multimedia communications. 2. Wireless communication systems. 3. Mobile communication systems. I. Mayer,
`Georg, 1970- I. IMS. II. Title.
`TK5105.15.P65 2008
`621.382/12 — de22
`
`2008032207
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`© 2009 John Wiley & Sons, Ltd
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`1.1. Whatis the Internet Protocol Multimedia Subsystem (IMS)?
`Fixed and mobile networks have gone through a major transition in the past 20 years.
`In the mobile world, first-generation (1G) systems were introduced in the mid-1980s.
`These networks offered basic services for users. The main emphasis was on speech and
`speech-related services. Second-generation (2G) systems in the 1990s brought some data
`services and more sophisticated supplementary services to the users. The third generation
`(3G and 3.5G)andits evolution (LTE) is now enabling faster data rates and various multi-
`media services. In the fixed side, traditional Public Switched Telephone Network (PSTN)
`and Integrated Services Digital Network (ISDN) networks have dominated traditional
`voice and video communication. In recent years the usage of the Internet has exploded
`and more and more users are taking advantage of faster and cheaper Internet connection
`such as Asymmetric Digital Subscriber Line (ADSL). These types of Internet connections
`enable always-on connectivity, which is a necessity for people to start using real-time
`communication means — e.g., chatting applications, online gaming, Voice over IP (VoIP).
`At the moment we are experiencing the fast convergence of fixed and mobile worlds
`as the penetration of mobile devices is increasing on a yearly basis. These mobile devices
`have large, high-precision displays, they have built-in cameras and a lot of resources for
`applications. They are always-on always-connected application devices. This redefines
`applications. Applications are no longer isolated entities exchanging information only
`with the user interface. The next generation of more exciting applications are peer-to-peer
`entities, which facilitate sharing: shared browsing, shared whiteboard, shared game expe-
`rience, shared two-way radio session (.e., Push to Talk Over Cellular). The concept of
`being connected will be redefined. Dialling a number and talking will soon be seen as a
`narrow subset of networking. The ability to establish a peer-to-peer connection between
`the new Internet Protocol (IP) enabled devices is the key required ingredient. This new
`paradigm of communications reaches far beyond the capabilities of the Plain Old Tele-
`phone Service (POTS).
`In order to communicate, IP-based applications must have a mechanism to reach the
`correspondent. The telephone network currently provides this critical task of establish-
`ing a connection. By dialling the peer, the network can establish an ad hoc connection
`
`The IMS: IP Multimedia Concepts and Services, Third Edition Miikka Poikselka and Georg Mayer
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`1 I
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`ntroduction
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`The IMS: IP Multimedia Concepts and Services
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`between any two terminals over the IP network. Thiscritical IP connectivity capability is
`offered only in isolated and single-service provider environments in the Internet; closed
`systems compete on user base, where user lock-in is key and interworking between ser-
`vice providers is an unwelcome feature. Therefore, we need a global system — the IP
`Multimedia Subsystem (IMS). It allows applications in IP-enabled devices to establish
`peer-to-peer and peer-to-content connections easily and securely. Our definition for the
`IMSis:
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`IMSis a global, access-independent and standard-based IP connectivity and
`service control architecture that enables various types of multimedia services
`to end-users using common Internet-based protocols.
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`Page 4
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`True integration of voice and data services increases productivity and overall effectiveness,
`while the development of innovative applications integrating voice, data and multimedia
`will create demands for new services, such as presence, multimedia chat, push to talk and
`conferencing. The skill to combine mobility and the IP network will be crucial to service
`success in the future.
`Figure 1.1 shows a converged communication network for the fixed mobile environ-
`ment. It is the IMS which introduces multimedia session control in the packet-switched
`domain and at the same timebrings circuit-switched functionality in the packet-switched
`domain. The IMSis a key technology for such network consolidation.
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`IP Transport
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`Figure 1.1
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`IMS in converged networks
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`Introduction
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`1.2 Fixed and Mobile Convergence
`the IMS
`Since the IMS architecture integrates both wireless and wireline networks,
`becomes an inexpensive medium for Fixed to Mobile Convergence (FMC). It is cur-
`rently one of the crucial strategic issues in the telecommunications industry. Trends in
`different regions and countries are different, but on a global level operators are facing
`increasing competition and declining prices for voice traffic, fixed lines and fixed minutes.
`At the same time, mobile voicetraffic is growing rapidly and substituting that of voice
`traffic over fixed lines. End users now expect high quality with reliable mobility and are
`using the Internet more as the penetration of broadband grows rapidly. Now, Voice over
`IP (VoIP)is starting to substitute PSTN. Meanwhile, key enabling technologies, such as
`smart phones,wireline and wireless broadband and IMSfor seamless service over differ-
`ent access types are readily available. Combined, this means that operators are looking
`for long-term evolutionary strategies towards converged, access-agnostic networks, with
`service integration and interoperability across domains and devices. From the end user’s
`perspective this delivers seamless end user experience across multiple locations, devices
`and services. Convergence can be viewed from three separate angles:
`
`e convergence of networks
`e convergence of services
`e convergence of devices
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`Convergence of Networks
`Network convergence simplifies the end user experience and dissolves the barriers and
`complexities that separate today’s network islands. The same services are available across
`all networks and, in an ideal world, appear and perform in exactly the same way, making
`usage easy, transparent and intuitive.
`From an operator’s perspective, the goal of network convergence is to migrate today’s
`separate PSTN, PLMN, backbone and IP networks to a fully converged network that
`supports any access technology. The full evolution includes a cost effective migration to
`an All-IP network using IMS as the unifying platform, allowing all new services to be
`accessed in a standard and consistent manner as shownin Figure 1.2 manner. Advancing
`in this evolution will be the key to an operator’s ability to reduce OPEX and CAPEX,
`and increasing competitiveness and profitability.
`Many locations, such as homes, enterprises and public places already have access
`networks available (xDSL, WLAN,cable etc.). When operators launch new services such
`as video streaming or hosted email they can take advantage of these existing networks,
`extending service access to more potential subscribers. In turn this will mean launching
`services to new market segments for new revenue opportunities. With multiple access
`networks operators can attract existing and new customers with an enhanced convergence
`service portfolio using unified billing.
`A converged core network is the key enabler for converged networks. Multi-access
`to a common, converged core network enables cost optimization for both mobile and
`hybrid operators. Re-use of existing access network infrastructure and integration with
`the service infrastructure results in both OPEX and CAPEX savings. And multi-access
`enables operators to introduce end-to-end quadruple-play services (voice, data, video/TV
`and mobility), to new customers.
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`The IMS: IP Multimedia Concepts and Services
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`ate s
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`Device Convergence
`Typically, a device is only used — in the main — for a single purpose and the support
`for its other functions is limited. PSTN phones,
`low end mobile phones and set-top
`boxes are good examples. Consumers use these devices for a single purpose. When
`they change tasks they change device and access network. This means service islands,
`which lead to mis-matched user experiences
`from different public and private
`networks. What’s needed are unifying devices that can access services in a similar and
`easy way.
`Smart phones are serious contenders for voice-plus multimedia services in a truly mobile
`environment. Multiple radio interfaces provide access over circuit and packet-switched
`networks (cellular, WLAN etc) and IMS allows services and applications to traverse
`different IP networks. Mobile phone development has been rapid in the last decade and
`new models take increasing advantage of new technologies. They incorporate the enhanced
`colour displays and high quality imaging features needed to support service consumption
`and the creation of own content. Plus the exponential growth of memory capacity and
`processing power means that smart phones can nowreplicate the applications currently
`employed in notebook PCs and PDAs.
`Consumers want the quality of fixed services with the flexibility of mobile and con-
`vergence lets this happen, by allowing service access through the most suitable access
`network, and byletting consumers choose the best device for the service. In many cases
`that device will be a smart phone, butit could just as easily be a PC or laptop with VoIP
`software or converged fixed clients who can share IM, presence etc with mobile devices,
`a fixed VoIP phone or even a TV with a set-top box.
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`Figure 1.2 Convergence of networks
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`IP-based access connection using the SIP protocol between the device andthe converged
`core network — so called ‘Native IP access’ — allows voice, video and other multimedia
`applications over any access network. Native IP access supports a wide variety of applica-
`tions in different devices, including mobile handsets, PC clients and SIP desktop phones.
`POTSphones too, can also be supported, via a comnection to an SIP-capable DSLAM
`or analog terminal adapter (ATA). Native IP access architecture allows the introduction
`of new rich IP multimedia services through IMS functionality, such as presence, media
`push, multimedia telephony, games and various other SIP enabled applications, furthering
`revenue streams for operators.
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`<i
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`Introduction
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`Service Convergence
`The mobility model has become ‘me-centric’, with my phone book, my contact infor-
`mation, my agenda, my messages, my availability and preferred communication method,
`my Internet, my pictures and video clips (received and shared), my personal and busi-
`ness email, my wall-paper, my music and so on. Multimedia services, such as Presence,
`Push-to-talk, messaging, interactive applications, data or video sharing plus streaming,
`browsing and downloading, are being delivered over fixed and mobile packet networks.
`To launch new services and applications quickly, operators can use IMSto eliminate the
`complexity of different service platformsin the network. Standards based Service Deliv-
`ery Framework (SDF) provides comprehensive lifecycle management, making the launch
`of new services and applications quicker and easier to integrate and operate; delivering
`solutions more speedily to market and reducing the total cost of ownership. In effect the
`operator can provision — and the end-user quickly and conveniently self-provision — the
`new services.
`VoIP and Instant Messaging are two developments that helped kick-start service con-
`vergence. VoIP has had a seismic impact on telephony within enterprises and, as the
`penetration of broadband access increases, so does the availability of this transport mech-
`anism within the home. Users also benefit from personalized VoIP,including same number,
`same contacts and the same supplementary services like call barring, call waiting, ring
`back tones, one voice mail, option for one postpaid bill or prepaid account, etc through any
`access network. IP DSLAMsare letting operators offer both DSL access and traditional
`two-wire POTS connections using a SIP client in the DSLAM. This development and
`others like fixed VoIP phones, Analog Telephony Adapters (ATA) and fixed soft switches
`place fixed line operators in an excellent position. They can offer multimedia services via
`DSL andattractive tariffs for analog POTS connected to an IP network, thereby main-
`taining existing services where required and evolving the core network to an JP-based
`solution. Smart phones, on the other hand, have WLAN interfaces so they can accessfixed
`broadband networks. This allows the mobile phone to be used as an IP phone and users
`to continue employing their personalized services at home, or via WLANs,connected to
`DSL, in hot spots or offices. Convergence in this case enables a practical combination
`of cellular and fixed broadband access. The user experience doesn’t change: the same
`voice and multimedia services are used in the same way. Fixed to Mobile Substitution
`and fixed VoIP are gradually replacing PSTN voice telephony. Multimedia services are
`being delivered over fixed and mobile packet networks. Operators must now decide on
`the kinds of services they wish to provide by themselves or by partners, to whom and
`in which regions. And what they might offer is no longer limited to traditional telecom
`services only, but perhaps entry into new businesses.
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`1.3 Example of IMS Services
`Switching on my Internet Protocol Multimedia Subsystem (IMS) enabled device, it will
`automatically register to the IMS network using information in the identity module (such
`as USIM). During registration both device and network are authenticated and my device
`will get my user identities from the network, After this single registration, all my services
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`will be available, including push to talk, presence, voice and video sessions, messaging
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`The IMS: IP Multimedia Concepts and Services
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`and multiplayer games. Moreover, my availability information is updated at the presence
`server as being “online” and listing my current applications.
`WhenI need to contact my friend Bob, I select Bob from my device’s phone book and,
`based on his presence information, I see immediately that he is available. After pressing
`the “green button’ on my device it will place an ‘ordinary’ call to him. The IMS network
`will take care of finding and setting up a Session Initiation Protocol (SIP) session between
`our devices, even though Bobis currently abroad. When mycall reaches Bob’s terminal
`he will see that the call is coming from meand, additionally, he sees a text string inserted
`by me (‘Free tickets to movie next Wednesday’). Bob answers, but tells me that he’s not
`sure whether he is able to come. We decide to check the issue again on Sunday. Before
`hanging up, Bob says to me, “You won’t believe what I saw today butjust wait a second,
`ll show you.’ Bobstarts streaming a video clip to me, and while I’m watchingthe video,
`Bob keeps explaining what happened in the zooearlier that day.
`Mike realizes that today is the birthday of his goodfriend Jill. Although he’s travelling
`and can’t meet her today, he wants to send Jill a personal birthday message. While Mike
`is sitting in a local coffee shop enjoying coffee and reading the latest news from the
`Internet using his brand-new Wireless Local Area Network (WLAN) device, he decides
`to send her a video clip as a birthday greeting. Jill is having a bath when she hears her
`phone ringing. She sees that she has received a message and checks it. She saves the
`video clip and decides to send something in return. Knowing that Mike knowsher weird
`sense of humour, she sendsapicture of herself taking a bath (Figure 1.3).
`Peter Simpson is a Londoner and a die-hard Arsenal fan. With sheer luck he has
`managed to get tickets to an Arsenal—Tottenham derby and sets off to see the game.
`There heis, sitting at the stadium during the match, when suddenlyhe gets anirresistible
`urge to makehis friend envious. He gets his mobile phone and makesa call to his friend
`John Clark, a Tottenham supporter. John is sitting at his desk and receives an incoming
`call pop-up on his PC screen, informing him that Peter is calling. He answers and they
`start to talk. Peter can’t contain himself and starts the video-sharing application while
`zooming onto the field. John receives an incoming video request and accepts the stream.
`The PC client starts to show the game, and with a pang of jealousy and disappointment
`John watches Arsenal score. ‘Nice goal, huh?’ asksPeter. ‘It ain’t over yet,’ says John,
`gritting his teeth, and ends the video stream. They continue to argue good-naturedly about
`the game and their teams over thephone.
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`Figure 1.3 Multimedia messaging
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`IP based server
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`IMS. finds the other
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`Find and connect
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`terminal and connects
`applications
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`the terminals with IP
`presence, messaging,
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`PoC.
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`IP based services
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`Any IP connection (e.g.
`possible between
`CDMA, GPRS, EDGE,
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`terminals!
`WCDMA,LTE, WLAN,
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`WiMAX, ADSL)
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`Figure 1.4 The role of the IMSin the packet switched networks
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`All the required communication takes place using the IP connectivity provided by the
`IMS as shown in Figure 1.4. The IMS offers the capability to select the best and most
`suitable communication media, to change the media during the session spontaneously,
`and use the preferred (SIP-capable) communication device over any IP access.
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`1.4 Where did it come from?
`The European Telecommunications Standards Institute (ETSI) was the standardization
`organization that defined the Global System for Mobile Communications (GSM) during
`the late 1980s and 1990s. ETSI also defined the General Packet Radio Service (GPRS) net-
`work architecture. The last GSM-only standard was produced in 1998, and in the same year
`the 3GPP was founded by standardization bodies from Europe, Japan, South Korea, the
`USA and China to specify a 3G mobile system comprising Wideband Code Division Mul-
`tiple Access (WCDMA)and Time Division/Code Division Multiple Access (TD-CDMA)
`radio access and an evolved GSM core network (www.3gpp.org/About/3gppagre.pdf).
`Most of the work and cornerstone specifications were inherited from the ETSI Special
`Mobile Group (SMG). The 3GPP originally decided to prepare specifications on a yearly
`basis, the first specification release being Release 99.
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`1.4.1 3GPP Release 99 (3GPP R99)
`It took barely a year to producethe first release — Release 1999. The functionality of
`the release was frozen in December 1999 although somebasespecifications were frozen
`afterward — in March 2001. Fast completion was possible because the actual work was
`divided between two organizations: 3GPP and ETSI SMG. 3GPP developed the services,
`system architecture, WCDMA and TD-CDMA radio accesses, and the common core
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`The IMS: IP Multimedia Concepts and Services
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`1.4.3 3GPP Releases 5 and 6
`Release 5 finally introduced the IMS as part of 3GPPspecifications. The IMSis supposed
`to be a standardized access-independentIP-based architecture that interworks with existing
`voice and data networks for both fixed (e.g., PSTN, ISDN, Internet) and mobile users
`(e.g., GSM, CDMA). The IMSarchitecture makes it possible to establish peer-to-peer
`IP communications with all types of clients with the requisite quality of services. In
`addition to session management, the IMSarchitecture also addresses functionalities that
`are necessary for complete service delivery (€.g.,
`registration, security, charging, bearer
`control, roaming). All in all, the IMS will form the heart of the IP core network.
`The content of Release 5 was heavily discussed and, finally,
`the functional content
`of 3GPP Release 5 was frozen in March 2002. The consequence of this decision was
`that many features were postponed to the next release — Release 6. After freezing the
`content, the work continued and reached stability at the beginning of 2004. The Release
`5 defines a finite architecture for SIP-based IP multimedia service machinery. It contains
`a functionality of logical elements, a description of how elements are connected, selected
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`network. ETSI SMG developed the GSM/Enhanced Data Rates for Global Evolution
`(EDGE) radio access.
`WCDMAradio access was the most significant enhancement to the GSM-based 3G
`system in Release 1999. In addition to WCDMA, UMTSTerrestrial Radio Access Network
`(UTRAN)introduced the Iu interface as well. Compared with the A and Gb interfaces,
`there are two significant differences. First, speech transcoding for Iu is performed in the
`core network. In the GSM it was logically a Base Transceiver Station (BTS)functionality.
`Second, encryption and cell-level mobility management for Iu are done in the Radio
`Network Controller (RNC). In GSM they were done in the Serving GPRS Support Node
`(SGSN) for GPRS services.
`The Open Service Architecture (OSA) was introduced for service creation. On the
`service side the target was to stop standardizing new services and to concentrate on
`service capabilities, such as toolkits (CAMEL, SIM Application Toolkit and OSA). This
`principle was followed quite well, even though the Virtual Home Environment (VHE),
`an umbrella concept that covers all service creation,still lacks a good definition.
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`1.4.2 3GPP Release 4
`After Release 1999, 3GPP started to specify Release 2000, including the so-called All-IP
`that was later renamed as the IMS. During 2000 it was realized that the development
`of IMS could not be completed during the year. Therefore, Release 2000 was split into
`Release 4 and Release 5.
`It was decided that Release 4 would be completed without the IMS. The most signif-
`icant new functionalities in 3GPP Release 4 were: the Mobile Switching Centre (MSC)
`Server—Media Gateway (MGW) concept, IP transport of core network protocols, Location
`Services (LCS) enhancements for UTRAN and multimedia messaging and IP transport
`for the Gb user plane.
`3GPP Release 4 was functionally frozen and officially completed in March 2001. The
`backward compatibility requirement for changes, essential for the radio interface, was
`enforced as late as September 2002.
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`Introduction
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`it is important
`protocols (see Chapter 2) and procedures (see Chapter 3). In addition,
`to realize that optimization for the mobile communication environment has been also
`designed in the form of user authentication and authorization based on mobile identities
`(see Chapter 11), definite rules at the user network interface for compressing SIP messages
`(see Section 3.18) and security (see Section 3.21) and policy control mechanisms (see
`Section 3.10.3) that allow radio loss and recovery detection. Moreover, important aspects
`from the operator point of view are addressed while developing the architecture, such
`as the charging framework (see Section 3.11) and policy (see Section 3.10), and service
`control (see Section 3.13).
`Release 6 IMS fixes the shortcomings in Release 5 IMSandalso contains novel fea-
`tures. Release 6 was completed in September 2005. If Release 5 created the IMS machine
`wecall Release 6 as the IMS application and interworking release. The Release 6 intro-
`duced standardized enhancementsfor services such as routing andsignalling modifications
`e.g. Public Service Identity (see Section 3.5.5 and Section 12.11), sharing a single user
`identity between multiple devices (see Section 3.7). Improvements in routing capabilities
`smoothed the road to complete new standardized services such as presence (see Chapter
`4), messaging (see Chapter 7), conferencing (see Chapter 8), PoC (see Chapter 6). In
`addition, IMS-CS voice interworking and WLAN access to IMS were completed. More-
`over, improvements in security, policy and charging control and overall architecture were
`also completed.
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`IMS Developmentin other Standardization Development Organizations
`1.4.4.
`While 3GPP has finalized its Release 5 and Release 6 other standardization develop-
`ment organizations have done parallel developments to define their IMS variants. Most
`notable development organizations having own variants are ETSI Telecommunications
`and Internet converged Services and Protocols for Advanced Networking (TISPAN), Third
`Generation Partnership Project 2 (3GPP2) and Cablelabs.
`TISPAN is the outcome of the merger of two ETSI bodies and it is building specifi-
`cations to enable migration from fixed circuit switched networks to fixed packet-based
`networks with an architecture that can serve in both, also known as Next Generation
`Network (NGN). December 2005 TISPAN declared that they have completed the first
`NGNrelease (Release 1) that contained IP multimedia component. This IP multimedia
`component was based on 3GPP Release 6 and 7 IMS with TISPAN specific extensions
`and modifications. Since 2005 TISPAN has been working with its Release 2 which is
`expected to be completed during 2008.
`3GPP2 created its IMS variant to support CDMA2000 access. This IMS variant is
`also known as Multimedia Domain (MMD). 3GPP2 has used 3GPP IMS specification
`as a starting point and at the time of writing 3GPP2 has three MMDreleases: MMD-O,
`MMD-A, MMD-B.
`Cablelabs is a developmentconsortium thatis defining specification for cable operators.
`An IMSlike building block is present in their PacketCable 2.0 release. Again Cablelabs
`is using 3GPP IMSas a baseline.
`Figure 1.5 depicts major developmentpaths of IMSstandards. Thisfigure clearly reveals
`that there exists fragmentation in the IMS standardization arena. Luckily the industry has
`taken decisive steps towards harmonized IMS, the common IMS. Common IMStechnol-
`ogy in all mobile and fixed ecosystems provides economies of scale to both the operators
`
`AT&T Exhibit 1022
`AT&T v. VoIP, IPR 2017-01384
`Page 11
`
`

`

`The IMS: IP Multimedia Concepts and Services
`
`“ TISPAN >
`= Release2 _
`
`3GPP
`
`Release8
`
`2.0
`
`Page 12
`
`and vendors in different ways. IMS vendors will be able to create the functionality once,
`and reuseit later. This meansfaster time to market, lower research and developmentcost
`due to eliminated replication effort. From an operator and service provider point of view
`it means that they will have a larger choice of vendors to select from and procurement
`cost of IMS products is lower. During 2007 3GPP and TISPAN made an agreement to
`stop IMSrelated developmentin TISPAN andfocusall IMS development to 3GPP. Based
`on this agreement lot of functions and procedures developed in TISPAN Release 1 were
`included in 3GPP Release 7. TISPAN Release2 is expected to be the last TISPANrelease
`on IMS matters and functions and procedures are expected to be harmonized in 3GPP
`Release 8. Some Packetcable ‘IMS’ features were already included in 3GPP Release 7
`and additional features and procedures originating from cable operators will be addressed
`in 3GPP Release 8. Harmonization of 3GPP2 MMD and 3GPPIMSis starting in Release
`8. Dueto late start full harmonization will probably happenin future 3GPP IMSreleases.
`
`_
`
`8GPP
`
`3GPP
`
`3GPP
`Release5 inFi
`PacketCable \
`
`Figure 1.5 Road to standardized common IMS standards
`
`1.4.5 3GPP Release 7 and common IMS
`3GPP Release 7 functional content was frozen in March 2007. It introduces two more
`access technologies (Data Over Cable Service Interface Specification (DOCSIS)! and
`xDSL?) andfeatures and procedures originating from those and other general improve-
`ments. This can be considered as a step towards the ultimate goal of single common IMS.
`Major new features in Release 7 are: IMS multimedia telephony including supplemen-
`tary services (see Chapter 9 and Chapter 12), SMS over any IP access (see Chapter7,
`Section 7.4), Voice Call Continuity (see Section 3.20 and Chapter 13), local numbering
`(see Section 3.16), Combining CS calls and IMSsessions (see Section 3.19), Transit IMS
`(see Section 3.15), Interconnection Border Control Function (IBCF)(see Section 2.2.6.2),
`' Access technology of Cablelabs.
`? Access technology of TISPAN.
`
`AT&T Exhibit 1022
`AT&Tv. VoIP, IPR 2017-01384
`
`AT&T Exhibit 1022
`AT&T v. VoIP, IPR 2017-01384
`Page 12
`
`

`

`Introduction
`
`Globally Routable User Agent’s URI (see Section 3.5.6 and Section 12.10), IMS emer-
`gency sessions (see Section 3.17), Identification of Communication Services in IMS(see
`Section 12.3.9) and new authentication model for fixed access (see Section 3.21.2.3).
`
`IETF is the protocol factory for Internet world and it is doing great work in this space but
`it does not define the ways that they are used, especially in the mobile domain. 3GPPis
`the body that took Session Initiation Protocol (SIP) as the control protocol for multimedia
`communication and 3GPP has built a finite architecture for SIP-based IP multimedia
`service machinery (the IMS). It contains a functionality of logical elements, a description
`of how elements are connected, selected protocols and procedures. 3GPP standardized
`solutions are needed to provide: interoperability between terminals from different vendors,
`interoperability between network elements from different vendors, interoperability across
`operator boundaries. The following advantages of 3GPP IMS against a pure IETF SIP
`service model can belisted:
`
`— charging entity information;
`
`