Über die Autorin bzw. den Autor

Miikka Poikselkä works for Nokia Siemens Networks, Finland.

Georg Mayer works for Nokia Mobile Phones, Finland. 

All the authors are involved with Third Generation Partnership Project Agreement (3GPP), Internet Engineering Task Force (IETF) and Open Mobile Alliance (OMA) standardization. 

Von der hinteren Coverseite

The 3rd edition of this highly successful text builds on the achievement of the first two editions to provide comprehensive coverage of IMS. It continues to explore the concepts, architecture, protocols and functionalities of IMS while providing a wealth of new and updated information. It is written in a manner that allows readers to choose the level of knowledge and understanding they need to gain about the IMS.

With 35% new material, The IMS,IP Multimedia Concepts and Services,3rd Edition has been completely revised to include updated chapters as well as totally new chapters on IMS multimedia telephony and IMS voice call continuity. Additional new material includes IMS transit, IMS local numbering, emergency sessions, identification of communication services in IMS, new authentication model for fixed access, NAT traversal and globally routable user agents URI. Detailed descriptions of protocol behaviour are provided on a level that can be used for implementation and testing.

Key features of the 3rd edition:

• Two new chapters on IMS multimedia telephony service and IMS Voice Call Continuity
• Updated information on Third Generation Partnership Project (3GPP) Release 7 level, including architecture, reference points and concepts
• Substantially extended coverage on IMS detailed procedures
• Completely rewritten and extended chapters on IMS services

Aus dem Klappentext

The 3^rd edition of this highly successful text builds on the achievement of the first two editions to provide comprehensive coverage of IMS. It continues to explore the concepts, architecture, protocols and functionalities of IMS while providing a wealth of new and updated information. It is written in a manner that allows readers to choose the level of knowledge and understanding they need to gain about the IMS.

With 35% new material, The IMS,IP Multimedia Concepts and Services,3^rd Edition has been completely revised to include updated chapters as well as totally new chapters on IMS multimedia telephony and IMS voice call continuity. Additional new material includes IMS transit, IMS local numbering, emergency sessions, identification of communication services in IMS, new authentication model for fixed access, NAT traversal and globally routable user agents URI. Detailed descriptions of protocol behaviour are provided on a level that can be used for implementation and testing.

Key features of the 3^rd edition:

• Two new chapters on IMS multimedia telephony service and IMS Voice Call Continuity
• Updated information on Third Generation Partnership Project (3GPP) Release 7 level, including architecture, reference points and concepts
• Substantially extended coverage on IMS detailed procedures
• Completely rewritten and extended chapters on IMS services

Auszug. © Genehmigter Nachdruck. Alle Rechte vorbehalten.

The IMS: IP Multimedia Concepts and Services

John Wiley & Sons

Chapter One

1.1 What is 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) and its evolution (LTE) is now enabling faster data rates and various multimedia 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 experience, shared two-way radio session (i.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 Telephone 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 establishing a connection. By dialling the peer, the network can establish an ad hoc connection between any two terminals over the IP network. This critical 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 service 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 IMS is:

IMS is 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.

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 environment. It is the IMS which introduces multimedia session control in the packet-switched domain and at the same time brings circuit-switched functionality in the packet-switched domain. The IMS is a key technology for such network consolidation.

1.2 Fixed and Mobile Convergence

Since the IMS architecture integrates both wireless and wireline networks, the IMS becomes an inexpensive medium for Fixed to Mobile Convergence (FMC). It is currently 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 voice traffic 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 IMS for seamless service over different 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:

convergence of networks

convergence of services

convergence of devices

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 shown in 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.

IP-based access connection using the SIP protocol between the device and the converged core network - so...