GSM switching services and protocols P1

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GSM switching services and protocols P1 GSM Switching, Services and Protocols: Second Edition. Jorg Eberspacher, È È Hans-Jorg Vogel and Christian Bettstetter È È Copyright q 2001 John Wiley & Sons Ltd Print ISBN 0-471-49903-X Online ISBN 0-470-84174-5 1 Introduction1.1 Digital, Mobile, Global: Evolution of NetworksCommunication everywhere, with everybody, and at any time ± we have come muchcloser to this goal during the last few years. Digitalization of communication systems,enormous progress in microelectronics, computers, and software technology, inventions ofef®cient algorithms and procedures for compression, security, and processing of all kindsof signals, as well as the development of ¯exible communication protocols have beenimportant prerequisites for this progress. Today, technologies are available that enable therealization of high-performance and cost-effective communication systems for manyapplication areas.In the ®eld of ®xed networks ± where the end systems (user equipment) are connected tothe network over a line (two-wire copper line, coaxial cable, glass ®ber) ± new networktechnologies (such as xDSL and cable modem) have been introduced, providing broadbandaccess to the Internet.The largest technological and organizational challenge is, however, the support of subscri-ber mobility. It can be distinguished between two kinds of mobility: terminal mobility andpersonal mobility.In the case of terminal mobility, the subscriber is connected to the network in a wirelessway ± via radio or light waves ± and can move with his or her terminal freely, even during acommunication connection. The degree of mobility depends on the type of mobile radionetwork. The requirements for a cordless in-house telephone are much less critical than fora mobile telephone that can be used in a car or train. If mobility is to be supported acrossthe whole network (or country) or even beyond the network (or national) boundaries,additional switching technology and administrative functions are required, to enable thesubscribers to communicate in wireless mode outside of their home areas.Such extended network functions are also needed to realize personal mobility and univer-sal reachability. This is understood to comprise the possibility of location-independent useof all kinds of telecommunication services ± including and especially in ®xed networks.The user identi®es himself or herself (the person), e.g. by using a chip card, at the placewhere he or she is currently staying and has access to the network. There, the samecommunication services can be used as at home, limited only by the properties of the2 1 Introductionlocal network or terminal used. A worldwide unique and uniform addressing is an impor-tant requirement.In the digital mobile communication system GSM (Global System for Mobile Commu-nication), which is the subject of this book, terminal mobility is the predominant issue.Wireless communication has become possible with GSM in any town, any country, andeven on any continent.GSM technology contains the essential ``intelligent functions for the support of personalmobility, especially with regard to user identi®cation and authentication, and for thelocalization and administration of mobile users. Here it is often overlooked that in mobilecommunication networks by far the largest part of the communication occurs over the®xed network part, which interconnects the radio stations (base stations). Therefore it is nosurprise that in the course of further development and evolution of the telecommunicationnetworks, a lot of thought is given to the convergence of ®xed and mobile networks.Today, GSM is used mainly for speech communication, but its use for mobile datacommunication is growing steadily. The GSM Short Message Service (SMS) is a greatsuccess story: several billion text messages are being exchanged between mobile userseach month. The driving factor for new (and higher bandwidth) data services is the wire-less access to the Internet. The key technologies that have been introduced in GSM, theGeneral Packet Radio Service (GPRS) and the Wireless Application Protocol (WAP), arealso explained in this book.The next generation of mobile communications is known as Universal Mobile Telecom-munication System (UMTS) in Europe and as International Mobile TelecommunicationSystem 2000 (IMT-2000) worldwide. The standardization has already progressed quite far,such that the ®rst netw ...