GSM Switching, Services and Protocols

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GSM Switching, Services and


GSM Switching, Services and Protocols: Second Edition. JoÈrg EberspaÈcher,
Hans-JoÈrg VoÈgel and Christian Bettstetter
Copyright q 2001 John Wiley & Sons Ltd
Print ISBN 0-471-49903-X Online ISBN 0-470-84174-5


1.1 Digital, Mobile, Global: Evolution of Networks
Communication everywhere, with everybody, and at any time ± we have come much
closer to this goal during the last few years. Digitalization of communication systems,
enormous progress in microelectronics, computers, and software technology, inventions of
ef®cient algorithms and procedures for compression, security, and processing of all kinds
of signals, as well as the development of ¯exible communication protocols have been
important prerequisites for this progress. Today, technologies are available that enable the
realization of high-performance and cost-effective communication systems for many
application areas.
In the ®eld of ®xed networks ± where the end systems (user equipment) are connected to
the network over a line (two-wire copper line, coaxial cable, glass ®ber) ± new network
technologies (such as xDSL and cable modem) have been introduced, providing broadband
access to the Internet.
The largest technological and organizational challenge is, however, the support of subscriber mobility. It can be distinguished between two kinds of mobility: terminal mobility and
personal mobility.
In the case of terminal mobility, the subscriber is connected to the network in a wireless
way ± via radio or light waves ± and can move with his or her terminal freely, even during a
communication connection. The degree of mobility depends on the type of mobile radio
network. The requirements for a cordless in-house telephone are much less critical than for
a mobile telephone that can be used in a car or train. If mobility is to be supported across
the whole network (or country) or even beyond the network (or national) boundaries,
additional switching technology and administrative functions are required, to enable the
subscribers to communicate in wireless mode outside of their home areas.
Such extended network functions are also needed to realize personal mobility and universal reachability. This is understood to comprise the possibility of location-independent use
of 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 place
where he or sh...
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