4.1
INTRODUCTION
Mobile telephony networks have been a phenomenal success story since their introduction in the mid- to late 1980s. This success is being built upon, and a number of operators (old and new) around the world are looking to provide the latest generation of mobile network technology labelled 3G for third generation. The 3G label is based on the generally accepted premise that the first-generation cellular networks are the analo- gue-based ones first made popular in the late 1970s and early 1980s (AMPS in the US, TACS in the UK, NMT450/900 in Scandinavian coun- tries and an NTT standard in Japan, more on these later), and that the second generation the digital cellular networks that arrived in the early 1990s (global system for mobile communications (GSM) in Europe, perso- nal digital cellular in Japan, D-AMPS or IS-54, IS-136 and IS-95 in the US, again more on these later in the chapter).
The 3G mobile networks are subject to a set of standards developed by the International Telecommunications Union (ITU) (formally CCITT), Europe Telecommunications Standards Institute (ETSI) and the European RACE project. This work was started as long ago as 1986.
The ITU concept is based around handset mobility, and the early programme was dubbed future public land mobile telephone system (FPLMTS). The concepts were expanded to include the idea that a user should be able to access any telecommunications service from any suita- ble terminal connected at any point on any network. This became known as personal mobility. The ITU went on to define the concept as Universal Personal Telecommunications (UPT). The ITU was dragging its feet on what the standard should finally look like and the choice of technology for FPLMTS. FPLMTS was eventually renamed international mobile commu-
Next Generation Network Services
Neill Wilkinson Copyrightq2002 John Wiley & Sons, Ltd
nications for use in the year 2000 (IMT2000). Figure 4.1 shows the road- map from first- through second- to third-generation network (IMT2000) standards. This figure also shows a number of other technologies that have been considered in the standardisation work as part of the change towards the ultimate aim of IMT2000. These are a mixture of satellite communications technologies (iridium and global star), paging technolo- gies and cordless telephony standards of which Digital Enhanced Cord- less Telephony (DECT) has seen the most recent and widespread use.
Work on advanced telecommunications services started in Europe even before the CCITT (ITU-T) work. In 1985, the European Commission spon- sored research and development in advanced communications technolo- gies in Europe (RACE). This was initially intended to lead research towards integrated broadband networks, but the work of one of the projects considering the implications of radio-based mobile communica- tions developed the idea of Universal Mobile Telecommunications System (UMTS). This work floundered for a while, but was kick-started in 1995, with the Bangemann report.
The recommendations that came out of this report produced the follow- ing roadmap:
† the regulatory framework for UMTS should be defined by the end of 1997;
† basic UMTS working should be available by 2002;
† full bandwidth capability should be available by 2005;
† additional spectrum allocation in 2008;
† a UMTS forum should be set up to provide guidance for organisations such as ETSI.
MOBILE NETWORKS 42
ETSI have been influential over the last 2 years in delivering significant standardisation under the 3rd Generation Partnership Programme (3GPP) and have been delivering on the recommendations laid out in the Bangemann report. This work has also incorporated the ideas and work on IMT2000 and the reader can treat UMTS and IMT2000 as synon- ymous.
So why the need for change, why are all these technologies having to change? Simply put mobility has become a ‘wanna have’ of modern society, it is trendy, affordable and practical to own a mobile ’phone, some might argue a necessity, as people take more control over their lives and jobs become more demanding, information and communication on the move is rapidly becoming the norm.
The GSM-based systems have gained enormous public subscription in both forms (GSM 900 and DCS-1800), not only in the UK, but also throughout Europe and the world. This has meant any change from GSM specification networks towards a so-called third generation would cause significant trauma. It is because of this, the move is seen to be evolutionary with a migration towards the new generation of networks and services.
It is also a given that a move away from the first-generation mobile systems, (TACS, AMPS, etc.) is a natural progression and to that end a move to free up the frequencies in the UK used for TACS and ETACS by 2005 has been undertaken. This combined with cost of maintaining old equipment is the reason why BT Cellnet (re-branded mmO2) pulled the plug on their analogue network at the end of 2000.
Under the 3G network systems, the aim is for users to be able to roam among countries that currently use different technologies and also for users to be capable of seamlessly moving between multiple networks, fixed and mobile, cordless and cellular. As a result, product longevity for core network and transmission components should be longer, and network operators should benefit from increased flexibility.
Universal Mobile Telecommunications System (UMTS) and more speci- fically 3G mobile systems have become infamous because of press about the licence auctions that a number of countries have run to sell off the potentially lucrative licences, only time will tell if these licences prove worth their money. That said the potential services offered by 3G networks are very exciting and look to have a potentially huge worldwide market. The change will not be easy as the mobile networks will undergo a similar change from a circuit switched infrastructure to a packet switched infrastructure as mobile telecos switch off their analogue services, and migrate their digital (GSM et al.) networks to a UMTS network.
4.2
MOBILE NETWORK ARCHITECTURE AND
COMPONENTS
After that brief pre´cis on the evolution and standardisation of the mobile networks, what are the actual components and how do they work.
All mobile phone systems are based on the cellular principle, which is a cluster of radio antennas arranged as cells all transmitting and receiving radio signals at different frequencies (Figure 4.2). The number of frequen- cies used can be reduced by allowing the reuse of the frequencies in cells that are sufficiently far apart to avoid interference.
What differentiates each system, analogue or cellular, is the way in which multiple voice signals are encoded between the handset and the radio station at the centre of the cell, called the base station.