Các mạng UTMS và công nghệ truy cập vô tuyến P1

EVOLVING MOBILE NETWORKSWhile the history of mobile communications is long [1–3], and the background of mo bile networks therebyx is also long, in this chapter we focus on the historic evolution in terms of network architecture and services starting with 2nd generation (2G) mobile systems. In particular we consider the development of the architecture of Global Systems for Mobile Communications (GSM), since it is by far the most widespread mobile system in the world today.
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Các mạng UTMS và công nghệ truy cập vô tuyến P1 The UMTS Network and Radio Access Technology: Air Interface Techniques for Future Mobile Systems Jonathan P. Castro Copyright © 2001 John Wiley & Sons Ltd Print ISBN 0-471-81375-3 Online ISBN 0-470-84172-9 EVOLVING MOBILE NETWORKSWhile the history of mobile communications is long [1–3], and the background of mobile networks therebyx is also long, in this chapter we focus on the historic evolution interms of network architecture and services starting with 2nd generation (2G) mobilesystems. In particular we consider the development of the architecture of Global Sys-tems for Mobile Communications (GSM), since it is by far the most widespread mobilesystem in the world today. This will provide the basis to cover the introduction of Uni-versal Mobile Telecommunication Services (UMTS) in relation to its Core Network(CN) and radio architectures. The latter will in turn serve as the platform to presentUMTS Radio Access Technology, which is one the aims of this book.1.1 THE GROWTH OF MOBILE COMMUNICATIONSToday wireless voice service is one of the most convenient and flexible means of mod-ern communications. GSM technology has been at the leading edge of this wirelessrevolution. It is the technology of choice in over 120 countries and for more than 200operators worldwide. Current estimates are that by the year 2001 there will be around600 million wireless subscribers (e.g. mobile telephone users), out of which more than50% will depend on GSM technology.As the wireless revolution has been unfolding, the Internet has also shown a phenome-nal growth simultaneously. The advent of the World Wide Web and web browsers haspropelled TCP/IP protocols into the main stream, and the Internet is widespread not †  ‚ v y y v € à 0 RELOH † … r i ,QWHUQHW v … p † i ˆ T Figure 1.1 The growth of mobile and internet services.2 The UMTS Network and Radio Access Technologyonly in the corporate environment but also in households. Large number of consumershave embraced the Internet and use it today to access information online, for interactivebusiness transactions, and e-commerce as well as electronic mail. Figure 1.1 illustratesthe growth in mobile and Internet subscribers.The success of mobile communications, i.e. the ubiquitous presence it has establishedand the emergence of the Internet point towards a tremendous opportunity to offer inte-grated services through a wireless network.One of the main market segments for wireless services besides corporate intra-net/internet access is the consumer sector. The availability of intelligent terminals1 ormultipurpose wireless telephones is already ushering a new era of the information age,where subscribers can receive directly through GSM-SMS: news, sport updates, stockquotes, etc. However, the progress of audiovisual techniques and the support for a Web-like interface in a new generation of terminals, will push consumers to a new era ofmultimedia communications with a focus on services rather than technology.To support the growth of Internet type services2 and future demands for wireless ser-vices, ETSI SMG and other standards bodies3 have completed or are now completingspecifications to provide a transition platform or evolution path for wireless networkslike GSM. Figure 1.2 illustrates the wireless data technology options.The technology options in Figure 1.2 can be summarized as follows:œ 14.4 kbits/s allows GSM data calls with a rate of 14.4 kbits/s per time slot, resulting in a 50% higher data throughput compared to the current maximum speed of 9.6 kbits/s.œ High Speed Circuit Switched Data (HSCSD) aggregates symmetrically or asym- metrically several circuit channels, e.g. 28.8 kbits/s for two time slots (2 + 2) or 43.2 kbits/s for three time slots (3 + 1).œ General Packet Radio Service (GPRS) enables GSM with Internet access at high spectrum efficiency by sharing time slots between different users. It affords data rates of over 100 kbits/s to a single user while offering direct IP connectivity.œ Enhanced Data Rate for GSM Evolution (EDGE) modifies the radio link modula- tion scheme from GMSK to 8QPSK. Thereby increasing by three times the GSM throughput using the same bandwidth. EDGE in combination with GPRS (E- GPRS) will deliver single user data rates of over 300 kbits/s.œ UMTS as 3rd generation wireless technology utilizes a Wideband CDMA or TD/CDMA transceiver. Starting with channel bandwidths of 5 MHz it will offer data rates up to 2 Mbits/s. UMTS will use new spectrum and new radio network configurations while using the GSM core infrastructure._______1 For example WAP terminals.2 Including voice or IP as a new trend.3 In the USA – T1P1, in Japan – ARIB, in Korea – TTA, and in China – CWTS.Evolving Mobile Networks 3 !Ãxà Ãxà 3DFNHW ...