tailieunhanh - GSM, cdmaOne and 3G systems P6

Các chương trước đã tập trung vào hai thế hệ thứ hai hàng đầu (2G) các hệ thống di động: GSM và IS-95. Các hệ thống này được triển khai ở nhiều nơi trên thế giới và sẽ tiếp tục hoạt động và phát triển trong thập kỷ tiếp theo như thế hệ thứ ba (3G) hệ thống được cán ra. Chúng tôi có thể hy vọng rằng các hệ thống 3G mới sẽ được hài hoà với các đối tác phát triển của họ 2G, và rằng quang phổ từ từ 2G sẽ được refarmed để cung cấp thêm. | GSM cdmaOne and 3G Systems. Raymond Steele Chin-Chun Lee and Peter Gould Copyright 2001 John Wiley Sons Ltd Print ISBN 0-471-49185-3 Electronic ISBN 0-470-84167-2 Chapter 6 Evolution of GSM and cdmaOne to 3G Systems Introduction The previous chapters have concentrated on the two leading second generation 2G cellular systems GSM and IS-95. These systems are deployed in many parts of the world and will continue to operate and evolve during the next decade as third generation 3G systems are rolled out. We may expect that the new 3G systems will be harmonised with their evolved 2G counterparts and that slowly 2G spectra will be refarmed to provide extra 3G spectra. No 3G systems are currently deployed although trials are in progress. As a consequence this chapter which deals with systems that are about to be deployed is treated in a qualitative manner describing how they will work rather than quantifying their performances. Before getting into detail let us briefly review how cellular communications arrived at today s position. The generation game There is no doubt that there was pent-up demand for public mobile telephony networks and when they arrived in the 1980s as the so-called first generation 1G analogue cellular networks they grew at phenomenal rates. These networks initially offered only telephony but the un-tethering of people from their fixed phones meant that they and businesses could operate in completely new ways. The Europeans identified in the early 1980s the need for a second generation 2G cellular system that would be totally digital. This 2G system became GSM and a brief history of GSM has already been provided in Section . The Europeans have a long view in cellular radio and in 1988 they launched their RACE 1043 project with 404 . INTRODUCTION 405 the aim of identifying the services and technologies for an advanced third generation 3G system for deployment by the year 2000 1 2 . Their 3G system soon became known as the universal .