tailieunhanh - Hệ thống 3G và mạng không dây thông minh P1

Although the number of cellular subscribers continues to grow worldwide [27], the predominantly speech-, data- and e-mail-oriented services are expected to be enriched by a whole host of new services in the near future. Thus the performance of the recently standardised Code Division Multiple Access (CDMA)third-generation (3G) mobile systems is expected to become comparableto, if not better than, that of their wired counterparts. | Third-Generation Systems and Intelligent Wireless Networking . Blogh L. Hanzo Copyright 2002 John Wiley Sons Ltd ISBNs 0-470-84519-8 Hardback 0-470-84781-6 Electronic Chapter Third-Generation CDMA Systems K. Yen and L. Hanzo Introduction Although the number of cellular subscribers continues to grow worldwide 27 the predominantly speech- data- and e-mail-oriented services are expected to be enriched by a whole host of new services in the near future. Thus the performance of the recently standardised Code Division Multiple Access CDMA third-generation 3G mobile systems is expected to become comparable to if not better than that of their wired counterparts. These ambitious objectives are beyond the capabilities of the present second-generation 2G mobile systems such as the Global System for Mobile Communications known as GSM 28 the Interim Standard-95 IS-95 Pan-American system or the Personal Digital Cellular PDC system 29 in Japan. Thus in recent years a range of new system concepts and objectives were defined and these will be incorporated in the 3G mobile systems. Both the European Telecommunications Standards Institute ETSI and the International Telecommunication Union ITU are defining a framework for these systems under the auspices of the Universal Mobile Telecommunications System UMTS 27 29-33 and the International Mobile Telecommunications scheme in the year 2000 IMT-2000 1 30 31 34 . Their objectives and the system concepts will be discussed in more detail in later sections. CDMA is the predominant multiple access technique proposed for the 3G wireless communications systems worldwide. CDMA was already employed in some 2G systems such as the IS-95 system and it has proved to be a success. Partly motivated by this successer both the Pan-European UMTS and the IMT-2000 initiatives have opted for a CDMA-based system although the European system also incorporates an element of TDMA. In this chapter we provide a rudimentary introduction to a range of CDMA .