n, 229 vertical distance, 296 transmit ON/OFF power, 199 video telephony, 234 transmit power control, 90 transport block concatenation, 167 wideband antenna, 297 transport channels, 72 wideband CDMA, 2 transport format set, 178 wider transmission rates, 231 transport network control plane, 69 WWW browsing, 37 TrCH multiplexing, 172 turbo coding, 167, 169 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 NETWORKS While 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 Sys- tems for Mobile Communications (GSM), since it is by far the most widespread mobile system 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 present UMTS Radio Access Technology, which is one the aims of this book. THE GROWTH OF MOBILE COMMUNICATIONS Today 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 wireless revolution. It is the technology of choice in over 120 countries and for more than 200 operators worldwide. Current estimates are that by the year 2001 there will be around 600 million wireless subscribers (e.g. mobile telephone users), out of which more than 50% 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 has propelled TCP/IP protocols into the main stre