-speed downstream only; later devices will sup- port high-speed, two-way service. EDGE is one technology that paves the way for the implementation of the Universal Mobile Telephony System (UMTS). According to the ETSI, UMTS will be a mobile communications system that can offer user benefits including high-quality wireless multimedia services to a convergent network of fixed, cellular and satellite components. It will deliver information directly to users and provide them with access to new and innovative services and applications. It will offer mobile personalized communications to the mass market regardless of location, network or terminal used. Native-mode GSM offers relatively low-speed data access. In response to demands for higher mobile bandwidth, a number of new technological add-ons have been created including the Generalized Packet Radio Ser- vice (GPRS), which can conceivably achieve higher data rates by cluster- ing as many as eight 14.4 Kbps channels to offer as much as 115 Kbps to the mobile user. There are, of course, downsides to this model including the ability to support fewer simultaneous users because of channel clus- tering, and the need to build an overlay on the existing network to sup- port packet-mode data transport. Nevertheless, GPRS deployment is proceeding apace. The third generation of wireless systems (3G) offers broadband access to wireless users over a high user count, digital network. One access pro- tocol that will be deployed is CDMA. In CDMA networks, there is no channelization per se. The Reality There are effectively two evolutionary 3G paths underway in the United States, one rooted in GSM, the other in CDMA. Both have merit, both will undoubtedly survive for some time to come, but they are different and must be explained. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Chapter 6 The