er suited to meet the demand of this bursty data need than the traditional circuit-switched wireless data sys- items. GPRS allocates the bandwidth independently in the uplink and downlink. Another goal for GPRS is to enable GSM operators to enter the wireless packet data market in a cost-efficient manner. First, they must be able to provide data services without changing their entire infrastructure. The 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. GPRS Introduction Chapter 2 initial GPRS standards make use of standard GSM radio systems. This also includes GSM standard modulation schemes and TDMA framing struc- tures. By doing this, the cost implications are minimized in the cell equip- ment. Second, GSM operators must have flexibility to deploy GPRS without having to commit their entire network to it. GPRS provides the dynamic allocation and assignment of radio channels to packet services according to the demand. Evolution of Wireless Data Data support over first-generation (1G) wireless networks started with Advanced Mobile Phone System (AMPS), circuit-switched data communica- tions, as shown in the graph in Figure 2-7. This worked by attaching a cel- lular modem (a standard modem that supports the AMPS wireless interface) with a laptop computer. This began the evolution to the first wire- less packet data networks-Cellular Digital Packet Data (CDPD), with data rates up to 19.2 Kbps, as shown in the graph in Figure 2-8. CDPD works with AMPS networks and was initially designed for short intermittent transactions, such as credit card verification, e-mail, and fleet dispatch services. According to the Wireless Data Forum, CDPD covered 55 percent of the U.S. population as early as the third quarter of 1998 (3Q98). It has since grown to cover nearly 87 percent based on the proliferation of more Downloaded from Digital Engineering Library @ Mc