. Some statistics about the wireless roaming environment in Europe are as follows: 540 million roaming calls were made in February 2000. 750 million calls were predicted in June, July, and August 2000. Data will account for between 20 and 50 percent of all global wireless traffic by 2004. 8 billion short messages were sent in May 2000. 10 billion SMS messages were sent in December 2000. 1 billion SMS messages were sent per month in Europe alone in 2001. GSM grew at 80 percent in 1999; PCs grew at 22 percent. All terminals will be Internet-enabled by 2002 to 2003. More GSM terminals will be connected to the Internet than PCs by 2005. Wireless devices will access 30 percent of all Internet traffic by 2005. 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 The GSM Phase II Overlay Network The typical GPRS PLMN enables a mobile user to roam within a geo- graphic coverage area and receive continuous wireless packet data services. The user may move while actively sending and receiving data or may move during periods of inactivity. Either way, the network tracks the location of the mobile station SO incoming packets can be routed to the mobile station when they arrive. The GPRS PLMN interfaces with the mobile stations via the air interface. GPRS services will initially be provided using an enhanced version of the standard GSM interface. The operators will evolve their networks to incorporate more advanced radio interfaces in the future SO that they can deliver higher data rates to the end user. The GPRS PLMN interfaces as an overlay to traditional public packet data networks using standard Packet Data Protocols (PDPs), as shown in Figure 2-10. The network layer protocols supported for interfacing with packet data networks include X.25 and the IP. Through these networks, the Figure 2-10 The GPRS overlay Voice on GSM. POTS/P