. To supplement a circuit-switched network architecture with packet switching is quite a major upgrade. However, the GPRS standard is delivered in a very elegant manner- with network operators needing only to add a couple of new infrastructure nodes and make a software upgrade to some of the existing network ele- ments. With GPRS, the information is split into separate, but related pack- ets before being transmitted and reassembled at the receiving end. Packet switching is similar to a jigsaw puzzle-the image that the puzzle repre- sents is divided into pieces at the factory where it is made and then the pieces are placed into a plastic bag. During the transport of the new-boxed 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 Figure 2-11 User B The circuit-switched traffic example. User A IWF has modems used by mobiles Wireless Network Figure 2-12 User B The packet-switched User A example. Packet Switch Packet Switch Packet Wireless Network Network Packet BSC/MSC Switch puzzle from the factory to the end user, the pieces get all mixed up. When the final recipient receives the bag, all the pieces are reassembled into the original image. All the pieces are related and fit together, but the way they are transported and reassembled varies by system, as seen in Figure 2-13. The Internet is another example of this type of a packet data network. 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 GPRS Introduction Figure 2-13 The pieces of GPRS and GSM fit together. WCDMA Backbone Backbone Inter-operator Router Router Public Internet Backbone GPRS Radio Technologies Packet switching means that the GPRS radio resources are used only whe