osted at the base station sub- GPRS Network Gateway Gateway Internet Station GPRS Tunneling Protocol Figure 14.5 GPRS components 2.5G: Enhanced Data Services system. There is a requirement for some mobility management to locate the GPRS mobile station, as well as a new air interface for packet traffic (i.e., the GPRS hand- sets). Additional security features also need to be implemented, including firewalls and encryption. Finally, there is a requirement for GPRS-specific signaling. All in all, GPRS is a migration strategy. It allows you to add packet-based data services to the existing network with minimal changes. It does not require new fre- quency allocations or licensing of new spectrum, and it does not require a whole new infrastructure to be put in place. The key applications that GPRS supports include corporate e-mail, Internet e-mail, various information services, job dispatch, remote LAN access, file transfers, Web browsing, still image transfer, and, to some extent, moving images and video and audio. The data rates may be a bit low to support video and multimedia appli- cations with the performance that users want to see, SO GPRS is largely a tool for a variety of less complex data sessions. The GSM Association (GSMA; www.gsmworld.com) has established a techni- cal GPRS roaming platform that it calls Roamfest. Roamfest enables executives from GSMA member operators to meet, discuss, and reach bilateral agreements for GSM, GPRS, WLAN, and MMS interworking roaming. This program has been successful as a one-stop-shop to fast-track GSM roaming agreements. Of the 290 live GPRS networks at the end of 2005, nearly 60% had committed to the EDGE upgrade. EDGE builds on enhancements provided by GPRS and HSCSD tech- nologies. By using EDGE, operators can handle three times more subscribers than with GPRS, triple their data rate per subscriber, or add extra capacity to their voice communications. EDGE uses the same TDMA frame structure, logic channel, and 200KHz carrier bandwidth as today's GSM networks, which allow