nd Services Future Enhancements and Services Mobile Serving GPRS Support Node Gateway GPRS Figure 11-5 Station (SGSN) Support Node EDGE protocol stack. SNDCP Base Station SNDCP LLC Relay BSSGP BSSGP Frame Frame Relay Relay Physical Physical Physical Physical Layer Layer Layer Layer (GMSK (GMSK 8-PSK) 8-PSK) at the MAC layer (bottom half of Layer 2 in the OSI). Figure 11-5 shows the protocol stack for EDGE. The channel separations are 45 MHz and the carrier spacing is a 200- kHz channel capacity, the same as GSM and GPRS. The number of TDMA slots on each carrier is the same (eight) as the GSM and GPRS architecture. When a mobile station wants to transmit its data, it can request and use one to eight time slots per TDMA frame. Connectivity is handled via a packet-switched data network such as IP and X.25. These can be public data networks or private data networks. Although most carriers and service providers have plans to deploy enhanced mobile wireless services at higher speeds, the rollout of high- bandwidth wireless transport technology still faces many possibilities. On a positive note, widespread demand will be sufficient enough to support cel- lular enhancements like high-speed data services and expanded voice capacity. Competitive pressures will also compel service providers to upgrade. The International Telecommunication Union-Radiocommunica- tions Standardization Sector (ITU-R) has actually established five different standards that fall into the category of 3G/UMTS. Moreover, the telecom- munications industry is growing increasingly impatient to test the world markets for high-bandwidth wireless communication services. The ITU's International Mobile Telecommunications-2000 (IMT-2000) initiative may 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. Future Enhancements and Services Chapter 11 one day converge, but today, many 3G proposals