erminals will therefore be multiband 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 Future Enhancements and Services and multimode SO that they can work with different standards, old and new. Achieving such terminals at a cost that is comparable with contemporary single mode 2G terminals will become possible because of technological advances in semiconductor integration, radio architectures, and software radio. This part of the network consists of the Base Station System (BSS) and the necessary functionality to control access through the BSS. All radio functionality is contained within the UTRAN. Users' equipment will access the UTRAN with one of the three access modes: Frequency Division Duplex (FDD) nonsynchronous CDMA FDD synchronous multicarrier CDMA TDD TD-CDMA The access mode used will depend on location, conditions, user require- ments, and the operator's selected technology options. It is likely that UTRAN will not be the only AN connected to the CN. Subscribers may also have access via fixed, satellite, or cordless connections. Open Interfaces If a range of interconnection possibilities for different technologies from dif- ferent manufacturers is available, then it becomes important to define the various interfaces. Given the general architecture of UMTS, two interfaces will be of particular importance to the ANs. These will be the interface between the User Equipment (UE) and the UTRAN, and the interface between the UTRAN and the CN. The interface between the UE and the UTRAN is referred to as the U interface and is the radio link using an appropriate multiple access protocol. The interface between the UTRAN and the CN is referred to as the 1u interface. The interfaces in Figure 11-7 can be seen as a simple approach to describing the architecture. UTRAN Architecture The UTRAN itself can be subdivid