ed into two different logical elements, as shown in Figure 11-8. These two elements have defined functions and may (or may not) be implemented in different physical elements. These two ele- ments are the Radio Network Controller (RNC) and the Node B. 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 Figure 11-7 The architecture of 3G systems. Network UTRAN UMTS Terrestrial UTRAN Radio Access Network (UTRAN) Figure 11-8 The UTRAN Core Network architecture. Radio Network Subsystem (RNS) Radio Network Other Controller (RNC) Node B Node B Node B Node B The Node B is a logical element responsible for radio transmission and reception in one or more cells. In this respect, it could be physically imple- mented as a base station. 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 Radio Network Controller (RNC) As its name suggests, this is a control element. It is responsible for radio functionality and control of one or more Node Bs. The interface between the RNC and its associated Node B is called the lub interface. The RNC may be physically implemented as stand-alone or logically a part of some other element. Radio Network Subsystem (RNS) One RNC and its associated Node Bs are referred to collectively as the Radio Network Subsystem (RNS). The UTRAN may consist of one or more RNSs. The RNS provides all the functionality to establish, maintain, and clear radio connections. This functionality is therefore removed from the CN. In order to manage inter-RNS handovers, a defined interface exists between RNCs. This is called the lun interface. Core Network (CN) Many possibilities 