and Table 7.12. For all practical purposes, we illustrate the dimensioning for both the evolving and layered architecture, which is described in the forthcoming sections. 7.9.1 CN Analysis Assumptions Figure 7.12 [8] illustrates key CN elements which we refer to throughout the dimensioning process. Notice that here we imply a co-existence with 2nd generation elements, e.g. GSM. The next chapter describes the essential functions of this network. Services/ Service Application application Application layer Switching GMSC/Transit Server Server Control Point Server (+EDGE) Control Server Multimedia Gateways Multi-Service Backbone Network UTRAN Multimedia Internet Gateways Intranets Multimedia WCDMA User data Gateways Control Figure 7.12 The core network layer architecture reference. 7.9.1.1 Locating CN Nodes Logically, the starting point of the CN design and dimensioning will start by locating the main switching centres. In this field study we consider three sites: let us say they are within cities A-C of our country example in this chapter. Thus, we locate CN nodes in centres A, B, and C. 7.9.1.2 Locating RNC nodes The number of RNC nodes will depend on the traffic load and number of BS sites con- nected. Their location in general will vary according to chosen topology; thus, we can have a centralized or distributed network layout. The centralized layout implies placing the RNCs at the switching centres together with the CN nodes. The distributed option will in general expand beyond the CN sites. Each option has its trade-offs and will de- pend on the availability of the transmission infrastructure as well. For example, some of the advantages of a centralized RNC network, i.e. co-located with the CN nodes in- clude: Deploying 3G Networks Rapid implementation and integration processes, as well as the lower investment on the RNCs themselves. Today technology allows high capacity systems as better choices than small ones, because a higher grade of statistical multiplexing is gained in larger nodes than in smaller ones. 