Network Plan Core Network Planning CS- Core PS- Core NE dimensioning NE dimensioning CS- Core PS- Core Interface Planning Interface Planning CS- Core PS- Core Signalling Plan Signalling Plan Core Network Plan Figure 9.2 Core network planning process Network Analysis Information collection, again, an important part of the process. Information to be col- lected includes the existing/designed network topology (both radio and transmission), sub- scriber database (present and forecasted), topography of the region, traffic measurements etc. Quality and performance targets give direction to the analysis and design of the core network. In GSM core network planning, the MSC (switch) was one important network element around which the whole design process revolved. In 3G, as the functionalities ex- tend to MGW, the whole process will revolve around the two network elements, MSC and MGW, their inter-connection and the planning of the signalling network. Network Dimensioning The existing subscriber base and expected growth rate are important factors. Dimensioning should be done in such a way that, when implemented, the network will be able to handle the expanding traffic for the next few years. Network planning tools are used (see Appendix A). In third-generation networks, a twofold approach is taken for dimensioning the CS core network, that is, the network is dimensioned with respect to both the user plane and the control plane. And as we have seen, the MGW and MSC (or MSC server) are two elements that are responsible for the user plane and control plane traffic. Thus, dimensioning of the CS core involves dimensioning of the number of MGWs, the number of MSCs, and the signalling related to them. Dimensioning the number of MGWs is dependent on several factors, which mainly include the traffic distributions, subscriber database, location of elements like the MSC, 3G CORE NETWORK PLANNING AND OPTIMISATION RNC and external (other network) elements. The number of MGWs can also be calculated by the amount of area that needs to be