network analysis phase is required in the dimen- sioning phase. So, what is the output of the dimensioning exercise? It is the number of nodes CORE NETWORK PLANNING AND OPTIMISATION that are required for handling the subscribers (and traffic) efficiently for a longer period of time. Here is a brief overview of the major outputs of dimensioning of the switch network: expected traffic generated in the network the number of switches required to handle subscribers and traffic (both present and forecast) the most efficient location of the switches in the network how the switches will be connected to each other (i.e. transmission plan for the switches) the most efficient way to route the traffic. The traffic calculation is perhaps the most important aspect of switch planning. It has to be as accurate as possible and all the factors discussed in the previous section contribute to this. One such example is shown in Figures 4.2(a) and (b). When there is more than one switch or more than one external network (i.e. PSTN, other operator, etc.), the generation table becomes bigger and complicated as traffic flow from each of the switches to/from the other switches and external network need to be taken into account. Of all the traffic existing in a cellular network, some percentage is generated and terminated in the same network, while some traffic terminates in other networks and vice versa. MSC/LE Originating Outgoing to other networks <<<<< To own network Loop back of incoming Terminating Incoming from other networks Figure 4.2(a) Traffic flow External Network External Network Figure 4.2(b) Traffic generation (in erlangs) There follows a simple example. Usually there would be multiple switches, and in such cases the traffic scenario (also known as a traffic matrix) becomes more complicated; inputs like the number of subscribers calling from mobile to mobile, mobile to fixed and fixed to mobile are required. Example 1: Basics of a Traffic Calculation Consider, then, a simple core network with one switch. The present traffic 