ycle. In the initial network design step, an initial dimensioning is required for setting up the network to assign appropriate capacities for the links. In the network operation phase, the dimensioning may be updated upon the indications of non-satisfactory states. If adapting the bandwidth allocation is not sufficient for keeping the QoS, the network needs to be expanded. In this case a re-dimensioning of the network is invoked. It can be concluded that the dimensioning should consider different essential issues like the current traffic demand, the existing network topology, the applied traffic control, resource control, routing and traffic engineering techniques in the network. The network dimensioning has to meet the objective of minimizing the overall network costs while satisfying the QoS requirements. The following sections give a more detailed discussion dimensioning related issues in this framework and their implications for the dimensioning task. 4.2 Important Issues for UMTS Network Dimensioning Initial Network Design Traffic Analysis Dimensioning Topology Design Routing Issues Initial Dimensioning (capacity assignment/ bandwidth allocation) New Network monitoring Network Operation Network Management Traffic Control Routing Optimization Resource Control Dimensioning Update Rerouting (bandwidth adaptation) configuration Extended Network Extension Planning Extension Request Topology Adaptation Re-dimensioning (capacity extension) Routing Optimization Figure 4.1: An overview of dimensioning issues 4.2.1 Traffic Analysis The first fundamental issue to consider for network dimensioning is an accurate estimation for the traffic that is carried by the network. It comprises basically three aspects: traffic classification, traffic distribution, and traffic characterization. Traffic Classification The traffic, which will be offered in the network, needs to be classified with respect to the characteristics and required QoS. It is not practicable to consider every characteristic of each application, as this would m