ensioning for Multi-lub RAN Scenario 8.4.1 Dimensioning Approaches Figure 8.12 illustrates a star-structured multi-lub IP RAN, where a DiffServ QoS scheme is applied to classify different service classes and guarantee QoS requirements of the individual service classes. To deploy the DiffServ QoS architecture throughout the IP RAN, every Node B and the RNC as well as the connecting IP routers need to provide the DiffServ QoS function for both uplink and downlink transmissions. As can be seen from Figure 8.12, the DiffServ QoS function is performed on each last mile link and the backbone link individually. Assuming that each Node B serves a group of elastic traffic flows of the UEs, on the last mile link the applied DiffServ QoS scheme firstly maps the multiple elastic traffic flows to a number of service classes, i.e. Per Hop Behaviors (PHBs), and then forwards them to the corresponding buffers before sending them down to the link. The applied scheduler decides at what time which buffer can be served, according to the given priority of each PHB. As a result, the last mile link carries several service classes, each being allocated to a share of complete IP bandwidth that is assigned to the last mile link according to its defined priority. When the traffic flows of the different Node Bs are aggregated on the backbone link, the total number of the elastic traffic flows carried by the backbone link will be the sum of the number of flows of each Node B, and the total amount of elastic traffic traversing on backbone link will be the sum of the amount of traffic from all last mile links. It is assumed that throughout the IP RAN, the provided DiffServ PHBs and the related DiffServ QoS functions such as mapping, marking, dropping, and scheduling are configured the same at every DiffServ node (i.e. at the Node B, the RNC, and the IP routers). Thus, the backbone link allows the same types of service classes (PHBs) and experiences the same DiffServ functions as each last mile link. In the context of this thesis, the applied s