cheduler at each last mile link and the backbone link is a combination of Weighted Fair Queue (WFQ) and Strict Priority (SP) scheduling. The corresponding QoS structure is presented in section 3.4.2.3. At the end, the backbone link transmits the same set of service classes (PHBs) as each last mile link and each of the service classes will be allocated a share of the entire IP bandwidth that is assigned to the backbone link according to its priority level and WFQ weight. 8.4 Dimensioning for Elastic Traffic in IP-Based UTRAN last mile link elastic traffic DiffServ flows of Node B 1 Class 1 elastic DiffServ Class 2 traffic flows DiffServ Class 3 of Node B 2 backbone link elastic DiffServ traffic flows of Node B n last mile link Figure 8.12: A star topology multi-lub IP RAN using DiffServ QoS for IP transport The analytical models for dimensioning a single IP-based lub link for elastic traffic have been presented in Chapter 7.3, which considers the impact of the DiffServ QoS function applied at the IP transport layer. As seen in section 7.3.1, for elastic traffic the analytical dimensioning models are extensions of the M/G/R-PS model in case that there is no restriction on the number of concurrently transmitted elastic traffic flows, and the M/G/R/N- PS model in case that a maximum of N (N>R) elastic traffic flows are transported simultaneously. Section 7.3.3 explains the detailed procedures for dimensioning a single IP- based lub link with the proposed analytical models from section 7.3.1. In this proposed dimensioning approach, it is assumed that Assured Forwarding (AF) and Best Effort (BE) PHBs carry elastic traffic and each PHB (AF or BE) serves one Non Real Time (NRT) RAB service. The task of dimensioning is to derive a minimum required IP bandwidth that guarantees the QoS requirement of each DiffServ service class. To apply the previously developed analytical models used for a single link to dimension the star-structured multi-lub IP RAN, first of all the QoS requirements for the individual links through the l