 dimensioning for combined traffic scenarios (transmitting HSPA traffic together with Rel99 traffic in the same radio access network) are also investigated and various traffic separation approaches are explored. Chapter 7 presents the dimensioning for the IP-based lub transport for the single link scenario. In the IP transport network, the DiffServ QoS architecture is considered. The proposed analytical models for the Rel99 ATM-based transport network are extended for the IP-based transport, taking into consideration of the IP specific QoS scheme and transport functions. The extended analytical models are validated for the IP-based lub transport network through simulations. Additionally in this chapter the performance and the dimensioning of the IP-based lub is compared with the ATM-based lub. In chapter 8, the dimensioning for multiple lubs with a star network topology is investigated. For this case, dimensioning approaches are proposed to extend the analytical models, which are developed for the single link scenario, to dimension the capacity of the last mile link for each Node B and the backbone link individually. And the calculated link capacities are verified to be able to meet the desired QoS through simulations. In addition, overbooking is investigated in detail for dimensioning the backbone link. By applying the extended analytical models, the optimum overbooking factor can be derived. Through comparing the analytical results with simulation results in various network scenarios, the 1.5 Thesis Overview presented analytical models are proven to provide accurate estimation on the bandwidth dimensioning and the optimum overbooking. Finally, Chapter 9 gives a summary of this thesis and summarizes the most important achievements and results. Additionally, interesting issues for further research are pointed out. 2 UMTS Evolution With the dramatic development and expansion of 3G cellular networks all over the world, a profound evolution is taking place in the UMTS networks and continuing to unfold towards wider 