d the resulting capital expenditures of installing transport links and assigning capacities will be considerably high, especially on the lub interface which connects a Node B to its serving RNC. Each lub interface carries the traffic of all UEs which are served by the connecting Node B. In order to save the overall infrastructure cost, the lub interface is usually assigned with a limited bandwidth. Thus, the lub interface is easy to be under-provisioned and hence may cause performance degradation to the user traffic. In this context, the lub interface is regarded as one of the major capacity bottlenecks in the UMTS radio access network. According to the one-way delay estimation from the UE to the core network given in 3GPP TR 25.853 [3GP01c], it can be seen that the lub delay contributes a considerable portion. On the other hand, the air interface and the related radio control functions like power control or channel allocation also define strict delay requirements for the lub interface. These delay requirements should be guaranteed over the lub interface for all types of traffic. The lub must deliver the content of a frame on time to the base stations for transmission over the air. Excessively delayed frames are discarded [3GP02e]. In such a network environment, the ability to appropriately dimension the lub interface is a fundamental pillar of the UMTS network design and optimization processes. Therefore, the ultimate goal of this thesis is to investigate important aspects related to network dimensioning, and develop analytical methods to accurately estimate the required minimum capacity for the lub interface, based on the amount as well as the characteristic of the aggregated traffic on the lub interface and the desired QoS. 1 Introduction 1.3 Important Challenges for UMTS Network Dimensioning The evolution of UMTS wireless technologies as well as the derived new applications and services will greatly influence the development and the use of UMTS, and further cause considerable impact on the UMTS network dimens