os are considered: pure elastic traffic, pure circuit-switched traffic, or a mix of both traffic types. In this thesis, for each traffic type, different QoS requirements are investigated. The QoS requirements determine the objective of dimensioning and the selection of suitable analytical dimensioning models. Two kinds of QoS are considered: user-relevant QoS and network- relevant QoS. User-relevant QoS refers to the QoS related to the individual user flow; while network-relevant QoS measures are used to evaluate the quality of the transport network such as packet delay, packet drop ratio, and link utilization (see Chapter 4 for a detailed description). The relevant user QoS for the elastic traffic flows used in this thesis is throughput, which specifies the amount of data that can be transferred in a certain time period. Specifically, in this thesis, the notion of throughput is the average transaction time for transmitting a specific file size. The proposed dimensioning model for guaranteeing this QoS for the elastic traffic is based on the processor sharing model. It can be applied for dimensioning in UMTS networks to meet the desired per user application layer throughput. One of the main contributions of this thesis is proposing a number of extensions of the process sharing model to incorporate important UMTS radio and transport functions and network topologies, and to demonstrate the applicability of the theoretical model through extensive simulations. For circuit-switched traffic the considered user QoS is connection reject ratio, as this traffic type is subject to the admission control function. The presented corresponding dimensioning model is based on the Erlang loss model. In the mixed traffic scenario, it is assumed that there is complete bandwidth sharing between the two traffic types. A dimensioning approach is suggested for the mixed traffic scenarios in this thesis to consider the bandwidth sharing and its achieved multiplexing gain. For dimensioning to meet the desired network-relevant QoS, the pro