ning for various traffic scenarios and UMTS radio access networks, considering certain transport solutions, QoS mechanisms and network topologies in use. Traffic Scenarios When dimensioning multi-service UMTS networks, it is not practicable to consider every characteristic of each application. Usually, only a few typical traffic types (or traffic classes) are defined and various applications are mapped upon them. Each traffic type has its own specific QoS requirements and traffic characteristics. In this thesis two fundamental types of traffic are distinguished: elastic and circuit-switched traffic. Elastic traffic is generated by non real time applications and is typically carried by the Transmission Control Protocol (TCP). Typical applications are Internet services like web browsing or file download. Circuit-switched traffic is associated with real time applications, which is delay- sensitive and have strict QoS requirements concerning the transport of packets over networks such as packet delay, delay jitter and packet loss. Typical applications in this traffic class comprise voice and audio or video conferencing. In order to guarantee the required stringent 1 Introduction QoS, they can reserve a certain bandwidth though the network in order to ensure a minimum transport bandwidth. In this context, they are called as circuit-switched traffic and controlled by admission control function. These two traffic types are identified as the two main traffic classes served in the current UMTS networks. Voice, which is typically considered as circuit-switched traffic, has been the most important service in mobile networks. In UMTS Rel99, voice is still the main service. With the evolution towards a high-speed UMTS networks, elastic traffic is growing rapidly in UMTS and becoming prevailing. Due to the importance of these two traffic types in the UMTS networks, they are chosen to be considered for network dimensioning in the frame- work of this thesis. Based on the two basic traffic classes, three different traffic scenari