ake the dimensioning process too complex. Thus, it is recommended that only a few traffic classes should be defined and the overall set of applications and services mapped upon them. The traffic classes identify the required QoS that the network has to deliver for them. The implementation of mapping the applications to traffic classes in the network is technology dependent. In this thesis, two basic traffic classes are distinguished: (1) elastic traffic, for which QoS correlates with the total time that it takes to transfer bulk data of a certain size, i.e. application delay or throughput; 4 Framework of UMTS Network Dimensioning (2) circuit-switched traffic, which reserves certain bandwidth in order to guarantee the end-to-end delay, delay jitter and packet loss, and thus is subject to admission control. Elastic traffic is generated by data-centric applications (e.g. ftp, web, e-mail). In the Internet, this type of traffic is normally carried by the TCP protocol, which adapts its transmission rate to the currently available bandwidth. The circuit-switched traffic relates to delay-sensitive applications (e.g. voice, video conferencing) which use other transport protocols like Real-time Transport Protocol (RTP). Traffic Distribution It is an important task to predict traffic patterns, which depend on the popularity of services and the prevalent application mix. In the context of network dimensioning, traffic distribution refers to traffic quantity, traffic mix, and geographic distributions. Traffic quantity defines the amount of traffic which is carried in the network. With the ongoing development of the UMTS network, the traffic increases continuously. Thus for network dimensioning, not only the temporary traffic quantity but also the traffic growth and its growth rate are crucial factors to be considered. The traffic mix reflects the portions of different applications and services running in the network. In the early phase of UMTS networks, the voice services contribute the main portion of the overall traffic, b