rom a significant increase in network capacity for data services. Beyond HSPA, further improvements are already being proposed, i.e. HSPA+ and Long Term Evolution (LTE) are currently making their way through the standardization process. A detailed introduction of the UMTS network evolutions is presented in Chapter 2. These evolutions will not only offer a much improved service experience for UMTS users but also enable new services such as IPTV, Voice over IP, multi-player gaming, high resolution video, and also provide high speed for popular Internet applications like web browsing, Skype, YouTube, etc. The UMTS evolution and the resultant new applications and services are changing the nature of traffic in the current and future UMTS networks significantly, having a huge impact 1.3 Important Challenges for UMTS Network Dimensioning on the amount of traffic and its distribution as well as on the flow and packet-level characteristics. As a consequence, the evolution of the traffic pattern, traffic quantity and traffic flow characteristics will have considerable impact on the UMTS network dimensioning. Especially the "bandwidth greedy" applications pose great problems for the network dimensioning, as they often cause severe traffic congestions within the network. In order to avoid such congestion, network capacities have to be expanded. More detailed explanations on the implications of traffic and network dimensioning are given in Chapter 4. Nevertheless, it is not yet possible to predict typical traffic patterns for future UMTS networks, as these will depend on the popularity of future services and the prevalent application mix (telecommunications VS. data). The fact that traffic cannot be accurately estimated before the network is in operation stresses the need for a continuous network dimensioning throughout network operation phase. Once the amount, distribution and characteristics of the offered traffic are determined by means of monitoring, the dimensioning can be used to adapt the network capacities to support 