tes the highest traffic load at the user level, thus it is more suitable to model the web traffic in the nowadays UMTS networks and especially for the HSPA networks which are dedicated for transmitting the high speed packet-switched data. Thus the ETSI web traffic model is used in this thesis for generating the web traffic. 5.8.3 File Transfer Traffic Model File transfer (ftp) application has similar statistical behavior like web browsing, but the main difference is that one large objects of web browsing is considered as one file transfer. Since one session only contains one file transfer, there is no reading time. One user can have several ftp downloading sessions. The following figure shows the general traffic model for the ftp service. It consists of ON and OFF period where each ON period represents one file transfer. ON Period ON Period OFF Period File Size Interarrival Time Figure 5.10: File transfer (ftp) traffic model 5.8 Traffic Models The file transfer traffic model in the MOMENTUM project [TWP*02] defines a Lognormal distributed file size distribution. The probability density function of Lognormal is given below [KLL01]: (5.5) where o' is the standard deviation of the natural logarithms and u is the mean of the natural logarithms. In the MOMENTUM file transfer traffic model, u is set to 30580 bytes and o' is 3.6674. However, in this thesis this file transfer traffic model is not used. Instead, for validating the analytical dimensioning models in Chapter 6, a constant file size distribution is used. 6 Dimensioning for Single ATM-Based Iub This chapter presents the methodologies for dimensioning a single lub link in the UMTS Re199 of an ATM-based UTRAN, with both simulation and analytical approaches. Novel analytical models are proposed in this chapter, which allow the dimensioning of a single lub link for various traffic types and different QoS requirements. The traffic considered in this thesis is classified essentially into two main categories: circuit-switched traffic and elastic traffic (see Chapter 