 main differences between the BRA scenario against the multiple RABs scenario (discussed in the last section) are, that, in the BRA scenario the peak rate per user flow is changing over time and moreover there are no multiple traffic classes with various fixed RAB types and different QoS requirements. The concerned QoS for dimensioning in case of BRA is the average transfer delay or throughput of all traffic flows. In the framework of this thesis, an approximation is suggested for dimensioning the lub link when BRA function is in use. The main idea of this method is to reuse the single rate M/G/R-PS model, but R is derived from the mean data rate. In the investigated scenarios, it is assumed that there is no CAC function applied to the elastic traffic flows. Therefore the blocking model is not considered in this case. Assuming that there are in total K RAB types available in UMTS. Let qj denote the percentage of the RAB type j in use over time. It is calculated as the ratio of the average number of flows assigned to the RAB type j denoted as Nj over the average total number of flows of all RAB types over a long time period. It indicates the average proportion of the RAB type j. Let rj denote the respective peak rate of RAB type j. Thus the average of the various peak rates peak_avg is derived from equation (6.35). (6.35) An average round trip time RTTavo is calculated in the same way, assuming the round trip time resulting from each RAB type. is RTT; (6.36) With the mean peak rate peak_avg and the mean around trip time RTT avg , the overall average transfer delay or average throughput can be calculated by the single rate M/G/R-PS model, assuming that all elastic traffic flows have the same average peak rate. Given the link capacity C, the M/G/R-PS model is then described with R=Ravg where Ravg = Thus, the average transfer delay for an amount of data of size x can be calculated with equation (6.26) and (6.27). 6.3.7.5 Extension for case of Mixing with Circuit-Switched Traffic Normally, the UMTS network contains bo