 different traffic loads per Node B. The dimensioning results are represented by the normalized capacity (defined in section 4.3). It is seen that in Figure 8.28 that for both last mile link and the backbone link, with RAB 128 kbps the IP transport requires less link capacity than the ATM transport for meeting the same QoS target, because the RAB 128 kbps can achieve a higher bandwidth efficiency in the IP transport. It is the same conclusion that is obtained for the single lub link scenario presented in section 7.4. It can be further observed in Figure 8.28 that the backbone link can achieve higher cost efficiency due to a higher multiplexing gain is achieved from aggregating the traffic from different number of Node Bs. Figure 8.29 shows the overbooking factor calculated from the dimensioned last mile link and backbone link bandwidths. It can be observed that the obtained overbooking gain is larger than 1. Moreover the ATM-based UTRAN has higher overbooking factor than the IP-based UTRAN, because the ATM transport has lower last mile utilization as shown in Figure 8.28 and thus achieves a higher multiplexing gain over the lub backbone link. If given the same capacity for the last mile link in both ATM and IP based multi-lub RAN, it can be expected that for the service class of RAB 128kbps the overbooking factor for the IP-based UTRAN will be higher due to a higher bandwidth efficiency of RAB 128kbps in the IP transport. Dimensioning of last mile link (ATM vs. IP) Dimensioning of backbone link (ATM vs. IP) ATM based UTRAN ATM based UTRAN IP-based UTRAN IP-based UTRAN traffic load per Node B (kbps) traffic load per Node B (kbps) Figure 8.28: ATM vs. IP- dimensioning of last mile link and backbone link 8 Dimensioning for Multi-lub RAN Scenario Overbooking (ATM VS. IP) ATM-based UTRAN IP-based UTRAN traffic load per Node B (kbps) Figure 8.29: ATM vs. IP- overbooking factor over traffic load From this example and the conclusions drawn from the single lub link dimensioning comparison in section 7.4, it can be expecte