sired QoS requirements of different traffic types will have direct influence on the overbooking results. The higher of the QoS requirements, the lower overbooking can be achieved. In the mixed traffic scenarios, the percentage of RT traffic will have influence on the achieved overbooking gain. The higher percentage of RT traffic, the higher the overbooking that can be achieved. This is due to that RT traffic is given higher priority and as well it has lower bandwidth demands than the NRT traffic. Thus when there is more portion of RT traffic, there will be more bandwidth saving and thus higher overbooking gain. In addition to finding out the above important factors and their individual influences on the overbooking, analytical approaches, which are proposed in the preceding sections for dimensioning the multi-lub RAN for different types of traffic and transport networks, are applied in this section to analytically derive an appropriate overbooking factor for dimensioning the backbone link for a defined QoS. The validations are performed for different network and traffic scenarios for both ATM and IP based UTRAN. For investigated network scenarios, the presented validation results demonstrate that all proposed analytical approaches are able to derive the optimum overbooking factor for the backbone link and the calculated overbooking factors are quite accurate compared to the ones obtained from the simulations. At the end, the overbooking of the ATM and IP based UTRAN is compared. The comparison results show that the achieved overbooking gain is dependent on the bandwidth efficiency of each RAB type in the individual ATM and IP transport network. 9 Conclusion and Outlook An important way for improving the cost-efficiency of UMTS networks is efficient design and use of existing network infrastructure. The radio access network is considered as one of the most important economic aspects for the network planning and bandwidth dimensioning due to its limited and expensive transport resources. With the rapid expansion of