inant (4) Voice dominant 1.6Mbps 1.6Mbps 2.5Mbps 2.5Mbps last mile utilization last mile utilization Figure A.34: Optimum OB factor vs. last mile utilization (various last mile links) Figure A.35 shows the overbooking as a function of the last mile link capacity for 2 Node B and 4 Node Bs, given a packet-switched traffic dominant scenario where the offered per Node B traffic consists of 87% web traffic, occupying in average 30% of the last mile link bandwidth. The left chart is the selected optimum OB factor and the right one is the corresponding backbone link utilization. It is seen from Figure A.35 that when the last mile A.19 Investigating Overbooking in the ATM-Based UTRAN link rates increases from 1.6 Mbps to 3 Mbps, the allowed maximum OB factor gets increased as well as the backbone link utilization for both 2 and 4 Node Bs. And having 4 Node Bs can obtain higher overbooking than having 2 Node Bs. The reason of improved overbooking with a higher last mile link bandwidth has been explained, i.e. more statistical multiplexing gain is achieved with a higher last mile link bandwidth for the bursty data traffic. last mile link cpacity [kbps] last mile link capacity [kbps] Figure A.35: Optimum OB factor VS. last mile link capacity (packet-switched dominant) Overbooking under different number of Node Bs This part evaluates the impact of different number of Node Bs on the setting of the optimum OB _factor. The investigated scenario is a packet-switched dominant traffic with 85% web traffic generated by each Node B. The last mile link is set to 1 E1 for each Node B. In Figure A.36 the left diagram shows the chosen optimum overbooking factors over different last mile utilizations, for 2, 4, 16 and 50 Node Bs respectively. The right one presents the relations of optimum overbooking factors over different number of Node Bs for various last mile utilizations. It can be observed from both figures that more Node Bs connected to the backbone link results in a better overbooking. The left figure demonstrates that the optim