maximally utilize the backbone bandwidth while satisfying the QoS of UTRAN transport network as well as the end users. In the following investigations, the QoS requirements in UTRAN is that the acceptable FP PDU delay value considered for voice service is 10ms for 99% of voice packet transmissions and 30ms for data services for 99% of packet-switched packet transmissions. Those packets whose experienced FP PDU delays violate the given values would be discarded. That means, we allow maximum 1% packet loss ratio for both voice and packet-switched services. For the end users, the required average transfer delay for Appendix transferring average 25Kbyte page should be within a maximum defined value, e.g. 2.5 seconds in the presented examples, and the voice packet delay should be lower than 100ms [3GP06c]. Impact of overbooking Figure A.32 shows the impact of setting of overbooking factors. The given scenario consists of 4 Node Bs where the last mile link is set to 1 E1 (2 Mbps). Each Node B transmits a mixture of packet-switched web and circuit-switched voice traffic with 85% web traffic, and the total offered load per Node B is around 40% of the last mile link. PS web voice overbooking factor overbooking factor overbooking factor overbooking factor Figure A.32: Impact of overbooking It is seen from Figure A.32 that when OB factor is increased from 1 to 2.5, the backbone link utilization is improved by more than 50%. But the UTRAN network performance in terms of the packet loss ratio of both voice and packet-switched packets are gravely depredated with higher OB factor, especially when OB_factor is larger than 1.6. When OB factor is set to 2.5, the packet loss ratio for voice reaches above 80% and for packet- switched about 70%. To satisfy 1% packet loss ratio as the QoS target for both services, OB factor need to be configured below 1.4 in this example. Furthermore, the end user performance is also seriously influenced by the overbooking. It can be seen that there is a rapid increase of the application delays for bo