 results are validated by simulations. Figure 8.17 presents an example of transmitting circuit-switched traffic. The simulated scenario and parameters are: There are 4 Node Bs in the RAN, structured as a star network architecture (see Figure 8.1 (a)), each last mile link has a bandwidth of 1.3 Mbps Source traffic: voice traffic with AMR codec (traffic model is described in Table 5.2), transmitted with the peak data rate peak =12.2 kbps and the configured CAC guaranteed bit rate at last mile rm =12.4 kbps On the backbone link, the desired QoS is 1% packet loss ratio (qos bb = 1 %) Figure 8.17(a) presents the achieved overbooking for different amounts of the offered traffic per last mile link (represented by last mile utilization in the figure). In the graph, in addition to the calculated values obtained from the analytical approach, the simulated overbooking factors are also shown for comparisons. For each offered traffic level, the analytical approach as presented in section 8.2.1 sums up the offered traffic from each Node B and applies the MMPP/D/1 queuing model to calculate the required backbone link bandwidth for reaching 1% packet loss ratio QoS target. With the simulation approach, the dimensioned bandwidth is obtained by performing a number of simulations with different bandwidth settings and choosing the one which meets the 1% packet loss ratio in the simulations. Figure 8.17(b) shows the relative error of the calculated overbooking factor compared to the simulated ones. Both graphs of Figure 8.17 demonstrate that the proposed MMPP/D/1 model is certainly capable of deriving an appropriate overbooking factor for the backbone link for the 1% packet loss ratio QoS. Same as the investigations presented in Appendix A.19, given a fixed last mile link when the last mile utilization is increasing (i.e. more traffic coming from each Node B), the possible multiplexing gain on the backbone link is decreasing and thus the resultant overbooking factor declines. 8.5 Overbooking of the lub Backbone Link voice scenario: 4