iency of IP based UTRAN. They allow multiplexing multiple radio frames (FP PDU) into one UDP/IP packet, and thus reduce the relative UDP/IP transport overheads. It can be seen in Figure 7.6 that for AMR voice and low RAB rate bearers such as RAB 64 kbps, the ATM-based UTRAN achieves higher efficiency than the IP-based UTRAN. This is because that the radio frame sizes of low RAB rate bearers are relatively small, and thus the added UDP/IP/Ethernet overhead of the IP transport network is larger compared to the ATM transport. On the other hand, the bandwidth efficiency of the IP-based UTRAN increases for higher RAB rate and even exceeds the efficiency of the ATM-based UTRAN when the RAB rates are 128kbps or above. This is because that with higher RAB rate, the radio frame sizes are larger and thus the overhead of UDP/IP/Ethernet is relatively smaller than the one in the ATM-based UTRAN. Appendix A.22 shows that when multiplexing scheme is applied in the IP-based UTRAN, with either CIP or LIPE, the bandwidth efficiency is significantly better compared with not using multiplexing scheme in the IP-based lub, and even better than the ATM-based one, by combining several frames into one IP packet. Bandwidth Efficiency AMR Voice RAB 64kbps RAB 128kbps RAB 384kbps RAB Type Figure 7.6: Bandwidth Efficiency: ATM vs. IP The following results compare the dimensioning of a single lub link in the ATM and IP- based UTRAN. In the given examples, the considered user-relevant QoS for elastic traffic is the end-to-end application delay indicated by a target delay factor, and for circuit-switched traffic the connection reject ratio as a result of CAC. Figure 7.7 compares the required lub link bandwidths of the ATM and the IP (without multiplexing scheme) over different voice traffic loads, for meeting 1% and 5% CAC connection reject ratio (blocking). The dimensioning results are derived from Erlang-B formula while considering the individual transport overheads of both transport networks. 7 Dimensioning for Single IP-Based lub Dimension