 is an increasing multiplexing gain with larger traffic load, and thus the required normalized capacity approaches one. Figure 7.5(b) demonstrates the influence of the circuit-switched traffic (voice in this example) on the required capacity. It shows that more percentage of voice traffic requires less bandwidth, similar conclusions are obtained in the mixed traffic scenario with a single ATM-based lub (presented in section 6.3.10). higher QoS requirement web traffic + 20% Voice lower QoS requirement web traffic + 80% Voice 800 1000 1200 1400 1600 1800 2000 2200 Traffic load (kbps) Traffic load (kbps) (a) different QoS requirements (b) different voice portions Figure 7.5: Capacity vs. traffic load 7.4 Comparing the ATM and IP-Based Iub When comparing the ATM and the IP transport, their individual transport network overheads, applied QoS or multiplexing schemes are different. This results in significant differences on overall network and end user performances and in turn the network dimensioning results. This section compares the achieved performances and bandwidth requirements of the ATM and IP based UTRAN. At first, Bandwidth Efficiency of both networks is compared in Figure 7.6. Effective bandwidth utilization in the UTRAN is directly related to the transport costs. High bandwidth efficiency means low transport network costs. In the context of this thesis, it is defined as the ratio of the data payload size (without transport network layer protocol headers) to the total bits of transmitting this payload on the physical link. In Figure 7.6, the bandwidth efficiency is calculated by estimating the total protocol layer overheads in both ATM and IP transport. In the following comparisons, the IP transport does not apply any multiplexing scheme. That 7.4 Comparing the ATM and IP-Based lub means, each radio frame (i.e. FP PDU) is encapsulated into one UDP/IP packet. In Appendix A.22, two optional multiplexing schemes Composite IP (CIP) and Lightweight IP Encapsulation (LIPE) can be used to improve the bandwidth effic