corresponding dimensioning results are presented in Chapter 7 for a single IP-based lub and in Chapter 8 for a multi-lub RAN network scenario. 5.6 Simulation Model of HSPA The HSPA is the extensions of the UMTS Rel99. In the framework of this thesis, the UTRAN network for the HSPA is based on the ATM. The HSPA simulation model was established in the framework of the HSDPA project by the Communication Networks group in the University of Bremen. The HSPA simulation model was built separately from the UMTS Rel99 simulation model, but it was developed under the same simulation environment as for the Rel99 simulation model described in section 5.3, and as well it was implemented based on the OPNET ATM workstation and ATM server models adding the HSPA specific functions and protocol layers. The model structure is in accordance with the common simulation model framework presented in section 5.2, including the modeling of groups of HSPA UEs and their corresponding communication nodes in the external networks, the air interface, the Node B, the RNC and the lub interface. The HSPA simulation model includes the modeling of HSDPA for the downlink and HSUPA for the uplink separately. For each of them, the individual new protocol entities, the air interface, the MAC scheduler, and the related traffic control functions are modeled separately. When performing simulations, HSDPA and HSUPA can run simultaneously or independently. More detailed introduction on the HSPA simulation model is given in Appendix A.10. 5.7 Simulation Model of Combined UMTS Rel99 and HSPA 5.7 Simulation Model of Combined UMTS Rel99 and HSPA Usually, the HSPA services are provided on the existing UMTS Rel99 networks. To model such a network with both HSPA and Rel99 traffic, an approach was developed in this thesis to combine the Re199 simulation model and the HSPA simulation model. The implemented approach is illustrated in Figure 5.7. It models a network with one Node B and one RNC which are connected with each other via a single lub link. Here the modeled