TS related functions and protocol layers are implemented. Figure 5.3 shows the implementation of the UMTS Rel99 network model according to the designed structure given in Figure 5.2. In this structure, the modified ATM workstation model is used to model groups of UEs and the Node B including the air interface in between, while the modified ATM server model is used to model the RNC, the core network, and the corresponding nodes in the external network. The UMTS radio protocol layers, i.e. RLC, MAC and FP, are implemented above the AAL/ATM. Applications Applications Transport layers Corresponding Corresponding Transport layers IIIII Air Interface Core Network NodeB UTRAN Figure 5.2: UMTS Rel99 Simulation Model Structure 5 Introduction of Simulation Models Corresponding Nodes [trans lub (ATM Link) Node B Figure 5.3: Modeling of UMTS Rel99 (ATM-based UTRAN) in OPNET As shown in Figure 5.3, the UE part comprises all the modules above the ATM protocol stack including the implemented RLC and MAC protocol layer functions. The Node B part includes the FP protocol layer, the underlying AAL/ATM layer, and the ATM physical layer. Between the Node B and UE functionalities there is a simplified air interface model. On the other side, the RNC part consists of the physical layer, AAL/ATM layer, and in addition all UMTS radio protocols (i.e. RLC, MAC and FP protocols). Above the RNC part, a simplified core network and the corresponding nodes of the UEs are modeled. A brief introduction of the developed Re199 simulation model has been published in [WL*06]. The following introduces in detail the implemented UMTS Rel99 channels, network components, related radio and transport network layer protocols, and specific transport network resource management and traffic control functions. General Modeling In the Rel99 simulation model, it is assumed that there is sufficient radio resource (i.e. capacity, power, code) at the air interface, as the resources in the lub transport network is the major concern in this work. That means the user pe