ious UMTS networks as illustrated in Figure 5.1. The simulation model is designed as a layered network model. It consists of several main components: groups of UEs and their corresponding nodes serving as the traffic source and sink, the air interface, the core network, and the UTRAN network which comprises Node B, RNC, and the lub interface. Corresponding Corresponding Air Interface Core Network NodeB UTRAN Figure 5.1: Simulation Model Framework 5.2 Simulation Model Framework In this framework, for simplification of the simulation model, the UEs are not modeled as individual nodes distributing over the network, but instead all UE entities are created inside the same module where each UE connection is represented by an application session. Similarly, the corresponding nodes for individual UE connections are not modeled as separate servers or network nodes, but as the sink of individual UE applications. The UE entity includes all the protocol layers and functions related to applications, transport protocols, and UMTS radio access protocols. The applications are defined with traffic models, which define a set of parameters for characterizing the source traffic. The application traffic is carried by a specific transport protocol. The selection of transport protocol depends on the application type and the user preference. With UMTS radio access protocols, the user traffic is mapped to the UMTS transport channels. For the QoS managements, each UE entity can specify its QoS requirements and measure the obtained QoS on the user level. The modeling of the UTRAN network including Node B, RNC and the lub interface is the most important part of this framework. It requires a detailed and accurate modeling on the protocol stacks of the lub user plane, the logical and transport channels for transmitting the user data, the required resource management and traffic control functions in the UTRAN, the applied QoS mechanisms, and various technologies for the building transport network. The air interface model is implemented between