 dimensioning rules can be derived and the proposed analytical dimensioning approaches can be verified. This chapter introduces in detail different UMTS simulation models which have been developed and used in this thesis. The simulation models of the UMTS Re199 with the ATM-based UTRAN and the UMTS with the IP-based UTRAN were developed by the author in the framework of the MATURE project. The main objective of this project is the dimensioning of the UTRAN lub interface. The simulations of HSPA (HSDPA and HSUPA) were using the HSPA simulation models established in the context of another project by Communication Networks working group of the University of Bremen. At the beginning of this chapter, the main requirements on the simulation models are defined. Then a basic framework for setting up the simulation models is described. Afterwards, the simulation environment and detailed introductions on the modeling of different UMTS networks are given. The last section introduces different traffic models. 5.1 Requirements of Simulation Models In the framework of this thesis, the basic requirement of the simulation model is to model a complete UMTS system following the 3GPP specifications, which consists of the fundamental UMTS network components, the relevant UMTS functions and protocol stacks, individual user groups and the related external networks. The simulation model needs to provide end-to-end data communication paths between the UEs and their corresponding communication entities in the external networks. However, to save the simulation effort it is not necessary to model every UMTS component and function in detail depending on the focus of the simulation task. As introduced in the first chapter, the scope of this thesis is to dimension the UMTS radio access network with main focus on the lub interface (only considering the user plane). According to this scope, the simulation models can be designed to have a detailed and accurate modeling of the lub interface (user plane) including its related network nodes, protoc