which is the key interface considered for dimensioning in this thesis. The related transport technologies, resource control and traffic control functions for the lub 1 Introduction transport network are introduced in detail. This chapter provides a profound understanding of the UMTS system and its important functions related to dimensioning. In Chapter 4, a general framework for the UMTS network dimensioning is presented. In the proposed dimensioning framework, the objectives of UMTS network dimensioning are defined, and related important aspects which need to be particularly considered in the dimensioning process are discussed. Based on the proposed framework, a detailed dimensioning procedure which is used in this thesis is described. Chapter 5 introduces in detail the UMTS simulation models which have been developed and used in this thesis, including the simulation models for HSPA and UMTS Re199 with ATM and IP based transport. Besides, an overview of different traffic models is given. Among them several traffic models are selected in this thesis, which are described in detail. In Chapter 6 the dimensioning for the ATM-based lub transport is investigated in detail with dedicated focus on the single link scenario. In this thesis, both Rel99 and HSPA radio access networks are based on the ATM transport technology. Their individual dimensioning results are presented in this chapter. For the UMTS Rel99 network, novel and elaborate analytical models are developed for dimensioning of the lub link. The proposed analytical models carefully consider different traffic scenarios, various QoS requirements, and important UMTS radio and transport functions, etc. Through simulations it is demonstrated that the proposed analytical models are able to capture relevant characteristics and provide accurate dimensioning results, and thus can be applied for network dimensioning. The dimensioning for HSPA networks are mainly based on simulations, from which general guidelines for dimensioning are derived in this thesis. In addition,