exponential averaging. More detailed description on WRED algorithm and its required parameters are given in Appendix A.5. 4 Framework of UMTS Network Dimensioning This chapter provides an overview of dimensioning issues in the UMTS radio access network, which arises in planning and operation of UMTS networks. At first, the main objectives of the UMTS network dimensioning are defined. Then various important aspects which need to be particularly considered in the dimensioning process are addressed. Based on that, a general framework for UMTS network dimensioning is proposed in this thesis and the corresponding dimensioning procedure is presented. At last an overview of the dimensioning approaches used in this thesis is given. 4.1 Objectives of UMTS Network Dimensioning In order to perform network dimensioning, a clear objective is necessary. In the framework of this thesis, cost and quality of service are the main objectives for dimensioning processes within the context of network planning and operation. The ultimate goal of network dimensioning is to minimize the cost while maximizing QoS. However, these two factors are usually negatively correlated, and thereby the service provider has to find a right balance and tradeoff between them. 4.1.1 Network Costs Normally the network costs have two main categories: the expenditures associated with building a network and with running it. In this thesis, the network cost only considers the cost for leasing link bandwidths. For a given transport technology, usually the higher the link capacity, the higher is the network cost. 4.1.2 Quality of Service The European Telecommunications Standards Institute (ETSI) and the International Telecommunications Union (ITU) define QoS as the quality perceived by the end user [ITU93]. The IETF network working group provides a more concrete definition where QoS is defined as the service requirements that need to be met by the network while transporting a traffic flow [CNRS98]. In this thesis, the term quality of service (QoS) is used based