tiple links scenario with a star network topology. In the latter case, the gain on the bandwidth utilizations of multiplexing the traffic from the individual links should be considered for a proper dimensioning. 4.5 Conclusion In this thesis, in order to validate the accuracy of the analytical models, relative error is used. Given a value a measured from simulation and b is the calculated value derived from the analytical model, and then the resultant relative error a is calculated with equation (4.1). (4.1) 4.5 Conclusion In the framework of this thesis, the network cost and QoS serve as the main objectives for the dimensioning processes: costs have to be minimized while QoS needs to be maximized. In this thesis, the network cost only considers the cost for link capacities, and two types of QoS are considered for dimensioning: user-relevant QoS and network-relevant QoS. dimensioning is strongly related to a number of important issues like traffic demand, network topology, traffic control and resource control functions as well as applied routing and traffic engineering techniques. Hence these issues need to be particularly considered in the dimensioning process. In this thesis, a general dimensioning framework and dimensioning procedure are proposed for the task of UMTS radio access network dimensioning. Different dimensioning approaches can be applied, which are basically categorized into simulation approach and analytical approach. The simulation approach relies on building simulation models and performing simulations, while the analytical approach is mainly based on queuing theory. Different queuing models can be employed to model flow or packet level behaviors in order to estimate the user or network related QoS that can be achieved under a given link capacity. 5 Introduction of Simulation Models Simulation is a practical and scientific approach to analyze a complex system. In this thesis, simulation is used to investigate the dimension of the UMTS radio access networks. From the simulation results, important