leagues at the institute whom I have not only considered my co-workers but also my friends: especially Wenmin Chen, Chunlei An, Liang Zhao, Yi Chen, Koojana Kuladinithi, Asanga Udugama, Bernd-Ludwig Wenning, and Markus Becker, for sharing many technical and sometimes not-so-technical discussions. Additionally, I also very much thank Thushara Lanka Weerawardane, Yasir Naseer Zaki and Umar Toseef for having numerous technical discussions and exchange of research ideas. Finally, I would like to thank my family, especially my mum for encouraging and supporting me all the time. Special thanks to Claas for his continual support, his patience and understanding throughout the past many years. Xi Li Abstract This thesis studies the dimensioning for UMTS Radio Access Networks. In this thesis, dimensioning is investigated with specific focus on the transport network of the lub interface, which connects the Node B with the RNC. This interface is considered as one of the most important economic factors for the UMTS network dimensioning. In order to cover large urban and rural areas, a large number of Node Bs are required and thus the transport resources for the lub interface become considerably costly. The ultimate goal of this thesis is to investigate important aspects related to the UMTS radio access network dimensioning, and to propose novel analytical methods to provide suitable estimations on the required transport capacity for the UMTS radio access network in order to achieve maximum utilization of the transport resources. In order to provide a comprehensive investigation on the dimensioning of the lub interface, various traffic types, different evolutions of UMTS radio access networks as well as different transport solutions, QoS mechanisms and network topologies are studied in this thesis. In the framework of this thesis, UMTS Rel99 is considered as the basic UMTS network. Furthermore, evolved UMTS networks such as HSDPA and HSUPA, and the evolved transport from ATM to IP are investigated. For each evolution of the UM