Load and resource management in UMTS radio access network under congestion conditions: Dissertation

The objective of this work was to find possible ways to improve the capacity of the radio interface of the UMTS system. Especially congestion conditions were considered in the study. The motivation for this work was the increasing popularity of the UMTS: more and more operators were launching their commercial 3G services, but there was little experience in dealing with congestions in the UMTS - the technology was too young and congestion trials too difficult. On the other hand, experience from the UMTS's ancestor, the GSM system, showed that lack of proper resource management leads to unexpected problems: in various situations, GSM operators experienced severe degradation of services in their networks, sometimes even complete blocking. This happened even though the indicated load was still well below the expected capacity limits. The reasons were usually improper load monitoring and unbalanced, non-optimal resource utilisation. And the operators had no means to solve the problem. Therefore, in case of the UMTS, it was very important to foresee possible threats and prepare appropriate tools in advance, so that such situations could be avoided in this system. The first contribution of this work is a more holistic approach to the problem of the resource management and the load control. Also the focus on the congestion conditions was not very common in other studies. The general system level simulator created for this purpose was also unique at the time when it was made. The need for such a simulator was acknowledged by the European Union and the simulator was a part of project co-financed by the Union. The simulator enabled practical verification of applicability of the implemented resource management techniques. Simulations proved also that some dynamic processes that take place in the radio interface and that are neglected in the theoretical model of the interface can affect the system's capacity. It was therefore clear that in some cases the model may yield inaccurate estimations of the system capacity. Such too optimistic results could lead to incorrect system planning, so the problem had a very practical meaning. In this work the model was enhanced and the problem analysed both theoretically and practically through simulations. This is the most important contribution of this work.