Abstract
This thesis examines the mechanisms improving user terminal mobility in a wireless cellular network. It addresses the problem of the lack of self-organisation in the cell reselection algorithms used in the mobile radio access networks. This mechanism is an autonomous terminal mobility procedure used when moving between cells. This work refers to the practical examples of the evolution of cellular technologies specified by 3rd Generation Partnership Project (3GPP). Furthermore, this thesis is based on the detailed system analysis of the cell reselection procedure, aiming to identify areas where the system could be improved by the application of the self-organising design approach. It studies how the performance of the cell measurements mechanism, allowing a terminal mobility in the network could be increased by using the self-organising concept, in terms of the better cell reselection performance and the terminal energy efficiency trade-off. The main goal of these improvements is providing better quality of service, enhanced user experience and increased network operational performance while minimising maintenance costs. The main contributions of this thesis can be summarised as follows. Firstly, it investigates the autonomously controlled user terminal mobility, its drawbacks, and limitations during the mobility between macro cells. Then, techniques increasing the energy efficiency of the terminal, without compromising the system performance during the cell reselection, are identified. Also, signalling protocol aspects during the cell reselection algorithm are studied and performance improvements are proposed. Furthermore, an evaluation and optimization of the cell reselection performance is undertaken, considering different system level and user experience criteria. It draws on simulation results to analyse the serving cell quality, mobility measurements effort impacting terminal energy efficiency and the related performance trade-offs. Finally, a self-organising approach based framework, with a practical example of the possible mechanism allowing a cost efficient self-optimization of the autonomously controlled mobility is proposed.