Recent years have witnessed rapid increase in mobile subscribers, since the use of mobile devices is spreading rapidly. More specifically, there has been an ' explosion ' of data traffic from mobile users. This fact necessitates the development of new networks and the improvement of existing ones, in order to support increased capabilities, so that the users can be served much better.

This thesis focuses on the improvement of already existing third-generation networks. Specifically, aims to improve the quality of software used by a specific component of third- generation networks (3G), the SGSN. More specifically, the software product that is tested is the "Flexi NS" of NOKIA. Furthermore, this thesis studies the way that software technology contributes to the increase of the quality of the software produced and the reduction of production costs and upkeep. Also, the role of the inclusion of Continuous Integration (CI) in the software production stages is examined. As to the methodology followed, firstly we pinpoint the fundamentals of mobile networks and software engineering. Secondly, a study of the existing software development techniques and the position of the SGSN on third-generation network architecture follows. Then, we present the tools for the creation of a CI system. Subsequently, an extensive analysis of the creation and operation of the CI system used for the needs of NOKIA Flexi NS is presented. In addition, we include of an analysis of the results and conclusions, generated by the above application. Finally, ideas for future study are discussed.