\newpage{} \section*{\vfill{} Erklärung} Hiermit erkläre ich, dass ich diese Abschlussarbeit selbständig verfasst habe, keine anderen als die angegebenen Quellen/Hilfsmittel verwendet habe und alle Stellen, die wörtlich oder sinngemäß aus veröffentlichten Schriften entnommen wurden, als solche kenntlich gemacht habe. Darüber hinaus erkläre ich, dass diese Abschlussarbeit nicht, auch nicht auszugsweise, bereits für eine andere Prüfung angefertigt wurde. \vspace{3cm} \begin{minipage}[t][1\totalheight]{0.35\textwidth} Ort, Datum \\(Place, Date) \end{minipage}\hfill{} \begin{minipage}[t][1\totalheight]{0.45\textwidth} Unterschrift \\(Signature) \end{minipage} \newpage{} \section*{\vfill{} Acknowledgment} I would like to thank my supervisors Konrad Meier and Dennis Wehrle for their help and encouragement during the thesis. Besides the help from my supervisors I would like to thank my family and friends who supported me through my master's degree, and the entire Communication Systems department for their support, free coffee and to Prof. Dr. Gerhard Schneider for making all the required hardware available. I would like to thank Prof. Dr. Christian Schindelhauer for writing the recommendation letter so that the DAAD could extend my scholarship and stay in Freiburg. I would like to thank my friend Mirza Hamza from the Telecommunications department on the faculty of Electrical Engineering in Sarajevo for proofreading the AGPS chapter. I would like to thank Sebastian Schmelzer for his LaTeX tips, Michael Pereira Neves and Jonathan Bauer for lending me their cell phones to test my localization system as well as Johan Latocha for patiently explaining words I did not understand in the German language and for showing me Inkscape. I would like to thank Richard Zahoransky for the helpful discussions about various GSM topics. Thanks to Holger Hans Peter Freyther as well, who gave me tips on how to modify OpenBSC to make an independent data channel interface with a cell phone. Things which have not been done before are always intellectually seductive and this kept me motivated and working during the tough periods. \newpage \section*{Abstract} This thesis examines the possibility to localize mobile users inside of GSM networks. While the number of mobile users grow it is possible to provide them with assistance information with regard to their location and increase profits. The GPS receivers inside of smart phones are exploited to provide the position. This work investigates how complicated it is to implement the localization protocol RRLP inside of the existing GSM networks and to provide assistance data for the GPS receivers to deliver faster and more accurate positions. To obtain the estimated positions two GSM hardware platforms have been deployed, dedicated and undedicated GSM hardware. Software for processing assistance data has been developed. The generated data by the developed software were sent to the employed smart phones. More than half of the tested smart phones delivered their position. The obtained results provide a study how the localization system could be deployed for assisting GSM users in avoidance of traffic jams as well as the risks of such systems if it is abused.