New mobile networks of the third and evolved second generation have been deployed that enable a mobile accessible, always available wireless Internet. To exploit the full potential from those new mobile access network technologies, and to meet high user expectations, these networks need to be well designed, dimensioned and deployed. An important basis for these tasks are accurate traffic models, and sound traffic estimates. However, such knowledge does not yet exist for mobile networks. In this thesis, measurements from commercially deployed General Packet Radio Service (GPRS) networks are investigated to derive novel knowledge on mobile network usage and its traffic characteristics to fill this gap.