ABSTRACT
Currently, voice and data traffic are treated separately in wireless networks such as Global System for Mobile Communication (GSM)[1] and General Packet Radio Service (GPRS)[2] systems. The release 1 definition of third-generation (3G) wireless systems also kept this separation. Wireless voice traffic is routed through the circuit-switched infrastructure whereas data traffic is routed through the packet network. To explain this integration, we look at GPRS integration in the existing GSM network. As shown in Fig. 1, two new GPRS-dedicated nodes, SGSN (serving GPRS support node) and GGSN (gateway GPRS support node), are added in the existing GSM network. An SGSN is responsible for the delivery of data packets to and from the mobile station within its service area. Its tasks include packet routing and transfer, mobility management (attach/ detach and location management), logical link management, and the authentication and charging functions. The location register of the SGSN stores the location information and user profiles of all GPRS users registered within the SGSN. GGSN acts as an interface between the GPRS backbone and the external packet data networks. It converts GPRS packets coming from the SGSN into an appropriate PDP (packet data protocol) format and sends them out on thecorrespondingpacket data network. In theother direction, the PDP addresses of incoming data packets are converted in to the GSM addresses of the destination. The addressed packets are sent to the responsible SGSN. For this purpose, the SGSN stores the current SGSN address of the user and the user’s profile in its location register. GGSN also performs the authentication and charging function.
