The Functionality of the GPRS Gb Interface and
Its Implementation in an Experimental System



Abstract: The increasing need for data communication causes pressure on developing new data transfer techniques. General Packet Radio Service (GPRS) is a new technique for mobile networks, e.g. GSM, which provides high-speed packet switched data service. Packet switched data transfer techniques allow the network to serve more simultaneous users and are more suitable for bursty applications than circuit switched techniques. In the future the most important application of the GPRS is probably mobile access to the private and public IP networks (e.g., Internet). The large existing GSM network base and GPRS's suitability for packet switched data transfer, e.g. IP, can be seen as the key factors for GPRS's success.

This master's thesis focuses on the GPRS Gb interface. This interface is located between the Base Station Sub-system (BSS) and the Serving GPRS Support Node (SGSN). The Gb interface is considered to be an open interface enabling the use of the GPRS core networks and radio networks from different manufacturers, and different radio network technologies. The latter enables also the use of the GPRS core network with the 3rd Generation mobile radio systems.

In this thesis all protocol layers of the Gb interface are studied in detail. The Gb interface protocols are Base Station Sub-system GPRS Protocol (BSSGP), Network Service Control, Frame Relay, and a physical layer protocol. In addition, their implementations into an experimental GPRS network are described.

Keywords: GPRS, GSM, Gb, interface, BSSGP, Network Service Control, Frame Relay