GPRS is usually attempts to reuse the existing GSM network elements as much as possible. There are new entities called GPRS supports nodes (GSN) which are responsible for delivery and routing of data packets between mobile stations and external packets networks. There are two types of GSNs,

1. Serving GPRS Support Node (SGNS)
2. Gateway GPRS Support Node (GGNS)

There is new database called GPRS register which is located with HLR. It stores routing information’s and maps the IMSI to a PDN address. Thus, GPRS Reference Architecture is shown as:

SGSN: It is at the same hierarchical level as the MSC. Whatever the MSC does for voice, SGSN does for Packet Data. The tasks of SGSN include packet switching, routing and transfer, mobility management and location management, logical link management and authentication and charging functions SGSN processes the registration of new mobile subscriber and keeps a record of the location inside a given service area.

GGSN: It acts as an interface between GPRS backbone network and the external packet data networks. GGSN’s function is similar to that of a router in a LAN. It maintains the routing information that is necessary to tunnel the protocol data units to the SGSNs.

GPRS Network enhancements: Some existing GSM network elements must also be enhanced in order to support packet data. The BSS system needs enhancements to recognize and send packet data. This includes BTS upgrade to allow transportation of user data to the SGSN. Also the BTS needs to be upgraded to support packet data transmission between the BTS and the MS. HLR and VLR also require enhancements so the queries from GSNs may handled. MS also needs enhancements