The following nodes are involved in GPRS call flow. MS – BTS – BSC – SGSN – GGSN & HLR.
The interface between BSC and SGSN is called Gb interface. Now a days we are commonly using TDM or IP interface for GB interface.
For GPRS access the following scenario’s are happening.
1. GPRS Location Update – in this the SGSN contacts with the HLR and then do the LU. It includes checking the subscriber information, Authentication etc.
2. PDP context activation. In this SGSN contacts with the GGSN and a tunnel connectivity is obtained between MS and GGSN. GGSN connects with external ISP.
With this above process MS will be in contact with ISP and the user will be able to access GPRS.