Thanks for your reply.
Basically without IN (which means CAMEL in GSM and INAP in fixed n/w) how we used to support pre-paid calls in visiting network?.
According to what i have understood is in CAMEL we look into the T_CSI Or O_CSI flag and decide on using CAMEL for terminating or originating calls.
( In IN these T_CSI and O_CSI work like trigger points for pre-paid user calls, if i am not wrong). According to me, when first time pre-paid user is detected the “MAP messages which flow between VLR and HLR for getting the user related information) will basically hold these flags. So, VLR maintains these flags!!!!!. Again not sure.
And when GMSC or VMSC decide to apply CAMEL for orig/term call the request (INIT-DP) will be sent to gsmSCF (a process running on HLR) from gsmSSF ( a process running on MSC).
The point to note is, the VMSC’s gsmSSF will interact with (gsmSSF)HLR of the pre-paid user home network. Please correct me if i am not wrong.
And then gsmSCF will reply with Request Reports (ApplyCharging,EventReportBCSM,Connect… etc) and when the call gets disconnected the Reports generated @ VMSC will be reported to HLR, which update the billing system.
How pre-paid was support without CAMEL is still a question?. One possible answer can be VMSC maintains the CDR’s and we collect manually or using X.25 link from VMSC and update these CDR’s on HLR. But the problem is if user makes a call whose cost is more then the present available balance in his/her account then above said will not work.
And i have one more point which requires your support to know better, how does OSS (Operator Specific Services) will be supported using CAMEL?.
I tried to understand this point, and have the following idea. CAMEL supports play-announcement, now to play announcement ( which is specific to an operator), the VMSC can use gsmSRF of per-paid user’s home network.
I mean, the gsmSCF which requests VMSC (gsmSSF) to handle play-announcement will refer gsmSRF of pre-paid’s home network.
But i am not sure. Please clarify my understandings.