PRE-PAID CALL FLOW

If u output the VLR data of a prepaid subscriber in the serving MSC, you will see O-CSI (Originating Camel Subscriber Info) in the VLR Data. This O-CSI data is the address of SCP (IN Server). This SCP address acts as an trigger, during every MOC (Mobile Orig. Call). Hence, when a Prepaid subscriber makes an call, the OCSI triggers an signalling event between the MSC (SSP) & the IN Server (SCP). The MSC (SSP) send IDP0 (Initial Detection Point) Message to the IN Server, with all the relevant data like Called Number (B No), Current MSC address, LAC, CI etc. The SCP (IN Server) based on the MSC address in IDP0, determines if the Prepaid subscriber is in Home PLMN or VPLMN (Roaming). And based on Called No & MSC address, determines the Tarrif for that particular call ( The Tarrif is defined in the TARRIF TABLE in the SCP for each MSC address). If the IN Server (SCP) determines that the subscriber has sufficent balance to make the call, it send CONTINUE message to the MSC (SSP). And hence MSC continue with call setup. This signalling connection between SCP (IN) & SSP (MSC) is maintained through out the call.You will not find the T-CSI data in the VLR data of prepaid subscriber because, the SCP address is present in the HLR. Hence the HLR, triggers the signalling connection with SCP, when a Prepaid Subscriber recieves an incoming call and sends the IDP0 to the SCP (IN) with same details as B Party No, MSC address etc...... The SCP (IN) monitors the Call continously and if the Balance becomes insufficient during the call, it sends the Release message to the MSC, for terminating the Call.

The signalling connection between MSC (SSP) & IN (SCP) is maintained throughout the call. The IN constantly monitors, if the prepaid subscriber has sufficient balance to continue the call. And, during the call, if IN determines that the prepaid subscriber do not have sufficient balance to continue the call, it sends DISCONNECT message to MSC for releasing the call.........

Pre-paid SMS Flow

Well, the concept for SM-MO (Short Message Mob Originated) is similar to the Voice CAll. However, there is some differnce in the implementaion. There are two possible scenarios: 1) MSC/VLR Supports CAP-3: If VMSC/VLR supports CAP-3, the VMSC/VLR is capable of SMS Trigger to SCP ie. the MSC triggers an IDP message to SCP & if the SCP sends CONTINUE msg after veryfying balance, the MSC sends the SM-MO to the SMSC and then the whole SMS delivering process continues........2) MSC/VLR supports CAP-2/CAP-1 only: In this scenario, the VMSC/VLR is not capable of triggering IDP msg to SCP on detecting an SM-MO message. It forwards the SM to the SMSC without communicating with SCP. However, some SMSCs are capable of Triggering an signalling transaction with SCP(IN). The SMSC verfies the balance with SCP & delivers the SM, after getting CONTINUE msg from SCP !!!!!

What are difference between phase 1,2 and 3 in camel.

With CAP 3 capability, MSC can generate trigger to IN for SMS...... Hence online charging is possible for Prepaid Subscribers with CAP 3 capabilty as compared to CAP 2 or CAP 1 capability.....

SCP ( the control Point ) , SDP( Service Data point) , SMP( The management point ) are main components of IN.

WHEN U MAKE A CALL ...VLR ASKS THE SDP FOR THE SERVICES OF TEH A NUMBER. AND RESERVERS SOME AMOUNT FOR THE SAME. EVERY TIME UR CALL COMPLETES 1 PULSE AGAIN THE VLR ASKS THE SDP IF THE A NUMBER HAVE ENOUGH BALANCE.THIS IS ALL DONE AT CAMEL

VLR/HLR doesnt know anything about the charging and balance. It is only the IN nodes, here SDP which holds the subscribers credit and matches if there are sufficient amt. to make a call.