Prepaid roaming-CAMEL call scenario
Figure 8.15 shows the signaling message flow for an outgoing call initiated by a roamer in a visited network. For example purposes, MSISDN-A, which belongs to the PLMN-A, is shown visiting in the PLMN-B. Assume that the roamer is already authenticated and registered in the PLMN-B.
1. The roamer dials in the destination number that belongs to the PLMN-C.
2. The serving VMSC receives a setup message and checks subscription data for A in its VLR to determine if it has active O-CSI. The VLR has updated subscription data received previously during the update location procedure with the HPLMN. As explained in Section 8.2.3, the O-CSI identifies the roamer as having originating
TABLE 8-13 CAMEL Information Flow for Short Message Service
|
CAMEL operation |
Description |
 |
|
|
Activity test GPRS ack |
Response to IF activity test. |
|
Apply charging report GPRS |
Report sent by the gprsSCF to the gsmSSF in response to the IF applying charging GPRS. |
|
Entity released GPRS |
The gprsSCF informs the gsmSCF that a GPRS session has been detached. |
|
Event report GPRS |
A GPRS event notification sent to the gsmSCF in response to the IF request report GPRS event. |
|
Initial DP GPRS |
Used by the gprsSCF to get instructions from the gsmSCF on detection of a trigger at a detection point. |
 |
|
|
Activity test GPRS |
Used to check if the gsmSCF and the gprsSSF relationship is in existence. Appropriate actions are taken to recover the relationship if no response is received. |
|
Applying charging GPRS |
Used to instruct the gprsSSF to apply charging mechanisms to control the charging of a GPRS session or a PDP context. |
|
Applying charging report GPRS ack |
Response to the IF applying charging GPRS. |
|
Cancel GPRS |
Request to the gprsSSF to cancel all EDPs and report. |
|
Connect GPRS |
Used to request the gprsSSF to modify the APN that established a PDP context. |
|
Continue GPRS |
Request to the gprsSSF to continue the processing that had previously been suspended. |
|
Entity released GPRS ack |
Response to the IF entity released GPRS. |
|
Event report GPRS ack |
Response to the IF event report GPRS. |
|
Furnish charging information GPRS |
Request to include information in the CAMEL-specific logical call record. |
|
Release GPRS |
Instruction by the gsmSCF to tear down an existing GPRS session or PDP context. |
|
Request report GPRS event |
Instruction to monitor an event and send a notification on event detection. |
|
Reset timer GPRS |
Used to reset gprsSSF timer. |
|
Send charging information GPRS |
Used to send an e-parameter to the gsmSSF. This includes advice of charge. |
 |
|
|
Delete subscriber data |
Instruction to delete CAMEL subscription data from an SGSN. |
|
Insert subscriber data |
Used by the HLR to insert subscriber data in the SGSN. |
 |
|
|
Insert subscriber data ack |
A response to IF insert subscriber data. |
|
Update GPRS location |
Used by the SGSN to indicate to the HLR the CAMEL phases supported by the SGSN. |
TABLE 8-14 CAMEL Information Flow for Short Message Service
|
CAMEL operation |
Description |
 |
|
|
Event report SMS |
Notification of an event to the gsmSCF. A previous IF, request report SMS event, triggers this event monitoring. |
|
Initial DP SMS |
Request for the instructions from the gsmSCF on detection of a trigger at DP. |
 |
|
|
Connect SMS |
Used to request gsmSSF/gprsSSF to perform the actions to route the short message to a specific destination (for MO-SMS) or to deliver the short message to the MS. |
|
Furnish charging information SMS |
Request to include information in the CAMEL-specific logical MO-SMS or MT-SMS record. |
|
Release SMS |
Request to tear down an existing SMS transfer. |
|
Request report SMS event |
Instruction to start monitoring an event and send notification when the event is detected. |
|
Reset timer SMS |
Instruction to reset a gsmSSF/gprsSSF timer. |
 |
|
|
Delete subscriber data |
Used by the HLR to delete CAMEL subscription data from a VLR/SGSN. |
|
Insert subscriber data |
Used by the HLR to insert CAMEL subscription data in a VLR/SGSN. |
 |
|
|
Insert subscriber data ack |
A response to the IF insert subscriber data. |
|
Update GPRS location |
Used by the SGSN to introduce to the HLR the CAMEL phases and CAMEL Phase 4 CSIs offered by the SGSN. |
 |
|
|
Continue CAMEL SMS handling |
Instruction to the MSC to continue CAMEL-specific handling. |
|
Send info for MO-SMS ack |
Used to transport MO-SMS related subscription data from the VLR to the MSC. |
 |
|
|
Send info for MT-SMS |
Used to request the VLR to provide information to handle an MT-SMS. |
CAMEL services. It contains the trigger information that is required to invoke CAMEL service logic for a roamer-originated call.
3. If the O-CSI is present, the VMSC suspends the call and examines O-CSI to get the gsmSCF address to establish a CAMEL control relationship.
TABLE 8-15 CAMEL Information Flow for Short Message Service
|
CAMEL operation |
Description |
 |
|
|
SS invocation notification |
MSC uses this to notify the gsmSCF of a supplementary service invocation. |
 |
|
|
Delete subscriber data |
The HLR uses this to delete subscription data from a VLR. |
|
Insert subscriber data |
The HLR uses this to update a VLR with certain subscriber data. |
|
SS invocation notification |
The HLR uses this to notify the gsmSCF of a supplementary service invocation. |
 |
|
|
Invoke SS result |
The VLR uses this to transfer SS-CSI to the MSC. This is sent on successful invocation of supplementary services ECT and MPTY. |
|
Send info for incoming call ack |
The VLR uses this to send SS-CSI to the MSC. This is sent on successful invocation of supplementary service CD. |
4. The VMSC (gsmSSF) sends an initial DP with an armed BCSM DP event as collected info to request instructions from the gsmSCF. This information flow also includes other mandatory information elements such as the service key and the called and calling party numbers.
5. The gsmSCF instructs the VMSC by sending the a request report BCSM event’ (RRBE) to monitor for a call-related event and notify back.
6. The gsmSCF sends an advice of charge for that particular leg of a call, using send charging info.
7. The gsmSCF then sends a request to include specific call-related information in the final CDR generated for this call, using furnish charging information.
8. The gsmSCF sends instructions to the gsmSSF on the charging mechanism for this call using apply charging. This includes information such as the maximum call duration time after which the call shall be released and the tariff switch time until the next tariff switch applies.
9. The gsmSCF then requests the gsmSSF to continue the call processing and connect the call, using routing information included in connect.
10. The VMSC sends ISUPIAM to the destination PLMN (PLMN-C in this case).
TABLE 8-16 CAMEL Information Flow for Short Message Service
|
CAMEL operation |
Description |
 |
|
|
Mobility management event notification |
Used to notify the gsmSCF of a mobility management event. |
 |
|
|
Update GPRS location |
Used by the SGSN to provide information about supported CAMEL phases to the HLR. |
 |
|
|
Update location |
Used by the VLR to provide information about supported CAMEL phases to the HLR. |
 |
|
|
Restore data |
Used by the VLR to provide information about supported CAMEL phases to the HLR. |
 |
|
|
Delete subscriber data |
The HLR uses this to delete subscription data from a VLR. |
|
Insert subscriber data |
The HLR uses this to update a VLR with certain subscriber data. |
11. The VMSC send an alerting message to A on receiving ISUP ACM from the PLMN-C.
12. On receiving the ISUP ANM message from PLMN-C, the VMSC sends a connect message to the MS and establishes a connection to enable speech conversation.
13. The VMSC contacts the gsmSCF to report an O answer event and to get further instructions.
14. During the call, the gsmSSF may send an apply charging report to the gsmSCF. This may include information as to whether the call leg should be released because of maximum call duration time expiry.
15. If any of the parties involved releases the call, the VMSC coordinates with the destination PLMN and release all the resources. It reports back to the gsmSCF an O disconnect event. It then sends a final charge report to the gsmSCF, using apply charging report.
Figure 8-15 Procedure for a roamer-originated call.
16. The gsmSCF invokes a USSD procedure with the HLR to send credit balance information to the prepaid roamer.
