To rectify the fault, determine the causes of the conversion and of the uncertain
elements (subscribers, time, and MSCs involved).
? Causes of the conversion
1. The location update request sent from the MSC does not indicate the supported
phase of CAMEL.
The MSCs of the two vendors are involved. Therefore, the conversion is not caused
by the unavailability of CAMEL phase.
2. The HLR does not send the O-CSI for a location update because of incorrect data
configuration.
Relevant data configuration includes the following:
– MAP version
– MAP functional flow
– CAMEL phase
– O-CSI template
– VLR type
– CAMEL-Roaming-Agreement template
? Causes of the uncertain elements

Possibly, the code streams of the messages from the MSs are lost.

Analysis on the causes of the conversion
1. Run the commands LST VLRTYP, LST MAPCONF, and LST OCSITPL on the
HLR9820 SMU client. The outputs show that for the three VLRs, the VLR number
type is LOCAL, the supported version of MAP is GSMPHASE3, and the supported
phase of CAMEL is PHASE2
2. Trace the messages of the involved subscribers, and collect the messages sent
over D interface. The traced messages show that the location update requests sent
from the VLR do not indicate the supported phase of CAMEL and the VLR capability.
Run the commands LST OCSITPL and LST MAPSERV. The outputs show that the
value of the parameter CMCCSUPP is FALSE. That is, if a VLR does not indicate the
support of CAMEL, the HLR considers that the VLR supports CAMEL phase 1.
According to the configuration of the O-CSI template, where
HPLMNROAM_SUPLPCAMEL is set to AllowLocationUpdateWithMOCall, the HLR
does not send the O-CSI. Therefore, the service flow is normal.
3. If the supported version of MAP is too low, the supported version of CAMEL is not
included in the location update request. The messages on the VLR and the HLR
show that MAP version is negotiated between the HLR and the VLR. The HLR
accepts GSM phase 2 rather than GSM phase 3. GSM phase 2 does not support
CAMEL. Therefore, the HLR does not send the O-CSI.
? Analysis on the causes for the HLR rejecting GSM phase 3
Check the default NCC template. The result is NCC template 0.
Query the configuration of NCC template 0. The output shows that the value of
Update location is MAPV2.
If the number of the VLR that sends a location update request is different from the
VLR number type configured on the HLR, the HLR considers the MAP configured in
the default NCC template as the version of MAP supported by the VLR. To view the
VLR number type configured on the HLR, run the LST VLRTYP command on the
HLR9820 SMU client. If the actual VLR number is different from the configured VLR
number type, a negotiation on the version of MAP is activated between the HLR and
the VLR.

The VLR number type configured for the three VLRs is LOCAL. The difference
between the actual VLR number and the configured data results in loss of code
streams. Error codes occur inevitably during data transfer in any systems. For invalid
VLR numbers and non-existing VLR numbers, the HLR9820 uses GSM phase 2,
which does not support CAMEL. Thus, the HLR does not send the O-CSI.
Change the parameter Update location to MAPV3 in the default NCC template.
The fault is rectified.

thanks for the doc

useful information

helpful indeed. thanks

nice share. want to know more about this.

thanks for the document. really useful.

useful information

nice share. want to know more about this.

well described doc. thanks

useful document, thanks