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Assume we connect to HLR A via direct C7 links.
We configure the following GT:

IMSI GT: K'63902
HLR Number GT: K'254722
MSISDN GT: K'254722

For outgoing call with called number B (MSISDN) K'254722205887, IMSI of calling party A K'639021111111111, how will the MSC identify HLR A as the one serving called number B?

During Location Update the MSC will use IMSI GT to address the HLR A, how does the MSC change IMSI to MSISDN in order to obtain number that matches HLR Number GT in order to request for subscriber data in Location Update Request Message?

Edited by: TELECON on 09/06/2011 - 10:10
During call MSC sends the SRI

During call MSC sends the SRI message towards HLR
So u want to know how MSC decide the HLR
Actually IN SRI message the CALLED PARTY GT is your B no. not your HLR GT. and from MSC Your own MSIDN series is routed towards HLR . So MSS sends this SRI message towards HLR with CgPa as its own GT & CdPa as B no. and at HLR also our own Series defined in SCCP GT table.

Before SRI

Thanks Vikas, before sending SRI, MSS querries GT Tables to identify HLR serving the called party then sends SRI to it. Right? Assuming we have many HLR, how to choose.
You got any tutorial I may understand more...

Ok lets take an example with

Ok lets take an example with two HLR & two series
1:-HLR A---HLR GT- K'254722
2:-HLR B--HLR GT- K'254723

1:-MSISDN SERIES:-K'254745 its belongs to HLR A
2:-MSISDN SERIES:-K'254746 its belongs to HLR B

So when u make call to K'254745, in SRI message CdPa is K'254745 which is routed towards HLR-A from MSS in SCCP GT Table

And When u make call to K'254723, in SRI message CdPa is K'254723 which is routed towards HLR-B from MSS in SCCP GT Table

I hope now you are able to understand

When there is New MSISDN series comes in Market it should defined in SCCP GT table also towards its HLR from MSS

OK I now understand

Thanks alot for the info,
What of the second part where I was wondering how IMeSI is translated to HLR GT during location update??
Because MS request for Location update using IMSI but the HLR is addressed using GT with notation different from IMSI, how are the two mapped?
Thanks for your assistance..
Good day

During Location update Our

During Location update Our IMSI is first converted to MGT.Suppose our IMSI is 404903xxxxxxx it will converted to MGT it will delete our NCC & MNC part from IMSI & add our NDC
IMSI-404903xxxxx404 is NCC 903 is MNC so in IMSI analysis both of these are deleted and NDC say 919653 is added and routed towards corresponding HLR in SCCP GT Table


Thanks dude,
Now for a converged HLR system, say CSDB platform: do we need to configure CSDB GT like we do for individual stand alone HLRs? So we only add IMSI GT for Location Update and Roaming and MSISDN GT for calling?

If we connect to CSDB via STP, what should be the address after translation; SPC+ old GT or SPC+ new GT..

Where does the CC+NDC come from

After getting IMSI= MCC+MNC+MSIN MSS replace MCC+MNC by CC+NDC, where does the CC+NDC information comes from? I am confused because at this stage MSS does not know MSISDN of the phone requesting for a location update....?

IMSI GT Analysis

This Analysis is defined in IMSI GT analysis
where we allow IMSIs for roamng in our PLMN .Defination is done for IMSI to MGT conversion.

Roaming with CAP1

Hi Frndz,

While inbound roaming CAP 1 testing .HPLMN required calling number or called number or both to correlate the call.

Pls suggest me on this.

Roaming with CAP1

i think HPLMN need both information:
calling number is needed by HPLMN IN system and HPLMN HLR to check whether it has privilege to make outgoing call or not. called number information will be sent GMSC to route the call to spesific destination.
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Roaming with CAP

Please send me the ebook link,
Thanks in advance
[email protected]

GT Analysis

So each switch needs to have a table of the MCC->CC and MNC-> NDC? Is there a way to send a query to an STP with the IMSI and have it return the MGT or HLR of the associated network? If you want to allow anyone to roam on your network, how do you get a list of NDC so you can properly construct the SCCP CdPN?

Where does the CC+NDC come from


IMSI is in E.212 format.IMSI is converted to the Mobile Global Title (MGT) format, standard E.214, which is similar to but different from E.164 number (more or less a telephone number). Usually there will be a mapping table in MSC/VLR for E.212 to E.214 mapping.


Thanks Tharel.As i am trying

Thanks Tharel.As i am trying to call VPLMN number,here two internl legs will form.IDP reaching to IN returning with Connect number of Local (HPLMN MSC) from again my MSC ISUP is reaching to MSC from there once again request will reach to IN .After correlation from IN it will send real called number to his MSC.from there again ISUP leg will form VPLMN Number.

Here my doubt is my carrier suppressing calling number in 1st ISUP leg may cause call fail.To correlate call from IN side what exactly required from IN side.

Roaming with CAP1

Hi Frendz,

Issue has resolved.
We are using Erricsson IN,in this CAMEL phase 1 databse key will generate in range 000-999.It is used as correlating fist IDP and second IDP from HPLMN GMSC(SSP).calling party number is must in second IDP.My carrier was suppressing CLI,calls were getting failed.

How to Get HLR GT from IMSI GT

Hi All,
Suppose the IMSI GT is 40477 and is translated to 919436 then what will be the HLR GT.

How to Get HLR GT from IMSI GT

Hi All,

Suppose the IMSI GT translation is 40477------>919436 then how do the MSC get the HLR GT from the above translation