SRI to HLR

[fabulous]

Hello all,

I am a new actor in this forum and I hope that I will be able to give as much help as I could receive from you.

Here is my question:

When a subscriber A sends an SMS to a subscriber B, I would like to ensure that the subscriber B belongs to my HPLMN (related to the Mobile Number Portability).
It is possible to have this confirmation from the HLR by requested it with an SRI containing subscribers B MSISDN; if the HLR returns the corresponding IMSI then it is still in my HPLMN, if not the subscribers is ported "OUT".
But is it always possible??? For example when B has its mobile device swithed off, ...

I think that the HLR is able to give this information whatever the subscriber status but I need a confirmation.

Thank you in advance for your help.

Fabrice

[RussCrush]

It is possible to have this confirmation from the HLR by requested it with an SRI containing subscribers B MSISDN; if the HLR returns the corresponding IMSI then it is still in my HPLMN, if not the subscribers is ported "OUT".
But is it always possible??? For example when B has its mobile device swithed off, ...

 The SRI_SM is sent to locate sub B, and return the IMSI from the home HLR and the last known MSC address (Loc info with LMSI) that the home HLR has. The IMSI returned on the SRI_SM will determine whether sub B is ported out or not. In an SRI_SM, the Calling SSN is an 8 (MSC) and the Called SSN is a 6 (HLR).

 If sub B is turned off, then when the MO_FSM is sent, the response will be "absent subscriber".

 Does that help? Or did I miss the question?

[fabulous]

Thank you Russcrush for your answer.

Could you please confirm my understanding about your following answers:

[The IMSI returned on the SRI_SM will determine whether sub B is ported out or not]
Does it mean that the determination is done on whether the IMSI is present or not in HLR Database?

[If sub B is turned off, then when the MO_FSM is sent, the response will be "absent subscriber"]
Does it mean that the IMSI cannot be retrieved from the HLR (with the same SRI_SM) when subscriber B is turned off?

Thank u

[RussCrush]

Lets see...

[Does it mean that the determination is done on whether the IMSI is present or not in HLR Database?]

If the HLR does not have the number for sub B within it's database, it will launch an SRI_SM into the network to locate the sub B. If it gets an answer, the IMSI will be in the response (USUALLY!!). The HLR usually only launches into the network when there is an Interop SMS agreement between operators, otherwise an permanent error is returned, and no IMSI.

Boring background stuff here: The IMSI range is a 5 or 6 digit number issued by the GSMA that makes up the first numbers of the 15 digit IMSI assigned to a subscriber (Example: 23410 is the IMSI range for O2, UK. An IMSI for a given sub would start with 23410), if the response to an SRI_SM contains the IMSI range beginning with 23415, that would mean that the sub is a customer of Vodafone UK.

[Does it mean that the IMSI cannot be retrieved from the HLR (with the same SRI_SM) when subscriber B is turned off?]

The IMSI is always returned (USUALLY!!) whether the phone is on or off, roaming or homing. The SRI_SM is attempting to locate the network of sub B. Once this dialogue is completed, the followup message is a MO_FSM, which would return the response "absent subscriber" if the phone was off.

 Understand, this scenario applies only in a Homer to Homer SMS signaling, and is different if either party is roaming.

(USUALLY!!) indicates that the IMSI can be a pseudo-IMSI (not real) generated by a Store and Forward or virtual HLR application, but I am trying to keep it simple.

 How am I doing?

[fabulous]

Hello RussCrush.

Thank you for your very clear explanations.

Last question:

Is it possible to avoid the HLR to send an SRI_SM into the network when subscriber B is not in the HLR database?

Thank u

[RussCrush]

 Absolutely.

 The HLR will only launch SRI_SM messages to those MSISDN line ranges that it has routes for. No route, no message launch, and an error is replied back to the SMSC, and phone, indicating that either the "message failed" or "phone number invalid (can't remember the exact phrase)".

 There is a way (depending on the equipment) to bar destinations as well.

 Hope that helps. Good luck!!