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HLR Addressing

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HLR Addressing


I am new to this forum but appreciate all the quality information and knowledge from members. I am hoping there is someone out there that can help me with a question I have regarding a project I am currently working on. I am looking to understand how HLRs are identified on SS7 routing network, based on the IMSIs the store.

At a high level the project I am working on is the interconnection of an external HLR (lets call it HLRx) into an existing operators network.

As I understand it this HLRx will need to appear as a new network element within the operators existing SS7 network (ie have its own GT address for signaling routing). But this HLR will contain subscriber information for a subset of the operators IMSIs range (we are an MVNO, integrating our own HLR, and using an sub-range of the operators IMSI range) i.e sub-range could be:
40468 5500000000 to
40468 5599999999

So during the LU procedure (or any call setup procedure) the operators signaling network will need to address HLRx's GT for this sub-range of IMSIs, so as to retrieve subscriber information. Can someone please inform me how this is achieved? Is it that this sub-range if IMSIs is held in a reference table maintained within SCCP GT Tables for example?

I hope I have explained my situation accurately, any help would be greatly appreciated!

Thanks and regards

Hi Hamish, it is not needed

Hi Hamish,

it is not needed for MSC/VLR or SGSN to know HLR GT in order to set up communication with it - in fact this would make roaming configuration a night-mare. To allow others nodes to address HLR based on subscriber IMSI there is used so called Mobile Global Title addressing: MCC->CC, MNC->NC and IMSI digits are appended. MGT is then used as a SCCP CalledPartyAddress. This way MSC/VLR or SGSN is able to deliver message destined to HLR to the subcscriber's home network. Since only Home network knows which IMSI resides in which HLR, Home network must establish based on IMSI digits correct GT Analysis/Routing to route messages with given MGT to the corresponding HLR.

Hope this info helps..

Hi TomiZet, Thanks for your

Hi TomiZet,

Thanks for your reply, its been a while since I posted but I was hoping you could help with some clarifications?

I am familiar with the MGT addressing and routing for normal roaming scenarios, but our scenario will be slightly different, and perhaps I can try to explain it in a different way.

We will sell our service & SIM card in France for example, this SIM will have multiple IMSIs ie France SFR, T-Mobile UK, Vodafone NL etc up to 8 IMSIs, and one master roaming IMSI profile for any countries outside these where the subscriber might roam to. The subscribers profile and SIM data (for all IMSIs), will be loaded into our HLR located in France. When a customer travels from France to the UK, selection rules on the SIM will ensure that the T-Mobile IMSI is passed to the network based on the MCC+ MNC, so this means that the T-Mobiles network will view the IMSI as a local subscriber, however his subscription data is not held on a T-Mobile's HLR, it is held on our HLR located in France. So in this scenario the standard MGT translation & routing will not work, because the IMSI is seen as a local to the T-Mobile network, the issue is that the T-Mobile network will need to identify that this IMSIs subscription data is held in our HLR, and route messages to the correct location, otherwise this IMSI will not be able to authenticate to the T-Mobile network.

So this is the reason for my original post on maintaining a reference table in the SCCP, so that the T-Mobile SCCP function recognises that this subrange of its own IMSIs in fact belongs to our HLR, and can therefore route messages to the correct HLR.

Does this clarify our scenario a little more, any feedback on this approach would be greatly appreciated, and specifically any information or thoughts relating to the configuration that would be necessary on the SCCP to facilitate this kind of routing based on a subrange of IMSIs, would be great?

Thanks and regards


SIM will have multiple IMSIs ie France SFR, T-Mobile UK, Vodafone NL etc up to 8 IMSIs (ie you purchased the IMSI range from the operator rite?),
The VLR will generate the UL request with predefined TT value i guess so it can differentiate the UL request and route to the correct HLR. if i am wrong correct me.