Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors

IMSI Unknown in HLR

  • This topic has 13 replies, 1 voice, and was last updated 6 years ago by Ayat.
Viewing 14 posts - 1 through 14 (of 14 total)
  • Author
  • #63883

    Hello all,

    We’ve got few numbers in our network trying all day long to access network. They got rejected by the network because IMSI is unknown from the HLR.

    THE IMSI state in the HLR is “not connected”.

    What can be done for thoses IMSI because they generate huge LU attempts then congestionning radios ressources SDCCH and SCCP ressources.

    Thanks .



    interesting. i’m sure some people know better about this situation than I, but if i were in your position, i would check manually where those IMSI are coming from (were they sold in your country, in your operator, or elsewhere ?)
    then you can check in which cells those bad IMSI are located (by doing A-interface trace, unless there is another solution ?)



    Hello pix,

    We have captured A interface and saw exactly the value of IMSI.
    other informations are also available : old MCC + MNC which comes from our network but the LAC value is from another network ( unknown network ).

    We print (with NSS guys) , the state of those IMSI in the HLR but we’ve got same results : IMSI not connected. But all those IMSI are registered in AuC Center.

    NSS guys told me that it can may be numbers that have been deleted because of subscribers not having done any “cost activity” for 3 months..

    My problem is that i am BSS guy and I need to reduce SDCCH signaling in order to avoid congestion.




    For yesterday only,from 00:00 to 23:59 , we record 6870 LU failures done by thoses 3 IMSI. All LU failures with the same cause : IMSI unknown in HLR.




    so you are in this weird situation:

    you are asked to drive 100 passengers from A to B in a bus in less than 30 minutes, while singing great songs and providing a fantastic guide-tour performance.
    but you don’t have a bus.

    so how can you do all this if you don’t even have a bus ?

    clearly, your BSS problem is just caused by this HLR misconfiguration. Your job is done here, report the problem and its root cause to your boss, and move on 🙂



    Hi Atto

    Please do a trace and check the TAC number of the phones used by those IMSI.
    If they use ZTE phones (A35 for example) then you have the same problem as some networks are facing now:
    If a deleted Sim is inserted in some ZTE phones, it will send LU requests every approx 2 sec unless the person itself takes out the deleted sim from the phone or unless you create again the deleted sim and call the guy to stop.


    Thanks for ur help guys.

    Yeah, We have huge number of ZTE phones in our country.

    I was thinking of some kind of solution coming from NSS guys by changing for example parameters in MSC -Server or HLR.
    If it doesn’t exist, What can i do , nothing , just reporting the issue.

    Thanks again.


    Of course it is the phones the root cause. They said there was bug in the software..
    Hope it is not your case because it is difficult to withdraw 1000 phones from the market or recreate deleted sims everyday…


    do you have an EIR in your network ? or any other way to know the IMEI of the phone making the LU ?

    by knowing the IMEI you can detect the manufacturer of the faulty phones, see if it’s indeed ZTE or another one.

    thanks phone, great info.


    I ll check this later pix. For now it is weekend . I need to relax otherwise i ll be crazy.


    Hello Pix,

    No EIR in my network , and Astellia captures from A interface seems not being able to provide IMEI number even if it is integrated through their analyser GUI ( Activity analysis ).

    No other way for the moment to get IMEI information.



    Hi Atto

    You are right, IMEI is not sent in LU request messages, so no way to see the IMEI in the traces.
    What you can do to check:
    1. go to Astellia AA
    2. open the latest AA base (real time analysis)
    3. take distribution of IMSI doing the most failed LU – cause (Rej)IUH
    4. Reactivate 5 of those IMSI with test numbers and call them immediately to know which phone they are using
    5. Get the same phone to test yourself the scenario.



    Hi Anno or Phone, we are facing the same issue with our customers and inbound roamers at our network ? what shall we do in order to prevent this kind of failure?


    Hello all

    we are facing the same problem in our Network with ZTE and Huawei vendors

    we delete inactive SIMs from HLR
    we receive this error IMSI unknown in HLR” from HLR

    and we notice huge LOC UP attempts and it effect the radio resources, it is clear under 2G netwrok more than 3G.

Viewing 14 posts - 1 through 14 (of 14 total)
  • The forum ‘Telecom Design’ is closed to new topics and replies.