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IMSI detach in GSM

  • This topic has 15 replies, 1 voice, and was last updated 14 years ago by Pix.
Viewing 15 posts - 1 through 15 (of 16 total)
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  • #46900 Reply
    Moni
    Guest

    Hi,
    Can IMSI detach message be sent by MS during an ongoing MM Connection Management procedure (say call running) ?
    regards,
    Moni

    #46901 Reply
    Pix
    Guest

    Hello Moni,

    According to specs, when a MS is powering down (no more battery for instance), it sends an IMSI DETACH.

    If the MS is fine (full battery) there shouldn’t be any IMSI detach.

    #46902 Reply
    VK
    Guest

    IMSI detach can only happen when the phone is properly switched off.

    On no coverage/battery, only ‘no response’ to the paging message would be possible. Though possibilities are there for the scenario mentioned by you. On the border of your coverage area. The time is very small. Hence I would say remote chances.

    #46903 Reply
    Pix
    Guest

    VK,

    Before the battery is totally empty, the MS switches off by itelf, therefore it might have enough time to send an imsi detach… since it is not define in the standard, i guess it is manufacturer’s dependent.

    What do you think ?

    Regards,
    Pix

    #46904 Reply
    paraHO
    Guest

    I shall have another go…

    Having worked in handset manufacturing in the past causes for IMSI-detach:

    1) power off handset
    2) SIM removed from handset
    3) SIM loose (causes make/break) when inserted into handset
    4) Where handset in GPRS modes and switches to IMSI-detach to select non-GPRS services

    (part 1)

    #46905 Reply
    paraHO
    Guest

    (part 2)

    Handsets generate comfort signals for users when battery about to drain. Unlikely issue IMSI-detach as handset is closing doewn apps and links to SIM at that point.

    Also some handset manfacturers in past allowed battery to be disconnected for 5-seconds during call to connect new fully charged battery.

    #46906 Reply
    Pix
    Guest

    Hello ParaHO,

    Thanks for your very precise answer.

    I don’t understand your sentence : Unlikely issue IMSI-detach as handset is closing doewn apps and links to SIM at that point.

    Can you explain ?
    Are you really sure about it, or 50/50 ?

    Regards,
    Pix

    #46907 Reply
    paraHO
    Guest

    Thanks.

    Can’t say 100% every handset because I not see every handset. The protocol for handset power off is different from low battery power. It needs to be different as user could connect handset to PSU when power low. When battery drain the handset sets in motion a recovery process to protect memory, close down any running apps, save memory and PIN management etc. To burst to the network with a packet to inform BTS / VLR of IMSI detach wouldn’t be relevant – as AFAIK.

    #46908 Reply
    paraHO
    Guest

    Pix reason I can’t be 100% certain is GSM02.07 B.1.17

    paraHO

    #46909 Reply
    paraHO
    Guest

    Pix also look at GSM11.10-1 version 4.28.1 August 2000 Section 35 Low battery voltage detection – which supports my thoughts about handset not RF transmitting at low battery – thus unlikely IMSI detach.

    #46910 Reply
    VK
    Guest

    Yes, IMSI detach can happen in two different cases (Switch off / Phone switching off itself on low battery). If the battery is old, there might be a chance for it to sleep without detaching. On all other scenarios, not reachable would be the case.

    #46911 Reply
    Pix
    Guest

    ParaHO, sorry I was away for a while. Thanks for the precisions.

    So, as far as the 3GPP goes, a “low battery” phone which is automatically shutting down should not send an IMSI DETACH.

    Thank 🙂

    Pix

    #46912 Reply
    Rajiv Gujral
    Guest

    Hi all,

    If on the running call and battery of the MS goes down then “IMSI Detach” message will not be sent.

    #46913 Reply
    VK
    Guest

    Dear Rajiv,

    Yes, the phone will not tell IMSI detach if the battery is very old & can not withstand even few minutes since showing low battery. Tested with various phones, battery conditions.

    Modern phones are now very smart.

    #46914 Reply
    Dude
    Guest

    I think the issue here is, it depends on the handset in use. According to 3gpp specs, it is not mandatory to send an IMSI DETACH message when the battery is low. That does not mean that if a manufacturer wants to include it they are forbidden…they are free to, as long as they stick to the stipulated protocol for handset power off. In summary, it is possible to have a handset sending an IMSI DETACH message, depending on manufacturer, but it is not critical for handset designers.

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