Monday, December 12, 2011

Detach Request (UE initiated)

·            The UE shall initiate the detach procedure when:

-          the UE is switched off
            -          the USIM is removed from the UE
-          the EPS capability of the UE is disabled (detach for EPS services only)
-          the UE in CS/PS mode 1 or CS/PS mode 2 of operation wishes to detach for both EPS services and non-EPS services or for non-EPS services only via a combined detach procedure etc...

·            The UE initiates the  detach procedure by sending a DETACH REQUEST message

·            The Detach type IE included in this message indicates the type of detach. 4-bits are used for this purpose. 3-bits (LSBs) indicate whether the detach is for ‘EPS detach’ or ‘IMSI detach’ or ‘Combined EPS/IMSI detach’. Bit-4 indicates if it is ‘normal detach’ or ‘switch off

·            If the UE has a valid GUTI, the UE shall set the EPS mobile identity IE as GUTI. If the UE does not have a valid GUTI, then it shall populate the EPS mobile identity IE with its IMSI. If the UE has neither a valid GUTI nor a valid IMSI (with no USIM or invalid USIM), then the UE shall populate the EPS mobile identity IE with its IMEI

·            If the UE is to be switched off, the UE shall try for a period of 5 seconds to send the DETACH REQUEST message. During this period, the UE may be switched off as soon as the DETACH REQUEST message has been sent

·            When the DETACH REQUEST message is received by the network, with the Detach type IE set to ‘switch off’, the network shall not send a DETACH ACCEPT message to the UE

·            When the DETACH REQUEST message is received by the network, with the Detach type IE set to ‘normal detach’, the network shall send a DETACH ACCEPT message to the UE

·            If the Detach type IE set to ‘normal detach and if the UE doesn’t receive DETACH ACCEPT message before the timer T3421 is expired, it shall re-transmit the DETACH REQUEST message. Upon the 5th expiry of T3421 timer, the UE shall perform local detach

·            The network and the UE shall deactivate the EPS bearer context(s) locally without peer-to-peer signalling between the UE and the MME
Reference: 3GPP TS 24.301
Example: DETACH REQUEST for EPS services only (switch off)

15 comments:

  1. Hi!I'm new here!May I ask you a question?What's the differences between EPS services & non-EPS services?Can't find the exactly definition in the related-spec.In my view,EPS services afford services(PS & CS) using LTE equipment,and the non-EPS services using 2G/3G equipment. am i right?Thanks!

    ReplyDelete
  2. non-EPS services are those provided by CS domain where as EPS services are provided by PS domain. refer to 24301

    ReplyDelete
  3. Hi
    When does the UE triggers Detach type IE = normal detach.
    Thx

    ReplyDelete
  4. Normal detach could be due to detach initiated by the UE for EPS services only or non-EPS services only etc

    ReplyDelete
  5. I was doing LTE integration with Lg Lucid UE. It sends detach request after 28sec of successful attach. How can I stop unwanted detach procedure initiated by UE. It says "Normal Detach+EPS Detach" in detach request. Any idea about how to avoid it.

    ReplyDelete
    Replies
    1. Hello, I have the same problem with a Samsung phone. I don't understand the reason for EPS Detach. Can anyone please explain ?

      Delete
    2. Hi,
      Akhilesh Kaushik/Dincer Beken
      there are may possible reason for this kind of detach one is
      If it is a IMS capable phone then it might be trying to attach to IMS PDN with PCO containing PCSCF addressrequest but in ActivateDefaultEPSBearerContextRequest message might be n/w is not assigning PCSF address in PCO.
      solution:
      Include the PCSCF address.i.e. for protocol Id 1 see 24.008 protocol configuration Options for more detail
      As i was also encountering the same issue with Samsung S3/S4

      Delete
  6. I want to disconnect only from non eps services. Is there any AT command supported for that?

    ReplyDelete
  7. Hi,
    Akhilesh Kaushik/Dincer Beken
    there are may possible reason for this kind of detach one is
    If it is a IMS capable phone then it might be trying to attach to IMS PDN with PCO containing PCSCF addressrequest but in ActivateDefaultEPSBearerContextRequest message might be n/w is not assigning PCSF address in PCO.
    solution:
    Include the PCSCF address.i.e. for protocol Id 1 see 24.008 protocol configuration Options for more detail
    As i was also encountering the same issue with Samsung S3/S4

    ReplyDelete

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    ReplyDelete
  9. how can you describe it in physical situation then?

    like removal of battery is a detach with type switch off? and whats normal detach in that case?

    ReplyDelete
    Replies
    1. I don't think that the UE gets a chance to even transmit "detach request" message when the battery is removed

      Delete
  10. Hi,
    Can you kindly explain me the detach cause "Explicit IMSI detach indication via A-IF(EAIF)".

    Thanks ...

    ReplyDelete
    Replies
    1. This procedure is used by the MME to indicate to the VLR that the UE has been detached from EPS services and
      therefore the SGs association between the MME and the VLR has to be deactivated.

      The procedure is also used by the MME to indicate to the VLR when a combined tracking area update procedure has
      been rejected by the MME.

      The Explicit IMSI detach from EPS services procedure aborts any other ongoing procedure related to this UE on the
      SGs interface in the MME and in the VLR.

      Delete