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)


  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!

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

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

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

  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.

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

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