User's Manual

Ver.
CHAPTER 4. Message Flow
2600-00FKQFGA2
1.0
Detach by UE
The figure below shows the message flow of the Detach procedure initiated by the UE.
Figure 18. Detach Procedure by UE
Step Description
1)~2) The UE transmits the NAS DETACH REQUEST message to the MME. This NAS
message is used to start setting up an S1 connection when the UE is in Idle mode.
3) The active EPS bearers and their context information for the UE and MME which are in
the S-GW are deactivated when the MME transmits the Delete Session Request message
for each PDN connection.
4) When receiving the Delete Session Request message from the MME, the S-GW releases
the related EPS bearer context information and replies with the Delete Session Response
message.
5)~6) If the detachment procedure has been triggered by reasons other than disconnection of
power, the MME transmits the DETACH ACCEPT message to the UE.
7) The MME sets the Cause IE value of the UE CONTEXT RELEASE COMMAND message
to ‘Detach’ and transmits this message to the Indoor Pico Cell to release the S1-MME
signal connection for the UE.
8) If the RRC connection has not yet been released, the Indoor Pico Cell transmits the
RRCConnectionRelease message to the UE in Requested Reply mode. Once a reply to
this message is received from the UE, the Indoor Pico Cell removes the UE context.
9) The Indoor Pico Cell returns the UE CONTEXT RELEASE COMPLETE message to the
MME and confirms that S1 is released. By doing this, the signal connection between the
MME and Indoor Pico Cell for the UE is released. This step must be performed
immediately after step 7).
UE
MME
S-GW
EPC
1) ULInformationTransfer
3) Delete Session Request
2) UPLINK NAS TRANSPORT
(DETACH REQUEST)
4) Delete Session Response
5) DOWNLINK NAS TRANSPORT
(DETACH ACCEPT)
7) UE CONTEXT RELEASE COMMAND
9) UE CONTEXT RELEASE COMPLETE
6) DLInformationTransfer
(DETACH ACCEPT)
8) RRCConnectionRelease
(Detach)
Indoor Pico Cell
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