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LTE: When does an UE trigger Tracking Area complete message towards the network ?

+2 votes

Is this message mandatory to be triggered by UE towards network as part of tracking area update procedure or only at some special cases it is triggered ?

posted Feb 7, 2016 by Vikram Singh

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1 Answer

+1 vote

UE triggers tracking area update procedure to report its location to MME at the granularity of tracking area.
In the connected mode (EMM-REGISTERED, ECM-CONNECTED and RRC-CONNECTED) , MME knows the current location of an UE at the cell and a tracking area level but when the UE moves from connected to Idle mode (EMM-REGISTERED, ECM-IDLE and RRC-IDLE) mode, MME tracks the UE based on the tracking area identity (TAI) list, this is the list MME sends to UE in the attach accept or tracking area update accept message.

Assuming UE is in idle mode and found an another cell that has better signal strength and performed cell re-selection.
Since the new cell belongs to different tracking area that is not the part of TAI list assigned to UE, tracking area update procedure is initiated by UE to network.

In tracking are update request message, UE sends old GUTI and it may get new GUTI from MME in TAU accept message.
When UE gets new GTUI in TAU accept message and it acknowledges to MME by using the TAU complete message.
The same information is captured in 24.301 spec. Please have a look and still you have any doubt then send me the message.

answer Feb 7, 2016 by Vimal Kumar Mishra
Similar Questions
+3 votes

There are two ways for tracking area update procedure to get triggered from UE to network . One is known as periodic and other one as non-periodic.

+1 vote

I know tracking area list is provided by MME to UE to track UE in idle mode. I want to know what is the purpose of having different kind of tracking area type like "consecutive tracking area codes belonging to one plmn" , "non-consecutive tracking area codes belong to one PLMN".

+4 votes

There are couple of procedures are defined which consist of NAS as well as RRC signalling messages exchange.
Some of the NAS message sends to an UE through RRC Connection Reconfiguration message as piggybacked and some as DL Info transfer.

I want to know, Is there any procedure exists in lte when an UE receives RRC Connection Reconfiguration along with NAS message and responds back to network with NAS message first and then Reconfiguration Complete to eNodeB.

Usually, I saw UE sends RRC Connection Reconfiguration Complete message first then NAS response message.

+3 votes

How does MME make out which tracking area is neighbor of which one ?

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