TRACKING AREA UPDATE REQUEST

The purposes of sending the tracking area update request by the UE to the network

Message type: TRACKING AREA UPDATE REQUEST

Direction: UE to network

Tracking Area Update (TAU) become applicable after the UE has completed the attach procedure and has moved into the EPS Mobility Management (EMM) REGISTERED state. They can be triggered in either RRC Idle mode or RRC Connected mode, but the UE must be in RRC Connected mode to actually complete the procedure.

TAU Procedure is used for:

->Normal TAU due to mobility, i.e when the UE enters a tracking area which is not included within the list of tracking area with which the UE is registered.

-> Periodic TAU after the T3412 timer expires. The value of T3412 is initialized during the attach procedure within attach accept message. Periodic TAU confirm to the network that the UE is still present.

->Registering with the CS domain for non-EPS services when UE is already attached for EPS services. This involves completing an IMSI attach as part of the TAU procedure.

->Registering with the EPS after an incoming inter-system change, e.g. Reselecting LTE network after being camped on the UMTS network.

->Re-registering with the EPS after CS Fallback connection has been completed.

->MME load balancing. The UE initiates a TAU procedure if the eNodeB release connection using a cause value of ‘Load balancing TAU required

-> Updating the UE specific DRX cycle.

->indicating that a UE has selected a Closed Subscriber Group cell whose CSG identity is not included within the UE allowed CSG list.

Mandatory Information Element

Protocol discriminator

Security header type

Tracking area update request message identity

EPS update type

NAS key set identifier

Old GUTI

Information Element	Presence
Protocol discriminator	M
Security header type	M
Tracking area update request message identity	M
EPS update type	M
NAS key set identifier	M
Old GUTI	M
Non-current native NAS key set identifier	O
GPRS ciphering key sequence number	O
Old P-TMSI signature	O
Additional GUTI	O
NonceUE	O
UE network capability	O
Last visited registered TAI	O
DRX parameter	O
UE radio capability information update needed	O
EPS bearer context status	O
MS network capability	O
Old location area identification	O
TMSI status	O
Mobile station classmark 2	O
Mobile station classmark 3	O
Supported Codecs	O
Additional update type	O
Voice domain preference and UE’s usage setting	O
Old GUTI type	O
Device properties	O
MS network feature support	O
TMSI based NRI container	O