LTE Tracking Area Update - EventHelix.com

1 CellNew E-UTRANNew EPCOld EPCCNUEeNodeBNew MMENew ServingGWOld MMEPDN GWHSSLTE Tracking area Update A Tracking area Update takes place if: - UE detects it has entered a new Tracking area that is not in the list of TAIs that the UE registered with the network; - the periodic Tracking area Update timer has expired; - UE was in UTRAN PMM_Connected state ( URA_PCH) when it reselects to E UTRAN; - UE was in GPRS READY state when it reselects to E UTRAN; - the TIN indicates "P-TMSI" when the UE reselects to E-UTRAN ( due to bearer configuration modifications performed on GERAN/UTRAN); - the RRC connection was released with release cause "load re-balancing TAU required"; - a change of the UE Core Network Capability and/or UE Specific DRX Parameters information of the UE.

2 Generated with EventStudio System Designer ( ) TAU RequestUE Core Network Capability,old GUTI,last visited TAI,active flag,EPS bearer status,P-TMSI Signature,additional GUTI,KSIASME,NAS sequence number,NAS-MAC,KSISGSN The UE initiates the TAUprocedure by sending a TAUR equest message. The messageincludes RRC parametersindicating the Selected Networkand the old RequestUE Core Network Capability,old GUTI,last visited TAI,active flag,EPS bearer status,P-TMSI Signature,additional GUTI,KSIASME,NAS sequence number,NAS-MAC.

3 KSISGSN The enodeb derives the MMEfrom the RRC parameterscarrying the old GUMMEI andthe indicated Selected enodeb forwards the TAUR equest message together withthe TAI+ECGI of the cell fromwhere it received the messageand with the Selected Networkto the new Requestold GUTI,complete TAU Request message,P-TMSI Signature,MME Address,UE validated The new MME uses the GUTI received from the UE to derivethe old MME/S4 SGSN address,and sends a Context Requestmessage to the old MME toretrieve user ResponseIMSI,ME Identity (if available),MSISDN,unused EPS Authentication Vectors,KSIASME,KASME,EPS Bearer Context(s),Serving GW signaling Address and TEID(s),ISR Supported, UE Core Network Capability,UE Specific DRX Parameters The old MME responds with aContext Response PDN GW Address andTEID(s) (for GTP-based S5/S8)or GRE Keys (PMIP-basedS5/S8 at the PDN GW(s) foruplink traffic) and the TI(s)

4 , ispart of the EPS Bearer Supported is indicated if theold MME is capable to activateISR for the UE. The MSISDN isincluded if the old MME has itstored for that / SecurityAuthentication / SecurityAuthentication and securityfunctions are if Serving GW change isneeded The new MME determines torelocate the Serving GW as theCellNew E-UTRANNew EPCOld EPCCNUEeNodeBNew MMENew ServingGWOld MMEPDN GWHSSold Serving GW cannot continueto serve the AcknowledgeServing GW change indication The new MME sends a ContextAcknowledge message to theold MME.

5 Serving GW changeindication indicates a newServing GW has been GWs and HSS in UEContext The old MME marks in its UEcontext that the information inthe GWs and the HSS MM Context The MME constructs an MMcontext for the Network Resources forinactive EPS Bearers The MME verifies the EPSbearer status received from theUE with the bearer contextsreceived from the old MME andreleases any network resourcesrelated to EPS bearers that arenot active in the Bearer RequestIMSI,bearer contexts,MME Address and TEID,Type,the Protocol Type over S5/S8,RAT type Since the new MME selected anew Serving GW it sends aCreate Bearer Request messageto the selected new Serving PDN GW address isindicated in the bearer indicates to the ServingGW to send the Update BearerRequest the PDN GW.

6 TheProtocol Type specifies theprotocol to be used over S5/S8interface. RAT type indicates achange in radio access. If thePDN GW requested UE'slocation info, the MME alsoincludes the User LocationInformation IE in this Bearer RequestServing GW Address and TEID,RAT type The Serving GW informs thePDN GW about the radio access type isincluded in the message. UserLocation Information IE mayalso Bearer ResponseMSISDN,PDN GW address and TEID(s) The PDN GW updates its bearercontexts and returns an UpdateBearer Response message.

7 TheMSISDN is included if the PDNGW has it stored in its bearer context The Serving GW updates itsbearer context. This allows theServing GW to route bearerPDUs to the PDN GW whenreceived from Bearer ResponseCheck if subscription data ispresent The new MME verifies whetherit holds subscription data forthe UE identified by the GUTI,the additional GUTI or by theIMSI received with the contextdata from the old CN node. Nosubscription data is E-UTRANNew EPCOld EPCCNUEeNodeBNew MMENew ServingGWOld MMEPDN GWHSSU pdate LocationMME Identity,IMSI, Update Type,MME Capabilities Since there is no subscriptiondata in the new MME for thisUE, the new MME sends anUpdate Location Requestmessage to the HSS.

8 UpdateType indicates that only theMME registration shall beupdated in HSS. Update Typeindicates whether HSS shouldcancel location to the other RATas well. The MME capabilitiesindicate the MME's support forregional access LocationIMSI,Cancellation Type The HSS sends the messageCancel Location to the old MMEwith Cancellation Type set toUpdate MM Context Delete the mobility managementcontext on the old Location AckIMSI The old MME acknowledgeswith the message CancelLocation Location AckIMSI,Subscription Data The HSS acknowledges theUpdate Location Requestmessage by sending an UpdateLocation Ack message to thenew UE's presence in the newTracking area The new MME validates theUE's presence in the (new) is no access restriction,so allow the Tracking areaupdate to go AcceptGUTI,TAI list,EPS bearer status,KSIASME,NAS sequence number,NAS-MAC The MME sends a TAU Acceptmessage to the UE.

9 GUTI isincluded if the MME allocates anew GUTI. If the "active flag" isset in the TAU Request messagethe user plane setup procedurecan be activated in conjunctionwith the TAU Accept with EventStudio System Designer ( ) EXPLORE MORE LTE IMS