6.9 Service registration and location update

23.2213GPPArchitectural requirementsRelease 17TS

6.9.1 Introduction

Service registration (attach) in the respective CN domain is done initially (after UE being detached due to e.g. power off). When a registration area is changed a location update is performed. In addition, periodic registration can be performed. Here follows descriptions of when the respective CN registration area is changed.

NOTE: It is not here defined which different registration procedures that are needed.

6.9.2 Location area update

LA update is initiated by the UE to inform the CS domain of the CN that the UE has entered a new LA. In case the new LA is in an area served by another CN node, the LA update also triggers the registration of the subscriber in the new CN node and a location update for CS services towards the HLR/HSS.

LA update is only initiated by the UE when the UE is in state CS-IDLE, and this independently of the PS state. If the UE is CS-IDLE but RRC connected, which means that the UE is in PS-CONNECTED state, LA update is initiated by the UE when it receives information indicating a new LA.

6.9.3 Tracking and Routing area update

TA/RA update is initiated by the UE to inform the PS domain of the CN that the UE has entered a new TA/RA. In case the new TA/RA is in an area served by another CN node, the TA/RA update also triggers the registration of the subscriber in the new CN node and a location update for PS services towards the HSS.

TA/RA update is initiated by the UE when the UE is in state PS-IDLE, and this independently of the CS state. If the UE is PS-IDLE but UTRAN RRC connected, which means that the UE is in CS-CONNECTED state, RA update is initiated by the UE when it receives information indicating a new RA.

When the UE is in PS-CONNECTED state the UE initiates TA/RA update when TAI/RAI in MM system information changes.

6.9.4 Combined updates

The GSM radio interface combined procedures and their support via the Gs interface is the starting point for the support of combined updates. With E-UTRAN access combined update procedures may be used by MME and MSC.