Behaviour of the UE in state EMM-DEREGISTERED and state EMM-REGISTERED
General
In this subclause, the detailed behaviour of the UE in the states EMM-DEREGISTERED and EMM-REGISTERED is described.
UE behaviour in state EMM-DEREGISTERED
The state EMM-DEREGISTERED is entered in the UE, when:
- the detach or combined detach is performed either by the UE or by the MME
- the attach request is rejected by the MME
- the tracking area update request is rejected by the MME
- the service request procedure is rejected by the MME
- the UE deactivates all EPS bearer contexts locally
- the UE is switched on; or
- when an inter-system change from S1 mode to non‑3GPP access is completed and the non‑3GPP access network provides PDN connectivity to the same EPC.
In state EMM-DEREGISTERED, the UE shall behave according to the substate(NORMAL-SERVICE, LIMITED-SERVICE, ATTEMPTING-TO-ATTACH, PLMN-SEARCH, NO-IMSI, ATTACH-NEEDED, NO-CELL-AVAILABLE)
Primary substate selection
Selection of the substate after power on
When the UE is switched on, the substate shall be PLMN-SEARCH if the USIM is available and valid. The substate chosen after PLMN-SEARCH, following power on is:
- if no cell can be selected, the substate shall be NO-CELL-AVAILABLE;
- if no USIM is present, the substate shall be NO-IMSI;
- if a suitable cell has been found and the PLMN or tracking area is not in the forbidden list, then the substate shall be NORMAL-SERVICE;
- if the selected cell is in a forbidden PLMN or a forbidden tracking area, then the UE shall enter the substate LIMITED-SERVICE;
- if the UE is in manual network selection mode and no cell of the selected PLMN has been found, the UE shall enter the substate NO-CELL-AVAILABLE; and
- if the selected cell is a non-3GPP cell, the substate shall be NO-CELL-AVAILABLE.
Detailed description of UE behaviour in state EMM-DEREGISTERED
NORMAL-SERVICE
The UE shall perform an attach or combined attach procedure.
LIMITED-SERVICE
The UE shall perform an attach or combined attach procedure when entering a cell which provides normal service.
The UE may perform attach for emergency bearer services.
ATTEMPTING-TO-ATTACH
The UE shall:
- perform an attach or combined attach procedure on the expiry of timers T3411 or T3402;
- perform an attach or combined attach procedure when the UE enters a new cell in a different tracking area, and the tracking area of the new cell is not in the list of forbidden tracking areas; and
- perform an attach procedure upon request of the upper layers to establish a PDN connection for emergency bearer services.
PLMN-SEARCH
The UE shall perform PLMN selection. If a new PLMN is selected, the UE shall reset the attach attempt counter and perform the attach or combined attach procedure
The UE may perform attach for emergency bearer services when entering a cell which provides limited service.
NO-IMSI
The UE shall perform cell selection
The UE may perform attach for emergency bearer services.
ATTACH-NEEDED
The UE shall start the attach or combined attach procedure, if still needed, as soon as the access is allowed in the selected cell for one of the access classes of the UE.
If the attach procedure was requested by upper layers to establish a PDN connection for emergency bearer services, the UE shall initiate the attach procedure if the "access class 10" bit broadcasted in the cell indicates that access for emergency calls is allowed.
NO-CELL-AVAILABLE
The UE shall perform cell selection according to and choose an appropriate substate when a cell is found. When the lower layers indicate to prepare for an S101 mode to S1 mode handover and the PLMN identity of the target cell provided with this indication is not in one of forbidden PLMN lists, the UE shall enter substate NORMAL-SERVICE.
NOTE: It is assumed that the UE can determine the PLMN identity of networks supporting cdma2000®HRPD access from the information broadcast over the radio interface. For the purpose of S101 mode to S1 mode handover, the UE can use the PLMN identity of the visited cdma2000® HRPD network also as PLMN identity of the target cell.
Substate when back to state EMM-DEREGISTERED from another EMM state
When returning to state EMM-DEREGISTERED, the UE shall select a cell.
The substate depends on the result of the cell selection procedure, the outcome of the previously performed EMM specific procedures, on the EPS update status of the UE, on the tracking area data stored in the UE and on the presence of the USIM:
- If no cell has been found, the substate is NO-CELL-AVAILABLE, until a cell is found.
- If no USIM is present or if the inserted USIM is considered invalid by the UE, the substate shall be NO-IMSI.
- If the selected cell is in a tracking area where the UE is allowed to roam, the substate shall be NORMAL-SERVICE.
- If an attach shall be performed (e.g. network requested re-attach), the substate shall be ATTEMPTING-TO-ATTACH.
- If a PLMN reselection is needed, the substate shall be PLMN-SEARCH.
- If the selected cell is in a tracking area where the UE is not allowed to roam, the substate shall be LIMITED-SERVICE; and
- if the selected cell is a non-3GPP cell, the substate shall be NO-CELL-AVAILABLE.
UE behaviour in state EMM-REGISTERED
The state EMM-REGISTERED is entered at the UE, when:
- the attach or combined attach procedure is performed by the UE.
In state EMM-REGISTERED, the UE shall behave according to the substate .
Editor's note: A new substate for UEs attached for emergency bearer services served by a cell with limited services may be required, and this is FFS.
Detailed description of UE behaviour in state EMM-REGISTERED
NORMAL-SERVICE
The UE:
- shall perform normal, periodic and combined tracking area updating and
- shall respond to paging.
ATTEMPTING-TO-UPDATE
The UE:
- shall not send any user data;
- shall perform tracking area updating on the expiry of timers T3411 or T3402;
- shall perform tracking area updating when the tracking area of the serving cell has changed and this tracking area is not in the list of forbidden tracking areas; and
- shall perform a tracking area updating procedure upon request of the upper layers to establish a PDN connection for emergency bearer services.
LIMITED-SERVICE
The UE:
- shall perform cell selection/reselection.
- may respond to paging (with IMSI); and
- may perform attach for emergency bearer services.
PLMN-SEARCH
The UE may enter this substate when it is in automatic network selection mode and the maximum allowed number of subsequently unsuccessful tracking area updating have been performed. The UE may also enter this substate as a result of a tracking area update rejected by the network or as a result of a service request rejected by the network . If a new PLMN is selected, the UE shall reset the tracking area updating attempt counter and perform the tracking area updating or combined tracking area updating procedure.
UPDATE-NEEDED
The UE:
- shall not send any user data;
- shall not send signalling information unless as a response to paging;
- shall perform a tracking area updating procedure upon request by the upper layers to establish a PDN connection for emergency bearer services, if the "access class 10" bit broadcasted in the cell indicates that access for emergency calls is allowed;
- shall perform cell selection/reselection according to and
- shall enter the appropriate new substate depending on the EPS update status as soon as the access is allowed in the selected cell for one of the access classes of the UE.
NO-CELL-AVAILABLE
The UE shall perform cell selection/reselection.
ATTEMPTING-TO-UPDATE-MM
The UE:
- shall perform cell selection/reselection.
- shall be able to receive and transmit user data and signalling information; and
- shall perform combined tracking area updating procedure indicating "combined TA/LA updating with IMSI attach" on the expiry of timers T3411 or T3402 or when the UE enters a tracking area not in the list of registered tracking areas.
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