EMM sublayer states
EMM sublayer states in the UE
The following are the possible EMM states of an EMM entity in the UE.
Main states
The EPS capability is disabled in the UE. No EPS mobility management function shall be performed in this state.
In the state EMM-DEREGISTERED, no EMM context has been established and the UE location is unknown to an MME and hence it is unreachable by an MME. In order to establish an EMM context, the UE shall start the attach or combined attach procedure .
A UE enters the state EMM-REGISTERED-INITIATED after it has started the attach or the combined attach procedure and is waiting for a response from the MME.
In the state EMM-REGISTERED an EMM context has been established and a default EPS bearer context has been activated in the UE. When the UE is in EMM-IDLE mode, the UE location is known to the MME with an accuracy of a list of tracking areas containing a certain number of tracking areas. When the UE is in EMM-CONNECTED mode, the UE location is known to the MME with an accuracy of a serving eNodeB. The UE may initiate sending and receiving user data and signalling information and reply to paging. Additionally, tracking area updating or combined tracking area updating procedure is performed.
A UE enters the state EMM-DEREGISTERED-INITIATED after it has requested release of the EMM context by starting the detach or combined detach procedure and is waiting for a response from the MME
A UE enters the state EMM-TRACKING-AREA-UPDATING-INITIATED after it has started the tracking area updating or combined tracking area updating procedure and is waiting for a response from the MME.
EMM-SERVICE-REQUEST-INITIATED
A UE enters the state EMM-SERVICE-REQUEST-INITIATED after it has started the service request procedure and is waiting for a response from the MME.
Substates of state EMM-DEREGISTERED
The state EMM-DEREGISTERED is subdivided into a number of substates as described in this subclause. Valid subscriber data are available for the UE before it enters the substates, except for the substate EMM-DEREGISTERED.NO-IMSI.
EMM-DEREGISTERED.NORMAL-SERVICE
The substate EMM-DEREGISTERED.NORMAL-SERVICE is chosen in the UE, if the EPS update status is EU1 or EU2, in the meantime a cell has been selected and the PLMN or tracking area is not in the forbidden list.
EMM-DEREGISTERED.LIMITED-SERVICE
The substate EMM-DEREGISTERED.LIMITED-SERVICE is chosen in the UE, if the EPS update status is EU3, and it is known that a selected cell is unable to provide normal service (e.g. the selected cell is in a forbidden PLMN, is in a forbidden tracking area or has a CSG ID not included in the UE's Allowed CSG list).
EMM-DEREGISTERED.ATTEMPTING-TO-ATTACH
The substate EMM-DEREGISTERED.ATTEMPTING-TO-ATTACH is chosen in the UE, if the EPS update status is EU2, and a previous attach was rejected.
EMM-DEREGISTERED.PLMN-SEARCH
The substate EMM-DEREGISTERED.PLMN-SEARCH is chosen in the UE, if the UE with a valid USIM is switched on.
EMM-DEREGISTERED.NO-IMSI
The substate EMM-DEREGISTERED.NO-IMSI is chosen in the UE, if the UE is switched on without a valid USIM inserted.
EMM-DEREGISTERED.ATTACH-NEEDED
Valid subscriber data are available for the UE and for some reason an attach must be performed as soon as possible. This substate can be entered if the access class is blocked due to access class control, or if the network rejects the NAS signalling connection establishment.
EMM-DEREGISTERED.NO-CELL-AVAILABLE
No E-UTRAN cell can be selected. This substate is entered after a first intensive search failed when in substate EMM-DEREGISTERED.PLMN-SEARCH. Cells are searched for at a low rhythm. No EPS services are offered.
Substates of state EMM-REGISTERED
EMM-REGISTERED.NORMAL-SERVICE
The substate EMM-REGISTERED.NORMAL-SERVICE is chosen by the UE as the primary substate when the UE enters the state EMM-REGISTERED.
EMM-REGISTERED.ATTEMPTING-TO-UPDATE
The substate EMM-REGISTERED.ATTEMPTING-TO-UPDATE is chosen by the UE if the tracking area updating or combined tracking area updating procedure failed due to a missing response from the network. No EMM procedure except the tracking area updating or combined tracking area updating procedure shall be initiated by the UE in this substate. No data shall be sent or received.
EMM-REGISTERED.LIMITED-SERVICE
The substate EMM-REGISTERED.LIMITED-SERVICE is chosen in the UE, if the cell the UE selected is known not to be able to provide normal service.
EMM-REGISTERED.PLMN-SEARCH
The substate EMM-REGISTERED.PLMN-SEARCH is chosen in the UE, while the UE is searching for PLMNs.
EMM-REGISTERED.UPDATE-NEEDED
The UE has to perform a tracking area updating or combined tracking area updating procedure, but access to the current cell is barred. This state can be entered if the access class is blocked due to access class control, or if the network rejects the NAS signalling connection establishment. No EMM procedure except tracking area updating or combined tracking area updating or service request as a response to paging shall be initiated by the UE in this substate.
EMM-REGISTERED.NO-CELL-AVAILABLE
E-UTRAN coverage has been lost. In this substate, the UE shall not initiate any EMM procedures except for cell and PLMN reselection.
EMM-REGISTERED.ATTEMPTING-TO-UPDATE-MM
A combined attach procedure or a combined tracking area updating procedure was successful for EPS services only. User data and signalling information may be sent and received.
EMM-REGISTERED.IMSI-DETACH-INITIATED
The UE performs a combined detach procedure for non-EPS services only (detach type "IMSI detach"). This substate is entered if the UE is attached for EPS and non-EPS services and wants to detach for non-EPS services only. User data and signalling information may be sent and received.
EPS update status
In order to describe the detailed UE behaviour, the EPS update (EU) status pertaining to a specific subscriber is defined.
The EPS update status is stored in a non-volatile memory in the USIM if the corresponding file is present in the USIM, else in the non-volatile memory in the ME, as described in annex C.
The EPS update status value is changed only after the execution of an attach or combined attach, network initiated detach, authentication, tracking area update or combined tracking area update, service request or paging for EPS services using IMSI procedure.
EU1: UPDATED
The last attach or tracking area updating attempt was successful.
EU2: NOT UPDATED
The last attach, service request or tracking area updating attempt failed procedurally, i.e. no response or reject message was received from the MME.
EU3: ROAMING NOT ALLOWED
The last attach, service request or tracking area updating attempt was correctly performed, but the answer from the MME was negative (because of roaming or subscription restrictions).
EMM sublayer states in the MME
EMM-DEREGISTERED
In the state EMM-DEREGISTERED, the MME has no EMM context or the EMM Context is marked as detached. The UE is detached. The MME may answer to an attach or a combined attach procedure initiated by the UE.
EMM-COMMON-PROCEDURE-INITIATED
The MME enters the state EMM-COMMON-PROCEDURE-INITIATED, after it has started a common EMM procedure and is waiting for a response from the UE.
EMM-REGISTERED
In the state EMM-REGISTERED, an EMM context has been established and a default EPS bearer context has been activated in the MME.
EMM-DEREGISTERED-INITIATED
The MME enters the state EMM-DEREGISTERED-INITIATED after it has started a detach procedure and is waiting for a response from the UE.
Coordination between EMM and GMM
If GMM and EMM are both enabled, a UE capable of S1 mode and A/Gb mode or Iu mode or both shall maintain one common registration for GMM and EMM indicating whether the UE is registered for packet services or not.
A UE that is not registered shall be in state GMM-DEREGISTERED and in state EMM-DEREGISTERED.
If the UE performs a successful attach or combined attach procedure in S1 mode, it shall enter substates GMM-REGISTERED.NO-CELL-AVAILABLE and EMM-REGISTERED.NORMAL-SERVICE.
If the UE performs a successful GPRS attach or combined GPRS attach procedure in A/Gb or Iu mode, it shall enter substates GMM-REGISTERED.NORMAL-SERVICE and EMM-REGISTERED.NO-CELL-AVAILABLE.
After successful completion of routing area updating or combined routing area updating and tracking area updating or combined tracking area updating procedures in both S1 mode and A/Gb or Iu mode, if the network has indicated that ISR is activated, the UE shall maintain registration and related periodic update timers in both GMM and EMM.
Coordination between EMM and MM
UEs that operate in CS/PS mode 1 or CS/PS mode 2 of operation shall use the combined EPS/IMSI attach procedure in order to attach to both EPS and non-EPS services.
UEs that operate in CS/PS mode 1 or CS/PS mode 2 of operation and are already attached to both EPS and non-EPS services shall use the combined tracking area updating and periodic tracking area updating procedures.
UEs that operate in CS/PS mode 1 or CS/PS mode 2 of operation and are already attached to both EPS and non-EPS services shall perform a combined detach procedure in order to detach for non-EPS services.
UEs that operate in CS/PS mode 1 or CS/PS mode 2 of operation should not use any MM timers related to MM specific procedures (e.g. T3210, T3211, T3212, T3213) while camped on E-UTRAN, unless the re-activation of these timers is explicitly described. If the MM timers are already running, the UE should not react on the expiration of the timers.
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