Depending on how they can be initiated, three types of EMM procedures can be distinguished:
1) EMM common procedures:
An EMM common procedure can always be initiated whilst a NAS signalling connection exists. The procedures
belonging to this type are:
Initiated by the network:
– GUTI reallocation;
– authentication;
– security mode control;
– identification;
– EMM information.
2) EMM specific procedures:
At any time only one UE initiated EMM specific procedure can be running. The procedures belonging to this
type are:
Initiated by the UE and used to attach the IMSI in the network for EPS services and/or non-EPS services, and
to establish an EMM context and a default bearer:
– attach and combined attach.
Initiated by the UE and used to attach the IMSI or IMEI for emergency bearer services, and to establish an
EMM context and a default bearer to a PDN that provides emergency bearer services:
– attach.
Initiated by the UE or the network and used to detach the IMSI in the network for EPS services and/or non-
EPS services and to release an EMM context and all bearers:
– detach and combined detach.
Initiated by the UE when an EMM context has been established:
– normal tracking area updating and combined tracking area updating (S1 mode only);
– periodic tracking area updating (S1 mode only).
The tracking area updating procedure can be used to request also the resource reservation for sending data.
3) EMM connection management procedures (S1 mode only):
Initiated by the UE and used to establish a secure connection to the network or to request the resource
reservation for sending data, or both:
– service request.
The service request procedure can only be initiated if no UE initiated EMM specific procedure is ongoing.
Initiated by the network and used to request the establishment of a NAS signalling connection or to prompt
the UE to re-attach if necessary as a result of a network failure:
– paging procedure.
Initiated by the UE or the network and used to transport NAS messages:
– transport of NAS messages;
– generic transport of NAS messages.
The transport of NAS messages procedure and the generic transport of NAS messages procedure cannot be
initiated while an EMM specific procedure or a service request procedure is ongoing.