A.2 NAS protocol states & state transitions

36.3003GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Overall descriptionRelease 17Stage 2TS

The NAS state model is based on a two-dimensional model which consists of EPS Mobility Management (EMM) states describing the mobility management states that result from the mobility management procedures e.g. Attach and Tracking Area Update procedures, and of EPS Connection Management (ECM) states describing the signalling connectivity between the UE and the EPC (see TS 23.401 [17]).

NOTE: The ECM and EMM states are independent of each other and when the UE is in EMM-CONNECTED state this does not imply that the user plane (radio and S1 bearers) is established.

The relation between NAS and AS states is characterised by the following principles:

– EMM-DEREGISTERED & ECM-IDLE ⇒ RRC_IDLE:

– Mobility: PLMN selection:

– UE Position: not known by the network.

– EMM-REGISTERED & ECM-IDLE ⇒ RRC_IDLE:

– Mobility: cell reselection;

– UE Position: known by the network at tracking area level.

– EMM-REGISTERED & ECM-CONNECTED with radio bearers established ⇒ RRC_CONNECTED.

– Mobility: handover;

– UE Position: known by the network at cell level.

Annex B (informative):
MAC and RRC Control

The E-UTRA supports control signalling in terms of MAC control signalling (PDCCH and MAC control PDU) and RRC control signalling (RRC message).