7.2 RRC 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

RRC uses the following states:

– RRC_IDLE:

– PLMN selection;

– DRX configured by NAS;

– Broadcast of system information;

– Paging;

– Cell re-selection mobility;

– The UE shall have been allocated an id which uniquely identifies the UE in a tracking area;

– No RRC context stored in the eNB and ng-eNB (except for a UE that supports User Plane CIoT EPS optimisation, as specified in TS 24.301 [20] and User Plane CIoT 5GS Optimisation, as specified in TS 24.501 [91], where a context may be stored for the resume procedure);

– Sidelink communication transmission and reception;

– Sidelink discovery announcement and monitoring;

– V2X sidelink communication transmission and reception;

– NR sidelink communication transmission and reception;

– MO-EDT;

– MT-EDT;

– Transmission using PUR.

– RRC_CONNECTED:

– UE has an E-UTRAN-RRC connection;

– UE has context in E-UTRAN;

– E-UTRAN knows the cell which the UE belongs to;

– Network can transmit and/or receive data to/from UE;

– Network controlled mobility (handover and inter-RAT cell change order to GERAN with NACC);

– Neighbour cell measurements;

– Sidelink communication transmission and reception;

– Sidelink discovery announcement and monitoring;

– V2X sidelink communication transmission and reception;

– NR sidelink communication transmission and reception;

– At PDCP/RLC/MAC level:

– UE can transmit and/or receive data to/from network;

– UE monitors control signalling channel for shared data channel to see if any transmission over the shared data channel has been allocated to the UE;

– UE also reports channel quality information and feedback information to eNB;

– DRX period can be configured according to UE activity level for UE power saving and efficient resource utilization. This is under control of the eNB.

E-UTRA connected to 5GC additionally supports RRC_INACTIVE state, which has the same characteristics as RRC_INACTIVE of NR connected to 5GC, as specified in TS 38.300 [79].