8 E-UTRAN identities

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

8.1 E-UTRA related UE identities

The following E-UTRA related UE identities are used at cell level:

– C-RNTI: unique identification used for identifying RRC Connection and scheduling;

– Semi-Persistent Scheduling C-RNTI: unique identification used for semi-persistent scheduling;

– Temporary C-RNTI: identification used for the random access procedure;

– TPC-PUSCH-RNTI: identification used for the power control of PUSCH;

– TPC-PUCCH-RNTI: identification used for the power control of PUCCH;

– SL-RNTI: identification used for sidelink communication scheduling;

– SL-V-RNTI: identification used for V2X sidelink communication scheduling;

– Random value for contention resolution: during some transient states, the UE is temporarily identified with a random value used for contention resolution purposes;

– SRS-TPC-RNTI: identification used for triggering group SRS and power control of SRS for SRS-only SCells;

– SL Semi-Persistent Scheduling V-RNTI: identification used for semi-persistent scheduling for V2X sidelink communication;

– UL Semi-Persistent Scheduling V-RNTI: identification used for multiple semi-persistent scheduling for UE capable of V2X communication;

– AUL C-RNTI: unique identification used for autonomous uplink scheduling;

– PUR-RNTI: identification used for transmission using PUR.

In DC, two C-RNTIs are independently allocated to the UE: one for MCG, and one for SCG.

The following UE identity is only used for E-UTRA connected to EPC:

– Resume ID: unique identification used for the RRC connection resume procedure;

The following UE identity is only used for E-UTRA connected to 5GC:

– I-RNTI: unique identification used for the RRC connection resume procedure in RRC_INACTIVE or for the User Plane CIoT 5GS Optimisation as specified for NR connected to 5GC in TS 38.300 [79];

8.2 Network entity related Identities

The following identities are used in E-UTRAN for identifying a specific network entity TS 36.413 [25]:

– Globally Unique MME Identity (GUMMEI): used to identify MME globally. The GUMMEI is constructed from the PLMN identity the MME belongs to, the group identity of the MME group the MME belongs to and the MME code (MMEC) of the MME within the MME group.

NOTE: GUMMEI or S-TMSI containing the MMEC is provided by the UE to the eNB according to TS 23.401 [17], TS 24.301 [20] and TS 36.331 [16].

– E-UTRAN Cell Global Identifier (ECGI): used to identify cells globally. The ECGI is constructed from the PLMN identity the cell belongs to and the E-UTRA Cell Identifier of the cell. The included PLMN is the one given by the first PLMN entry in SIB1 associated with the E-UTRA Cell Identifier of the cell, according to TS 36.331 [16].

– eNB Identifier (eNB ID): used to identify eNBs within a PLMN. The eNB ID is contained within the E-UTRA Cell Identifier of its cells.

– Global eNB ID: used to identify eNBs globally. The Global eNB ID is constructed from the PLMN identity the eNB belongs to and the eNB ID. The MCC and MNC are the same as included in the E-UTRAN Cell Global Identifier (ECGI).

– The Global eNB ID of RN is the same as its serving DeNB.

– Tracking Area identity (TAI): used to identify tracking areas allocated by EPC or 5GC. The TAI is constructed from the PLMN identity the tracking area belongs to and the TAC (Tracking Area Code) of the Tracking Area. The TACs allocated to an ng-eNB by EPC and 5GC are separate.

– CSG identity (CSG ID): used to identify a CSG within a PLMN.

– EPS Bearer ID / E-RAB ID:

– The value of the E-RAB ID used at S1 and X2 interfaces to identify an E-RAB allocated to the UE is the same as the EPS Bearer ID value used at the Uu interface to identify the associated EPS Bearer (and also used at the NAS layer as defined in TS 36.413 [25]).

– NR Cell Global Identifier (NCGI): specified in TS 38.300 [79].

– en-gNB Identifier (en-gNB ID): as specified for the gNB Identifier in TS 38.300 [79].

– Global en-gNB ID: as specified for the Global gNB ID in TS 38.300 [79].

The following identities are broadcast in every E-UTRAN cell (SIB1): CI, TAC, CSG ID (if any) and one or more PLMN identities.

8.3 Sidelink communication and V2X Sidelink Communication related identities

The following identities are used for sidelink communication and V2X sidelink communication:

– Source Layer-2 ID: Identifies the sender of the data in sidelink communication and V2X sidelink communication. The Source Layer-2 ID is 24 bits long and is used together with Destination Layer-2 ID and LCID for identification of the RLC UM entity and PDCP entity in the receiver;

– Destination Layer-2 ID: Identifies the target of the data in sidelink communication and V2X sidelink communication. For sidelink communication, the Destination Layer-2 ID is 24 bits long and is split in the MAC layer into two bit strings:

– One bit string is the LSB part (8 bits) of Destination Layer-2 ID and forwarded to physical layer as Group Destination ID. This identifies the target of the intended data in sidelink control information and is used for filtering of packets at the physical layer.

– Second bit string is the MSB part (16 bits) of the Destination Layer-2 ID and is carried within the MAC header. This is used for filtering of packets at the MAC layer.

– In case of V2X sidelink communication, Destination Layer-2 ID is not split and is carried within the MAC header.

No Access Stratum signalling is required for group formation and to configure Source Layer-2 ID, Destination Layer-2 ID and Group Destination ID in the UE. These identities are either provided by higher layer or derived from identities provided by higher layer. In case of groupcast and broadcast, the ProSe UE ID, as specified in TS 23.303 [62], provided by higher layer is used directly as the Source Layer-2 ID and the ProSe Layer-2 Group ID, as specified in TS 23.303 [62], provided by higher layer is used directly as the Destination Layer-2 ID in the MAC layer. In case of one-to-one communications, the ProSe UE ID, as specified in TS 23.303 [62], provided by higher layer is used directly as the Source Layer-2 ID or the Destination Layer-2 ID in the MAC layer. In case of V2X sidelink communication, higher layer provides Source Layer-2 ID and Destination Layer-2 ID, as specified in TS 23.285 [72].

8.4 MBMS related identities

The following identities are used for SC-PTM transmission:

– SC-RNTI: Identifies transmissions of the SC-MCCH, and for NB-IoT UEs, BL UEs or UEs in enhanced coverage identifies SC-MCCH change notification;

– SC-N-RNTI: Identifies SC-MCCH change notification for UEs other than NB-IoT UEs, BL UEs or UEs in enhanced coverage;

– G-RNTI: Identifies transmissions of a SC-MTCH, and for NB-IoT UEs, BL UEs or UEs in enhanced coverage identifies SC-MCCH change notification.