5.3.3 RRC connection establishment

38.3313GPPNRProtocol specificationRadio Resource Control (RRC)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.3.3.1 General

Figure 5.3.3.1-1: RRC connection establishment, successful

Figure 5.3.3.1-2: RRC connection establishment, network reject

The purpose of this procedure is to establish an RRC connection. RRC connection establishment involves SRB1 establishment. The procedure is also used to transfer the initial NAS dedicated information/ message from the UE to the network.

The network applies the procedure e.g.as follows:

– When establishing an RRC connection;

– When UE is resuming or re-establishing an RRC connection, and the network is not able to retrieve or verify the UE context. In this case, UE receives RRCSetup and responds with RRCSetupComplete.

5.3.3.1a Conditions for establishing RRC Connection for NR sidelink communication/discovery/V2X sidelink communication

For NR sidelink communication/discovery, an RRC connection establishment is initiated only in the following cases:

1> if configured by upper layers to transmit NR sidelink communication/discovery and related data is available for transmission:

2> if the frequency on which the UE is configured to transmit NR sidelink communication is included in sl-FreqInfoList within SIB12 provided by the cell on which the UE camps; and if the valid version of SIB12 does not include sl-TxPoolSelectedNormal for the concerned frequency; or

2> if the frequency on which the UE is configured to transmit NR sidelink discovery is included in sl-FreqInfoList within SIB12 provided by the cell on which the UE camps; and if the valid version of SIB12 does not include sl-DiscTxPoolSelected or sl-TxPoolSelectedNormal for the concerned frequency;

For L2 U2N Relay UE in RRC_IDLE, an RRC connection establishment is initiated in the following cases:

1> if any message is received from a L2 U2N Remote UE via SL-RLC0 as specified in 9.1.1.4 or SL-RLC1 as specified in 9.2.4;

For V2X sidelink communication, an RRC connection is initiated only when the conditions specified for V2X sidelink communication in clause 5.3.3.1a of TS 36.331 [10] are met.

NOTE: Upper layers initiate an RRC connection (except if the RRC connection is initiated at the L2 U2N Relay UE upon reception of a message from a L2 U2N Remote UE via SL-RLC0 or SL-RLC1). The interaction with NAS is left to UE implementation.

5.3.3.2 Initiation

The UE initiates the procedure when upper layers request establishment of an RRC connection while the UE is in RRC_IDLE and it has acquired essential system information, or for sidelink communication as specified in clause 5.3.3.1a.

The UE shall ensure having valid and up to date essential system information as specified in clause 5.2.2.2 before initiating this procedure.

Upon initiation of the procedure, the UE shall:

1> if the upper layers provide an Access Category and one or more Access Identities upon requesting establishment of an RRC connection:

2> perform the unified access control procedure as specified in 5.3.14 using the Access Category and Access Identities provided by upper layers;

3> if the access attempt is barred, the procedure ends;

1> if the UE is acting as L2 U2N Remote UE:

2> establish a SRAP entity as specified in TS 38.351 [66], if no SRAP entity has been established;

2> apply the specified configuration of SL-RLC0 as specified in 9.1.1.4;

2> apply the SDAP configuration and PDCP configuration as specified in 9.1.1.2 for SRB0;

1> else:

2> apply the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1;

2> apply the default MAC Cell Group configuration as specified in 9.2.2;

2> apply the CCCH configuration as specified in 9.1.1.2;

2> apply the timeAlignmentTimerCommon included in SIB1;

1> start timer T300;

1> initiate transmission of the RRCSetupRequest message in accordance with 5.3.3.3;

5.3.3.3 Actions related to transmission of RRCSetupRequest message

The UE shall set the contents of RRCSetupRequest message as follows:

1> set the ue-Identity as follows:

2> if upper layers provide a 5G-S-TMSI:

3> set the ue-Identity to ng-5G-S-TMSI-Part1;

2> else:

3> draw a 39-bit random value in the range 0..2³⁹-1 and set the ue-Identity to this value;

NOTE 1: Upper layers provide the 5G-S-TMSI if the UE is registered in the TA of the current cell.

1> if the establishment of the RRC connection is the result of release with redirect with mpsPriorityIndication (either in NR or E-UTRAN):

2> set the establishmentCause to mps-PriorityAccess;

1> else:

2> set the establishmentCause in accordance with the information received from upper layers;

NOTE 2: In case the L2 U2N Relay UE initiates RRC connection establishment triggered by reception of message from a L2 U2N Remote UE via SL-RLC0 or SL-RLC1 as specified in 5.3.3.1a, the L2 U2N Relay UE sets the establishmentCause by implementation, but it can only set the emergency, mps-PriorityAccess, or mcs-PriorityAccess as establishmentCause if the same cause value is in the message received from the L2 U2N Remote UE via SL-RLC0.

1> if ta-Report is configured with value enabled and the UE supports TA reporting:

2> indicate TA report initiation to lower layers;

The UE shall submit the RRCSetupRequest message to lower layers for transmission.

If the UE is a RedCap UE and the RedCap-specific initial downlink BWP is not associated with CD-SSB, the UE may continue cell re-selection related measurements as well as cell re-selection evaluation, otherwise the UE shall continue cell re-selection related measurements as well as cell re-selection evaluation. If the conditions for cell re-selection are fulfilled, the UE shall perform cell re-selection as specified in 5.3.3.6.

NOTE 3: For L2 U2N Remote UE in RRC_IDLE, the cell (re)selection procedure as specified in TS 38.304 [20] and relay (re)selection procedure as specified in 5.8.15.3 are performed independently and up to UE implementation to select either a cell or a L2 U2N Relay UE.

5.3.3.4 Reception of the RRCSetup by the UE

The UE shall perform the following actions upon reception of the RRCSetup:

1> if the RRCSetup is received in response to an RRCReestablishmentRequest; or

1> if the RRCSetup is received in response to an RRCResumeRequest or RRCResumeRequest1:

2> if sdt-MAC-PHY-CG-Config is configured:

3> instruct the MAC entity to stop the cg-SDT-TimeAlignmentTimer, if it is running;

3> instruct the MAC entity to start the timeAlignmentTimer associated with the PTAG, if it is not running;

2> if srs-PosRRC-InactiveConfig is configured:

3> instruct the MAC entity to stop the inactivePosSRS-TimeAlignmentTimer, if it is running;

2> discard any stored UE Inactive AS context and suspendConfig;

2> discard any current AS security context including the K_RRCenc key, the K_RRCint key, the K_UPint key and the K_UPenc key;

2> release radio resources for all established RBs except SRB0 and broadcast MRBs, including release of the RLC entities, of the associated PDCP entities and of SDAP;

2> release the RRC configuration except for the default L1 parameter values, default MAC Cell Group configuration, CCCH configuration and broadcast MRBs;

2> indicate to upper layers fallback of the RRC connection;

2> discard any application layer measurement reports which were not transmitted yet;

2> inform upper layers about the release of all application layer measurement configurations;

2> stop timer T380, if running;

1> perform the cell group configuration procedure in accordance with the received masterCellGroup and as specified in 5.3.5.5;

1> perform the radio bearer configuration procedure in accordance with the received radioBearerConfig and as specified in 5.3.5.6;

1> if stored, discard the cell reselection priority information provided by the cellReselectionPriorities or inherited from another RAT;

1> stop timer T300, T301, T319;

1> if T319a is running:

2> stop T319a;

2> consider SDT procedure is not ongoing;

1> if T390 is running:

2> stop timer T390 for all access categories;

2> perform the actions as specified in 5.3.14.4;

1> if T302 is running:

2> stop timer T302;

2> perform the actions as specified in 5.3.14.4;

1> stop timer T320, if running;

1> if the RRCSetup is received in response to an RRCResumeRequest, RRCResumeRequest1 or RRCSetupRequest:

2> if T331 is running:

3> stop timer T331;

3> perform the actions as specified in 5.7.8.3;

2> enter RRC_CONNECTED;

2> stop the cell re-selection procedure;

2> stop relay (re)selection procedure if any for L2 U2N Remote UE;

1> consider the current cell to be the PCell;

1> perform the L2 U2N Remote UE configuration procedure in accordance with the received sl-L2RemoteUE-Config as specified in 5.3.5.16;

1> perform the sidelink dedicated configuration procedure in accordance with the received sl-ConfigDedicatedNR as specified in 5.3.5.14;

1> if the UE has radio link failure or handover failure information available in VarRLF-Report and if the RPLMN is included in plmn-IdentityList stored in VarRLF-Report:

2> if reconnectCellId in VarRLF-Report is not set, and if the received RRCSetup is in response to an RRCSetupRequest:

3> if the UE supports RLF-Report for conditional handover and if choCellId in VarRLF-Report is set:

4> set timeUntilReconnection in VarRLF-Report to the time that elapsed since the radio link failure or handover failure experienced in the failedPCellId stored in VarRLF-Report;

3> else:

4> set timeUntilReconnection in VarRLF-Report to the time that elapsed since the last radio link failure or handover failure;

3> set nrReconnectCellId in reconnectCellId in VarRLF-Report to the global cell identity and the tracking area code of the PCell;

1> if the UE supports RLF report for inter-RAT MRO NR as defined in TS 36.306 [62], and if the UE has radio link failure or handover failure information available in VarRLF-Report of TS 36.331 [10] and if the RPLMN is included in plmn-IdentityList stored in VarRLF-Report of TS 36.331 [10]:

2> if reconnectCellId in VarRLF-Report of TS 36.331[10] is not set:

3> set timeUntilReconnection in VarRLF-Report of TS 36.331[10] to the time that elapsed since the last radio link failure or handover failure in LTE;

3> set nrReconnectCellId in reconnectCellId in VarRLF-Report of TS 36.331[10] to the global cell identity and the tracking area code of the PCell;

1> set the content of RRCSetupComplete message as follows:

2> if upper layers provide a 5G-S-TMSI:

3> if the RRCSetup is received in response to an RRCSetupRequest:

4> set the ng-5G-S-TMSI-Value to ng-5G-S-TMSI-Part2;

3> else:

4> set the ng-5G-S-TMSI-Value to ng-5G-S-TMSI;

2> if upper layers selected an SNPN or a PLMN and in case of PLMN UE is either allowed or instructed to access the PLMN via a cell for which at least one CAG ID is broadcast:

3> set the selectedPLMN-Identity from the npn-IdentityInfoList;

2> else:

3> set the selectedPLMN-Identity to the PLMN selected by upper layers from the plmn-IdentityInfoList;

2> if upper layers provide the ‘Registered AMF’:

3> include and set the registeredAMF as follows:

4> if the PLMN identity of the ‘Registered AMF’ is different from the PLMN selected by the upper layers:

5> include the plmnIdentity in the registeredAMF and set it to the value of the PLMN identity in the ‘Registered AMF’ received from upper layers;

4> set the amf-Identifier to the value received from upper layers;

3> include and set the guami-Type to the value provided by the upper layers;

2> if upper layers provide one or more S-NSSAI (see TS 23.003 [21]):

3> include the s-NSSAI-List and set the content to the values provided by the upper layers;

2> if upper layers provide onboarding request indication:

3> include the onboardingRequest;

2> set the dedicatedNAS-Message to include the information received from upper layers;

2> if connecting as an IAB-node:

3> include the iab-NodeIndication;

2> if the SIB1 contains idleModeMeasurementsNR and the UE has NR idle/inactive measurement information concerning cells other than the PCell available in VarMeasIdleReport; or

2> if the SIB1 contains idleModeMeasurementsEUTRA and the UE has E-UTRA idle/inactive measurement information available in VarMeasIdleReport:

3> include the idleMeasAvailable;

2> if the UE has logged measurements available for NR and if the RPLMN is included in plmn-IdentityList stored in VarLogMeasReport:

3> include the logMeasAvailable in the RRCSetupComplete message;

3> if Bluetooth measurement results are included in the logged measurements the UE has available for NR:

4> include the logMeasAvailableBT in the RRCSetupComplete message;

3> if WLAN measurement results are included in the logged measurements the UE has available for NR:

4> include the logMeasAvailableWLAN in the RRCSetupComplete message;

2> if the sigLoggedMeasType in VarLogMeasReport is included:

3> if T330 timer is running and the logged measurements configuration is for NR:

4> set sigLogMeasConfigAvailable to true in the RRCSetupComplete message;

3> else:

4> if the UE has logged measurements available for NR:

5> set sigLogMeasConfigAvailable to false in the RRCSetupComplete message;

2> if the UE has connection establishment failure or connection resume failure information available in VarConnEstFailReport or VarConnEstFailReportList and if the RPLMN is equal to plmn-Identity stored in VarConnEstFailReport or in at least one of the entries of VarConnEstFailReportList:

3> include connEstFailInfoAvailable in the RRCSetupComplete message;

2> if the UE has radio link failure or handover failure information available in VarRLF-Report and if the RPLMN is included in plmn-IdentityList stored in VarRLF-Report, or

2> if the UE has radio link failure or handover failure information available in VarRLF-Report of TS 36.331 [10], and if the UE is capable of cross-RAT RLF reporting and if the RPLMN is included in plmn-IdentityList stored in VarRLF-Report of TS 36.331 [10]:

3> include rlf-InfoAvailable in the RRCSetupComplete message;

2> if the UE has successful handover information available in VarSuccessHO-Report and if the RPLMN is included in plmn-IdentityList stored in VarSuccessHO-Report:

3> include successHO-InfoAvailable in the RRCSetupComplete message;

2> if the UE supports storage of mobility history information and the UE has mobility history information available in VarMobilityHistoryReport:

3> include the mobilityHistoryAvail in the RRCSetupComplete message;

2> if the UE supports uplink RRC message segmentation of UECapabilityInformation:

3> may include the ul-RRC-Segmentation in the RRCSetupComplete message;

2> if the RRCSetup is received in response to an RRCResumeRequest, RRCResumeRequest1 or RRCSetupRequest:

3> if speedStateReselectionPars is configured in the SIB2:

4> include the mobilityState in the RRCSetupComplete message and set it to the mobility state (as specified in TS 38.304 [20]) of the UE just prior to entering RRC_CONNECTED state;

1> submit the RRCSetupComplete message to lower layers for transmission, upon which the procedure ends.

5.3.3.5 Reception of the RRCReject by the UE

The UE shall:

1> perform the actions as specified in 5.3.15;

5.3.3.6 Cell re-selection or cell selection or relay (re)selection while T390, T300 or T302 is running (UE in RRC_IDLE)

The UE shall:

1> if cell reselection occurs while T300 or T302 is running; or

1> if relay reselection occurs while T300 is running; or

1> if cell changes due to relay reselection while T302 is running:

2> perform the actions upon going to RRC_IDLE as specified in 5.3.11 with release cause ‘RRC connection failure’;

1> else:

2> if cell selection or reselection occurs while T390 is running; or

2> cell change due to relay selection or reselection occurs while T390 is running:

3> stop T390 for all access categories;

3> perform the actions as specified in 5.3.14.4.

5.3.3.7 T300 expiry

The UE shall:

1> if timer T300 expires:

2> reset MAC, release the MAC configuration and re-establish RLC for all RBs that are established;

2> if the UE supports RRC Connection Establishment failure with temporary offset and the T300 has expired a consecutive connEstFailCount times on the same cell for which connEstFailureControl is included in SIB1:

3> for a period as indicated by connEstFailOffsetValidity:

4> use connEstFailOffset for the parameter Qoffsettemp for the concerned cell when performing cell selection and reselection according to TS 38.304 [20] and TS 36.304 [27];

NOTE 1: When performing cell selection, if no suitable or acceptable cell can be found, it is up to UE implementation whether to stop using connEstFailOffset for the parameter Qoffsettemp during connEstFailOffsetValidity for the concerned cell.

2> if the UE supports multiple CEF report:

3> if the UE has connection establishment failure information or connection resume failure information available in VarConnEstFailReport and if the RPLMN is equal to plmn-identity stored in VarConnEstFailReport; and

3> if the cell identity of current cell is not equal to the cell identity stored in measResultFailedCell in VarConnEstFailReport and if the maxCEFReport-r17 has not been reached:

4> append the VarConnEstFailReport as a new entry in the VarConnEstFailReportList;

2> if the UE has connection establishment failure information or connection resume failure information available in VarConnEstFailReport and if the RPLMN is not equal to plmn-identity stored in VarConnEstFailReport; or

2> if the cell identity of current cell is not equal to the cell identity stored in measResultFailedCell in VarConnEstFailReport:

3> reset the numberOfConnFail to 0;

2> if the UE supports multiple CEF report and if the UE has connection establishment failure informatoin or connection resume failure information available in VarConnEstFailReportList and if the RPLMN is not equal to plmn-identity stored in any entry of VarConnEstFailReportList:

3> clear the content included in VarConnEstFailReportList;

2> clear the content included in VarConnEstFailReport except for the numberOfConnFail, if any;

2> store the following connection establishment failure information in the VarConnEstFailReport by setting its fields as follows:

3> set the plmn-Identity to the PLMN selected by upper layers (see TS 24.501 [23]) from the PLMN(s) included in the plmn-IdentityInfoList in SIB1;

3> set the measResultFailedCell to include the global cell identity, tracking area code, the cell level and SS/PBCH block level RSRP, and RSRQ, and SS/PBCH block indexes, of the failed cell based on the available SSB measurements collected up to the moment the UE detected connection establishment failure;

3> if available, set the measResultNeighCells, in order of decreasing ranking-criterion as used for cell re-selection, to include neighbouring cell measurements for at most the following number of neighbouring cells: 6 intra-frequency and 3 inter-frequency neighbours per frequency as well as 3 inter-RAT neighbours, per frequency/ set of frequencies per RAT and according to the following:

4> for each neighbour cell included, include the optional fields that are available;

NOTE 2: The UE includes the latest results of the available measurements as used for cell reselection evaluation, which are performed in accordance with the performance requirements as specified in TS 38.133 [14].

3> if available, set the locationInfo as follows:

4> if available, set the commonLocationInfo to include the detailed location information;

4> if available, set the bt-LocationInfo to include the Bluetooth measurement results, in order of decreasing RSSI for Bluetooth beacons;

4> if available, set the wlan-LocationInfo to include the WLAN measurement results, in order of decreasing RSSI for WLAN APs;

4> if available, set the sensor-LocationInfo to include the sensor measurement results as follows;

5> if available, include the sensor-MeasurementInformation;

5> if available, include the sensor-MotionInformation;

NOTE 3: Which location information related configuration is used by the UE to make the locationInfo available for inclusion in the VarConnEstFailReport is left to UE implementation.

3> set perRAInfoList to indicate the performed random access procedure related information as specified in 5.7.10.5;

3> if the numberOfConnFail is smaller than 8:

4> increment the numberOfConnFail by 1;

2> inform upper layers about the failure to establish the RRC connection, upon which the procedure ends;

The UE may discard the connection establishment failure or connection resume failure information, i.e. release the UE variable VarConnEstFailReport, 48 hours after the last connection establishment failure is detected.

The L2 U2N Relay UE either indicates to upper layers (to trigger PC5 unicast link release) or sends Notification message to the connected L2 U2N Remote UE(s) in accordance with 5.8.9.10.

5.3.3.8 Abortion of RRC connection establishment

If upper layers abort the RRC connection establishment procedure, due to a NAS procedure being aborted as specified in TS 24.501 [23], while the UE has not yet entered RRC_CONNECTED, the UE shall:

1> stop timer T300, if running;

1> reset MAC, release the MAC configuration and re-establish RLC for all RBs that are established.