SIB1

RRC message · TS 38.331 v19.4.0 (2026-09) · clause 6.2.2

SIB1 is an RRC message of 3GPP TS 38.331 (38331), the 5G NR Radio Resource Control (RRC) protocol.

First seen v15.0.0 (2018-01) · Last changed v18.4.0 (2024-12), in SIB1-v1800-IEs

Definition

SIB1 contains information relevant when evaluating if a UE is allowed to access a cell and defines the scheduling of other system information. It also contains radio resource configuration information that is common for all UEs and barring information applied to the unified access control.

SIB1 ::=        SEQUENCE {
    cellSelectionInfo                   SEQUENCE {
        q-RxLevMin                          Q-RxLevMin,
        q-RxLevMinOffset                    INTEGER (1..8)                                              OPTIONAL,   -- Need S
        q-RxLevMinSUL                       Q-RxLevMin                                                  OPTIONAL,   -- Need R
        q-QualMin                           Q-QualMin                                                   OPTIONAL,   -- Need S
        q-QualMinOffset                     INTEGER (1..8)                                              OPTIONAL    -- Need S
    }                                                                                                   OPTIONAL,   -- Cond Standalone
    cellAccessRelatedInfo               CellAccessRelatedInfo,
    connEstFailureControl               ConnEstFailureControl                                           OPTIONAL,   -- Need R
    si-SchedulingInfo                   SI-SchedulingInfo                                               OPTIONAL,   -- Need R
    servingCellConfigCommon             ServingCellConfigCommonSIB                                      OPTIONAL,   -- Need R
    ims-EmergencySupport                ENUMERATED {true}                                               OPTIONAL,   -- Need R
    eCallOverIMS-Support                ENUMERATED {true}                                               OPTIONAL,   -- Need R
    ue-TimersAndConstants               UE-TimersAndConstants                                           OPTIONAL,   -- Need R
    uac-BarringInfo                     SEQUENCE {
        uac-BarringForCommon                UAC-BarringPerCatList                                           OPTIONAL,   -- Need S
        uac-BarringPerPLMN-List             UAC-BarringPerPLMN-List                                         OPTIONAL,   -- Need S
        uac-BarringInfoSetList              UAC-BarringInfoSetList,
        uac-AccessCategory1-SelectionAssistanceInfo CHOICE {
            plmnCommon                           UAC-AccessCategory1-SelectionAssistanceInfo,
            individualPLMNList                   SEQUENCE (SIZE (2..maxPLMN)) OF UAC-AccessCategory1-SelectionAssistanceInfo
        }                                                                                                   OPTIONAL    -- Need S
    }                                                                                                   OPTIONAL,   -- Need R
    useFullResumeID                     ENUMERATED {true}                                               OPTIONAL,   -- Need R
    lateNonCriticalExtension            OCTET STRING                                                    OPTIONAL,
    nonCriticalExtension                SIB1-v1610-IEs                                                  OPTIONAL
}

Candidate change requests of v18.4.0

The CRs whose title or cover names this change, strong and likely matches only.

CR 5112 r1 (strong): Clarifications on cell barring behaviour [2Rx_XR_Device] [EM_Call_Exemption]
CR 5149 r2 (strong): Correction on Band Selection and Cell Barring for Aerial UEs

Fields (23)

Field	Description
cellSelectionInfo SEQUENCE { · OPTIONAL Cond Standalone since v15.3.0	Parameters for cell selection related to the serving cell.
q-RxLevMin Q-RxLevMin since v15.3.0	Parameter "Q rxlevmin " in TS 38.304 [20], applicable for serving cell.
q-RxLevMinOffset INTEGER (1..8) · OPTIONAL Need S since v15.3.0	Parameter "Q rxlevminoffset " in TS 38.304 [20]. Actual value Q rxlevminoffset = field value 2 [dB]. If absent, the UE applies the (default) value of 0 dB for Q rxlevminoffset . Affects the minimum required Rx level in the cell.
q-RxLevMinSUL Q-RxLevMin · OPTIONAL Need R since v15.3.0	Parameter "Q rxlevmin " in TS 38.304 [20], applicable for serving cell.
q-QualMin Q-QualMin · OPTIONAL Need S since v15.3.0	Parameter "Q qualmin " in TS 38.304 [20], applicable for serving cell. If the field is absent, the UE applies the (default) value of negative infinity for Q qualmin .
q-QualMinOffset INTEGER (1..8) · OPTIONAL Need S since v15.3.0	Parameter "Q qualminoffset " in TS 38.304 [20]. Actual value Q qualminoffset = field value [dB]. If the field is absent, the UE applies the (default) value of 0 dB for Q qualminoffset . Affects the minimum required quality level in the cell.
cellAccessRelatedInfo CellAccessRelatedInfo since v15.3.0
connEstFailureControl ConnEstFailureControl · OPTIONAL Need R since v15.3.0
si-SchedulingInfo SI-SchedulingInfo · OPTIONAL Need R since v15.3.0
servingCellConfigCommon ServingCellConfigCommonSIB · OPTIONAL Need R since v15.3.0	Configuration of the serving cell.
ims-EmergencySupport ENUMERATED {true} · OPTIONAL Need R since v15.3.0	Indicates whether the cell supports IMS emergency bearer services for UEs in limited service mode. If absent, IMS emergency call is not supported by the network in the cell for UEs in limited service mode.
eCallOverIMS-Support ENUMERATED {true} · OPTIONAL Need R since v15.3.0	Indicates whether the cell supports eCall over IMS services as defined in TS 23.501 [32]. If absent, eCall over IMS is not supported by the network in the cell.
ue-TimersAndConstants UE-TimersAndConstants · OPTIONAL Need R since v15.3.0	Timer and constant values to be used by the UE. The cell operating as PCell always provides this field.
uac-BarringInfo SEQUENCE { · OPTIONAL Need R since v15.3.0
uac-BarringForCommon UAC-BarringPerCatList · OPTIONAL Need S since v15.3.0	Common access control parameters for each access category. Common values are used for all PLMNs/SNPNs, unless overwritten by the PLMN/SNPN specific configuration provided in uac-BarringPerPLMN-List . The parameters are specified by providing an index to the set of configurations ( uac-BarringInfoSetList ). UE behaviour upon absence of this field is specified in clause 5.3.14.2.
uac-BarringPerPLMN-List UAC-BarringPerPLMN-List · OPTIONAL Need S since v15.3.0
uac-BarringInfoSetList UAC-BarringInfoSetList since v15.3.0
uac-AccessCategory1-SelectionAssistanceInfo CHOICE { · OPTIONAL Need S since v15.3.0	Information used to determine whether Access Category 1 applies to the UE, as defined in TS 22.261 [25]. If plmnCommon is chosen, the UAC-AccessCategory1-SelectionAssistanceInfo is applicable to all the PLMNs and SNPNs in plmn-IdentityInfoList and npn-IdentityInfoList . If individualPLMNList is chosen, the 1 st entry in the list corresponds to the first network within all of the PLMNs and SNPNs across the plmn-IdentityList and the npn-IdentityInfoList , the 2 nd entry in the list corresponds to the second network within all of the PLMNs and SNPNs across the plmn-IdentityList and the npn-IdentityInfoList and so on. If uac-AC1-SelectAssistInfo-r16 is present, the UE shall ignore the uac-AccessCategory1-SelectionAssistanceInfo .
plmnCommon UAC-AccessCategory1-SelectionAssistanceInfo since v15.3.0
individualPLMNList SEQUENCE (SIZE (2..maxPLMN)) OF UAC-AccessCategory1-SelectionAssistanceInfo since v15.3.0
useFullResumeID ENUMERATED {true} · OPTIONAL Need R since v15.3.0	Indicates which resume identifier and Resume request message should be used. UE uses fullI-RNTI and RRCResumeRequest1 if the field is present, or shortI-RNTI and RRCResumeRequest if the field is absent.
lateNonCriticalExtension OCTET STRING · OPTIONAL since v15.1.0
nonCriticalExtension SIB1-v1610-IEs · OPTIONAL since v15.1.0

Fields of SIB1-v1610-IEs (4)

Field	Description
idleModeMeasurementsEUTRA-r16 ENUMERATED{true} · OPTIONAL Need R since v16.1.0	This field indicates that a UE that is configured for EUTRA idle/inactive measurements shall perform the measurements while camping in this cell and report availability of these measurements when establishing or resuming a connection in this cell. If absent, a UE is not required to perform EUTRA idle/inactive measurements.
idleModeMeasurementsNR-r16 ENUMERATED{true} · OPTIONAL Need R since v16.1.0	This field indicates that a UE that is configured for NR idle/inactive measurements shall perform the measurements while camping in this cell and report availability of these measurements when establishing or resuming a connection in this cell. If absent, a UE is not required to perform NR idle/inactive measurements.
posSI-SchedulingInfo-r16 PosSI-SchedulingInfo-r16 · OPTIONAL Need R since v16.1.0
nonCriticalExtension SIB1-v1630-IEs · OPTIONAL since v16.1.0

Fields of SIB1-v1630-IEs (3)

Field	Description
uac-BarringInfo-v1630 SEQUENCE { · OPTIONAL Need R since v16.3.0
uac-AC1-SelectAssistInfo-r16 SEQUENCE (SIZE (2..maxPLMN)) OF UAC-AC1-SelectAssistInfo-r16 since v16.3.0	Information used to determine whether Access Category 1 applies to the UE, as defined in TS 22.261 [25]. The 1 st entry in the list corresponds to the first network within all of the PLMNs and SNPNs across the plmn-IdentityList and npn-IdentityInfoList , the 2 nd entry in the list corresponds to the second network within all of the PLMNs and SNPNs across the plmn-IdentityList and the npn-IdentityInfoList and so on. Value notConfigured indicates that Access Category1 is not configured for the corresponding PLMN/SNPN.
nonCriticalExtension SIB1-v1700-IEs · OPTIONAL since v16.3.0

Fields of SIB1-v1700-IEs (17)

Field	Description
hsdn-Cell-r17 ENUMERATED {true} · OPTIONAL Need R since v17.0.0	This field indicates this is a HSDN cell as specified in TS 38.304 [20].
uac-BarringInfo-v1700 SEQUENCE { · OPTIONAL Cond MINT since v17.0.0
uac-BarringInfoSetList-v1700 UAC-BarringInfoSetList-v1700 since v17.0.0
sdt-ConfigCommon-r17 SDT-ConfigCommonSIB-r17 · OPTIONAL Need R since v17.0.0
redCap-ConfigCommon-r17 RedCap-ConfigCommonSIB-r17 · OPTIONAL Need R since v17.1.0
featurePriorities-r17 SEQUENCE { · OPTIONAL Need R since v17.0.0	Indicates priorities for features, such as (e)RedCap, Slicing, SDT, MSG1-Repetitions and MSG3-Repetitions for Coverage Enhancements. These priorities are used to determine which FeatureCombinationPreambles the UE shall use when a feature maps to more than one FeatureCombinationPreambles , as specified in TS 38.321 [3]. A lower value means a higher priority. The network does not signal the same priority for more than one feature. The network signals a priority for all feature that map to at least one FeatureCombinationPreambles .
redCapPriority-r17 FeaturePriority-r17 · OPTIONAL Need R since v17.0.0
slicingPriority-r17 FeaturePriority-r17 · OPTIONAL Need R since v17.0.0
msg3-Repetitions-Priority-r17 FeaturePriority-r17 · OPTIONAL Need R since v17.1.0
sdt-Priority-r17 FeaturePriority-r17 · OPTIONAL Need R since v17.0.0
si-SchedulingInfo-v1700 SI-SchedulingInfo-v1700 · OPTIONAL Need R since v17.0.0
hyperSFN-r17 BIT STRING (SIZE (10)) · OPTIONAL Need R since v17.0.0	Indicates hyper SFN which increments by one when the SFN wraps around. This field is excluded when determining changes in system information, i.e. changes of hyper SFN should not result in system information change notifications.
eDRX-AllowedIdle-r17 ENUMERATED {true} · OPTIONAL Need R since v17.1.0	The presence of this field indicates that extended DRX for CN paging is allowed in the cell for UEs in RRC_IDLE or RRC_INACTIVE. The UE shall stop using extended DRX for CN paging in RRC_IDLE or RRC_INACTIVE if eDRX-AllowedIdle is not present.
eDRX-AllowedInactive-r17 ENUMERATED {true} · OPTIONAL Cond EDRX-RC since v17.1.0	The presence of eDRX-AllowedInactive-r17 indicates that extended DRX cycle equal to or shorter than 10.24 s for RAN paging is allowed in the cell for UEs in RRC_INACTIVE. The UE shall stop using extended DRX cycle equal to or shorter than 10.24 s for RAN paging in RRC_INACTIVE if eDRX-AllowedInactive-r17 is not present. The presence of eDRX-AllowedInactive-r18 indicates that extended DRX cycle longer than 10.24 s for RAN paging is allowed in the cell for UEs in RRC_INACTIVE. The UE shall stop using extended DRX cycle longer than 10.24 s for RAN paging in RRC_INACTIVE if eDRX-AllowedInactive-r18 is not present.
intraFreqReselectionRedCap-r17 ENUMERATED {allowed, notAllowed} · OPTIONAL Need S since v17.0.0	Controls cell selection/reselection to intra-frequency cells for RedCap UEs when this cell is barred, or treated as barred by the RedCap UE, as specified in TS 38.304 [20]. If not present, a RedCap UE treats the cell as barred, i.e.,the UE considers that the cell does not support RedCap.
cellBarredNTN-r17 ENUMERATED {barred, notBarred} · OPTIONAL Need S since v17.1.0	Value barred means that the cell is barred for connectivity to NTN, as defined in TS 38.304 [20]. Value notBarred means that the cell is allowed for connectivity to NTN. If not present, the UE considers the cell is not allowed for connectivity to NTN, as defined in TS 38.304 [20]. This field is only applicable to NTN-capable UEs. In an NTN cell, the network always includes cellBarredNTN and sets the cellBarred in MIB to barred .
nonCriticalExtension SIB1-v1740-IEs · OPTIONAL since v17.0.0

Fields of SIB1-v1740-IEs (2)

Field	Description
si-SchedulingInfo-v1740 SI-SchedulingInfo-v1740 · OPTIONAL Need R since v17.4.0
nonCriticalExtension SIB1-v1800-IEs · OPTIONAL since v17.4.0

Fields of SIB1-v1800-IEs (23)

Field	Description
ncr-Support-r18 ENUMERATED {true} · OPTIONAL Need S since v18.0.0	This field combines both the support of NCR and the cell status for NCR. If the field is present, the cell supports NCR and the cell is also considered as a candidate for cell (re)selection for NCR-node; if the field is absent, the cell does not support NCR and/or the cell is barred for NCR-node.
mt-SDT-ConfigCommonSIB-r18 MT-SDT-ConfigCommonSIB-r18 · OPTIONAL Need R since v18.0.0
musim-CapRestrictionAllowed-r18 ENUMERATED {true} · OPTIONAL Need R since v18.0.0	Indicates the UE is allowed to send the musim-CapRestrictionInd in RRCSetupComplete , RRCResumeComplete and RRCReestablishmentComplete messages.
featurePriorities-v1800 SEQUENCE { · OPTIONAL Need R since v18.0.0	Indicates priorities for features, such as (e)RedCap, Slicing, SDT, MSG1-Repetitions and MSG3-Repetitions for Coverage Enhancements. These priorities are used to determine which FeatureCombinationPreambles the UE shall use when a feature maps to more than one FeatureCombinationPreambles , as specified in TS 38.321 [3]. A lower value means a higher priority. The network does not signal the same priority for more than one feature. The network signals a priority for all feature that map to at least one FeatureCombinationPreambles .
msg1-Repetitions-Priority-r18 FeaturePriority-r17 · OPTIONAL Need R since v18.0.0
eRedCapPriority-r18 FeaturePriority-r17 · OPTIONAL Need R since v18.0.0
si-SchedulingInfo-v1800 SI-SchedulingInfo-v1800 · OPTIONAL Need R since v18.0.0
cellBarredATG-r18 ENUMERATED {barred, notBarred} · OPTIONAL Need S since v18.0.0	Value barred means that the cell is barred for connectivity to ATG, as defined in TS 38.304 [20]. Value notBarred means that the cell is allowed for connectivity to ATG. If not present, the UE considers the cell is not allowed for connectivity to ATG, as defined in TS 38.304 [20]. This field is only applicable to ATG-capable UEs.
cellBarredNES-r18 ENUMERATED {notBarred} · OPTIONAL Need R since v18.0.0	This field indicates the cell barring status for UEs supporting nes-CellDTX-DRX on the selected frequency band as described in 5.2.2.4.2.
mobileIAB-Cell-r18 ENUMERATED {true} · OPTIONAL Need R since v18.0.0	The presence of this field indicates that this is a mobile IAB cell.
eDRX-AllowedInactive-r18 ENUMERATED {true} · OPTIONAL Cond EDRX-RC since v18.0.0	The presence of eDRX-AllowedInactive-r17 indicates that extended DRX cycle equal to or shorter than 10.24 s for RAN paging is allowed in the cell for UEs in RRC_INACTIVE. The UE shall stop using extended DRX cycle equal to or shorter than 10.24 s for RAN paging in RRC_INACTIVE if eDRX-AllowedInactive-r17 is not present. The presence of eDRX-AllowedInactive-r18 indicates that extended DRX cycle longer than 10.24 s for RAN paging is allowed in the cell for UEs in RRC_INACTIVE. The UE shall stop using extended DRX cycle longer than 10.24 s for RAN paging in RRC_INACTIVE if eDRX-AllowedInactive-r18 is not present.
intraFreqReselection-eRedCap-r18 ENUMERATED {allowed, notAllowed} · OPTIONAL Need S since v18.0.0	Controls cell selection/reselection to intra-frequency cells for eRedCap UEs when this cell is barred, or treated as barred by the eRedCap UE, as specified in TS 38.304 [20]. If not present, an eRedCap UE treats the cell as barred, i.e., the UE considers that the cell does not support eRedCap.
nonServingCellMII-r18 ENUMERATED {true} · OPTIONAL Need R since v18.0.0	Indicates whether the MBSInterestIndication message for MBS broadcast reception on a non-serving cell is allowed to be transmitted to the serving gNB.
sdt-BeamFailureRecoveryProhibitTimer-r18 ENUMERATED {ms50, ms100, ms200, ms500, ms1000, ms1500, ms2000, ms3000} · OPTIONAL Need R since v18.1.0	The value of the prohibit timer used for RACH for beam failure indication during SDT as specified in TS 38.321 [3]. Value ms50 corresponds to 50 milliseconds, value ms100 corresponds to 100 milliseconds and so on.
eRedCap-ConfigCommon-r18 ERedCap-ConfigCommonSIB-r18 · OPTIONAL Need R since v18.1.0
cellBarredFixedVSAT-r18 ENUMERATED {barred, notBarred} · OPTIONAL Cond NTN since v18.1.0	Value barred means that the cell is barred for fixed VSAT UEs, as defined in TS 38.304 [20]. If not present, the cell is not allowed for fixed VSAT UEs. This field is ignored by non-VSAT UEs.
cellBarredMobileVSAT-r18 ENUMERATED {barred, notBarred} · OPTIONAL Cond NTN since v18.1.0	Value barred means that the cell is barred for mobile VSAT UEs, as defined in TS 38.304 [20]. If not present, the cell is not allowed for mobile VSAT UEs. This field is ignored by non-VSAT UEs.
reselectionMeasurementsNR-r18 ENUMERATED{true} · OPTIONAL Need R since v18.1.0	This field indicates that a UE that is configured for NR reselection measurements shall report availability of these measurements when establishing or resuming a connection in this cell.
cellBarred2RxXR-r18 ENUMERATED {barred} · OPTIONAL Need R since v18.1.0	Value barred means that the cell is barred for a 2Rx XR UE indicating supportOf2RxXR for the selected frequency band as specified in clause 5.2.2.4.2. This field is ignored by all UEs not indicating supportOf2RxXR for the selected frequency band. This field may be configured only if the cell operates in a frequency band where 4Rx antenna ports are mandated as specified in TS 38.101-1 [15]. If this field is absent on a cell operating in a frequency band where 4RX antenna ports are mandated, a 2RX XR UE shall treat the cell as not barred, as specified in TS 38.304 [20].
intraFreqReselection2RxXR-r18 ENUMERATED {allowed, notAllowed} · OPTIONAL Cond 2RxXR since v18.1.0	This field controls cell selection/reselection to intra-frequency cells for 2Rx XR UEs when this cell is barred or treated as barred by the 2Rx XR UE, as specified in TS 38.304 [20]. This field is ignored by all UEs that are not 2Rx XR UEs. This field may be configured only if the cell operates in a frequency band where 4Rx antenna ports are mandated, as specified in TS 38.101-1 [15].
barringExemptEmergencyCall-r18 ENUMERATED {true} · OPTIONAL Cond EM-Barring since v18.2.0	Indicates whether the cell allows emergency bearer services for UEs who would otherwise consider the cell as barred as specified in TS 38.304 [20].
n3c-Support-r18 ENUMERATED {true} · OPTIONAL Need R since v18.2.0	This field indicates the support of N3C MP. If the field is present, the UE can perform early detection of candidate N3C relay UEs. If absent, a UE is not required to perform early detection of candidate N3C relay UEs.
nonCriticalExtension SEQUENCE {} · OPTIONAL since v18.0.0