CG-Config

inter-node RRC message · TS 38.331 v19.4.0 (2026-09) · clause 11.2.2

CG-Config is an inter-node RRC message of 3GPP TS 38.331 (38331), the 5G NR Radio Resource Control (RRC) protocol.

First seen v15.1.0 (2018-04) · Last changed v19.3.0 (2026-06), in CG-Config-v1900-IEs

Definition

This message is used to transfer the SCG radio configuration as generated by the SgNB or SeNB. It can also be used by a CU to request a DU to perform certain actions, e.g. to request the DU to perform a new lower layer configuration.

CG-Config ::=                   SEQUENCE {
    criticalExtensions                  CHOICE {
        c1                                  CHOICE{
            cg-Config                           CG-Config-IEs,
            spare3 NULL, spare2 NULL, spare1 NULL
        },
        criticalExtensionsFuture            SEQUENCE {}
    }
}

Candidate change requests of v19.3.0

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

CR 5777 r1 (strong): Corrections on UE based TA measurement ID in the INM

Fields (7)

Field	Description
criticalExtensions CHOICE {
c1 CHOICE{
cg-Config CG-Config-IEs
spare3 NULL
spare2 NULL
spare1 NULL
criticalExtensionsFuture SEQUENCE {}

Fields of CG-Config-IEs (10)

Field	Description
scg-CellGroupConfig OCTET STRING (CONTAINING RRCReconfiguration) · OPTIONAL	Contains the RRCReconfiguration message (containing only secondaryCellGroup and/or measConfig and/or otherConfig and/or appLayerMeasConfig and/or conditionalReconfiguration , ltm-Config , and/or bap-Config and/or iab-IP-AddressConfigurationList ): - to be sent to the UE, used upon SCG establishment or modification (only when the SCG is not released by the SN), as generated (entirely) by the (target) SgNB. In this case, the SN sets the RRCReconfiguration message in accordance with clause 6 e.g. regarding the "Need" or "Cond" statements. or - including the current SCG configuration of the UE, when provided in response to a query from MN, or in SN triggered SN change in order to enable delta signaling by the target SN, or in SN triggered modification procedure in order to coordinate CHO or MN-initiated CPC with SCG reconfigurations (see TS 38.423 [35]). In this case, the SN sets the RRCReconfiguration message in accordance with clause 11.2.3. The field is absent if neither SCG (re)configuration nor SCG configuration query nor SN triggered modification procedure in order to coordinate CHO or MN-initiated CPC with SCG reconfigurations (see TS 38.423 [35]) nor SN triggered SN change is performed, e.g. at inter-node capability/configuration coordination which does not result in SCG (re)configuration towards the UE. The field is also absent upon an SCG release triggered by the SN. This field is not applicable in NE-DC.
scg-RB-Config OCTET STRING (CONTAINING RadioBearerConfig) · OPTIONAL	Contains the IE RadioBearerConfig : - to be sent to the UE, used to (re-)configure the SCG RB configuration upon SCG establishment or modification, as generated (entirely) by the (target) SgNB or SeNB. In this case, the SN sets the RadioBearerConfig in accordance with clause 6, e.g. regarding the "Need" or "Cond" statements. or - including the current SCG RB configuration of the UE, when provided in response to a query from MN or in SN triggered SN change or in SN triggered SN release or bearer type change between SN terminated bearer to MN terminated bearer in order to enable delta signaling by the MN or target SN. In this case, the SN sets the RadioBearerConfig in accordance with clause 11.2.3. The field is absent if neither SCG (re)configuration nor SCG configuration query nor SN triggered SN change nor SN triggered SN release is performed, e.g. at inter-node capability/configuration coordination which does not result in SCG RB (re)configuration.
configRestrictModReq ConfigRestrictModReqSCG · OPTIONAL	Used by SN to request changes to SCG configuration restrictions previously set by MN to ensure UE capabilities are respected and to indicate the configured/reserved SCG resources. E.g. can be used to request configuring an NR band combination whose use MN has previously forbidden. SN only includes this field in SN-initiated procedures unless this field is used to indicate configured/reserved SCG resources (corresponding to reservedResourceConfigNRDC and/or aggregatedBandwidthSN ) only.
drx-InfoSCG DRX-Info · OPTIONAL	This field contains the DRX long and short cycle configuration of the SCG. This field is used in (NG)EN-DC and NE-DC.
candidateCellInfoListSN OCTET STRING (CONTAINING MeasResultList2NR) · OPTIONAL	Contains information regarding cells that the source secondary node suggests the target secondary gNB to consider configuring.
measConfigSN MeasConfigSN · OPTIONAL
selectedBandCombination BandCombinationInfoSN · OPTIONAL since v15.6.0	Indicates the band combination selected by SN in (NG)EN-DC, NE-DC, and NR-DC. The SN should inform the MN with this field whenever the band combination and/or feature set it selected for the SCG changes (i.e. even if the new selection concerns a band combination and/or feature set that is allowed by the allowedBC-ListMRDC )
fr-InfoListSCG FR-InfoList · OPTIONAL since v15.2.0	Contains information of FR information of serving cells that include PScell and SCells configured in SCG.
candidateServingFreqListNR CandidateServingFreqListNR · OPTIONAL since v15.3.0	Indicates frequencies of candidate serving cells for In-Device Co-existence Indication (see TS 36.331 [10]).
nonCriticalExtension CG-Config-v1540-IEs · OPTIONAL

Fields of CG-Config-v1540-IEs (7)

Field	Description
pSCellFrequency ARFCN-ValueNR · OPTIONAL since v15.4.0	Indicates the frequency of PSCell in NR (i.e., pSCellFrequency ) or E-UTRA (i.e., pSCellFrequencyEUTRA ). In this version of the specification, pSCellFrequency is not used in NE-DC whereas pSCellFrequencyEUTRA is only used in NE-DC. pSCellFrequency indicates the absoluteFrequencySSB .
reportCGI-RequestNR SEQUENCE { · OPTIONAL since v15.6.0	Used by SN to indicate to MN about configuring reportCGI procedure. The request may optionally contain information about the cell for which SN intends to configure reportCGI procedure. In this version of the specification, the reportCGI-RequestNR is used in (NG)EN-DC and NR-DC whereas reportCGI-RequestEUTRA is used only for NE-DC.
requestedCellInfo SEQUENCE { · OPTIONAL since v15.6.0
ssbFrequency ARFCN-ValueNR since v15.6.0
cellForWhichToReportCGI PhysCellId since v15.6.0
ph-InfoSCG PH-TypeListSCG · OPTIONAL since v15.4.0	Power headroom information in SCG that is needed in the reception of PHR MAC CE of MCG
nonCriticalExtension CG-Config-v1560-IEs · OPTIONAL since v15.4.0

Fields of CG-Config-v1560-IEs (11)

Field	Description
pSCellFrequencyEUTRA ARFCN-ValueEUTRA · OPTIONAL since v15.6.0	Indicates the frequency of PSCell in NR (i.e., pSCellFrequency ) or E-UTRA (i.e., pSCellFrequencyEUTRA ). In this version of the specification, pSCellFrequency is not used in NE-DC whereas pSCellFrequencyEUTRA is only used in NE-DC. pSCellFrequency indicates the absoluteFrequencySSB .
scg-CellGroupConfigEUTRA OCTET STRING · OPTIONAL since v15.6.0	Includes the E-UTRA RRCConnectionReconfiguration message as specified in TS 36.331 [10]. In this version of the specification, the E-UTRA RRC message can only include the field scg-Configuration : - to be sent to the UE, used to (re-)configure the SCG configuration upon SCG establishment or modification (only when the SCG is not released by the SN), as generated (entirely) by the (target) SeNB. In this case, the SN sets the scg-Configuration within the EUTRA RRCConnectionReconfiguration message in accordance with clause 6 in TS 36.331 [10] e.g. regarding the "Need" or "Cond" statements. or - including the current SCG configuration of the UE, when provided in response to a query from MN, or in SN triggered SN change in order to enable delta signalling by the target SN. The field is absent if neither SCG (re)configuration nor SCG configuration query nor SN triggered SN change is performed, e.g. at inter-node capability/configuration coordination which does not result in SCG (re)configuration towards the UE. The field is also absent upon an SCG release triggered by the SN. This field is only used in NE-DC.
candidateCellInfoListSN-EUTRA OCTET STRING · OPTIONAL since v15.6.0	Includes the MeasResultList3EUTRA as specified in TS 36.331 [10]. Contains information regarding cells that the source secondary node suggests the target secondary eNB to consider configuring. This field is only used in NE-DC.
candidateServingFreqListEUTRA CandidateServingFreqListEUTRA · OPTIONAL since v15.6.0	Indicates frequencies of candidate serving cells for In-Device Co-existence Indication (see TS 36.331 [10]).
needForGaps ENUMERATED {true} · OPTIONAL since v15.6.0	In NE-DC, indicates whether the SN requests gNB to configure measurements gaps.
drx-ConfigSCG DRX-Config · OPTIONAL since v15.6.0	This field contains the complete DRX configuration of the SCG. This field is only used in NR-DC.
reportCGI-RequestEUTRA SEQUENCE { · OPTIONAL since v15.6.0	Used by SN to indicate to MN about configuring reportCGI procedure. The request may optionally contain information about the cell for which SN intends to configure reportCGI procedure. In this version of the specification, the reportCGI-RequestNR is used in (NG)EN-DC and NR-DC whereas reportCGI-RequestEUTRA is used only for NE-DC.
requestedCellInfoEUTRA SEQUENCE { · OPTIONAL since v15.6.0
eutraFrequency ARFCN-ValueEUTRA since v15.6.0
cellForWhichToReportCGI-EUTRA EUTRA-PhysCellId since v15.6.0
nonCriticalExtension CG-Config-v1590-IEs · OPTIONAL since v15.6.0

Fields of CG-Config-v1590-IEs (3)

Field	Description
scellFrequenciesSN-NR SEQUENCE (SIZE (1.. maxNrofServingCells-1)) OF ARFCN-ValueNR · OPTIONAL since v15.9.0	Indicates the frequency of all SCells with SSB configured in SCG. The field scellFrequenciesSN-EUTRA is used in NE-DC; the field scellFrequenciesSN-NR is used in (NG)EN-DC and NR-DC. In (NG)EN-DC, the field is optionally provided to the MN. scellFrequenciesSN-NR indicates absoluteFrequencySSB .
scellFrequenciesSN-EUTRA SEQUENCE (SIZE (1.. maxNrofServingCells-1)) OF ARFCN-ValueEUTRA · OPTIONAL since v15.9.0	Indicates the frequency of all SCells with SSB configured in SCG. The field scellFrequenciesSN-EUTRA is used in NE-DC; the field scellFrequenciesSN-NR is used in (NG)EN-DC and NR-DC. In (NG)EN-DC, the field is optionally provided to the MN. scellFrequenciesSN-NR indicates absoluteFrequencySSB .
nonCriticalExtension CG-Config-v1610-IEs · OPTIONAL since v15.9.0

Fields of CG-Config-v1610-IEs (2)

Field	Description
drx-InfoSCG2 DRX-Info2 · OPTIONAL since v16.1.0	This field contains the drx-onDurationTimer configuration of the SCG. This field is only used in (NG)EN-DC.
nonCriticalExtension CG-Config-v1620-IEs · OPTIONAL since v16.1.0

Fields of CG-Config-v1620-IEs (2)

Field	Description
ueAssistanceInformationSCG-r16 OCTET STRING (CONTAINING UEAssistanceInformation) · OPTIONAL since v16.2.0	Includes for each UE assistance feature associated with the SCG, the information last reported by the UE in the NR UEAssistanceInformation message for the SCG, if any.
nonCriticalExtension CG-Config-v1630-IEs · OPTIONAL since v16.2.0

Fields of CG-Config-v1630-IEs (2)

Field	Description
selectedToffset-r16 T-Offset-r16 · OPTIONAL since v16.3.0	Indicates the value used by the SN for scheduling SCG transmissions (i.e. $T_{proc,SCG}^{max},$ see TS 38.213 [13]). This field is used in NR-DC only when the fields nrdc-PC-mode-FR1-r16 or nrdc-PC-mode-FR2-r16 are set to dynamic. The SN can only indicate a value that is less than or equal to maxToffset received from MN. This field is used in NR-DC only when MN has included the field maxToffset in CG-ConfigInfo. Value ms0dot5 corresponds to 0.5 ms, value ms0dot75 corresponds to 0.75 ms, value ms1 corresponds to 1ms and so on.
nonCriticalExtension CG-Config-v1640-IEs · OPTIONAL since v16.3.0

Field

Description

selectedToffset-r16

T-Offset-r16 · OPTIONAL

since v16.3.0

Indicates the value used by the SN for scheduling SCG transmissions (i.e. $T_{proc,SCG}^{max},$ see TS 38.213 [13]). This field is used in NR-DC only when the fields nrdc-PC-mode-FR1-r16 or nrdc-PC-mode-FR2-r16 are set to dynamic. The SN can only indicate a value that is less than or equal to maxToffset received from MN. This field is used in NR-DC only when MN has included the field maxToffset in CG-ConfigInfo. Value ms0dot5 corresponds to 0.5 ms, value ms0dot75 corresponds to 0.75 ms, value ms1 corresponds to 1ms and so on.

nonCriticalExtension

CG-Config-v1640-IEs · OPTIONAL

since v16.3.0

Fields of CG-Config-v1640-IEs (3)

Field	Description
servCellInfoListSCG-NR-r16 ServCellInfoListSCG-NR-r16 · OPTIONAL since v16.4.1	Indicates the frequency band indicator, carrier center frequency, UE specific channel bandwidth and SCS of the serving cell(s) in the SCG in intra-band (NG)EN-DC. The field is needed when MN and SN operate serving cells in the same band for either contiguous or non-contiguous intra-band band combination or LTE NR inter-band band combinations where the frequency range of the E-UTRA band is a subset of the frequency range of the NR band (as specified in Table 5.5B.4.1-1 of TS 38.101-3 [34]) in (NG)EN-DC.
servCellInfoListSCG-EUTRA-r16 ServCellInfoListSCG-EUTRA-r16 · OPTIONAL since v16.4.1	Indicates the carrier frequency and the transmission bandwidth of the serving cell(s) in the SCG in intra-band NE-DC. The field is needed when MN and SN operate serving cells in the same band for either contiguous or non-contiguous intra-band band combination or LTE NR inter-band band combinations where the frequency range of the E-UTRA band is a subset of the frequency range of the NR band (as specified in Table 5.5B.4.1-1 of TS 38.101-3 [34]) in NE-DC.
nonCriticalExtension CG-Config-v1700-IEs · OPTIONAL since v16.4.1

Fields of CG-Config-v1700-IEs (3)

Field	Description
candidateCellInfoListCPC-r17 CandidateCellInfoListCPC-r17 · OPTIONAL since v17.0.0	Contains information regarding candidate target cells for Conditional PSCell Change (CPC) or inter-SN subsequent CPAC that the source secondary gNB suggests the target secondary gNB to consider configuring for CPC or subsequent CPAC, and/or that the source secondary gNB prepares for intra-SN subsequent CPAC configuration(s) which are delivered embedded within an RRC message generated by the MN. This field is only used in SN initiated CPC and SN initiated subsequent CPAC.
twoPHRModeSCG-r17 ENUMERATED {enabled} · OPTIONAL since v17.1.0	Indicates if the power headroom for SCG shall be reported as two PHRs (each PHR associated with a SRS resource set) is enabled or not.
nonCriticalExtension CG-Config-v1730-IEs · OPTIONAL since v17.0.0

Fields of CG-Config-v1730-IEs (3)

Field	Description
fr1-Carriers-SCG-r17 INTEGER (1..32) · OPTIONAL since v17.3.0	Indicates the number of FR1 or FR2 serving cells configured in SCG.
fr2-Carriers-SCG-r17 INTEGER (1..32) · OPTIONAL since v17.3.0	Indicates the number of FR1 or FR2 serving cells configured in SCG.
nonCriticalExtension CG-Config-v1800-IEs · OPTIONAL since v17.3.0

Fields of CG-Config-v1800-IEs (8)

Field	Description
candidateServingFreqRangeListNR-r18 CandidateServingFreqRangeListNR-r18 · OPTIONAL since v18.0.0	Indicates the candidate frequency ranges configured by SN for IDC. This field is only used in NR-DC.
candidateServingFreqListNR-r18 CandidateServingFreqListNR-r16 · OPTIONAL since v18.6.0	Indicates the candidate frequencies configured by SN for IDC. This field is only used in NR-DC.
idc-TDM-AssistanceConfig-r18 ENUMERATED {enabled} · OPTIONAL since v18.0.0	Indicates if the IDC TDM reporting is enabled for the UE by SN. This field is only used in NR-DC.
candidateCellInfoListSubsequentCPC-r18 CandidateCellInfoListCPC-r17 · OPTIONAL since v18.0.0	Contains information regarding candidate target cells for subsequent CPAC that candidate secondary gNB (or the serving secondary gNB in case of intra-SN subsequent CPAC configuration(s) which are delivered embedded within an RRC message generated by the MN) suggests the master gNB to consider configuring for subsequent CPAC. This field is only used in MN initiated and SN initiated subsequent CPAC. This field is only included in a CG-Config message which is contained within a CG-CandidateList message.
scpac-ReferenceConfigurationSCG-r18 ReferenceConfiguration-r18 · OPTIONAL since v18.0.0	Includes the reference configuration associated with the SCG for the candidate supporting subsequent CPAC.
subsequentCPAC-Information-r18 CandidateCellInfoListCPC-r17 · OPTIONAL since v18.1.0	Contains information about handling of stored subsequent CPAC configurations for the UE that the target secondary gNB suggests the master gNB to consider configuring for normal PSCell addition or change. It includes information about updates of execution conditions for the subsequent CPAC configurations that are to be kept at the PSCell addition/change.
successPSCell-Config-r18 SuccessPSCell-Config-r18 · OPTIONAL since v18.1.0	Include the successful PSCell change or addition report configuration in case of SN initiated PSCell change or CPC. The thresholdPercentageT304-SCG is not configured in this message.
nonCriticalExtension CG-Config-v1900-IEs · OPTIONAL since v18.0.0

Fields of CG-Config-v1900-IEs (3)

Field	Description
ltm-ReferenceConfigurationSCG-r19 ReferenceConfiguration-r18 · OPTIONAL since v19.0.0	The field contains the LTM reference configuration to be used at the SCG. This field is only used in NR-DC.
dummy INTEGER (1..maxNrofLTM-Configs-plus1-r18) · OPTIONAL since v19.3.0	This field is not used in the specification and MN ignores the received value.
nonCriticalExtension SEQUENCE {} · OPTIONAL since v19.0.0