5G NR: SIB1


5G NR system information in general is discussed in detail in the post 5G NR:System Information. This post discusses SIB1 in detail.
System Information (SI) in NR consists of a MIB and a number of SIBs, which are divided into Minimum SI and Other SI.
Minimum SI carries basic information required for initial access and for acquiring any other SI. Minimum SI consists of MIB and SIB1. For a UE to be allowed to camp on a cell, it must have acquired the contents of the Minimum SI from that cell.
As MIB and SIB1 are called as ‘minimum SI’, SIB1 alone is known as ‘Remaining Minimum System Information’ (RMSI).
SIB1 carries the most critical information required for the UE to access the cell e.g., random access parameters.
SIB1 includes information regarding the availability and scheduling of other SIBs e.g. mapping of SIBs to SI message, periodicity, SI-window size etc…
SIB1 also indicates whether one or more SIBs are only provided on-demand, in which case, it may also provide PRACH configuration needed by the UE to request for the required SI.
SIB1 also contains radio resource configuration information that is common for all UEs and cell barring information applied to the unified access control.
SIB1 is transmitted on the DL-SCH (logical channel: BCCH) with a periodicity of 160 ms and variable transmission repetition periodicity within 160 ms.
SIB1 is cell-specific SIB.
In order for the UE to decode SIB1, all the required information is obtained from MIB. Visit 5G NR: PBCH and MasterInformation Block (MIB).


Contests of SIB1
Overview of SIB1 contents presented below. Most of the SIB1 contents are discussed in detail in subsequent sections.
 SIB1

cellSelectionInfo

cellAccessRelatedInfo CellAccessRelatedInfo
connEstFailureControl ConnEstFailureControl
si-SchedulingInfo SI-SchedulingInfo
servingCellConfigCommon ServingCellConfigCommonSIB
ims-EmergencySupport ENUMERATED {true}
eCallOverIMS-Support ENUMERATED {true}
ue-TimersAndConstants UE-TimersAndConstants
uac-BarringInfo UAC-BarringInfo
useFullResumeID ENUMERATED {true}

cellSelectionInfo
The following table summarizes cellSelectionInfo fields.
cellSelectionInfo


q-RxLevMin Q-RxLevMin INTEGER (-70 … -22)
q-RxLevMinOffset INTEGER (1 … 8)

q-RxLevMinSUL Q-RxLevMin INTEGER (-70 … -22)
q-QualMin Q-QualMin INTEGER (-43 … -12)
q-QualMinOffset INTEGER (1 … 8)


Q-RxLevMin is used to indicate the required ‘minimum received RSRP level’ (in dBm) in the (NR) cell for cell selection and re-selection. Actual value Qrxlevmin = field value * 2 [dBm]. Refer to 38.304 cell selection/re-selection criterion.
q-RxLevMinOffset is an offset (in dB) that needs to be added to the signaled (not actual) value of Qrxlevmin. This is taken into account in the Srxlev evaluation (38.304) after a periodic search for a higher priority PLMN while the UE is camped normally on a VPLMN. If this field is absent, the UE applies a (default) value of 0 dB as an offset.
Q-RxLevMinSUL: If the UE supports SUL frequency for this cell, Qrxlevmin (explained above) is obtained from this field. Actual value Qrxlevmin = field value * 2 [dBm].
Q-QualMin is used to indicate the required ‘minimum received RSRQ level’ (in dB) in the (NR) cell for cell selection and re-selection. If this field is absent, the UE applies the (default) value of negative infinity for Qqualmin which means that quality (RSRQ) check will always pass irrespective of the received signal quality. Refer to 38.304 cell selection/re-selection criterion.
q-QualMinOffset is an offset (in dB) that needs to be added to the signaled value of Qqualmin. This is taken into account in the Squal evaluation (38.304) after a periodic search for a higher priority PLMN while the UE is camped normally on a VPLMN. If this field is absent, the UE applies a (default) value of 0 dB as an offset.
CellAccessRelatedInfo
CellAccessRelatedInfo is used to indicate cell access related information for the serving cell. The following table summarizes CellAccessRelatedInfo contents.
CellAccessRelatedInfo

plmn-IdentityList List of 1 to 12 PLMN-IdentityInfo
cellReservedForOtherUse ENUMERATED {true}

cellReservedForOtherUse indicates whether the cell is reserved. The field is applicable to all PLMNs. If a cell is reserved, camping is not allowed except for particular UEs.
plmn-IdentityList used to configure a set of PLMN-IdentityInfoList elements. Each of those elements contains a list of one or more PLMN identities and additional information associated with those PLMNs such as TAC, RANAC, cellIdentity etc...
PLMN-IdentityInfo
plmn-IdentityList  List of 1 to 12 PLMN-Identity (s)

trackingAreaCode TrackingAreaCode  BIT STRING (SIZE (24))
ranac RAN-AreaCode INTEGER (0 … 255)
cellIdentity CellIdentity BIT STRING (SIZE (36))
cellReservedForOperatorUse ENUMERATED {reserved,notReserved} 


cellReservedForOperatorUse indicates whether the cell is reserved for operator use (per PLMN). If a cell is reserved, camping is not allowed except for particular UEs.
plmn-IdentityList within PLMN-IdentityInfo indicates a list of PLMN identities, each of those is identified by an MCC and an MNC.
trackingAreaCode indicates Tracking Area Code to which the cell indicated by cellIdentity belongs to. It is used to identify a tracking area within the scope of a PLMN. The absence of the field indicates that the cell only supports PSCell/SCell functionality (per PLMN). At acquisition of SIB1, UE considers a cell as barred if the trackingAreaCode (per PLMN) is not present.
RAN-AreaCode is used to identify a RAN area within the scope of a Tracking Area. RAN area code is used when configuring RAN Notification Area. When a UE in RRC_INACTIVE state reselects to a new cell that belongs to a different RAN Notification area, the UE needs to perform RNA update.
CellIdentity is used to unambiguously identify a cell within a PLMN.
ConnEstFailureControl
ConnEstFailureControl is used to configure parameters for connection establishment failure control. When an RRCSetupRequest is sent by the UE, timer T300 is started and the UE considers the connection establishment attempt as failed if it doesn’t receive a response from the gNB before T300 expires.
If the timer T300 expires connEstFailCount times, then the UE starts a timer given by connEstFailOffsetValidity and reduces RSRP/RSRQ quality by connEstFailOffset parameter Qoffsettemp in 38.304) when performing cell selection/re-selection. Basically, for a period of time given by connEstFailOffsetValidity, the UE makes the cell a bit worse by adding a negative offset to Srxlev and Squal. The following table summarizes ConnEstFailureControl fields.
ConnEstFailureControl

connEstFailCount ENUMERATED {n1, n2, n3, n4} 
connEstFailOffsetValidity ENUMERATED {s30, s60, s120, s240, s300, s420, s600, s900}
connEstFailOffset INTEGER (0..15)

connEstFailCount is number of times that the UE detects T300 expiry on the same cell before applying connEstFailOffset.
connEstFailOffset is the parameter Qoffsettemp in 38.304. If this field is absent, the value of infinity shall be used for Qoffsettemp.
connEstFailOffsetValidity is the amount of time (in seconds) that the UE applies connEstFailOffset before removing the offset from evaluation of the cell.
SI-SchedulingInfo
SI-SchedulingInfo contains information needed for acquisition of SI messages. SI scheduling procedure is thoroughly discussed in the post 5G NR: SystemInformation. The following table summarizes SI-SchedulingInfo contents.
SI-SchedulingInfo

schedulingInfoList List of 1 to 32 SchedulingInfo
si-WindowLength ENUMERATED {s5, s10, s20, s40, s80, s160, s320, s640, s1280}
si-RequestConfig SI-RequestConfig
si-RequestConfigSUL SI-RequestConfig
systemInformationAreaID BIT STRING (SIZE (24))

si-WindowLength is the length of the SI scheduling window in slots. Value s5 corresponds to 5 slots, value s10 corresponds to 10 slots and so on. The network always configures si-WindowLength to be shorter than or equal to the si-Periodicity.
systemInformationAreaID indicates the system information area that the cell belongs to, if any. Any SIB with areaScope within the SI is considered to belong to this systemInformationAreaID. The systemInformationAreaID is unique within a PLMN.
Schedulinginfolist contains a list of scheduling information (maximum 32) for SI-messages. SchedulingInfo provides information whether the corresponding SI-message is being broadcasted or not, periodicity of SI-message and a list of SIBs mapped to this SI-message. For each SIB, SIB type, valueTag, areaScope flag are provided. areaScope indicates whether the SIB is area specific or not.
si-RequestConfig is the configuration of Msg1 resources that the UE uses for requesting SI-messages for which si-BroadcastStatus is set to notBroadcasting. If the field is absent the UE uses Msg3 to request SI-messages. The IE si- RequestConfigSUL is the corresponding configuration on SUL. The table below provides overview of SI-RequestConfig.
SI-RequestConfig
rach-ConfigSI RACH-ConfigGeneric
ssb-perRACH-Occasion ENUMERATED {oneEighth, oneFourth, oneHalf, one, two, four, eight, sixteen}
si-RequestPeriod ENUMERATED {one, two, four, six, eight, ten, twelve, sixteen}
si-RequestResources List of 1 to 32 SI-RequestResources
RACH-ConfigGeneric
prach-ConfigurationIndex INTEGER (0..255)
msg1-FDM ENUMERATED {one, two, four, eight}
msg1-FrequencyStart INTEGER (0..maxNrofPhysicalResourceBlocks-1) => INTEGER (0..274)
zeroCorrelationZoneConfig INTEGER (0..15)
preambleReceivedTargetPower INTEGER (-202 .. -60)
preambleTransMax ENUMERATED {n3, n4, n5, n6, n7, n8, n10, n20, n50, n100, n200}
powerRampingStep ENUMERATED {dB0, dB2, dB4, dB6}
ra-ResponseWindow ENUMERATED {sl1, sl2, sl4, sl8, sl10, sl20, sl40, sl80}
SI-RequestResources
ra-PreambleStartIndex INTEGER (0..63)
ra-AssociationPeriodIndex INTEGER (0..15)
ra-AssociationPeriodIndex INTEGER (0..15)

The table below provides overview of SchedulingInfo.
SchedulingInfo
si-BroadcastStatus ENUMERATED {broadcasting, notBroadcasting}
si-Periodicity ENUMERATED {rf8, rf16, rf32, rf64, rf128, rf256, rf512}
sib-MappingInfo List of 1 to 32 SIB-TypeInfo
SIB-TypeInfo
type ENUMERATED {sibType2, sibType3, … ,sibType9, spare8, spare7, …, spare1}
valueTag INTEGER (0..31)
areaScope ENUMERATED {true} 


ServingCellConfigCommonSIB
The IE ServingCellConfigCommonSIB is used to configure cell specific parameters of a UE's serving cell in SIB1. The contents of this IE are given in the below table.
ServingCellConfigCommonSIB

downlinkConfigCommon DownlinkConfigCommonSIB
uplinkConfigCommon UplinkConfigCommonSIB
supplementaryUplink UplinkConfigCommonSIB
n-TimingAdvanceOffset ENUMERATED {n0, n25600, n39936}
ssb-PositionsInBurst inOneGroup                      BIT STRING (SIZE (8))
groupPresence                  BIT STRING (SIZE (8))
ssb-PeriodicityServingCell ENUMERATED {ms5, ms10, ms20, ms40, ms80, ms160}
tdd-UL-DL-ConfigurationCommon TDD-UL-DL-ConfigCommon 
ss-PBCH-BlockPower INTEGER (-60 .. 50)

DownlinkConfigCommonSIB: As show in the following table, this IE provides common downlink parameters of a cell.
DownlinkConfigCommonSIB
frequencyInfoDL FrequencyInfoDL-SIB
initialDownlinkBWP  BWP-DownlinkCommon
bcch-Config modificationPeriodCoeff            ENUMERATED {n2, n4, n8, n16}
pcch-Config PCCH-Config

The IE FrequencyInfoDL-SIB provides basic parameters of a downlink carrier and transmission thereon. As shown in the below table, it consists of offsetToPointA, frequencyBandList which is a list of one or multiple frequency bands to which this carrier(s) belongs, scs-SpecificCarrierList which is set of carriers for different SCSs (numerologies) defined in relation to Point A.
FrequencyInfoDL-SIB
frequencyBandList MultiFrequencyBandListNR-SIB
offsetToPointA INTEGER (0 … 2199)
scs-SpecificCarrierList List of 1 to 5 SCS-SpecificCarrier
SCS-SpecificCarrier
offsetToCarrier INTEGER (0 … 2199)
subcarrierSpacing ENUMERATED {kHz15, kHz30, kHz60, kHz120, kHz240, spare3, spare2, spare1}
carrierBandwidth INTEGER (1 … 275)

The IE initialDownlinkBWP is used to configure the common parameters of initial downlink BWP. As shown in the below table, it contains cell specific PDCCH and PDSCH parameters of this BWP. PDCCH/PDSCH common parameters and IE BWP. The IE BWP is used to configure generic parameters for this BWP such as frequency domain location and bandwidth, SCS to be used, and an indication whether to use the extended CP.
BWP-DownlinkCommon
genericParameters BWP
pdcch-ConfigCommon SetupRelease { PDCCH-ConfigCommon }
pdsch-ConfigCommon SetupRelease { PDSCH-ConfigCommon }
BWP
locationAndBandwidth INTEGER (0 … 37949)
subcarrierSpacing ENUMERATED {kHz15, kHz30, kHz60, kHz120, kHz240, spare3, spare2, spare1}
cyclicPrefix ENUMERATED {extended}

-    bcch-config provides system information modification period related configuration. Actual modification period (in no. of radio frames) m = modificationPeriodCoeff * defaultPagingCycle.
-    pcch-config provides paging related configuration.
UplinkConfigCommonSIB: As show in the following table, this IE provides common uplink parameters of a cell.
UplinkConfigCommonSIB

frequencyInfoUL FrequencyInfoUL-SIB
initialUplinkBWP  BWP-UplinkCommon
timeAlignmentTimerCommon TimeAlignmentTimer

The IE FrequencyInfoUL-SIB provides basic parameters of a uplink carrier and transmission thereon. As shown in the below table, it consists of the following fields.
FrequencyInfoUL-SIB
frequencyBandList MultiFrequencyBandListNR-SIB
absoluteFrequencyPointA INTEGER (0 … 3279165)
scs-SpecificCarrierList List of 1 to 5 SCS-SpecificCarrier
p-Max P-Max
frequencyShift7p5khz ENUMERATED {true}
SCS-SpecificCarrier
offsetToCarrier INTEGER (0 … 2199)
subcarrierSpacing ENUMERATED {kHz15, kHz30, kHz60, kHz120, kHz240, spare3, spare2, spare1}
carrierBandwidth INTEGER (1 … 275)

-    frequencyBandList provides the frequency band indicator and a list of additionalPmax and additionalSpectrumEmission values.
-    absoluteFrequencyPointA is the absolute frequency of the reference resource block (CRB 0). Its lowest subcarrier is also known as Point A.
-    frequencyShift7p5khz enables the NR UL transmission with a 7.5 kHz shift to the LTE raster. If the field is absent, the frequency shift is disabled.
-    p-Max is the max value in dBm applicable for the cell. If this field is absent, the UE applies the maximum power according to TS 38.101-1.
-    scs-SpecificCarrierList is a set of carriers for different SCSs (numerologies), defined in relation to Point A. The network configures this for all SCSs that are used in UL BWPs configured in this serving cell.
The IE initialUplinkBWP is used to configure the common parameters of initial uplink BWP. As shown in the below table, it contains cell specific RACH, PUCCH and PUSCH parameters of this BWP. It contains PUCCH/PUSCH/RACH common parameters and IE BWP. The IE BWP is used to configure generic parameters for this BWP such as frequency domain location and bandwidth, SCS to be used, and an indication whether to use the extended CP.
BWP-UplinkCommon
genericParameters BWP
rach-ConfigCommon SetupRelease { RACH-ConfigCommon }
pusch-ConfigCommon SetupRelease { PUSCH-ConfigCommon }
pucch-ConfigCommon SetupRelease { PUCCH-ConfigCommon }
BWP
locationAndBandwidth INTEGER (0 … 37949)
subcarrierSpacing ENUMERATED {kHz15, kHz30, kHz60, kHz120, kHz240, spare3, spare2, spare1}
cyclicPrefix ENUMERATED {extended}

n-TimingAdvanceOffset: Value of N_TA-Offset to be applied for random access on this serving cell. If this field is absent, the UE applies the value defined for the duplex mode and frequency range of this serving cell according to Table 7.1.2-2 from 38.133.
ssb-PositionsInBurst defines time domain positions of the transmitted SSBs in an SS-burst set. ssb-PeriodicityServingCell configures the UEs with SSB periodicity. For more information, refer to 5GNR: Synchronization Signal/PBCH block (SSB)
tdd-UL-DL-ConfigurationCommon defines cell-specific TDD UL/DL configuration (shown in the table below). For more details see section 11.1 from 38.213.
TDD-UL-DL-ConfigCommon

referenceSubcarrierSpacing SubcarrierSpacing
pattern1 TDD-UL-DL-Pattern
pattern2 TDD-UL-DL-Pattern

referenceSubcarrierSpacing configures reference SCS and is used to determine the time domain boundaries in the UL-DL pattern which must be common across all subcarrier specific carriers, i.e., independent of the actual subcarrier spacing using for data transmission. Only the values 15, 30 or 60 kHz (FR1), and 60 or 120 kHz (FR2) are applicable.
TDD-UL-DL-Pattern provides the following configuration;
TDD-UL-DL-Pattern

dl-UL-TransmissionPeriodicity ENUMERATED {ms0p5, ms0p625, ms1, ms1p25, ms2, ms2p5, ms5, ms10}
nrofDownlinkSlots INTEGER (0 … maxNrofSlots) INTEGER (0 … 320)
nrofDownlinkSymbols INTEGER (0 … maxNrofSymbols-1) INTEGER (0 … 13)
nrofUplinkSlots INTEGER (0 … maxNrofSlots) INTEGER (0 … 320)
nrofUplinkSymbols INTEGER (0 … maxNrofSymbols-1) INTEGER (0 … 13)
dl-UL-TransmissionPeriodicity-v1530 ENUMERATED {ms3, ms4}


-    dl-UL-TransmissionPeriodicity: provides slot configuration periodicity i.e., periodicity of the DL-UL pattern. If the dl-UL-TransmissionPeriodicity-v1530 is signalled, UE shall ignore this field.
-    nrofDownlinkSlots: Number of consecutive full DL slots at the beginning of each DL-UL pattern. In release 15.7, the maximum value for this field is 80.
-    nrofDownlinkSymbols: Number of consecutive DL symbols in the beginning of the slot following the last full DL slot (as derived from nrofDownlinkSlots). The value 0 indicates that there is no partial- downlink slot.
-    nrofUplinkSlots: Number of consecutive full UL slots at the end of each DL-UL pattern. In release 15.7, the maximum value for this field is 80.
-    nrofUplinkSymbols: Number of consecutive UL symbols in the end of the slot preceding the first full UL slot (as derived from nrofUplinkSlots). The value 0 indicates that there is no partial-uplink slot.
ss-PBCH-BlockPower provides average EPRE of the resources elements that carry SSS (in dBm) that the NW used for SSB transmission.
ims-EmergencySupport: 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: Indicates whether the cell supports emergency call over IMS services.
UE-TimersAndConstants: This IE contains timers and constants used by the UE in RRC_CONNECTED, RRC_INACTIVE and RRC_IDLE. The table below summarizes different timers and constants from 38.331. Check section 7.1.1 from 38.331 for the purpose of the different timers and constants.
UE-TimersAndConstants
t300 ENUMERATED {ms100, ms200, ms300, ms400, ms600, ms1000, ms1500, ms2000}
t301 ENUMERATED {ms100, ms200, ms300, ms400, ms600, ms1000, ms1500, ms2000}
t310 ENUMERATED {ms0, ms50, ms100, ms200, ms500, ms1000, ms2000}
n310 ENUMERATED {n1, n2, n3, n4, n6, n8, n10, n20}
t311 ENUMERATED {ms1000, ms3000, ms5000, ms10000, ms15000, ms20000, ms30000}
n311 ENUMERATED {n1, n2, n3, n4, n5, n6, n8, n10}
t319 ENUMERATED {ms100, ms200, ms300, ms400, ms600, ms1000, ms1500, ms2000}
uac-BarringInfo contains information (shown below) about cell barring based upon Unified Access Barring (UAC).
uac-BarringInfo

uac-BarringForCommon UAC-BarringPerCatList

uac-BarringPerPLMN-List UAC-BarringPerPLMN-List

uac-BarringInfoSetList UAC-BarringInfoSetList

uac-AccessCategory1-

SelectionAssistanceInfo
plmnCommon UAC-AccessCategory1-SelectionAssistanceInfo
individualPLMNList List of 2 to 12 of UAC-AccessCategory1-SelectionAssistanceInfo

useFullResumeID: Indicates which resume identifier and Resume request message should be used when UE wants to transit to connected state from inactive state. The UE uses fullI-RNTI and RRCResumeRequest1 if the field is present, or shortI-RNTI and RRCResumeRequest if the field is absent. For more information, visit 5G NR: UE RRC States and StateTransitions.
Reference: 3GPP TS 38.331, 38.304. 38.213 and 38.300