SIB(System Information Block)

As the functionalities of LTE evolves and start interplay with other radio technologies (e.g, wlan, V2X, NR etc), the list of SIB is getting longer and longer. We first started with around 12 SIBs and now (as of Jan 2020. Release 15), the largest SIB Type number is SIB24. Followings are the whole SIB list as of now. This page is just a summary or point to each SIB with not much of the description, and I wrote separate notes for some SIBs that has critical functionalties. Follow the links in the description of each SIBs. Regarding how these SIBs are scheduled, refer to SIB scheduling page. Some of the SIBs are critical for the initial attach and should be detected/decoded before you attempt to attach to a cell. Often the contents of SIB get modified depending on the situation and UE should be able to get updated with the modified SIB based on SIB modification process.

SIB 1 : Cell Selection, Cell Access, SI Scheduling
SIB 2 : RACH, Access Barring, UL frequency Information, MBSFN Config
SIB 3 : Intra Frequency Cell Reselection
SIB 4 : Intra Frequency Neighbour Cell
SIB 5 : Inter Frequency Neighbour Cell
SIB 6 : UTRAN Neighbour Cell
SIB 7 : GERAN Neighbour Cell
SIB 8 : CDMA Neighbour Cell
SIB 9 : Home eNB Name for femtocell application
SIB 10/SIB11 : ETWS
SIB 12 : CMAS
SIB 14 : Extended Access Barring
SIB 13/SIB 15/SIB 20 : MBMS
SIB 16 : GPS
SIB 17 : WLAN
SIB 18/SIB 19/SIB 21 : Sidelink
SIB 24 : NR Neighbour Cell
SIB 25 - SIB 33 : UAC, V2X, EN-DC Band List, NR Sidelink, Resource Reservation, Disaster Roaming, NTN

The list kept growing after SIB24. In 36.331 v19.3.0 (Release 19), the largest LTE SIB type number is SIB33. SIB22 and SIB23 exist only as NB-IoT blocks, SIB22-NB and SIB23-NB, so the LTE list jumps from SIB21 to SIB24. I added one section at the end of this page for SIB25 to SIB33, and I brought the ASN.1 of SIB18 to SIB24 up to the same release.

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SIB 1

SIB1 is the first block the UE reads after the MIB. It tells the UE whether it may camp on the cell, and it tells the UE where every other SIB is. SIB1 uses a fixed schedule with an 80 ms period. The first transmission goes in subframe #5 of radio frames with SFN mod 8 = 0. The repetitions go in subframe #5 of all other radio frames with SFN mod 2 = 0. SIB1 also carries systemInfoValueTag. This tag covers most of the other SIBs, so a UE that sees an unchanged value can keep the SIBs it already stored.

: Cell Access Related Information - PLMN Identity List, PLMN Identity, TA Code, Cell identity & Cell Status

: Cell Selection Information - Minimum Receiver Level

: Scheduling Information - SI message type & Periodicity, SIB mapping Info, SI Window length

SIB 2

SIB2 carries the radio resource configuration that is common for all UEs. A UE needs it before it can send its first PRACH preamble, and the network always maps SIB2 to the first SI message in schedulingInfoList. Besides the items below, SIB2 also carries ue-TimersAndConstants, with T300, T301, T310, N310, T311 and N311, and timeAlignmentTimerCommon.

: Access Barring Information - Access Probability factor, Access Class Baring List, Access Class Baring Time

: Semi static Common Channel Configuration - Random Access Parameter, PRACH Configuration

: UL frequency Information - UL EARFCN, UL Bandwidth, additional emmission

: MBSFN Configuration

SIB 3

SIB3 holds the cell reselection parameters that are not tied to a list of neighbour cells. It has three groups. The first is cellReselectionInfoCommon, with q-Hyst and the speed state scaling. The second is cellReselectionServingFreqInfo, with s-NonIntraSearch, threshServingLow and the priority of the serving frequency. The third is intraFreqCellReselectionInfo, with q-RxLevMin, s-IntraSearch and t-ReselectionEUTRA. An idle UE compares its serving cell measurement with s-IntraSearch and s-NonIntraSearch to decide whether it needs to measure other cells.

: Information/Parameters for intra-frequency cell reselections

SIB 4

SIB4 lists the intra-frequency neighbour cells that need cell specific handling. A cell in intraFreqNeighCellList carries its physCellId and a q-OffsetCell. A cell in intraFreqExcludedCellList is a cell the UE does not reselect to. The UE does not need SIB4 to find neighbours on its own frequency, because it detects them from PSS and SSS.

: Information on intra-frequency neighboring cells

SIB 5

SIB5 describes the other E-UTRA carriers for inter-frequency reselection. Each entry in interFreqCarrierFreqList carries a dl-CarrierFreq, a cellReselectionPriority, threshX-High and threshX-Low. It can also carry per-cell offsets and an excluded cell list. Release 15 added measIdleConfigSIB-r15 for E-UTRA measurements in idle mode, and Release 16 added measIdleConfigSIB-NR-r16 for NR. The UE can report these measurements early, so the network can set up carrier aggregation or dual connectivity sooner.

: Information on inter-frequency neighboring cells

SIB 6

SIB6 is the UTRA counterpart of SIB5. It carries carrierFreqListUTRA-FDD and carrierFreqListUTRA-TDD, plus t-ReselectionUTRA. Each UTRA carrier in those lists has its own priority, threshX-High, threshX-Low and q-RxLevMin. The parameters are set per carrier, not per cell.

: Information for reselection to UMTS (UTRAN) cells

SIB 7

SIB7 does the same job for GERAN. It carries t-ReselectionGERAN and carrierFreqsInfoList. In that list, GERAN ARFCNs are grouped into sets, and each set shares one priority, one ncc-Permitted bitmap and one pair of thresholds.

: Information for reselection to GSM (GERAN) cells

SIB 8

SIB8 carries CDMA2000 information for both HRPD and 1xRTT. Besides the reselection parameters, it gives systemTimeInfo, which is the CDMA2000 system time. It also gives csfb-RegistrationParam1XRTT, which the UE uses to decide whether to perform a 1xRTT registration for CS fallback. A UE without CDMA2000 support has no use for this block.

: Information for reselection to CDMA2000 systems

SIB 9

SIB9 carries one useful field, hnb-Name. This is the name of the home eNB, coded in UTF-8 and up to 48 octets long. The UE can display the name, so the user can recognise a femtocell such as a CSG cell at home.

: Home eNodeB name – for future LTE femtocell applications

SIB 10 / SIB 11

SIB10 and SIB11 carry the ETWS warning. SIB10 is the primary notification, a short alert with messageIdentifier, serialNumber and warningType. SIB11 is the secondary notification, and it carries the warning text in up to 64 segments of warningMessageSegment. The network announces them with etws-Indication in a Paging message, and systemInfoValueTag does not cover them. Release 19 added warningAreaCoordinates-r19 to SIB10 and warningAreaCoordinatesSegment-r19 to SIB11.

: ETWS (Earthquake and Tsunami Warning System) information

SIB 12

SIB12 carries the CMAS warning. Like SIB11, it carries the warning text in segments, with a segment number and a last segment flag. The network announces it with cmas-Indication-r9 in a Paging message. Release 15 added warningAreaCoordinatesSegment-r15, which carries the geographical area where the warning applies.

: Commercial Mobile Alerting System (CMAS) information.

SIB 13

SIB13 tells the UE how to acquire the MCCH, the MBMS control channel, for one or more MBSFN areas. Each entry in mbsfn-AreaInfoList-r9 gives an MBSFN area ID and the MCCH repetition period, offset, modification period and subframe allocation. The field notificationConfig-r9 tells the UE where to look for the MCCH change notification.

: MBSFN (eMBMS) Area Configuration

: MCCH Configuration

SIB 14

SIB14 carries the Extended Access Barring parameters in eab-Param-r11. EAB lets the network bar the UEs configured for EAB, which are typically MTC devices, without barring ordinary users. The parameters can be common or per PLMN. The network announces a SIB14 change with eab-ParamModification-r11 in a Paging message, not through systemInfoValueTag.

: Extended Access Barring

SIB 15

SIB15 lists MBMS Service Area Identities, the SAIs, for the serving carrier and for neighbour carriers. A UE interested in an MBMS service compares these SAIs with the service it wants. In this way the UE can find the carrier that carries the service and prioritise that carrier during reselection.

: MBMS SAI (Service Area Identities) Configuration

SIB 16

SIB16 carries time information. It is GPS related because the UE can derive GPS time from it, but it carries no positioning data. The field timeInfoUTC counts UTC in 10 ms units since 1 January 1900. The count is referenced to the SFN boundary at or right after the end of the SI window that carries SIB16. The optional fields add daylight saving time, leap seconds and the local time offset.

: GPS Related Informatin

SIB 17

SIB17 supports traffic steering between E-UTRAN and WLAN. It carries wlan-OffloadInfoPerPLMN-List-r12, with one entry per PLMN in the same order as the PLMNs in SIB1. Each entry can carry offload thresholds and a list of WLAN identifiers.

: WLAN Configuration for LTE-WLAN Interworking

SIB 18

SIB18 enables Release 12 sidelink communication, the ProSe direct communication over PC5. Its presence tells the UE that the eNB supports the sidelink UE information procedure. The commConfig-r12 part gives the receive pools and the common transmit pools, and the Release 13 group adds relay related fields.

: Sidelink Information