SIB (System Information Block) in LTE

System Information Blocks (SIBs) are broadcast messages from the eNodeB to the UEs that contain essential information about the LTE system.

  • SIBs are transmitted on the Broadcast Channel (BCCH), which is a dedicated control channel that is always available. This ensures that UEs can always receive the latest system information, even if they are not actively connected to a cell.
  • SIBs are transmitted using the Physical Downlink Shared Channel (PDSCH), which is the same channel that is used to transmit data to UEs. This allows the eNodeB to transmit SIBs and data to UEs simultaneously, without having to switch between different channels.
  • The transmission schedule of SIBs is configurable, but there are some default settings that are typically used. SIB 1 is typically transmitted every 80 ms, SIB 2 is transmitted every 160 ms, and SIBs 3-5 are transmitted every 320 ms. These transmission schedules are designed to ensure that UEs receive all of the necessary system information in a timely manner.
  • SIBs are divided into two categories: static SIBs and dynamic SIBs. Static SIBs contain information that does not change frequently, such as the PLMN identity and cell identity. Dynamic SIBs contain information that may change frequently, such as the cell status and neighbour cell information.
  • Static SIBs are typically transmitted less frequently than dynamic SIBs. This is because the information in static SIBs is less likely to change. For example, the PLMN identity and cell identity are typically only changed when a new cell is added to the network or when an existing cell is removed.
  • Dynamic SIBs are typically transmitted more frequently than static SIBs. This is because the information in dynamic SIBs is more likely to change. For example, the cell status may change frequently due to changes in traffic load or interference conditions.
  • UEs are required to monitor the BCCH for SIBs. When a UE detects a new SIB, it stores the information in the SIB and updates its configuration accordingly. UEs also periodically check for updates to SIBs. This ensures that UEs always have the latest system information.
SIB 1Contains essential cell-specific information. Cell Selection, Cell Access, SI SchedulingIncludes cell identity, tracking area code, PLMN  for initial network connection.
SIB 2RACH, Access Barring, UL frequency Information, MBSFN ConfigOffers details about the RACH related info, Timers, UL power control.
SIB 3Cell-reselection parameters for INTRA-Frequency, INTER-Frequency and Inter-RATcell re-selection information common for intra-frequency, inter-frequency, and inter-RAT cell re-selection
SIB 4Details on Intra-frequency neighbouring cells.Assists devices in cell selection and handover when cells share the same frequency.
SIB 5Information on Inter-frequency neighbouring cells.Helps devices when cells operate on different frequencies.
SIB 6Information for Inter-RAT (Radio Access Technology) handovers.carries WCDMA neighbours information i.e. carries serving UTRA and neighbour cell frequencies useful for cell re-selection
SIB 7Cell-reselection parameters INTER RAT Frequency (GERAN)contains information relevant only for inter-RAT (GERAN) cell re-selection
SIB 8CDMA Neighbour Cellcarries CDMA-2000 EVDO frequencies, CDMA-2000 neighbour cell frequencies.
SIB 9contains a home eNB name (HeNB Name)HeNBs offer services exclusively to Closed Subscriber Groups. The HeNB name assists users in accurately selecting the corresponding CSGIdentity during manual network selection
SIB 10ETWS primary notificationETWS (Earthquake and Tsunami Warning System) information (Primary notification)
SIB 11ETWS secondary notificationETWS (Earthquake and Tsunami Warning System) information (Secondary notification)
SIB 12Commercial Mobile Alert Service (CMAS) information.CMAS notifications carry high emergency situations like Presiential Alerts, Threat Alerts

SIB 1 includes pertinent data used to assess whether a User Equipment (UE) is permitted to connect to a cell and establishes the scheduling parameters for other system information

  • SIB 1 is a mandatory SIB that must be transmitted by all eNodeBs.
  • SIB 1 is transmitted on the BCCH using the PDSCH.
  • The default transmission period for SIB 1 is 80 ms. However, the eNodeB can configure a different transmission period if necessary.

SystemInformationBlockType1 (SIB1) is a crucial broadcast message in LTE (Long-Term Evolution) networks, providing essential information to User Equipment (UE) for proper network operation. UE must follow specific procedures upon receiving SIB1, depending on their operational state and capabilities.

we’ll explore the actions UE should take when receiving SIB1 and SIB1-NB (Narrowband) under various conditions.

Receiving SystemInformationBlockType1 (SIB1)

Upon receiving SIB1, UE should adhere to the following procedures:

1. RRC_IDLE or RRC_CONNECTED with T311 Running:

  • If the UE is in RRC_IDLE or RRC_CONNECTED state with T311 running, and it is categorized as a Category 0 UE according to TS 36.306
  • If the ‘category0Allowed’ is not included in SIB1.


  • Consider the cell as barred in accordance with TS 36.304

2. RRC_CONNECTED with T311 Not Running and Supports Multi-Band Cells:

  • When UE is in RRC_CONNECTED state, T311 is not running, and the UE supports multi-band cells as indicated by bit 31 in ‘featureGroupIndicators.’


  • Disregard the ‘freqBandIndicator’ and ‘multiBandInfoList,’ if received, while in RRC_CONNECTED.
  • Forward the ‘cellIdentity’ to upper layers.
  • Forward the ‘trackingAreaCode’ to upper layers.

3. Default Actions:

  • In all other cases, the UE should follow these steps:


  • If the frequency band indicated in the ‘freqBandIndicator’ is supported by the UE and not a downlink-only band, or if the UE supports ‘multiBandInfoList,’ and one or more of the frequency bands indicated are supported and not downlink-only bands:
  • Forward the ‘cellIdentity’ to upper layers.
  • Forward the ‘trackingAreaCode’ to upper layers.
  • Further Actions if UE Supports MultiNS-Pmax:
  • If the UE is capable of multiNS-Pmax and the ‘freqBandInfo’ or ‘multiBandInfoList’ contains additionalSpectrumEmission in the ‘NS-PmaxList’ for the selected frequency band:
  • Apply the first listed additionalSpectrumEmission that it supports among the values in ‘NSPmaxList’ within ‘freqBandInfo’ or ‘multiBandInfoList.’
  • If ‘additionalPmax’ is present in the same entry of the selected additionalSpectrumEmission within ‘NS-PmaxList,’ apply it.
  • Otherwise, apply ‘p-Max.’
  • A UE uses the access barring information in SIB2 to determine whether it is allowed to access the network. For example, a UE that is not registered with the network may be barred from accessing the network.
  • A UE uses the RACH related configuration in SIB2 to determine how to access the RACH. For example, the UE uses this information to determine the preamble sequence that it should use and the number of times that it should transmit the preamble.
  • A UE uses the idle mode paging configuration in SIB2 to determine how it will be paged when new data is available for it. For example, the UE uses this information to determine the paging channel that it should monitor and the paging cycle.
  • A UE uses the PUCCH and PUSCH configuration in SIB2 to determine how it will transmit data on these channels. For example, the UE uses this information to determine the number of symbols that it should use to transmit data on the PUCCH and the maximum number of PDUs that it can transmit on the PUSCH in a single transmission.
  • A UE uses the uplink power control and SRS configuration in SIB2 to determine how it will adjust its transmit power on the uplink and how it will use SRS to measure the uplink channel conditions. For example, the UE uses this information to determine the power ramping step and the preamble initial received target power.
  • A UE uses the uplink carrier frequency and bandwidth information in SIB2 to determine the frequency and bandwidth of the uplink carrier. This information is used by the UE to configure its uplink transmitter and receiver.

SIB3 in LTE provides essential cell reselection parameters for various scenarios, including INTRA-Frequency, INTER-Frequency, and Inter-RAT (Radio Access Technology) scenarios.

  • Signalling Radio Bearer: Not Applicable (N/A)
  • RLC-Mode: Transparent Mode (TM)
  • Logical Channel: Broadcast Control Channel (BCCH)
  • Direction: From the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) to the User Equipment (UE)

Information on intra-frequency neighboring cells

Information on inter-frequency neighbouring cells

Information for reselection to UMTS (UTRAN) cells 

Information for reselection to GSM (GERAN) cells 

Information for reselection to CDMA2000 systems

Home eNodeB name – for future LTE femtocell applications

ETWS (Earthquake and Tsunami Warning System) information

Commercial Mobile Alerting System (CMAS) information.


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