System Information Block 1 (SIB-1) in LTE

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.’


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