5G NR System Information Type#3 – SIB 3

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In 5G NR, SIB3 contains neighboring cell related information relevant for intra-frequency cell re-selections only. It includes cells with specific re-selection parameters and blacklisted cells information.

Characteristics of NR System Information Type#3

  • Three types of System Information in 5G namely MSI , RMSI and OSI
  • SIB3 is the third types of System Information i.e. Other System Information (OSI)
  • SIB3  provides neighboring cell related information relevant for intra-frequency cell re-selections only, includes cells with specific re-selection parameters and blacklisted cells information.
  • SIB3 cell specific information can be provided for up to 16 intra frequency cells and up to 16 PCI ranges can be specified for blacklisting
  • SIB3  scheduling information is provided by SIB1 
  • SIB3 can be either broadcast periodically or broadcast on-demand or  sent in a dedicated manner to UEs
  • SIB3 is mapped to BCCH logical channel, DL-SCH transport channel and PDSCH physical channel

Transmission Details

  • Signalling radio bearer: Not Applicable
  • RLC-SAP: TM
  • Logical channels: BCCH
  • Transport Channel: DL-SCH
  • Physical Channel: PDSCH
  • Scrambling RNTI :  SI-RNTI
  • Direction: gNB to UE

SIB 3 Content Category

Below is the category list for content provided by NR SIB 3 message to UE.

    • Intra Freq Neigh Cell List
    • Intra Freq Black Cell List

Intra Freq Neigh Cell List

intraFreqNeighCellList structure of SIB3 contains a list of IntraFreqNeighCellInfo parameter, each containing information about an intra-frequency neighboring cell. The parameter IntraFreqNeighCellInfo contains a sequence of parameters like physCellId, q-OffsetCell, q-RxLevMinOffsetCell, q-RxLevMinOffsetCellSUL, and q- QualMinOffsetCell.

    • q-OffsetCell parameter is the Qoffsets,nas specified in 38.304 which configures offset between serving and the neighbor cell determined by physCellId. This offset (Qoffset) is used in the evaluation of cell-ranking (R-) criteria for the concerned neighbor. The higher the value of this field, the lower the rank of the concerned cell.

                                                                                     Rn = Qmeas,n – Qoffset – Qoffsettemp

    • q-RxLevMinOffsetCell parameter specifies the cell specific Rx level offset in dB to Qrxlevmin.  Qrxlevmin is used to indicate the required minimum received RSRP level in dBm  for cell selection and re-selection in NR cell. The cell specific offset q-RxLevMinOffsetCell is added to the corresponding Qrxlevmin to achieve the required minimum RX level in the concerned cell.
            • Actual value Qrxlevminoffsetcell = field value * 2 dB
    • q-RxLevMinOffsetCellSUL serves the same purpose as q-RxLevMinOffsetCell but if the UE supports SUL for neighbor cell
    • q-QualMinOffsetCell specifies the cell specific quality level offset in dB to Qqualmin. Qqualmin is used to indicate the required minimum received RSRQ level in dB  for cell selection and re -selection in NR cell. The cell specific offset q-QualMinOffsetCell is added to the corresponding Qqualmin to achieve the required minimum quality level in the concerned cell.

Intra Freq Black Cell List

intraFreqBlackCellList structure of SIB3 provides the list of blacklisted intra-frequency neighboring cells. It is possible to configure up to 16 PCIs ranges to be blacklisted. Each PCI range is characterized by a start value and the range of PCIs.

    • PCI range is encoded by using a start value and by indicating the number of consecutive PCIs (including start) in the range. E.g. start value = 15 and range = n8  means to blacklist PCIs 15, 16, 17, 18,19,20,21,22 and 23.

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