5G
NR system information in general is discussed in detail in the post 5G NR:System Information. This
post discusses SIB3 in detail.
SIB3 contains
neighbouring cell related information relevant for intra-frequency cell
re-selections only. It includes cells with specific re-selection parameters as
well as blacklisted cells.
General
Information
SIB3
is mapped to BCCH logical channel and is either broadcast
periodically on DL-SCH or broadcast on-demand on DL-SCH (i.e. upon request from
UEs in RRC_IDLE or RRC_INACTIVE) or sent in a dedicated manner on DL-SCH to UEs
in RRC_CONNECTED.
SIB3
is carried in SystemInformation (SI) messages,
which are transmitted on the DL-SCH. SIB1 contains scheduling
information for SI-message carrying SIB3. For more information about
scheduling of SI-messages, refer to 5G NR: System Information.
SIB3
can be configured to be cell specific or area specific, using an indication in SIB1.
The cell specific SIB is applicable only within a cell that provides the
SIB while the area specific SIB is applicable within an area
referred to as SI area, which consists of one or several cells and is
identified by systemInformationAreaID.
Contests of SIB3
Overview
of SIB3 contents presented below. Most of the SIB3 contents are
discussed in detail subsequently.
| SIB3 | |
| intraFreqNeighCellList | List of 1 to 16 IntraFreqNeighCellInfo |
| intraFreqBlackCellList | IntraFreqBlackCellList |
1.
intraFreqNeighCellList
As
shown below, intraFreqNeighCellList provides a list of intra-frequency
neighbouring cells with specific cell re-selection parameters.
| IntraFreqNeighCellInfo | |
| physCellId | INTEGER (0 … 1007) |
| q-OffsetCell | Q-OffsetRange |
| q-RxLevMinOffsetCell | INTEGER (1 … 8) |
| q-RxLevMinOffsetCellSUL | INTEGER (1 … 8) |
| q-QualMinOffsetCell | INTEGER (1 … 8) |
| Q-OffsetRange | |
| Q-OffsetRange (in dB) | ENUMERATED {-24, -22, -20, -18, -16, -14, -12, -10, -8, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24} |
intraFreqNeighCellList
contains a list of IntraFreqNeighCellInfo
IEs, each containing information about an intra-frequency neighbouring cell. The
IE IntraFreqNeighCellInfo consists of
physCellId, q-OffsetCell, q-RxLevMinOffsetCell, q-RxLevMinOffsetCellSUL, and
q-QualMinOffsetCell which are explained below.
physCellId identifies
the physical cell identity (PCI) of the concerned neighbouring cell.
q-OffsetCell is
the parameter Qoffsets,n in 38.304 which configures offset
between serving and the neighbour cell (determined by physCellId). This
offset (Qoffset) is used in the evaluation of cell-ranking (R-) criteria
for the concerned neighbouring cell. The higher the value of this field, the
lower the rank of the concerned cell.
Rn = Qmeas,n - Qoffset - Qoffsettemp
q-RxLevMinOffsetCell specifies
the cell specific Rx level offset in dB to Qrxlevmin. Qrxlevmin is
used to indicate the required ‘minimum received RSRP level’ (in dBm) in
the (NR) cell for cell selection and re-selection. 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 neighbouring
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) in
the (NR) cell for cell selection and re-selection. The cell specific offset q-QualMinOffsetCell
is added to the corresponding Qqualmin to achieve the required
minimum quality level in the concerned cell.
2.
intraFreqBlackCellList
intraFreqBlackCellList
provides a list of blacklisted intra-frequency
neighbouring cells. The following table summarises intraFreqBlackCellList
fields.
| IntraFreqBlackCellList | |
| IntraFreqBlackCellList | List of 1 to 16 PCI-Range |
| PCI-Range | |
| start | PhysCellId INTEGER (0 … 1007) |
| range | ENUMERATED {n4, n8, n12, n16, n24, n32, n48, n64, n84, n96, n128, n168, n252, n504, n1008, spare1} |
It
is possible to configure up to 16 PCI ranges to be blacklisted. Each PCI range
is characterised by a start value and the range
of PCIs as shown in the above table. Basically, the PCI range is encoded by
using a start value and by indicating the number of consecutive PCIs
(including start) in the range. For example, start = 5 and range = n4
would mean to blacklist PCIs 5, 6, 7, and 8.
Reference: 3GPP TS 38.331, and 38.304
