5G
NR system information in general is discussed in detail in the post 5G NR:System Information. This
post discusses SIB5 in detail.
SIB5 contains
information relevant only for inter-RAT cell re-selection i.e. information
about E-UTRA frequencies and E-UTRAs neighbouring cells relevant for cell re-
selection.
General
Information
SIB5
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.
SIB5
is carried in SystemInformation (SI) messages,
which are transmitted on the DL-SCH. SIB1 contains scheduling
information for SI-message carrying SIB5. For more information about
scheduling of SI-messages, refer to 5G NR:System Information.
SIB5
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 SIB5
Overview
of SIB5 contents presented below. Most of the SIB5 contents are
discussed in detail subsequently.
| SIB5 | |
| carrierFreqListEUTRA | List of 1 to 8 CarrierFreqEUTRA |
| t-ReselectionEUTRA | T-Reselection INTEGER (0 … 7) |
| t-ReselectionEUTRA-SF | SpeedStateScaleFactors |
carrierFreqListEUTRA
As
shown below, carrierFreqListEUTRA provides a
list of up to 8 entries of CarrierFreqEUTRA
each containing information about E-UTRA frequencies and E-UTRA neighbouring
cells relevant for cell re-selection. The contents of the IE CarrierFreqEUTRA
are given in the below table.
| CarrierFreqEUTRA | ||
| carrierFreq | INTEGER (0 … 262143) | |
| eutra-multiBandInfoList | List of 1 to 8 EUTRA-MultiBandInfo | |
| eutra-FreqNeighCellList | List of 1 to 8 EUTRA-FreqNeighCellInfo | |
| eutra-BlackCellList | List of 1 to 16 EUTRA-PhysCellIdRange | |
| allowedMeasBandwidth | ENUMERATED {mbw6, mbw15, mbw25, mbw50, mbw75, mbw100} | |
| presenceAntennaPort1 | BOOLEAN | |
| cellReselectionPriority | CellReselectionPriority | INTEGER (0 … 7) |
| cellReselectionSubPriority | CellReselectionSubPriority | ENUMERATED {0.2, 0.4, 0.6, 0.8} |
| threshX-High | ReselectionThreshold | INTEGER (0 … 31) |
| threshX-Low | ReselectionThreshold | INTEGER (0 … 31) |
| q-RxLevMin | INTEGER (-70 … -22) | |
| q-QualMin | INTEGER (-34 … -3) | |
| p-MaxEUTRA | INTEGER (-30 … 33) | |
| threshX-HighQ | ReselectionThresholdQ | INTEGER (0 … 31) |
| threshX-LowQ | ReselectionThresholdQ | INTEGER (0 … 31) |
carrierFreq indicates the ARFCN applicable for a downlink, uplink
or bi-directional (TDD) E-UTRA carrier frequency.
eutra-multiBandInfoList provides a
list (up to 8) of frequency bands in addition to the band represented by carrierFreq
for which cell reselection parameters are common, and a list of additionalPmax
and additionalSpectrumEmission values for corresponding band. This
information for each band is carried by the IE EUTRA-MultiBandInfo
and is given in the below table.
| EUTRA-MultiBandInfo | |
| eutra-FreqBandIndicator | INTEGER (1 … 256) |
| eutra-NS-PmaxList | List of 1 to 8 EUTRA-NS-PmaxValue |
| EUTRA-NS-PmaxValue | |
| additionalPmax | INTEGER (-30 … 33) |
| additionalSpectrumEmission | INTEGER (0 … 288) |
eutra-FreqNeighCellList provides a list (up to 8) of neighbour cell information
on the carrier frequency given by carrierFreq. This information is
carried by the IE EUTRA-FreqNeighCellInfo and is
given in the below table.
| EUTRA-FreqNeighCellInfo | |
| physCellId | INTEGER (1 … 256) |
| dummy | EUTRA-Q-OffsetRange |
| q-RxLevMinOffsetCell | INTEGER (1 … 8) |
| q-QualMinOffsetCell | INTEGER (1 … 8) |
| EUTRA-Q-OffsetRange | |
| EUTRA-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} |
eutra-BlackCellList provides
a list (up to 8) of blacklisted E-UTRA neighbouring cells on
the carrier frequency given by carrierFreq. This information is carried in
the form of PCI range by means of the IE EUTRA-PhysCellIdRange
and is given in the below table.
| EUTRA-PhysCellIdRange | |
| start | EUTRA-PhysCellId INTEGER (0 … 503) |
| range | ENUMERATED {n4, n8, n12, n16, n24, n32, n48, n64, n84, n96, n128, n168, n252, n504, spare2, spare1} |
- It
is possible to configure up to 8 PCI ranges to be blacklisted. Each PCI range
is characterized 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 physical cell identities (including start)
in the range. For example, start = 5 and range = n4 would mean to blacklist
PCIs 5, 6, 7, and 8.
allowedMeasBandwidth is
used to indicate the maximum allowed measurement bandwidth on a carrier
frequency. The values mbw6, mbw15, mbw25, mbw50, mbw75, mbw100 indicate
6, 15, 25, 50, 75 and 100 resource blocks, respectively.
presenceAntennaPort1 is
used to indicate whether all the neighbouring cells on the specified carrier frequency
use Antenna Port 1. When set to true, the UE may assume that at
least two cell-specific antenna ports are used in all neighbouring cells.
CellReselectionPriority provides
the absolute priority of the concerned carrier frequency and is used in the
cell reselection procedure. Value 0 means lowest priority and value 7 means
highest priority. It is a mandatory field.
The
IE CellReselectionSubPriority indicates
a fractional value to be added to the value of cellReselectionPriority to
obtain the absolute priority of the concerned carrier frequency for E-UTRA and
NR. Value oDot2 corresponds to 0.2, value oDot4 corresponds to
0.4 and so on. This is an optional field.
Absolute priority = cellReselectionPriority
+ CellReselectionSubPriority (if configured)
threshX-High is the
parameter ThreshX, HighP and threshX-HighQ
is the parameter ThreshX, HighQ in 38.304
section 5.2.4.5. These parameters are used in cell reselection procedure to a
cell on a higher priority inter-RAT frequency than serving frequency.
-
ThreshX,
HighP specifies Srxlev
(RSRP) threshold (in dB) used by the UE when reselecting towards a higher
priority RAT/frequency than the current serving frequency.
-
ThreshX,
HighQ specifies Squal
(RSRQ) threshold (in dB) used by the UE when reselecting towards a higher
priority RAT/frequency than the current serving frequency.
-
For
ThreshX, HighP, actual value = field value *2 (dB) and if the field is absent, a
default value of infinity shall be applied. For, ThreshX, HighQ, actual value = field value
and if the field is absent, a default value of 0 dB shall be applied.
The
higher priority inter-RAT cell reselection procedure is as follows;
-
If
threshServingLowQ is broadcast in SIB2 and a cell of a higher
priority EUTRAN RAT/frequency fulfils Squal > ThreshX, HighQ during a
time interval TreselectionRAT, the UE can perform reselection
to that cell.
-
Otherwise
(threshServingLowQ is not broadcast in SIB2), if a cell of a
higher priority RAT/frequency fulfils Srxlev > ThreshX, HighP during a
time interval TreselectionRAT, the UE can perform reselection
to that cell.
threshX-Low is the
parameter ThreshX, LowP and threshX-LowQ
is the parameter ThreshX, LowQ in 38.304
section 5.2.4.5. These parameters are used in cell reselection procedure to a
cell on a lower priority inter-RAT frequency than serving frequency.
-
ThreshX,
LowP specifies Srxlev
(RSRP) threshold (in dB) used by the UE when reselecting towards a lower
priority RAT/frequency than the current serving frequency.
-
ThreshX,
LowQ specifies Squal
(RSRQ) threshold (in dB) used by the UE when reselecting towards a lower
priority RAT/frequency than the current serving frequency.
-
For
ThreshX, LowP, actual value = field value *2 (dB) and if the field is absent, a
default value of infinity shall be applied. For, ThreshX, LowQ, actual value = field value
and if the field is absent, a default value of 0 dB shall be applied.
The
lower priority inter-RAT cell reselection procedure is as follows;
-
If
threshServingLowQ is broadcast in SIB2 and the serving
cell quality is below ThreshServing, LowQ and a cell
of a lower priority EUTRAN RAT/frequency fulfils Squal > ThreshX, LowQ
during a time interval TreselectionRAT, the UE can perform
reselection to that cell.
-
Otherwise
(threshServingLowQ is not broadcast in SIB2), if the serving cell
RSRP is below ThreshServing, LowP and a cell of a lower
priority RAT/frequency fulfils Srxlev > ThreshX, LowP during a time interval TreselectionRAT,
the UE can perform reselection to that cell.
Q-RxLevMin is used
to indicate the required ‘minimum received RSRP level’ (in dBm) in the
(NR) cell for re-selection. Actual
value Qrxlevmin = field value * 2 [dBm]. Refer
to 38.304 cell re-selection criterion.
Q-QualMin is used
to indicate the required ‘minimum received RSRQ level’ (in dB) in the
(NR) cell for cell re-selection. If this field is absent, the UE applies the
(default) value of negative infinity for Qqualmin which means
that quality (RSRQ) check will always pass irrespective of the received signal
quality. Refer to 38.304 cell re-selection criterion.
p-MaxEUTRA specifies
the maximum allowed transmission power in dBm on the (uplink) carrier EUTRA frequency.
t-ReselectionEUTRA is
the parameter TreselectionEUTRA in 38.304 and
specifies cell reselection timer value per EUTRA frequency.
t-ReselectionEUTRA-SF is
the parameter "Speed dependent ScalingFactor for TreselectionEUTRA"
in 38.304. Based on the current mobility state (high or medium), the UE multiplies
TreselectionEUTRA with sf-High or sf-Medium.
The value of TreselectionEUTRA after applying the respective
scaling factor will always be less than or equal to TreselectionEUTRA
before scaling. This in general implies that, the reselections are allowed
to occur faster (based on scaling factor) during medium or high mobility
states. The following table summarises the SpeedStateScaleFactors
contents.
| t-ReselectionEUTRA-SF: SpeedStateScaleFactors | |
| sf-Medium | ENUMERATED {oDot25, oDot5, oDot75, 1Dot0} |
| sf-High | ENUMERATED {oDot25, oDot5, oDot75, 1Dot0} |
Reference: 3GPP TS 38.331, and 38.304
