5G/NR - Carrier Bandwith Part Home : www.sharetechnote.com
Carrier Bandwidth Part
According to 38.211 4.4.5, A carrier bandwidth part is a contiguous set of physical resource blocks,selected from a contiguous subset of the common resource blocks for a given numerology(u) on a given carrier. It can be illustrated as below.
NOTE : Maximum 4 BWP can be specified in DL and UL. Following illustration is only an example showing the case of 3 BWP.
Point A indicates a common reference point for resource block grids and is obtained from the following higher-layer parameters as described in 38.211 - 4.4.4.2:
- PRB-index-DL-common for a PCell downlink represents the frequency offset between point A and the lowest subcarrier of the lowest resource block of the SS/PBCH block used by the UE for initial cell selection;
- PRB-index-UL-common for a PCell uplink in paired spectrum represents the frequency offset between point A and the frequency location based on ARFCN of the uplink indicated in SIB1;
- PRB-index-UL-common for a PCell uplink in unpaired spectrum represents the frequency offset between point A and the lowest subcarrier of the lowest resrouce block of the SS/PBCH block used by the UE for initial cell selection;
- PRB-index-DL-Dedicated for an SCell downlink represents the frequency offset between point A and the frequency location based on ARFCN in the higher-layer SCell configuration;
- PRB-index-UL-Dedicated for an SCell uplink represents the frequency offset between point A and the frequency location based on ARFCN in the higher-layer SCell configuration;
- PRB-index-SUL-common for a supplementary uplink represents the frequency offset between point A and the frequency location based on ARFCN in the higher-layer SUL configuration.
Carrier Bandwidth Part allocation for DL and UL
< Downlink >
- A UE can be configured with up to four carrier bandwidth parts
- Only one carrier bandwidth part can be active at a given time
- The UE is not expected to receive PDSCH, PDCCH, CSI-RS, or TRS outside an active bandwidth part.
< Uplink >
- A UE can be configured with up to four carrier bandwidth parts
- Only one carrier bandwidth part can be active at a given time
- If a UE is configured with a supplementary uplink
- The UE can in addition be configured with up to four carrier bandwidth parts in the supplementary uplink
- Only one carrier bandwidth part can be active at a given time
- The UE shall not transmit PUSCH or PUCCH outside an active bandwidth part.
Mapping between nCRB and nPRB
nCRB indicates a resource block location in common resource block, nPRB indicates a resource block within a specific carrier bandwidth part. In other words, you can think of nCRB is a position in an absolute (reference) coordinate system and nPRB is a position in a relative coordinate system. The relationship between nCRB and nPRB is defined as follows (38.211 v2.0.0 - 4.4.4.4).
This can be illustrated as an example shown below.
RRC Parameters for BandwidthPart Configuration
Following is based on 38.331 v15.1.0
BWP-Downlink ::= SEQUENCE {
bwp-Id BWP-Id,
bwp-Common BWP-DownlinkCommon
bwp-Dedicated BWP-DownlinkDedicated
...
}
BWP-DownlinkCommon ::= SEQUENCE {
genericParameters BWP,
pdcch-ConfigCommon SetupRelease { PDCCH-ConfigCommon }
pdsch-ConfigCommon SetupRelease { PDSCH-ConfigCommon }
...
}
BWP-DownlinkDedicated ::= SEQUENCE {
pdcch-Config SetupRelease { PDCCH-Config }
pdsch-Config SetupRelease { PDSCH-Config }
sps-Config SetupRelease { SPS-Config }
radioLinkMonitoringConfig SetupRelease { RadioLinkMonitoringConfig }
...
}
BWP-Uplink ::= SEQUENCE {
bwp-Id BWP-Id,
bwp-Common BWP-UplinkCommon
bwp-Dedicated BWP-UplinkDedicated
...
}
BWP-UplinkCommon ::= SEQUENCE {
genericParameters BWP,
rach-ConfigCommon SetupRelease { RACH-ConfigCommon }
pusch-ConfigCommon SetupRelease { PUSCH-ConfigCommon }
pucch-ConfigCommon SetupRelease { PUCCH-ConfigCommon }
...
}
BWP ::= SEQUENCE {
locationAndBandwidth INTEGER (0..37949),
subcarrierSpacing SubcarrierSpacing,
cyclicPrefix ENUMERATED { extended }
}
BWP-Id : An identifier for this bandwidth part. Other parts of the RRC configuration use the BWP-Id to associate themselves with a particular bandwidth part. The BWP ID=0 is always associated with the initial BWP and may hence not be used here (in other bandwidth parts).
The NW may trigger the UE to swtich UL or DL BWP using a DCI field. The four code points in that DCI field map to the RRC-configured
- BWP-ID as follows: For up to 3 configured BWPs (in addition to the initial BWP) the DCI code point is equivalent to the BWP ID
- (initial = 0, first dedicated = 1, ...). If the NW configures 4 dedicated bandwidth parts, they are identified by DCI code
- points 0 to 3. In this case it is not possible to switch to the initial BWP using the DCI field.
- Corresponds to L1 parameter 'UL-BWP-index'.
locationAndBandwidth : Frequency domain location and bandwidth of this bandwidth part defined commonly in a table. The location is given as distance (in number of PRBs) to point A (absoluteFrequencyPointA in FrequencyInfoDL). It Corresponds to L1 parameter 'DL-BWP-loc'. In case of TDD, a BWP-pair (UL BWP and DL BWP with the same bwp-Id) must have the same location
subcarrierSpacing : Subcarrier spacing to be used in this BWP for all channels and reference signals unless explicitly configured elsewhere. It corresponds to subcarrier spacing according to 38.211-Table 4.2-1. The value kHz15 corresponds to µ=0, kHz30 to µ=1, and so on. Only the values 15 or 30 kHz (<6GHz), 60 or 120 kHz (>6GHz) are applicable.
Reference
[1] NR Wide Bandwidth Operations by Jeongho Jeon, Intel Corporation