Band combinations in NR capabilities

supportedBandCombinationList

That's the first element to check to know which combination of bands are supported.The relevants fields are :

• ''bandList'' : works looks similar as EUTRA BandCombination : one or several band associated with a class (from A to Q). The class defines the number of contiguous carriers and the global bandwidth of the contiguous carriers. Class definitions are given in 38.101-1 for FR1 and 38.101-2 for FR2.

• ''featureSetCombination'' : An index in the ''featureSetCombinations'' table (begins at index 0)

We don't really care about the other fields for now.Usually, the list is not that big since it only includes bands requested upon capability enquiry.

Example :

{ bandList { nr: { bandNR 41, ca-BandwidthClassDL-NR a, ca-BandwidthClassUL-NR a }, nr: { bandNR 79, ca-BandwidthClassDL-NR a } }, featureSetCombination 2, ca-ParametersNR { parallelTxSRS-PUCCH-PUSCH supported, parallelTxPRACH-SRS-PUCCH-PUSCH supported, simultaneousRxTxInterBandCA supported, simultaneousRxTxSUL supported, diffNumerologyWithinPUCCH-GroupSmallerSCS supported }, supportedBandwidthCombinationSet '1'B },

FeatureSetCombinations

Each element of the ''featureSetCombinations'' list is an array of arrays.The first array's length is the number of bands in the corresponding band combination.If several band combination points to the same featureSetCombination, they have to have the same number of bands.

Then, for each band, there is an array of feature sets. All the bands of the combination shall have the same number of feature sets. The UE supports simultaneously the feature sets on the same position for each band.

The feature sets are referenced via an index to the ''FeatureSetDownlink'' or ''FeatureSetUplink''.This time, the index begins at index 1. index 0 is used to convey the information that the carrier is not supported (typically in UL)

If we continue our example :

featureSetCombinations { { { nr: { downlinkSetNR 1, uplinkSetNR 1 }, nr: { downlinkSetNR 2, uplinkSetNR 2 }, nr: { downlinkSetNR 3, uplinkSetNR 2 }, }, { nr: { downlinkSetNR 4, uplinkSetNR 0 }, nr: { downlinkSetNR 2, uplinkSetNR 0 }, nr: { downlinkSetNR 4, uplinkSetNR 0 }, } }

In this example, we see that we have two bands and 3 possibilities for each band.

Since band79 doesn't have the UL, the uplinkSetNR are all 0.

We can read the array like this:

If the UE uses the featureSet 1 for band 49, then it shall use featureSet 4 for band 79.

But what is a feature set ?

FeatureSetDownlink / FeatureSetUplink

A feature set indicates a set of features that the UE supports on the carriers corresponding to one band entry in a band combination.The most important field is the ''featureSetListPerDownlink/UplinkCC'' which is an array of index to the ''FeatureSetDownlink/UplinkPerCC''. It contains the same number of elements that the number of contiguous carriers of the associated band (determined thanks to the bandwidth class).

In our example, since we have only class A, the featureSetsDownlink can be quite straightforward :

featureSets { featureSetsDownlink { { featureSetListPerDownlinkCC { 1 }, }, { featureSetListPerDownlinkCC { 2 }, }, { featureSetListPerDownlinkCC { 3 }, }, { featureSetListPerDownlinkCC { 4 }, }, }

FeatureSetDownlink/UplinkPerCC

Here we will find the actual parameters that the UE supports and the end of our journey through this impossible indirection scheme.

Most important fields (for Downlink) are :

• ''supportedSubcarrierSpacingDL''
• ''supportedBandwidthDL''
• ''maxNumberMIMO-LayersPDSCH''

Our example :

featureSetsDownlinkPerCC { { supportedSubcarrierSpacingDL kHz15, supportedBandwidthDL fr1: mhz50, maxNumberMIMO-LayersPDSCH fourLayers, supportedModulationOrderDL qam256 }, { supportedSubcarrierSpacingDL kHz30, supportedBandwidthDL fr1: mhz50, maxNumberMIMO-LayersPDSCH fourLayers, supportedModulationOrderDL qam256 }, { supportedSubcarrierSpacingDL kHz30, supportedBandwidthDL fr1: mhz100, maxNumberMIMO-LayersPDSCH twoLayers, supportedModulationOrderDL qam256 }, { supportedSubcarrierSpacingDL kHz30, supportedBandwidthDL fr1: mhz50, maxNumberMIMO-LayersPDSCH twoLayers, supportedModulationOrderDL qam256 }, }

Putting it all together

So, based on how the featureSets are arranged in the featureSetCombination and on the actual content of the featureSets, we can determine that :

• The UE can support 50MHz/15kHz/MIMO4 (1) or 100MHz/30kHz/MIMO2 (3) on band 49 aggregated only with 50MHz/30kHz/MIMO2 (4) on band 79.
• It can support 50MHz/30kHz/MIMO4 (2) on both aggregated bands.
• It doesn't support 100MHz/30kHz/MIMO4 or 100MHz/15kHz for the 49 + 79 combination

What about NSA/ENDC

EN/DC uses the same mechanism but the different elements are scattered a bit everywhere.The bandCombinationList and featureSetCombinations are in the EUTRA-NR capabilities.The FeatureSets and FeatureSetsPerCC are in EUTRA and NR capabilities, depending on the band they refer to ...