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QCL (Quasi Co Location)

 

According to R1-1700771, QCL is defined as follows :

    Two antenna ports are said to be quasi co-located if properties of the channel over which a symbol on one antenna port is conveyed can be inferred from the channel over which a symbol on the other antenna port is conveyed

 

Don't get disappointed if this does not sound clear to you. It is same to me as well. I may not understand the detailed physics and mathematics behind this forever, but I think I need to know at least some high level parameters about this.

 

It will take long time to get real / practical meaning of this statement. If you are familiar with the definition of Antenna port in LTE, you would noticed that the definition shown here is very similar to Antenna Port in LTE except a couple of words.

 

Simply put you may think that Antenna port defines the correlation between symbols within a same antenna port and QCL defines the correlation between symbols from different antenna ports.

 

 

 

QCL Types

 

"38.214 - 5.1.5   Antenna ports quasi co-location" defines four difference types of QCL as listed below.

 

QCL Type

Description

QCL-TypeA

Doppler shift, Doppler spread, average delay, delay spread

QCL-TypeB

Doppler shift, Doppler spread'

QCL-TypeC

Average delay, Doppler shift

QCL-TypeD

Spatial Rx parameter

 

 

 

Triggering TCI

 

I wrote this table based on the descriptions in "38.214 - 5.1.5   Antenna ports quasi co-location"

 

Steps

Direction

Description

1

UE <-- NW

RRC Configures TCI related parameters

2

UE <-- NW

NW Send MAC CE Activation Commnd

3

UE

UE recieves the PDSCH carrying the MAC CE

4

UE --> NW

UE sends HARQ ACK at slot n

5

UE/NW

TCI configured in Transmission Configuration Indication of DCI 1_1 is applied from the slot (n + 3 subrames + 1).

 

 

 

Mapping between QCL-Type configurations and TCI-RS-Set / DMRS

 

Which QCL-Type is applied is determined by TCI-RS-Set and DMRS. "38.214 - 5.1.5   Antenna ports quasi co-location" states about the mapping between QCL-Type and TCI-RS-Set as follows.

 

TCI-RS-Set

QCL-Type

a CSI-RS resource in a CSI-RS resource set is configured with TRS-Info

QCL-TypeC' or {QCL-TypeC' and QCL-TypeD'} configurations with SS/PBCH block or QCL-TypeD' with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter CSI-RS-ResourceRep.

CSI-RS resource is in a CSI-RS resource set configured without TRS-Info and without CSI-RS-ResourceRep

QCL-TypeA' or QCL-TypeB' configuration with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter TRS-Info or QCL-TypeD' with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter CSI-RS-ResourceRep

CSI-RS resource in a CSI-RS resource set is configured with CSI-RS-ResourceRep

QCL-TypeA' configuration with CSI-RS in a CSI-RS resource set configured with higher layer parameter TRS-Info or {QCL-TypeC' and QCL-TypeD'} configurations with SS/PBCH block or {QCL-TypeD} with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter CSI-RS-ResourceRep

DM-RS of CORESET scheduling the PDSCH

QCL-TypeA' configuration with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter TRS-Info or {QCL-TypeA' and QCL-TypeD'} configuration with SS/PBCH block if UE is not configured with CSI-RS in a CSI-RS resource set configured with higher layer parameter TRS-Info or QCL-TypeD' with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter CSI-RS-ResourceRep

DM-RS of PDSCH

QCL-TypeA' configuration with a CSI-RS resource in a CSI-RS resource set configured without higher layer parameter TRS-Info and without CSI-RS-ResourceRep or QCL-TypeA' configuration with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter TRS-Info or {QCL-TypeA' and QCL-TypeD'} configuration with SS/PBCH block if UE is not configured with a CSI-RS resource in a CSI-RS resource set with higher layer parameter TRS-Info or QCL-TypeD' with a CSI-RS resource in a CSI-RS resource set configured with higher layer parameter CSI-RS-ResourceRep or {QCL-TypeA' and QCL-TypeD'} configuration with CSI-RS resource in a CSI-RS resource set configured without higher layer parameter TRS-Info and without CSI-RS-ResourceRep.

 

 

 

RRC Messages on QCI

 

 

PDSCH-Config ::=                        SEQUENCE {

    dataScramblingIdentityPDSCH             INTEGER (0..1007)    OPTIONAL,

    dmrs-DownlinkForPDSCH-MappingTypeA      SetupRelease { DMRS-DownlinkConfig }  OPTIONAL,   

    dmrs-DownlinkForPDSCH-MappingTypeB      SetupRelease { DMRS-DownlinkConfig }  OPTIONAL,  

    tci-StatesToAddModList                  SEQUENCE (SIZE(1..maxNrofTCI-States))

                                                OF TCI-State    OPTIONAL,   -- Need N

    tci-StatesToReleaseList                 SEQUENCE (SIZE(1..maxNrofTCI-States))

                                                OF TCI-StateId  OPTIONAL,   -- Need N

    vrb-ToPRB-Interleaver                   ENUMERATED {n2, n4},

    resourceAllocation                      ENUMERATED { resourceAllocationType0,

                                                         resourceAllocationType1,

                                                         dynamicSwitch},

    pdsch-AllocationList                    SEQUENCE (SIZE(1..maxNrofDL-Allocations))

                                                OF PDSCH-TimeDomainResourceAllocation ,

    pdsch-AggregationFactor                 ENUMERATED { n2, n4, n8 } OPTIONAL, 

    rateMatchPatternToAddModList            SEQUENCE (SIZE (1..maxNrofRateMatchPatterns))

                                                 OF RateMatchPattern    OPTIONAL, -- Need N

    rateMatchPatternToReleaseList           SEQUENCE (SIZE (1..maxNrofRateMatchPatterns))

                                                 OF RateMatchPatternId     OPTIONAL, -- Need N

    rateMatchPatternGroup1                  SEQUENCE (SIZE (1..maxNrofRateMatchPatterns))

                                                 OF RateMatchPatternId     OPTIONAL, -- Need R

    rateMatchPatternGroup2                  SEQUENCE (SIZE (1..maxNrofRateMatchPatterns))

                                                 OF RateMatchPatternId     OPTIONAL, -- Need R

    rbg-Size                                ENUMERATED {config1, config2},

    mcs-Table                               ENUMERATED {qam64, qam256},

    maxNrofCodeWordsScheduledByDCI          ENUMERATED {n1, n2} OPTIONAL,   -- Need R

    prb-BundlingType                    CHOICE {

        static                                  SEQUENCE {

            bundleSize                              ENUMERATED { n4, wideband }  OPTIONAL  

        },

        dynamic                                 SEQUENCE {

            bundleSizeSet1                          ENUMERATED { n4,

                                                                 wideband,

                                                                 n2-wideband,

                                                                 n4-wideband

                                                                }  OPTIONAL,   -- Need S

            bundleSizeSet2                          ENUMERATED { n4,

                                                                 wideband

                                                                } OPTIONAL    -- Need S

        }

    },

    zp-CSI-RS-ResourceToAddModList          SEQUENCE (SIZE (1..maxNrofZP-CSI-RS-Resources))

                                                OF ZP-CSI-RS-Resource   OPTIONAL,   -- Need N

    zp-CSI-RS-ResourceToReleaseList         SEQUENCE (SIZE (1..maxNrofZP-CSI-RS-Resources))

                                                OF ZP-CSI-RS-ResourceId OPTIONAL,   -- Need M

    aperiodic-ZP-CSI-RS-ResourceSetsToAddModList    SEQUENCE (SIZE (1..maxNrofZP-CSI-RS-Sets))

                                                OF ZP-CSI-RS-ResourceSet   OPTIONAL, -- Need N

    aperiodic-ZP-CSI-RS-ResourceSetsToReleaseList   SEQUENCE (SIZE (1..maxNrofZP-CSI-RS-Sets))

                                                OF ZP-CSI-RS-ResourceSetId   OPTIONAL, -- Need N

    sp-ZP-CSI-RS-ResourceSetsToAddModList   SEQUENCE (SIZE (1..maxNrofZP-CSI-RS-Sets))

                                                OF ZP-CSI-RS-ResourceSet     OPTIONAL, -- Need N

    sp-ZP-CSI-RS-ResourceSetsToReleaseList  SEQUENCE (SIZE (1..maxNrofZP-CSI-RS-Sets))

                                                OF ZP-CSI-RS-ResourceSetId   OPTIONAL, -- Need N

 

    ...

}

 

 

TCI-State ::=            SEQUENCE {

    tci-StateId               TCI-StateId,

    qcl-Type1                       QCL-Info,

    qcl-Type2                       QCL-Info          OPTIONAL,   -- Need R

    ...

}

 

QCL-Info ::=                   SEQUENCE {

    cell                             ServCellIndex    OPTIONAL,   -- Need R

    bwp-Id                           BWPId            OPTIONAL, -- Cond CSI-RS-Indicated

    referenceSignal                     CHOICE {

        csi-rs                              NZP-CSI-RS-ResourceId,

        ssb                                 SSB-Index

    },

    qcl-Type                            ENUMERATED {typeA, typeB, typeC, typeD},

    ...

}

 

 

NZP-CSI-RS-ResourceSet ::=          SEQUENCE {

    nzp-CSI-ResourceSetId               NZP-CSI-RS-ResourceSetId,   

    nzp-CSI-RS-Resources                SEQUENCE (SIZE (1..maxNrofNZP-CSI-RS-ResourcesPerSet))

                                                OF NZP-CSI-RS-ResourceId,

    repetition                          ENUMERATED { on, off } OPTIONAL,

    aperiodicTriggeringOffset           INTEGER(0..4)          OPTIONAL,   -- Need S

    trs-Info                            ENUMERATED {true}      OPTIONAL,   -- Need R

    ...

}

 

trs-Info : Indicates that the antenna port for all NZP-CSI-RS resources in the CSI-RS resource set is same. If the field is absent or released the UE applies the value "false  

 

 

ControlResourceSet ::=                  SEQUENCE {

    controlResourceSetId                    ControlResourceSetId,

    frequencyDomainResources                BIT STRING (SIZE (45)),

    duration                                INTEGER (1..maxCoReSetDuration),

                                                       //maxCoReSetDuration = 3  

    cce-REG-MappingType CHOICE {

        interleaved                             SEQUENCE {

            reg-BundleSize                          ENUMERATED {n2, n3, n6},

            interleaverSize                         ENUMERATED {n2, n3, n6},

            shiftIndex                              INTEGER(0..maxNrofPhysicalResourceBlocks-1)

        },

        nonInterleaved                          NULL

    },,

    precoderGranularity ENUMERATED {sameAsREG-bundle, allContiguousRBs},

    tci-StatesPDCCH                 SEQUENCE(SIZE (1..maxNrofTCI-StatesPDCCH)) OF TCI-StateId

    tci-PresentInDCI                ENUMERATED {enabled}                OPTIONAL

    pdcch-DMRS-ScramblingID         BIT STRING (SIZE (16))              OPTIONAL

}

 

 

 

Reference

 

[1] 3GPP TSG-RAN WG1 #87ah-NR - R1-1700771 : On spatial QCL definition