5G/NR - Enhanced Massive MIMO  




Enhanced Massive MIMO

Massive MIMO has been a key component for achieving such a high throughput promised by 5G/NR. So you may guess that Enhancement of Massive MIMO would be for even higher throughput, but it is not. In terms of throughput, we already have almost all the capability with Release 15. We already got max 8 CC CA in FR2 and 256 QAM. The only remaining technology to push up the throughput even further would be 2 codewords in both FR1 and FR2, 8 layers in FR1 and 400 Mhz bandwidth in FR2, but it doesn't seem to be the target for Release 16.

Major focus for Release 16 is to increase the stability of MIMO connection and more robust recovery process for beam failure.

The list of the feature to enhance Massive MIMO in Release 16 in comparison to Release 15 is described as follows in RP-200474 and Ref [1].

Release 15

Release 16

Support of Beam-Based Operation


CSI codebook : Upto 32 ports


CSI Type I Codebook : Basic Closed Loop MIMO


CSI Type II Codebook : High Resulution, MU-MIMO

Enhanced Type II Codebook

  •   Overhead reduction by compressing the CSI report in the frequency domain.
  •   Extending the CSI type II codebook to rank larger than two


Multi-TRP/Multi-Panel transmission enhancements

  •   Single PDCCH scheduling multiple TRP
  •   Individual PDCCH scheduling each individual TRP
  •   Uplink control signaling for non-coherent joint transmission
  •   Max two TRP/panel for simultaneous multi-TRP/panel reception


Multi-beam operation enhancement

  •   Reduced latency and overhead
  •   Beam Failure Recovery for SCell
  •   Measurement Report of L1-SINR


Low PAPR Reference Signal

  •   New Sequences for PDSCH/PUSCH DMRS
  •   New DMRS sequences for PI/2-BPSK-based PUSCH/PUCCH

Multi TRP (Transmission and Reception Point)

One of the most frequently mentioned feature related to enahanced massive MIMO would be the featured called Multi TRP. This is a feature that enable gNB to use more than one TRP to communicate to a UE. There are a couple of different ways for this type of communication and it can be summarized as in the following illustration.

    (A) TRP1 and TRP2 is transmitting two two different PDSCH but control signal (PDCCH/DCI) for the two PDSCH is transmitted by TRP1. In this case, if there is some problem in radio link with TRP1 and PDCCH reception fails, the communication via TRP2 is impacted as well.

    (B) TRP1 and TRP2 is transmitting two two different PDSCH and each TRP is transmitting its own corresponding PDCCH/DCI. In this case, if there is any problem in radio link with one of the TRPs, the communication via other TRP can be intact.

    (C) This scenario shows the case where TRP1 and TRP2 is used to jointly process the DL and UL signal (Similar scenario as CoMP)


Codebook Type II Enhancement

This is not a new feature. It is an enhanced feature for an existing feature. Type II codebook is already there in Release 15. Then what will be changed in Release 16 ? Unfortunately it is not each to precisely point out the difference unless you look into the codebook equation itself.

  • Number of supported layers is increased from 2 (Rel 15) to 4 (Rel 16).
  • Codebook itself will get more sophisticated in Rel 16 comparing to Rel 15. This would not look obvious unless you analyze the codebook equation to the very detailed level. I did this analysis in my codebook page. If you take a close at the equation and compare it to Rel 15 equation, you would notice that the granularity of amplitude and phase parameter is improved in Rel 16.



A new DMRS sequence is introduced in release 16 mainly which can be summarized as below.

UE Capability Information

Phy-ParametersFRX-Diff ::= SEQUENCE {


    simultaneousReceptionDiffTypeD-r16 ENUMERATED {supported}


    ssb-csirs-SINR-measurement-r16 SEQUENCE {

        maxNumberSSB-CSIRS-OneTx-CMR-r16         ENUMERATED {n8, n16, n32, n64},

        maxNumberCSI-IM-NZP-IMR-res-r16          ENUMERATED {n8, n16, n32, n64},

        maxNumberCSIRS-2Tx-res-r16               ENUMERATED {n0, n4, n8, n16, n32, n64},

        maxNumberSSB-CSIRS-res-r16               ENUMERATED {n8, n16, n32, n64, n128},

        maxNumberCSI-IM-NZP-IMR-res-mem-r16      ENUMERATED {n8, n16, n32, n64, n128},

        supportedCSI-RS-Density-CMR-r16          ENUMERATED {one, three, oneAndThree},

        maxNumberAperiodicCSI-RS-Res-r16         ENUMERATED {n2, n4, n8, n16, n32, n64},

        supportedSNIR-meas-r16                   ENUMERATED {ssbWithCSI-IM, ssbWithNZP-IMR,

                                                             csirsWithNZP-IMR, csi-RSWithoutIMR}



    nonGroupSINR-reporting-r16                        ENUMERATED {n1, n2, n4} OPTIONAL,

    groupSINR-reporting-r16                           ENUMERATED {supported}

    simultaneousTCI-ActMultipleCC-r16                 ENUMERATED {supported} OPTIONAL,

    simul-SpatialRelationUpdatePUCCHResGroup-r16      ENUMERATED {supported}

    defaultSpatialRelationPathlossRS-r16              ENUMERATED {supported}




Phy-ParametersFR2 ::= SEQUENCE {


    defaultSpatialRelationPathlossRS-r16         ENUMERATED {supported} OPTIONAL,

    spatialRelationUpdateAP-SRS-r16              ENUMERATED {supported} OPTIONAL,




MIMO-ParametersPerBand ::= SEQUENCE {


    maxNumberSCellBFR-r16                        ENUMERATED {n1,n2,n4,n8}

    multiDCI-multiTRP-Parameters-r16 SEQUENCE {

        overlapPDSCHsFullyFreqTime-r16           INTEGER (1..2) OPTIONAL,

        overlapPDSCHsInTimePartiallyFreq-r16     ENUMERATED {supported} OPTIONAL,

        outOfOrderOperationDL-r16 SEQUENCE {

            supportPDCCH-ToPDSCH-r16             ENUMERATED {supported} OPTIONAL,

            supportPDSCH-ToHARQ-ACK-r16          ENUMERATED {supported} OPTIONAL

        } OPTIONAL,

        outOfOrderOperationUL-r16                ENUMERATED {supported} OPTIONAL,

        separateCRS-RateMatching-r16             ENUMERATED {supported} OPTIONAL,

        defaultQCL-PerCORESETPoolIndex-r16       ENUMERATED {supported} OPTIONAL,

        maxNumberActivatedTCI-States-r16 SEQUENCE {

            maxNumberPerCORESET-Pool-r16         ENUMERATED {n1, n2, n4, n8},

            maxTotalNumberAcrossCORESET-Pool-r16 ENUMERATED {n2, n4, n8, n16}

        } OPTIONAL



    lowPAPR-DMRS-PDSCH-r16                       ENUMERATED {supported} OPTIONAL,

    lowPAPR-DMRS-PUSCHwithoutPrecoding-r16       ENUMERATED {supported} OPTIONAL,

    lowPAPR-DMRS-PUCCH-r16                       ENUMERATED {supported} OPTIONAL,

    lowPAPR-DMRS-PUSCHwithPrecoding-r16          ENUMERATED {supported} OPTIONAL,

    csi-ReportFrameworkExt-r16                   CSI-ReportFrameworkExt-r16 OPTIONAL,

    codebookParametersAddition-r16               CodebookParametersAddition-r16 OPTIONAL,

    codebookComboParametersAddition-r16          CodebookComboParametersAddition-r16 OPTIONAL,



Phy-ParametersCommon ::= SEQUENCE {


    maxTotalResourcesForAcrossFreqRanges-r16 SEQUENCE {

        maxNumberResWithinSlotAcrossCC-AcrossFR-r16   ENUMERATED {n2, n4, n8, n12, n16,

                                                                 n32, n64, n128} OPTIONAL,

        maxNumberResAcrossCC-AcrossFR-r16             ENUMERATED {n2, n4, n8, n12, n16, n32,

                                                                  n40, n48, n64, n72, n80, n96,

                                                                  n128, n256} OPTIONAL



    harqACK-separateMultiDCI-MultiTRP-r16 SEQUENCE {

        maxNumberLongPUCCHs-r16                       ENUMERATED {longAndLong, longAndShort,

                                                                  shortAndShort} OPTIONAL





FeatureSetDownlinkPerCC-v1620 ::= SEQUENCE {

    multiDCI-MultiTRP-r16                              MultiDCI-MultiTRP-r16 OPTIONAL,

    supportFDM-SchemeB-r16                             ENUMERATED {supported} OPTIONAL



MultiDCI-MultiTRP-r16 ::= SEQUENCE {

    maxNumberCORESET-r16                               ENUMERATED {n2, n3, n4, n5},

    maxNumberCORESETPerPoolIndex-r16                   INTEGER (1..3),

    maxNumberUnicastPDSCH-PerPool-r16                  ENUMERATED {n1, n2, n3, n4, n7}



CA-ParametersNR-v1610 ::= SEQUENCE {


    blindDetectFactor-r16                      INTEGER (1..2) OPTIONAL,


    codebookParametersPerBC-r16                CodebookParameters-v1610 OPTIONAL,


    codebookComboParametersAdditionPerBC-r16   CodebookComboParametersAdditionPerBC-r16 OPTIONAL



CodebookParametersAddition-r16 ::= SEQUENCE {

   etype2-r16 SEQUENCE {

      etype2R1-r16 SEQUENCE {

         supportedCSI-RS-ResourceListAdd-r16   SEQUENCE (SIZE (1..maxNrofCSI-RS-ResourcesExt-r16))

                                                OF INTEGER (0..maxNrofCSI-RS-ResourcesAlt-1-r16)


      etype2R2-r16 SEQUENCE {

         supportedCSI-RS-ResourceListAdd-r16   SEQUENCE (SIZE (1..maxNrofCSI-RS-ResourcesExt-r16))

                                                 OF INTEGER (0..maxNrofCSI-RS-ResourcesAlt-1-r16)

      } OPTIONAL,

      paramComb7-8-r16                         ENUMERATED {supported} OPTIONAL,

      rank3-4-r16                              ENUMERATED {supported} OPTIONAL,   

      amplitudeSubsetRestriction-r16           ENUMERATED {supported} OPTIONAL


   etype2-PS-r16 SEQUENCE {

      etype2R1-PortSelection-r16               SEQUENCE {

         supportedCSI-RS-ResourceListAdd-r16     SEQUENCE (SIZE (1..maxNrofCSI-RS-ResourcesExt-r16)

                                                ) OF INTEGER (0..maxNrofCSI-RS-ResourcesAlt-1-r16)


      etype2R2-PortSelection-r16 SEQUENCE {

         supportedCSI-RS-ResourceListAdd-r16    SEQUENCE (SIZE (1..maxNrofCSI-RS-ResourcesExt-r16))

                                                 OF INTEGER (0..maxNrofCSI-RS-ResourcesAlt-1-r16)


   rank3-4-r16                                  ENUMERATED {supported} OPTIONAL



Reference :

[1] The 5G Evolution:3GPP Releases 16-17 (5G Americas)