CSI reference signals are transmitted on one, two, four or eight antenna ports using p = 15 , p =15,16 , p =15,...,18 and p =15,...,22 , respectively.

CSI-RS exists because CRS does not scale. CRS supports at most four antenna ports and occupies resource elements in every resource block of every subframe. CSI-RS is sparse instead. Each pair of ports shares two resource elements per resource block pair, and the eNB sends it only in configured subframes. That is cheap enough to support eight ports in Release 10.

The sentence above is the Release 10 picture. 36.211 v19.3.0 now allows 1, 2, 4, 8, 12, 16, 20, 24, 28 or 32 antenna ports. The larger counts are built by aggregating several 4 port or 8 port configurations in the same subframe. Let's look at where one configuration sits in the resource grid, then at when it is sent, and finally at the RRC message that sets it up.

• Locations of CSI Reference Signal
• Timing - Periodicity of CSI Reference Signal
• How does RRC configure the CSI-RS ?
• Reference

Locations of CSI Reference Signal

Every CSI-RS port needs a subcarrier and an OFDM symbol inside the resource block pair. 36.211 gives both through one index, the CSI reference signal configuration. The index points to a pair (k', l') in a table, and the formula below then adds a fixed frequency offset for each pair of ports.

In 36.211(V10.7.0) - 6.10.5.2 Mapping to resource elements, the location of CSI reference signal is defined as below.

• The frequency location is k = k' + 12m plus a port offset. With normal cyclic prefix the offset is 0 for ports 15 and 16, -6 for 17 and 18, -1 for 19 and 20, and -7 for 21 and 22. With extended cyclic prefix it is 0, -3, -6 and -9.
• The time location is l = l' + l'', with l'' = 0 or 1, for configurations 0 to 19 with normal cyclic prefix. So the two resource elements of a port pair sit on two adjacent OFDM symbols. Configurations 20 to 31 use l = l' + 2l'' instead.
• The weight w_l'' is the orthogonal cover code. It separates the two ports of a pair, which share the same two resource elements.
• The sequence index m' is shifted by half the difference between the largest and the actual bandwidth. So the centre of the band always carries the same part of the sequence.

<36.211(V10.7.0)-Table 6.10.5.2-1: Mapping from CSI reference signal configuration to (k', l' ) for normal cyclic prefix.>

• Configurations 0 to 19 are valid for frame structure types 1 and 2. Configurations 20 to 31 are for frame structure type 2 only.
• The number of configurations shrinks as the port count grows. With 1 or 2 ports there are 20 plus 12 configurations, with 4 ports 10 plus 6, and with 8 ports 5 plus 3.
• The column n_s mod 2 gives the slot. Configurations 0, 5, 10 and 11 are in the first slot, and all the others are in the second slot.

Following is based on 36.211 Figure 6.10.5.2-1: Mapping of CSI reference signals (CSI configuration 0, normal cyclic prefix). This is an example showing the location of CSI RS when the CSI Reference Configuration 0 (i.e, k' = 9, l' = 5) is applied for the subframe with normal cyclic prefix.

• All eight ports use OFDM symbols 5 and 6 of slot 0, which matches l' = 5 and n_s mod 2 = 0 for configuration 0.
• Counted from the bottom of the resource block, ports 15 and 16 sit on subcarrier 9 and ports 17 and 18 on subcarrier 3. Ports 19 and 20 sit on subcarrier 8, and ports 21 and 22 on subcarrier 2. These are the offsets 0, -6, -1 and -7 of the formula above.
• Each pair of ports is drawn on the same two resource elements. The orthogonal cover code, not the position, tells them apart.

<36.211(V10.7.0)-Table 6.10.5.2-2: Mapping from CSI reference signal configuration to (k', l' ) for extended cyclic prefix.>

• Extended cyclic prefix has 16 configurations for frame structure types 1 and 2, numbered 0 to 15, and 12 more for type 2 only, numbered 16 to 27.
• With 8 ports only configurations 0 to 3 and 16 to 18 exist.

Beyond eight ports, 36.211 v19.3.0 Table 6.10.5-1 builds the port count from several configurations in the same subframe. Each aggregated configuration has 4 or 8 ports, and it comes from configurations 0 to 19 with normal cyclic prefix, or 0 to 15 with extended cyclic prefix. The table below lists the combinations. For these larger counts, the higher layer parameter CDMType selects CDM2, CDM4 or, for 32 ports, CDM8.

< Aggregation of CSI-RS configurations, based on 36.211 v19.3.0 Table 6.10.5-1 >

• One index gives the position : resourceConfig selects (k', l') and the slot, and the port number adds a fixed subcarrier offset.
• Two ports share two resource elements : the orthogonal cover code w_l'' separates them.
• More ports mean fewer choices : 8 ports have only 5 configurations that work in FDD, against 20 for 1 or 2 ports.
• Release 13 and 14 aggregate configurations : 12 to 32 ports are built from 4 port or 8 port configurations in the same subframe.

Timing - Periodicity of CSI Reference Signal

CSI-RS is not sent in every subframe. One index, I_CSI-RS from 0 to 154, gives both the period and the subframe offset. The eNB can set it separately for non-zero power and zero power CSI-RS, as the table below shows.

<36.211(V10.7.0)-Table 6.10.5.3-1: CSI reference signal subframe configuration.>

• The period is 5, 10, 20, 40 or 80 subframes, and the offset is I_CSI-RS minus the first index of its row.
• A subframe carries CSI-RS when (10n_f + ⌊n_s/2⌋ - Δ_CSI-RS) mod T_CSI-RS = 0.
• For example, I_CSI-RS = 0 gives T = 5 and Δ = 0, so CSI-RS is in subframes 0 and 5 of every frame. I_CSI-RS = 20 gives T = 20 and Δ = 5, so it is in subframe 5 of every second frame.

A subframe that passes this test can still lose its CSI-RS. The UE assumes that no CSI-RS is sent where it would collide with SystemInformationBlockType1, and in PCell subframes configured for paging with the cell-specific paging configuration. In TDD, the DwPTS of special subframe configurations 0, 5, 9 and 10 with normal cyclic prefix carries no CSI-RS either. The example I_CSI-RS = 0 above runs into the SIB1 rule, because SIB1 is sent in subframe 5 of every even frame.

Release 11 reuses the same table for CSI-IM in transmission mode 10. CSI-IM-Config-r11 carries its own resourceConfig-r11 and subframeConfig-r11, with the same ranges as the NZP CSI-RS, and the UE measures interference on those resource elements. 36.213 clause 7.2.6 expects every CSI-IM resource to overlap completely with a zero power CSI-RS configuration, so the serving cell sends nothing there. A TM10 UE can therefore see three periodic patterns built from one table. NZP CSI-RS gives the channel, CSI-IM gives the interference, and ZP CSI-RS marks the resource elements that PDSCH avoids.

Release 14 adds aperiodic CSI-RS. A CSI-RS resource configured through csi-RS-ConfigNZP-ApList-r14 or csi-RS-ConfigZP-ApList does not follow this periodic rule.

• One index gives period and offset : I_CSI-RS selects both, with periods from 5 to 80 subframes.
• Zero power CSI-RS has its own index : the eNB can mute resource elements with a different period from its non-zero power CSI-RS.

How does RRC configure the CSI-RS ?

The two tables above take effect only when RRC fills in their indices. The capture below comes from an RRCConnectionReconfiguration that sets up one non-zero power CSI-RS, one zero power CSI-RS and the Release 12 and 13 extensions. The red lines mark the CSI-RS fields.

Capture : radioResourceConfigDedicated inside RRCConnectionReconfiguration, shown as a decoder tree. The values come from one recorded exchange and not from the specification.

+-rrcConnectionReconfiguration-r8 ::= SEQUENCE [000100]
  +-measConfig ::= SEQUENCE OPTIONAL:Omit
  +-mobilityControlInfo ::= SEQUENCE OPTIONAL:Omit
  +-dedicatedInfoNASList ::= SEQUENCE OF OPTIONAL:Omit
  +-radioResourceConfigDedicated ::= SEQUENCE [000001] OPTIONAL:Exist
  | +-srb-ToAddModList ::= SEQUENCE OF OPTIONAL:Omit
  | +-drb-ToAddModList ::= SEQUENCE OF OPTIONAL:Omit
  | +-drb-ToReleaseList ::= SEQUENCE OF OPTIONAL:Omit
  | +-mac-MainConfig ::= CHOICE OPTIONAL:Omit
  | +-sps-Config ::= SEQUENCE OPTIONAL:Omit
  | +-physicalConfigDedicated ::= SEQUENCE [0000000000] OPTIONAL:Exist
  | | +-pdsch-ConfigDedicated ::= SEQUENCE OPTIONAL:Omit
  | | +-pucch-ConfigDedicated ::= SEQUENCE OPTIONAL:Omit
  | | +-pusch-ConfigDedicated ::= SEQUENCE OPTIONAL:Omit
  | | +-uplinkPowerControlDedicated ::= SEQUENCE OPTIONAL:Omit
  | | +-tpc-PDCCH-ConfigPUCCH ::= CHOICE OPTIONAL:Omit
  | | +-tpc-PDCCH-ConfigPUSCH ::= CHOICE OPTIONAL:Omit
  | | +-cqi-ReportConfig ::= SEQUENCE OPTIONAL:Omit
  | | +-soundingRS-UL-ConfigDedicated ::= CHOICE OPTIONAL:Omit
  | | +-antennaInfo ::= CHOICE OPTIONAL:Omit
  | | +-schedulingRequestConfig ::= CHOICE OPTIONAL:Omit
  | | +-EXTENSION ::= SEQUENCE [00011111]
  | |   +-VERSION-BRACKETS1 ::= SEQUENCE OPTIONAL:Omit
  | |   +-VERSION-BRACKETS2 ::= SEQUENCE OPTIONAL:Omit
  | |   +-VERSION-BRACKETS3 ::= SEQUENCE OPTIONAL:Omit
  | |   +-VERSION-BRACKETS4 ::= SEQUENCE [0101000000] OPTIONAL:Exist
  | |   | +-csi-RS-ConfigNZPToReleaseList-r11 ::= SEQUENCE OF OPTIONAL:Omit
  | |   | +-csi-RS-ConfigNZPToAddModList-r11 ::= SEQUENCE OF SIZE(1..maxCSI-RS-NZP-r11[3]) [1] OPTIONAL:Exist
  | |   | | +-CSI-RS-ConfigNZP-r11 ::= SEQUENCE [1]
  | |   | |   +-csi-RS-ConfigNZPId-r11 ::= INTEGER (1..maxCSI-RS-NZP-r11[3]) [1]
  | |   | |   +-antennaPortsCount-r11 ::= ENUMERATED [an8]
  | |   | |   +-resourceConfig-r11 ::= INTEGER (0..31) [0]
  | |   | |   +-subframeConfig-r11 ::= INTEGER (0..154) [0]
  | |   | |   +-scramblingIdentity-r11 ::= INTEGER (0..503) [0]
  | |   | |   +-qcl-CRS-Info-r11 ::= SEQUENCE [0] OPTIONAL:Exist
  | |   | |   | +-qcl-ScramblingIdentity-r11 ::= INTEGER (0..503) [0]
  | |   | |   | +-crs-PortsCount-r11 ::= ENUMERATED [n1]
  | |   | |   | +-mbsfn-SubframeConfigList-r11 ::= CHOICE OPTIONAL:Omit
  | |   | |   +-EXTENSION ::= SEQUENCE [1]
  | |   | |     +-VERSION-BRACKETS1 ::= SEQUENCE [1] OPTIONAL:Exist
  | |   | |       +-csi-RS-ConfigNZPId-v1310 ::= INTEGER (minCSI-RS-NZP-r13[4]..maxCSI-RS-NZP-r13[24]) [4]
  | |   | +-csi-RS-ConfigZPToReleaseList-r11 ::= SEQUENCE OF OPTIONAL:Omit
  | |   | +-csi-RS-ConfigZPToAddModList-r11 ::= SEQUENCE OF SIZE(1..maxCSI-RS-ZP-r11[4]) [1] OPTIONAL:Exist
  | |   | | +-CSI-RS-ConfigZP-r11 ::= SEQUENCE
  | |   | |   +-csi-RS-ConfigZPId-r11 ::= INTEGER (1..maxCSI-RS-ZP-r11[4]) [1]
  | |   | |   +-resourceConfigList-r11 ::= BIT STRING SIZE(16) [0000000000000000]
  | |   | |   +-subframeConfig-r11 ::= INTEGER (0..154) [0]
  | |   | |   +-EXTENSION ::= SEQUENCE
  | |   | +-epdcch-Config-r11 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-pdsch-ConfigDedicated-v1130 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-cqi-ReportConfig-v1130 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-pucch-ConfigDedicated-v1130 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-pusch-ConfigDedicated-v1130 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-uplinkPowerControlDedicated-v1130 ::= SEQUENCE OPTIONAL:Omit
  | |   +-VERSION-BRACKETS5 ::= SEQUENCE [00000001] OPTIONAL:Exist
  | |   | +-antennaInfo-v1250 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-eimta-MainConfig-r12 ::= CHOICE OPTIONAL:Omit
  | |   | +-eimta-MainConfigPCell-r12 ::= CHOICE OPTIONAL:Omit
  | |   | +-pucch-ConfigDedicated-v1250 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-cqi-ReportConfigPCell-v1250 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-uplinkPowerControlDedicated-v1250 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-pusch-ConfigDedicated-v1250 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-csi-RS-Config-v1250 ::= SEQUENCE [11] OPTIONAL:Exist
  | |   |   +-zeroTxPowerCSI-RS2-r12 ::= CHOICE [setup] OPTIONAL:Exist
  | |   |   | +-setup ::= SEQUENCE
  | |   |   |   +-zeroTxPowerResourceConfigList-r12 ::= BIT STRING SIZE(16) [0000000000000000]
  | |   |   |   +-zeroTxPowerSubframeConfig-r12 ::= INTEGER (0..154) [0]
  | |   |   +-ds-ZeroTxPowerCSI-RS-r12 ::= CHOICE [setup] OPTIONAL:Exist
  | |   |     +-setup ::= SEQUENCE
  | |   |       +-zeroTxPowerCSI-RS-List-r12 ::= SEQUENCE OF SIZE(1..maxDS-ZTP-CSI-RS-r12[5]) [1]
  | |   |         +-ZeroTxPowerCSI-RS-r12 ::= SEQUENCE
  | |   |           +-zeroTxPowerResourceConfigList-r12 ::= BIT STRING SIZE(16) [0000000000000000]
  | |   |           +-zeroTxPowerSubframeConfig-r12 ::= INTEGER (0..154) [0]
  | |   +-VERSION-BRACKETS6 ::= SEQUENCE [0] OPTIONAL:Exist
  | |   | +-pdsch-ConfigDedicated-v1280 ::= SEQUENCE OPTIONAL:Omit
  | |   +-VERSION-BRACKETS7 ::= SEQUENCE [0000000001010] OPTIONAL:Exist
  | |   | +-pdsch-ConfigDedicated-v1310 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-pucch-ConfigDedicated-r13 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-pusch-ConfigDedicated-r13 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-pdcch-CandidateReductions-r13 ::= CHOICE OPTIONAL:Omit
  | |   | +-cqi-ReportConfig-v1310 ::= SEQUENCE OPTIONAL:Omit
  | |   | +-soundingRS-UL-ConfigDedicated-v1310 ::= CHOICE OPTIONAL:Omit
  | |   | +-soundingRS-UL-ConfigDedicatedUpPTsExt-r13 ::= CHOICE OPTIONAL:Omit
  | |   | +-soundingRS-UL-ConfigDedicatedAperiodic-v1310 ::= CHOICE OPTIONAL:Omit
  | |   | +-soundingRS-UL-ConfigDedicatedAperiodicUpPTsExt-r13 ::= CHOICE OPTIONAL:Omit
  | |   | +-csi-RS-Config-v1310 ::= SEQUENCE [1] OPTIONAL:Exist
  | |   | | +-eMIMO-Type-r13 ::= CHOICE [setup] OPTIONAL:Exist
  | |   | |   +-setup ::= CHOICE [nonPrecoded-r13]
  | |   | |     +-nonPrecoded-r13 ::= SEQUENCE [11111]
  | |   | |       +-p-C-AndCBSRList-r13 ::= SEQUENCE OF SIZE(1..2) [1] OPTIONAL:Exist
  | |   | |       | +-P-C-AndCBSR-r13 ::= SEQUENCE
  | |   | |       |   +-p-C-r13 ::= INTEGER (-8..15) [-8]
  | |   | |       |   +-cbsr-Selection-r13 ::= CHOICE [nonPrecoded-r13]
  | |   | |       |   | +-nonPrecoded-r13 ::= SEQUENCE
  | |   | |       |   |   +-codebookSubsetRestriction1-r13 ::= BIT STRING SIZE(ALIGNED)
  | |   | |       |   |   +-codebookSubsetRestriction2-r13 ::= BIT STRING SIZE(ALIGNED)
  | |   | |       |   +-EXTENSION ::= SEQUENCE
  | |   | |       +-codebookConfigN1-r13 ::= ENUMERATED [n1]
  | |   | |       +-codebookConfigN2-r13 ::= ENUMERATED [n1]
  | |   | |       +-codebookOverSamplingRateConfig-O1-r13 ::= ENUMERATED [n4] OPTIONAL:Exist
  | |   | |       +-codebookOverSamplingRateConfig-O2-r13 ::= ENUMERATED [n4] OPTIONAL:Exist
  | |   | |       +-codebookConfig-r13 ::= INTEGER (1..4) [1]
  | |   | |       +-csi-IM-ConfigIdList-r13 ::= SEQUENCE OF SIZE(1..2) [1] OPTIONAL:Exist
  | |   | |       | +-CSI-IM-ConfigId-r13 ::= INTEGER (1..maxCSI-IM-r13[24]) [1]
  | |   | |       +-csi-RS-ConfigNZP-EMIMO-r13 ::= CHOICE [setup] OPTIONAL:Exist
  | |   | |         +-setup ::= SEQUENCE [1]
  | |   | |           +-nzp-resourceConfigList-r13 ::= SEQUENCE OF SIZE(1..2) [1]
  | |   | |           | +-NZP-ResourceConfig-r13 ::= SEQUENCE
  | |   | |           |   +-resourceConfig-r13 ::= INTEGER (0..31) [0]
  | |   | |           |   +-EXTENSION ::= SEQUENCE
  | |   | |           +-cdmType-r13 ::= ENUMERATED [cdm2] OPTIONAL:Exist
  | |   | +-ce-Mode-r13 ::= CHOICE OPTIONAL:Omit
  | |   | +-csi-RS-ConfigNZPToAddModListExt-r13 ::= SEQUENCE OF SIZE(1..maxCSI-RS-NZP-v1310[21]) [1] OPTIONAL:Exist
  | |   | | +-CSI-RS-ConfigNZP-r11 ::= SEQUENCE [1]
  | |   | |   +-csi-RS-ConfigNZPId-r11 ::= INTEGER (1..maxCSI-RS-NZP-r11[3]) [1]
  | |   | |   +-antennaPortsCount-r11 ::= ENUMERATED [an8]
  | |   | |   +-resourceConfig-r11 ::= INTEGER (0..31) [0]
  | |   | |   +-subframeConfig-r11 ::= INTEGER (0..154) [0]
  | |   | |   +-scramblingIdentity-r11 ::= INTEGER (0..503) [0]
  | |   | |   +-qcl-CRS-Info-r11 ::= SEQUENCE [0] OPTIONAL:Exist
  | |   | |   | +-qcl-ScramblingIdentity-r11 ::= INTEGER (0..503) [0]
  | |   | |   | +-crs-PortsCount-r11 ::= ENUMERATED [n1]
  | |   | |   | +-mbsfn-SubframeConfigList-r11 ::= CHOICE OPTIONAL:Omit
  | |   | |   +-EXTENSION ::= SEQUENCE [1]
  | |   | |     +-VERSION-BRACKETS1 ::= SEQUENCE [1] OPTIONAL:Exist
  | |   | |       +-csi-RS-ConfigNZPId-v1310 ::= INTEGER (minCSI-RS-NZP-r13[4]..maxCSI-RS-NZP-r13[24]) [4]
  | |   | +-csi-RS-ConfigNZPToReleaseListExt-r13 ::= SEQUENCE OF OPTIONAL:Omit
  | |   +-VERSION-BRACKETS8 ::= SEQUENCE [0] OPTIONAL:Exist
  | |     +-cqi-ReportConfig-v1320 ::= SEQUENCE OPTIONAL:Omit
  | +-EXTENSION ::= SEQUENCE [00000]
  |   +-VERSION-BRACKETS1 ::= SEQUENCE OPTIONAL:Omit
  |   +-VERSION-BRACKETS2 ::= SEQUENCE OPTIONAL:Omit
  |   +-VERSION-BRACKETS3 ::= SEQUENCE OPTIONAL:Omit
  |   +-VERSION-BRACKETS4 ::= SEQUENCE OPTIONAL:Omit
  |   +-VERSION-BRACKETS5 ::= SEQUENCE OPTIONAL:Omit
  +-securityConfigHO ::= SEQUENCE OPTIONAL:Omit
  +-nonCriticalExtension ::= SEQUENCE OPTIONAL:Omit

The NZP configuration maps straight onto the tables. The fields antennaPortsCount-r11 an8 and resourceConfig-r11 0 give eight ports at (k', l') = (9,5) in slot 0, which is the example grid above. The field subframeConfig-r11 0 gives a period of 5 subframes with offset 0. scramblingIdentity-r11 replaces the physical cell identity when the UE generates the CSI-RS sequence.

The ZP configuration is a 16 bit bitmap over the four port column of Table 6.10.5.2-1 or 6.10.5.2-2. The most significant bit is configuration 0. In this capture every bit is zero, so it mutes no resource elements. Several other values are defaults as well, such as index 0 and scrambling identity 0. So the capture shows where each field sits, rather than a working deployment. The field qcl-CRS-Info-r11 is also present, but pdsch-ConfigDedicated-v1130, which carries qcl-Operation, is absent. 36.331 says the eNB configures qcl-CRS-Info only for a UE with qcl-Operation set to typeB.

The later groups show how CSI-RS grew. The group csi-RS-Config-v1250 adds a second zero power CSI-RS and the zero power resources of the discovery signal. The group csi-RS-Config-v1310 adds the eMIMO configuration, here nonPrecoded with codebookConfigN1, N2, the oversampling factors and cdmType cdm2. The listing below is the current definition of the two Release 11 IEs in the capture.

Following is based on 36.331 v19.3.0 (Release 19)

CSI-RS-ConfigNZP-r11 ::=        SEQUENCE {
    csi-RS-ConfigNZPId-r11          CSI-RS-ConfigNZPId-r11,
    antennaPortsCount-r11           ENUMERATED {an1, an2, an4, an8},
    resourceConfig-r11              INTEGER (0..31),
    subframeConfig-r11              INTEGER (0..154),
    scramblingIdentity-r11          INTEGER (0..503),
    qcl-CRS-Info-r11                SEQUENCE {
        qcl-ScramblingIdentity-r11      INTEGER (0..503),
        crs-PortsCount-r11              ENUMERATED {n1, n2, n4, spare1},
        mbsfn-SubframeConfigList-r11    CHOICE {
                release                     NULL,
                setup                       SEQUENCE {
                    subframeConfigList          MBSFN-SubframeConfigList
                }
        }                                                               OPTIONAL    -- Need ON
    }                                                                   OPTIONAL,   -- Need OR
    ...,
    [[  csi-RS-ConfigNZPId-v1310        CSI-RS-ConfigNZPId-v1310        OPTIONAL    -- Need ON
    ]],
    [[  transmissionComb-r14            NZP-TransmissionComb-r14        OPTIONAL,   -- Need OR
        frequencyDensity-r14            NZP-FrequencyDensity-r14        OPTIONAL    -- Need OR
    ]],
    [[  mbsfn-SubframeConfigList-v1430  CHOICE {
                release                     NULL,
                setup                       SEQUENCE {
                    subframeConfigList-v1430    MBSFN-SubframeConfigList-v1430
                }
        }                                                               OPTIONAL    -- Need OP
    ]]
}
CSI-RS-ConfigZP-r11 ::=     SEQUENCE {
    csi-RS-ConfigZPId-r11       CSI-RS-ConfigZPId-r11,
    resourceConfigList-r11      BIT STRING (SIZE (16)),
    subframeConfig-r11          INTEGER (0..154),
    ...
}

Compared with the capture, the current CSI-RS-ConfigNZP-r11 has three more extension groups. Release 14 adds transmissionComb-r14 and frequencyDensity-r14, which thin the CSI-RS in frequency, and mbsfn-SubframeConfigList-v1430.

• RRC carries only indices : resourceConfig and subframeConfig point into the 36.211 tables, and the UE derives the resource elements itself.
• NZP and ZP are separate objects : the UE measures on NZP CSI-RS, and it rate matches PDSCH around ZP CSI-RS.
• The IE kept growing after Release 11 : extension groups add the Release 13 identity range, the Release 14 comb and density, and the MBSFN list.

Reference

• 36.211 : 3GPP - E-UTRA Physical channels and modulation, v19.3.0. Clause 6.10.5 with Table 6.10.5-1, Table 6.10.5.2-1, Table 6.10.5.2-2 and Table 6.10.5.3-1.
• 36.331 : 3GPP - E-UTRA Radio Resource Control (RRC); Protocol specification, v19.3.0. CSI-RS-ConfigNZP, CSI-RS-ConfigZP, CSI-IM-Config and PDSCH-ConfigDedicated.
• 36.213 : 3GPP - E-UTRA Physical layer procedures, v19.4.0. Clause 7.2.6, CSI-IM resource definition.