# lteDMRS

UE-specific demodulation reference signals

## Syntax

``sym = lteDMRS(enb,chs)``
``sym = lteDMRS(enb,chs,opts)``

## Description

example

````sym = lteDMRS(enb,chs)` returns the downlink UE-specific demodulation reference signal (DM-RS) symbols for transmission in a single subframe, given structures containing the cell-wide settings, and the PDSCH configuration settings. For more information, see DM-RS Associated with PDSCH.```

example

````sym = lteDMRS(enb,chs,opts)` allows control of the format of the returned symbols with the options cell array, `opts`. ```

## Examples

collapse all

Map DM-RS symbols for 4 layers onto an 8 antenna grid.

Initialize cell-wide settings for RMC `'R.1'` (10 MHz bandwidth, 1 RB allocation) and change to Release 10 transmission (`'Port7-14'`). Use `enb.PDSCH` for the channel configuration structure input. Generate and map DM-RS without clearing the REs that should not be mapped because of the DM-RS on other ports.

```enb = lteRMCDL('R.1'); enb.PDSCH.TxScheme = 'Port7-14'; enb.PDSCH.NLayers = 4; ntxants = 8; enb.PDSCH.W = lteCSICodebook(enb.PDSCH.NLayers,ntxants,[0 0]).'; subframe = ones(lteResourceGridSize(enb,ntxants)); enb.PDSCH.NTxAnts = size(enb.PDSCH.W,2); dmrsInd = lteDMRSIndices(enb,enb.PDSCH); dmrs = lteDMRS(enb,enb.PDSCH); subframe(dmrsInd) = dmrs;```

View the size of the output symbols, indices, and the Release 10 transmission `subframe`.

`size(dmrs)`
```ans = 1×2 192 1 ```
`size(dmrsInd)`
```ans = 1×2 192 1 ```
`size(subframe)`
```ans = 1×3 600 14 8 ```

Map non-precoded DM-RS symbols onto an 4 layer grid, and clear the REs which should not be used because of the DM-RS of other ports.

Initialize cellwide settings for RMC `'R.1'` (10 MHz bandwidth, 1 RB allocation) and change to Release 10 transmission (`'Port7-14'`). Generate and map DM-RS clearing the REs that should not be used because of the DM-RS on other ports.

```enb = lteRMCDL('R.1'); enb.PDSCH.TxScheme = 'Port7-14'; enb.PDSCH.NLayers = 4; subframe = ones(lteResourceGridSize(enb,enb.PDSCH.NLayers)); dmrsInd = lteDMRSIndices(enb,enb.PDSCH,'rs+unused'); dmrs = lteDMRS(enb,enb.PDSCH,'rs+unused'); subframe(dmrsInd) = dmrs; size(dmrs)```
```ans = 1×2 96 1 ```
`size(dmrsInd)`
```ans = 1×2 96 1 ```
`size(subframe)`
```ans = 1×3 600 14 4 ```

## Input Arguments

collapse all

eNodeB cell-wide settings, specified as a structure containing these parameter fields.

Parameter FieldRequired or OptionalValuesDescription
`NDLRB`Required

Scalar integer from 6 to 110

Number of downlink resource blocks. (${N}_{\text{RB}}^{\text{DL}}$)

`NCellID`Required

Integer from 0 to 503

Physical layer cell identity

`NSubframe`Required

0 (default), nonnegative scalar integer

Subframe number

`CyclicPrefix`Optional

`'Normal'` (default), `'Extended'`

Cyclic prefix length

`DuplexMode`Optional

`'FDD'` (default), `'TDD'`

Duplexing mode, specified as:

• `'FDD'` for Frequency Division Duplex or

• `'TDD'` for Time Division Duplex

The following parameters are dependent upon the condition that `DuplexMode` is set to `'TDD'`.

`TDDConfig`Optional

0, 1 (default), 2, 3, 4, 5, 6

`SSC`Optional

0 (default), 1, 2, 3, 4, 5, 6, 7, 8, 9

Special subframe configuration (SSC)

PDSCH-specific channel transmission configuration, specified as a structure that can contain these parameter fields.

Parameter FieldRequired or OptionalValuesDescription
`PRBSet`Required

Integer column vector or two-column matrix

Zero-based physical resource block (PRB) indices corresponding to the slot wise resource allocations for this PDSCH. `PRBSet` can be assigned as:

• a column vector, the resource allocation is the same in both slots of the subframe,

• a two-column matrix, this parameter specifies different PRBs for each slot in a subframe,

• a cell array of length 10 (corresponding to a frame, if the allocated physical resource blocks vary across subframes).

PRBSet varies per subframe for the RMCs `'R.25'`(TDD), `'R.26'`(TDD), `'R.27'`(TDD), `'R.43'`(FDD), `'R.44'`, `'R.45'`, `'R.48'`, `'R.50'`, and `'R.51'`.

`TxScheme`Optional

`'Port5'` (default), `'Port7-8'`, `'Port8'`, `'Port7-14'`

DM-RS-specific transmission scheme, specified as one of the following options.

Transmission schemeDescription
`'Port5'`Rel-8 single-antenna port, port 5
`'Port7-8'`Rel-9 single-antenna port, port 7 if `NLayers` is 1. Rel-9 dual-layer transmission, ports 7 and 8 if `NLayers` is 2.
`'Port8'`Rel-9 single-antenna port, port 8
`'Port7-14'`Rel-10 up to 8 layer transmission, ports 7–14 if `NLayers` a value from 1 to 8.

`NLayers`Optional

1 (default), 2, 3, 4, 5, 6, 7, 8

Number of transmission layers.

`W`Optional

Numeric matrix, `[]` (default)

`NLayers`-by-P precoding matrix for the wideband UE-specific beamforming of the DM-RS. P is the number of transmit antennas. An empty matrix, `[]`, signifies no precoding.

The following parameter is applicable when `TxScheme` is set to `'Port7-8'`, `'Port8'`, or `'Port7-14'`.

`NSCID`Optional

0 (default), 1

Scrambling identity (ID)

The following parameter is applicable when `TxScheme` is set to `'Port5'`.

`RNTI`Required

0 (default), scalar integer

Radio network temporary identifier (RNTI) value (16 bits)

Symbol generation options, specified as a character vector, cell array of character vectors, or string array. Values for `opts` when specified as a character vector include (use double quotes for string):

OptionValuesDescription
Symbol style

`'ind'` (default), `'mat'`

Style for returning DM-RS symbols, specified as one of the following options.

• `'ind'` — returns the DM-RS symbols as an NRE-by-1 vector (default)

• `'mat'` — returns the DM-RS symbols as a matrix. To form a matrix, a column may contain duplicate entries. In this style, each column contains symbols for —

• an individual port or layer, if symbols are not precoded,

• or the projected layers per transmit antenna if symbols are precoded.

NRE is the number of resource elements.

Symbol format

`'rsonly'` (default), `'rs+unused'`

Format for returning DM-RS symbols, specified as one of the following options.

• `'rsonly'` — returns only active DM-RS symbols (default)

• `'rs+unused'` — returns include zeros for the RE locations that should be unused because of DM-RS transmission on another port or layer. This format is equivalent to precoding with `W` set to `eye(NLayers)`.

Example: `{'ind','rs+unused'}`, returns the DM-RS symbols as a column vector that includes zeros for the RE locations that should be unused because of DM-RS transmission on another port or layer.

Data Types: `char` | `string` | `cell`

## Output Arguments

collapse all

DM-RS symbol sequences, returned as an NRE-by-1 numeric column vector, or a numeric matrix. NRE is the number of resource elements. The `opts` input offers alternative output styles or formats.

`sym` contains the non-precoded or precoded DM-RS symbol sequences concatenated for all the layers, or the transmit antennas for the transmission scheme. The symbols are always ordered as they should be mapped using `lteDMRSIndices` into an M-by-N-by-P array representing the subframe grid across either the non-precoded PDSCH layers or precoded transmit antennas. M is the number of subcarriers, N is the number of symbols, and P is the number of layers, or antennas.

Since precoding projects the DM-RS in each PDSCH layer onto all `NTxAnts` transmit antennas, the output contains the concatenation of all DM-RS across all layers, which are then duplicated in all `chs``.``NTxAnts` planes of the 3-D grid.

• The output is returned empty unless `chs``.``TxScheme` is set to one of the schemes related to DM-RS, specifically `'Port5'`, `'Port7-8'`, `'Port8'`, or `'Port7-14'`.

• If the `chs``.``TxScheme` is single port, `chs``.``NLayers` = 1 implicitly.

• The output does not include any elements allocated to PBCH, PSS, and SSS. If the subframe contains no DM-RS, an empty vector is returned.

• If the precoding matrix, field `chs``.`W, is not present or is empty, the output is returned containing only the concatenated non-precoded DM-RS symbols for the `NLayers` ports.

• Otherwise, the output, `sym`, contains all DM-RS symbol values after they are precoded using the `NLayers`-by-`NTxAnts` beamforming matrix, W, onto `NTxAnts` transmit antennas. The symbols are ordered by:

• The concatenation of DM-RS symbols per layer/port if not precoded

• The projected layers per transmit antenna if precoded.

Data Types: `double`
Complex Number Support: Yes

collapse all

### DM-RS Associated with PDSCH

As specified in TS 36.211, Section 6.10.3, UE-specific demodulation reference signal (DM-RS) associated with the physical downlink shared channel (PDSCH):

• are transmitted in a single subframe on antenna ports p=5, p=7, p=8, or p=7, 8,..., (`NLayers`+6).

• are present and are a valid reference for PDSCH demodulation only if the PDSCH transmission is associated with the corresponding antenna port according to TS 36.213, Section 7.1.

• are transmitted only on the physical resource blocks upon which the corresponding PDSCH is mapped.

These DM-RS are for use with Release 8, 9, and 10 non-codebook-based PDSCH transmission schemes.

## References

[1] 3GPP TS 36.211. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.

[2] 3GPP TS 36.213. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.