# lteDMRSIndices

UE-specific DM-RS resource element indices

## Syntax

``ind = lteDMRSIndices(enb,chs)``
``ind = lteDMRSIndices(enb,chs,opts)``

## Description

example

````ind = lteDMRSIndices(enb,chs)` returns the indices of the downlink UE-specific demodulation reference signal (DM-RS) resource elements (RE) in a subframe, given structures containing the cell-wide settings, and the PDSCH settings. For more information, see DM-RS Associated with PDSCH.```

example

````ind = lteDMRSIndices(enb,chs,opts)` formats the returned indices using options specified by `opts`.```

## Examples

collapse all

Generate DM-RS Resource Element (RE) indices in default format for RMC R.28.

Initialize cell-wide parameters to RMC R.28 using the `lteRMCDL` function. Use `enb.PDSCH` for the channel configuration structure. Generate the RE indices.

```enb = lteRMCDL('R.28'); ind = lteDMRSIndices(enb,enb.PDSCH);```

View first four rows of index column vector

`size(ind)`
```ans = 1×2 24 1 ```
`ind(1:4)`
```ans = 4x1 uint32 column vector 1801 1805 1809 3603 ```

Generate 0-based Resource Element indices in subscript form for RMC R.28. The resultant matrix has three columns, with each row representing [subcarrier, symbol, antenna port].

Initialize cell-wide parameters to RMC R.28 using the `lteRMCDL` function.

`enb = lteRMCDL('R.28');`

Generate zero-based RE indices in subscript form.

`ind = lteDMRSIndices(enb,enb.PDSCH,{'0based','sub'});`

View first four rows of index matrix.

`size(ind)`
```ans = 1×2 24 3 ```
`ind(1:4,:)`
```ans = 4x3 uint32 matrix 0 3 0 4 3 0 8 3 0 2 6 0 ```

## 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. (${N}_{\text{RB}}^{\text{DL}}$)

`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)

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

Integer from 0 to 503

Physical layer cell identity

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.

`NTxAnts`Optional0 (default), nonnegative integer

Number of transmission antenna ports. This argument is only present for UE-specific demodulation reference symbols.

Index generation options, specified as a character vector, cell array of character vectors, or string array. For convenience, you can specify several options as a single character vector or string scalar by a space-separated list of values placed inside the quotes. Values for `opts` when specified as a character vector include (use double quotes for string):

OptionValuesDescription
Indexing style

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

Style for the returned indices, specified as one of the following options.

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

• `'mat'` — returns the indices as a matrix. If not precoded, each column contains indices for an individual layer/port. If precoded, each column contains symbols for a transmit antenna. To form a matrix, a column can contain duplicate entries.

• `'sub'` — returns the indices as an NRE-by-3 matrix. in ```[subcarrier, symbol, antenna]``` subscript row style.

NRE is the number of resource elements.

Index base

`'1based'` (default), `'0based'`

Base value of the returned indices. Specify `'1based'` to generate indices where the first value is 1. Specify `'0based'` to generate indices where the first value is 0.

Indexing format

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

Format for the returned indices, specified as one of the following options.

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

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

Example: `'ind 1based rs+unused'`, `"ind 1based rs+unused"`, `{"ind","1based","rs+unused"]`or `{'ind','1based','rs+unused'}` specify the same formatting options.

Example: `'ind rsonly'`, `"ind rsonly"`, `{'ind','rsonly'}`, or `["ind","rsonly"]` specify the same formatting options.

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

## Output Arguments

collapse all

DM-RS resource element indices, returned as a linear indexing NRE-by-1 column vector, a linear indexing matrix, or a numeric 3-column matrix. The `opts` input offers alternative output styles or formats.

`ind` can directly index the DM-RS elements in 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.

Data Types: `uint32`

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.