# lteDMRSIndices

UE-specific DM-RS resource element indices

## 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

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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

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

Parameter FieldRequired or OptionalValuesDescription
NDLRBRequired

Scalar integer from 6 to 110

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

NSubframeRequired

0 (default), nonnegative scalar integer

Subframe number

CyclicPrefixOptional

'Normal' (default), 'Extended'

Cyclic prefix length

DuplexModeOptional

'FDD' (default), 'TDD'

Duplexing mode, specified as either:

• 'FDD' for Frequency Division Duplex

• 'TDD' for Time Division Duplex

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

TDDConfigOptional

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

SSCOptional

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'.
NCellIDRequired

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
PRBSetRequired

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'.

TxSchemeOptional

'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.

NLayersOptional

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

Number of transmission layers.

NTxAntsOptional0 (default), nonnegative integer

Number of transmission antenna ports. This argument is present only 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

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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

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### 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.

## Version History

Introduced in R2014a