# Documentation

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# lteDMRS

UE-specific demodulation reference signals

## 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

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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)
size(dmrsInd)
size(subframe)
ans =

192     1

ans =

192     1

ans =

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)
size(dmrsInd)
size(subframe)
ans =

96     1

ans =

96     1

ans =

600    14     4

## Input Arguments

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eNodeB cell-wide settings, specified as a structure that can contain these parameter fields.

Parameter FieldRequired or OptionalValuesDescription
NDLRBRequired

Scalar integer from 6 to 110

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

NCellIDRequired

Integer from 0 to 503

Physical layer cell identity

NSubframeRequired

0 (default), nonnegative scalar integer

Subframe number

CyclicPrefixOptional

'Normal' (default), 'Extended'

Cyclic prefix length

DuplexModeOptional

'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'.

TDDConfigOptional

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

SSCOptional

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
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.

WOptional

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'.

NSCIDOptional

0 (default), 1

Scrambling identity (ID)

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

RNTIRequired

0 (default), scalar integer

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

Symbol generation options, specified as a character vector or a cell array of character vectors containing the following values.

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 | cell

## Output Arguments

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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

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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. "Physical Channels and Modulation." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA). URL: http://www.3gpp.org.

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