lteDMRS

UE-specific demodulation reference signals

Syntax

sym = lteDMRS(enb,chs)

sym = lteDMRS(enb,chs,opts)

Description

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.

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

Examples

Map PDSCH DM-RS Symbols to Grid

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 to Grid

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

enb — eNodeB cell-wide settings

structure

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

Parameter Field	Required or Optional	Values	Description
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	Uplink–downlink configuration
SSC	Optional	0 (default), 1, 2, 3, 4, 5, 6, 7, 8, 9	Special subframe configuration (SSC)

chs — PDSCH-specific channel transmission configuration

structure

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

Parameter Field	Required or Optional	Values	Description
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 scheme Description '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)

opts — Symbol generation options

character vector | cell array of character vectors | string array

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):

Option	Values	Description
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

sym — DM-RS symbol sequences

N_RE-by-1 numeric column vector (default) | numeric matrix

DM-RS symbol sequences, returned as an N_RE-by-1 numeric column vector, or a numeric matrix. N_RE 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.

For more information, see DM-RS Associated with PDSCH.

Data Types: double
Complex Number Support: Yes

More About

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.