lteEqualizeMIMO

MMSE-based joint downlink equalization and combining

Syntax

[out,csi] = lteEqualizeMIMO(enb,chs,in,hest,noiseest)

Description

[out,csi] = lteEqualizeMIMO(enb,chs,in,hest,noiseest) performs joint equalization and combining of the received PDSCH symbols in in, given cell-wide settings structure, enb, PDSCH configuration structure, chs, channel estimate, hest, and noise power estimate, noiseest. MMSE equalization is performed on the product of the channel matrix and precoding matrices. Thus, it performs MMSE equalization between transmit and receive layers and returns the result, out.

Examples

Equalize and Deprecode PDSCH Symbols

Equalize and deprecode the PDSCH symbols for RMC R.11 in a MIMO configuration. The PDSCH symbols are extracted from a transmit resource grid. An ideal (identity) channel estimate and ideal (zero) noise estimate are created. The channel and noise estimates are used to equalize and deprecode the PDSCH symbols.

Initialize cell-wide configuration structure, enb. Generate and populate transmit resource grid for RMC R.11.

rmccfg.RC = 'R.11';
ncodewords = 2;
enb = lteRMCDL(rmccfg, ncodewords);
enb.TotSubframes = 1;
[~,txGrid] = lteRMCDLTool(enb, {[1;0] [0;1]});

Extract the PDSCH symbols from this transmit grid.

[ind,indInfo] = ltePDSCHIndices(enb, enb.PDSCH, enb.PDSCH.PRBSet);
pdschSym = txGrid(ind);

Create an ideal, or identity, channel estimate and an ideal, or zero, noise estimate.

hest = permute(repmat(eye(enb.CellRefP), [1 1 indInfo.Gd]), [3 1 2]);
nest = 0.0;

Equalize and deprecode the PDSCH symbols, using the channel and noise estimates.

[out,csi] = lteEqualizeMIMO(enb, enb.PDSCH, pdschSym, hest, nest);
deprecoded = lteDLDeprecode(enb,enb.PDSCH,out);

Input Arguments

enb — Cell-wide settings

structure

Cell-wide settings, specified as a structure with the following 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
CyclicPrefix	Optional	'Normal' (default), 'Extended'	Cyclic prefix length
CellRefP	Required	1, 2, 4	Number of cell-specific reference signal (CRS) antenna ports
NSubframe	Required	0 (default), nonnegative scalar integer	Subframe number
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 enb.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)
The following parameter fields are dependent upon the condition that chs.TxScheme is set to 'SpatialMux' or 'MultiUser'.
CFI	Required	1, 2, or 3 Scalar or if the CFI varies per subframe, a vector of length 10 (corresponding to a frame).	Control format indicator (CFI) value. In TDD mode, CFI varies per subframe for the RMCs ('R.0', 'R.5', 'R.6', 'R.6-27RB', 'R.12-9RB')

Data Types: struct

chs — PDSCH configuration

structure

PDSCH configuration, specified as a structure with the following fields.

Parameter Field	Required or Optional	Values	Description
NLayers	Required	Integer from 1 to 8	Number of transmission layers (downlink modulation)
RNTI	Required	0 (default), scalar integer	Radio network temporary identifier (RNTI) value (16 bits)
TxScheme	Required	'CDD', 'SpatialMux', 'MultiUser'	Transmission scheme, specified as one of the following options. Transmission scheme Description 'CDD' Large delay cyclic delay diversity 'SpatialMux' Closed loop spatial multiplexing 'MultiUser' Multi-user MIMO
The following parameters are dependent upon the condition that TxScheme is set to 'SpatialMux' or 'MultiUser'.
PMISet	Required	Integer vector with element values from 0 to 15.	Precoder matrix indication (PMI) set. It can contain either a single value, corresponding to single PMI mode, or multiple values, corresponding to multiple or subband PMI mode. The number of values depends on CellRefP, transmission layers and TxScheme. For more information about setting PMI parameters, see ltePMIInfo.
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'.

Data Types: struct

in — Received PDSCH input symbols

numeric matrix

Received PDSCH input symbols, specified as a numeric matrix of size M-by-NRxAnts, where M is the number of received symbols for each of NRxAnts receive antennas.

Data Types: double
Complex Number Support: Yes

hest — Channel estimate

3-D numeric array

Channel estimate, specified as a 3-D numeric array of size M-by-NRxAnts-by-enb.CellRefP, where:

• M is the number of received symbols in in,

• NRxAnts is the number of receive antennas,

• enb.CellRefP is the number of cell-specific reference signal antenna ports.

Data Types: double

noiseest — Noise power estimate

numeric scalar

Noise power estimate, specified as a numeric scalar. This argument is an estimate of the noise power spectral density per RE on rxgrid. Such an estimate is provided by the lteDLChannelEstimate function.

Data Types: double

Output Arguments

out — Equalized output symbols

numeric matrix

Equalized output symbols, returned as a numeric matrix of size M-by-NU, where

• M is the number of received symbols for each receive antenna

• NU is the number of transmit layers

Data Types: double
Complex Number Support: Yes

csi — Soft channel state information

numeric matrix

Soft channel state information, returned as a numeric matrix of size M-by-NU, the same size as out. This argument contains soft channel state information and provides an estimate, via MMSE, of the received gain for each received layer.

Data Types: double