lteEqualizeMMSE
MMSE equalization
Description
[
returns
equalized data in multidimensional array, out
,csi
]
= lteEqualizeMMSE(rxgrid
,channelest
,noiseest
)out
.
MMSE equalization is applied to the received data resource grid in
the matrix, rxgrid
, using the channel information
in the channelest
matrix. noiseest
is
an estimate of the received noise power spectral density.
Alternatively, the input channelest
can
be provided as a 3-D array of size NRE-by-NRxAnts
-by-P,
and the input rxgrid
can be provided as a matrix
of size NRE-by-NRxAnts
. In this
case, the first two dimensions have been reduced to one dimension
by appropriate indexing through the frequency and time locations of
the resource elements of interest, typically for a single physical
channel. The outputs, out
and csi
,
are of size (N×M)-by-P.
Examples
Equalize MMSE for RMC R.4
Equalize the received signal for RMC R.4 after channel estimation. Use the MMSE equalizer.
Create cell-wide configuration structure and generate transmit signal. Configure propagation channel.
enb = lteRMCDL('R.4'); [txSignal,~,info] = lteRMCDLTool(enb,[1;0;0;1]); chcfg.DelayProfile = 'EPA'; chcfg.NRxAnts = 1; chcfg.DopplerFreq = 70; chcfg.MIMOCorrelation = 'Low'; chcfg.SamplingRate = info.SamplingRate; chcfg.Seed = 1; chcfg.InitPhase = 'Random'; chcfg.InitTime = 0; txSignal = [txSignal; zeros(15,1)]; N = length(txSignal); noise = 1e-3*complex(randn(N,chcfg.NRxAnts),randn(N,chcfg.NRxAnts)); rxSignal = lteFadingChannel(chcfg,txSignal)+noise;
Perform synchronization and OFDM demodulation.
offset = lteDLFrameOffset(enb,rxSignal); rxGrid = lteOFDMDemodulate(enb,rxSignal(1+offset:end,:));
Create channel estimation configuration structure and perform channel estimation.
cec.FreqWindow = 9; cec.TimeWindow = 9; cec.InterpType = 'Cubic'; cec.PilotAverage = 'UserDefined'; cec.InterpWinSize = 3; cec.InterpWindow = 'Causal'; [hest,noiseEst] = lteDLChannelEstimate(enb, cec, rxGrid);
Equalize and plot received and equalized grids.
eqGrid = lteEqualizeMMSE(rxGrid, hest, noiseEst); subplot(2,1,1) surf(abs(rxGrid)) title('Received grid') xlabel('OFDM symbol') ylabel('Subcarrier') subplot(2,1,2) surf(abs(eqGrid)) title('Equalized grid') xlabel('OFDM symbol') ylabel('Subcarrier')
Equalize MMSE for RMC R.5
This example applies MMSE equalization on the received signal for reference measurement channel (RMC) R.5, after channel estimation.
Set the DL reference measurement channel to R.5
enb = lteRMCDL('R.5');
Set channel estimator configuration PilotAverage
field to UserDefined
. as follows: averaging window of 9 resource elements in both frequency and time domain, cubic interpolation with a casual window.
cec = struct('FreqWindow',9,'TimeWindow',9,'InterpType','cubic'); cec.PilotAverage = 'UserDefined'; cec.InterpWinSize = 1; cec.InterpWindow = 'Causal';
Generate the txWaveform
.
txWaveform = lteRMCDLTool(enb,[1;0;0;1]); n = length(txWaveform);
Apply some random noise to the transmitted signal and save as the rxWaveform
.
rxWaveform = repmat(txWaveform,1,2)+complex(randn(n,2),randn(n,2))*1e-3;
Next, demodulate the received data.
rxGrid = lteOFDMDemodulate(enb,rxWaveform);
Then, perform channel estimation.
[hest,n0] = lteDLChannelEstimate(enb,cec,rxGrid);
Finally, apply the MMSE equalization.
out = lteEqualizeMMSE(rxGrid,hest,n0);
Show scatter plot of one component carrier.
scatterplot(out(:,1))
Input Arguments
rxgrid
— Received data resource grid
3-D numeric array | 2-D numeric matrix
Received data resource grid, specified as a 3-D numeric array
or a 2-D numeric matrix. As a 3-D numeric array, it has size N-by-M-by-NRxAnts
,
where N is the number of subcarriers, M is
the number of OFDM symbols, and NRxAnts
is the
number of receive antennas.
Alternatively, as a 2-D numeric matrix, it has size NRE-by-NRxAnts
.
In this case, the first two dimensions have been reduced to one dimension
by appropriate indexing through the frequency and time locations of
the resource elements of interest, typically for a single physical
channel.
Data Types: double
Complex Number Support: Yes
channelest
— Channel information
4-D numeric array | 3-D numeric array
Channel information, specified as a 4-D numeric array or a 3-D
numeric array. As a 4-D numeric array, it has size N-by-M-by-NRxAnts
-by-P. N is
the number of subcarriers, M is the number of OFDM
symbols, NRxAnts
is the number of receive antennas,
and P is the number of transmit antennas. Each
element is a complex number representing the narrowband channel for
each resource element and for each link between transmit and receive
antennas. This matrix can be obtained using the channel estimation
command lteDLChannelEstimate
.
Alternatively, as a 3-D numeric array, it has size NRE-by-NRxAnts
-by-P.
In this case, the first two dimensions have been reduced to one dimension
by appropriate indexing through the frequency and time locations of
the resource elements of interest, typically for a single physical
channel.
Data Types: double
Complex Number Support: Yes
noiseest
— Noise power estimate
numeric scalar
Noise power estimate, specified as a numeric scalar. It is an
estimate of the received noise power spectral density per RE on rxgrid
.
Data Types: double
Output Arguments
out
— Equalized output data
3-D numeric array | 2-D numeric matrix
Equalized output data, returned as a 3-D numeric array or a 2-D numeric matrix. As a 3-D numeric array, it has size N-by-M-by-P, where N is the number of subcarriers, M is the number of OFDM symbols, and P is the number of transmit antennas.
Alternatively, if channelest
is provided
as a 3-D array, out
is a 2-D numeric matrix of
size (N×M)-by-P.
In this case, the first two dimensions have been reduced to one dimension
by appropriate indexing through the frequency and time locations of
the resource elements of interest, typically for a single physical
channel.
Data Types: double
Complex Number Support: Yes
csi
— Soft channel state information
3-D numeric array | 2-D numeric matrix
Soft channel state information, returned as a 3-D numeric array
of the same size as out
. As a 3-D numeric array,
it has size N-by-M-by-P,
where N is the number of subcarriers, M is
the number of OFDM symbols, and P is the number
of transmit antennas. csi
provides an estimate
(via MMSE) of the received RE gain for each received RE.
Alternatively, if channelest
is provided
as a 3-D array, csi
is a 2-D numeric matrix of
size (N×M)-by-P.
In this case, the first two dimensions have been reduced to one dimension
by appropriate indexing through the frequency and time locations of
the resource elements of interest, typically for a single physical
channel.
Data Types: double
Version History
Introduced in R2014a
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