Create a VHT format configuration object.

vht = wlanVHTConfig;

Generate a VHT-LTF signal.

txVHTLTF = wlanVHTLTF(vht);

Add white noise to the signal.

rxVHTLTF = awgn(txVHTLTF,1);

Demodulate the received signal.

y = wlanVHTLTFDemodulate(rxVHTLTF,vht);

Specify a VHT format configuration object and generate a VHT-LTF.

vht = wlanVHTConfig;
txltf = wlanVHTLTF(vht);

Multiply the transmitted VHT-LTF by 0.1 + 0.1i . Pass the signal through an AWGN channel.

rxltfNoNoise = txltf * complex(0.1,0.1);
rxltf = awgn(rxltfNoNoise,20,'measured');

Demodulated the received VHT-LTF with a symbol offset of 0.5.

dltf = wlanVHTLTFDemodulate(rxltf,vht,0.5);

Estimate the channel using the demodulated VHT-LTF. Plot the result.

chEst = wlanVHTLTFChannelEstimate(dltf,vht);
scatterplot(chEst)

The estimate is very close to the previously introduced 0.1+0.1i multiplier.

Generate a VHT waveform. Extract and demodulate the VHT long training field (VHT-LTF) to estimate the channel coefficients. Recover the data field by using the channel estimate and use this field to determine the number of bit errors.

Configure a VHT-format configuration object with two paths.

vht = wlanVHTConfig('NumTransmitAntennas',2,'NumSpaceTimeStreams',2);

Generate a random PSDU and create the corresponding VHT waveform.

txPSDU = randi([0 1],8*vht.PSDULength,1);
txSig = wlanWaveformGenerator(txPSDU,vht);

Pass the signal through a TGac 2x2 MIMO channel.

tgacChan = wlanTGacChannel('NumTransmitAntennas',2,'NumReceiveAntennas',2, ...
    'LargeScaleFadingEffect','Pathloss and shadowing');
rxSigNoNoise = tgacChan(txSig);

Add AWGN to the received signal. Set the noise variance for the case in which the receiver has a 9-dB noise figure.

nVar = 10^((-228.6+10*log10(290)+10*log10(80e6)+9)/10);
awgnChan = comm.AWGNChannel('NoiseMethod','Variance','Variance',nVar);
rxSig = awgnChan(rxSigNoNoise);

Determine the indices for the VHT-LTF and extract the field from the received signal.

indVHT = wlanFieldIndices(vht,'VHT-LTF');
rxLTF = rxSig(indVHT(1):indVHT(2),:);

Demodulate the VHT-LTF and estimate the channel coefficients.

dLTF = wlanVHTLTFDemodulate(rxLTF,vht);
chEst = wlanVHTLTFChannelEstimate(dLTF,vht);

Extract the VHT-Data field and recover the information bits.

indData = wlanFieldIndices(vht,'VHT-Data');
rxData = rxSig(indData(1):indData(2),:);
rxPSDU = wlanVHTDataRecover(rxData,chEst,nVar,vht);

Determine the number of bit errors.

numErrs = biterr(txPSDU,rxPSDU)

numErrs = 0

Recover VHT-Data field bits for a multiuser transmission using channel estimation on a VHT-LTF field over a quasi-static fading channel.

Create a VHT configuration object having a 160 MHz channel bandwidth, two users, and four transmit antennas. Assign one space-time stream to the first user and three space-time streams to the second user.

cbw = 'CBW160';
numSTS = [1 3];
vht = wlanVHTConfig('ChannelBandwidth',cbw,'NumUsers',2, ...
    'NumTransmitAntennas',4,'NumSpaceTimeStreams',numSTS);

Because there are two users, the PSDU length is a 1-by-2 row vector.

psduLen = vht.PSDULength

psduLen = 1×2

        1050        3156

Generate multiuser input data. This data must be in the form of a 1-by- N cell array, where N is the number of users.

txDataBits{1} = randi([0 1],8*vht.PSDULength(1),1);
txDataBits{2} = randi([0 1],8*vht.PSDULength(2),1);

Generate VHT-LTF and VHT-Data field signals.

txVHTLTF  = wlanVHTLTF(vht); 
txVHTData = wlanVHTData(txDataBits,vht);

Pass the data field for the first user through a 4x1 channel because it consists of a single space-time stream. Pass the second user's data through a 4x3 channel because it consists of three space-time streams. Apply white Gaussian noise to each user signal.

snr = 15;
H1 = 1/sqrt(2)*complex(randn(4,1),randn(4,1));
H2 = 1/sqrt(2)*complex(randn(4,3),randn(4,3));

rxVHTData1 = awgn(txVHTData*H1,snr,'measured');
rxVHTData2 = awgn(txVHTData*H2,snr,'measured');

Repeat the process for the VHT-LTF fields.

rxVHTLTF1  = awgn(txVHTLTF*H1,snr,'measured');
rxVHTLTF2  = awgn(txVHTLTF*H2,snr,'measured');

Calculate the received signal power for both users and use it to estimate the noise variance.

powerDB1 = 10*log10(var(rxVHTData1));
noiseVarEst1 = mean(10.^(0.1*(powerDB1-snr)));

powerDB2 = 10*log10(var(rxVHTData2));
noiseVarEst2 = mean(10.^(0.1*(powerDB2-snr)));

Estimate the channel characteristics using the VHT-LTF fields.

demodVHTLTF1 = wlanVHTLTFDemodulate(rxVHTLTF1,cbw,numSTS);
chanEst1 = wlanVHTLTFChannelEstimate(demodVHTLTF1,cbw,numSTS);

demodVHTLTF2 = wlanVHTLTFDemodulate(rxVHTLTF2,cbw,numSTS);
chanEst2 = wlanVHTLTFChannelEstimate(demodVHTLTF2,cbw,numSTS);

Recover VHT-Data field bits for the first user and compare against the original payload bits.

rxDataBits1 = wlanVHTDataRecover(rxVHTData1,chanEst1,noiseVarEst1,vht,1);
[~,ber1] = biterr(txDataBits{1},rxDataBits1)

ber1 = 0.4983

Determine the number of bit errors for the second user.

rxDataBits2 = wlanVHTDataRecover(rxVHTData2,chanEst2,noiseVarEst2,vht,2);
[~,ber2] = biterr(txDataBits{2},rxDataBits2)

ber2 = 0.0972

The bit error rates are quite high because there is no precoding to mitigate the interference between streams. This is especially evident for the user 1 receiver because it receives energy from the three streams intended for user 2. The example is intended to show the workflow and proper syntaxes for the LTF demodulate, channel estimation, and data recovery functions.