Recover L-SIG information transmitted in a noisy 2x2 MIMO channel, and calculate the number of bit errors present in the received information bits.

Set the channel bandwidth and sample rate.

chanBW = 'CBW40';
fs = 40e6;

Create a VHT configuration object corresponding to a 40 MHz 2x2 MIMO channel.

vht = wlanVHTConfig( ...
    'ChannelBandwidth',chanBW, ...
    'NumTransmitAntennas',2, ...
    'NumSpaceTimeStreams',2);

Generate the L-LTF and L-SIG field signals.

txLLTF = wlanLLTF(vht);
[txLSIG,txLSIGData] = wlanLSIG(vht);

Create a 2x2 TGac channel and an AWGN channel with an SNR=10 dB.

tgacChan = wlanTGacChannel('SampleRate',fs,'ChannelBandwidth',chanBW, ...
    'NumTransmitAntennas',2,'NumReceiveAntennas',2);

chNoise = comm.AWGNChannel('NoiseMethod','Signal to noise ratio (SNR)',...
    'SNR',10);

Pass the signals through the noisy 2x2 multipath fading channel.

rxLLTF = chNoise(tgacChan(txLLTF));
rxLSIG = chNoise(tgacChan(txLSIG));

Add additional white noise corresponding to a receiver with a 9 dB noise figure. The noise variance is equal to k*T*B*F, where k is Boltzmann's constant, T is the ambient temperature, B is the channel bandwidth (sample rate), and F is the receiver noise figure.

nVar = 10^((-228.6+10*log10(290) + 10*log10(fs) + 9 )/10);
rxNoise = comm.AWGNChannel('NoiseMethod','Variance','Variance',nVar);

rxLLTF = rxNoise(rxLLTF);
rxLSIG = rxNoise(rxLSIG);

Perform channel estimation based on the L-LTF.

demodLLTF = wlanLLTFDemodulate(rxLLTF,chanBW,1);
chanEst = wlanLLTFChannelEstimate(demodLLTF,chanBW);

Recover the L-SIG information bits.

rxLSIGData = wlanLSIGRecover(rxLSIG,chanEst,0.1,chanBW);

Verify that there are no bit errors in the recovered L-SIG data.

numErrors = biterr(txLSIGData,rxLSIGData)

numErrors = 0

Recover L-SIG information using the zero-forcing equalizer algorithm. Calculate the number of bit errors in the received data.

Create an HT configuration object.

cfgHT = wlanHTConfig;

Generate the L-SIG field and pass it through an AWGN channel.

[txLSIG,txLSIGData] = wlanLSIG(cfgHT);
rxSIG = awgn(txLSIG,20);

Recover the L-SIG field using the zero-forcing algorithm. The channel estimate is a vector of ones because fading was not introduced.

chEst = ones(52,1);
noiseVarEst = 0.1;
rxLSIGData = wlanLSIGRecover(rxSIG,chEst,noiseVarEst,'CBW20','EqualizationMethod','ZF');

Verify that there are no bit errors in the recovered L-SIG data.

numErrors = biterr(txLSIGData,rxLSIGData)

numErrors = 0

Recover the L-SIG field rom a channel that introduces a fixed phase and frequency offset.

Create a VHT configuration object corresponding to a 160 MHz SISO channel. Generate the transmitted L-SIG field.

cfgVHT = wlanVHTConfig('ChannelBandwidth','CBW160');
txLSIG = wlanLSIG(cfgVHT);

To introduce a 45 degree phase offset and a 100 Hz frequency offset, create a phase and frequency offset System object.

pfOffset = comm.PhaseFrequencyOffset('SampleRate',160e6,'PhaseOffset',45, ...
    'FrequencyOffset',100);

Introduce phase and frequency offsets to the transmitted L-SIG field, then pass it through an AWGN channel.

rxSIG = awgn(pfOffset(txLSIG),20);

Recover the L-SIG information bits, the failure check status, and the equalized symbols, disabling pilot phase tracking.

chEst = ones(416,1);
noiseVarEst = 0.01;
[recBits,failCheck,eqSym] = wlanLSIGRecover(rxSIG,chEst,noiseVarEst,'CBW160','PilotPhaseTracking','None');

Verify that the L-SIG passed the failure checks.

disp(failCheck)

   0

Visualize the phase offset by plotting the equalized symbols.

scatterplot(eqSym)
grid