wlanVHTSIGBRecover

Recover VHT-SIG-B bits in a perfect channel having 80 MHz channel bandwidth, one space-time stream, and one receive antenna.

Create a wlanVHTConfig object having a channel bandwidth of 80 MHz. Using the object, create a VHT-SIG-B waveform.

cfg = wlanVHTConfig('ChannelBandwidth','CBW80');
[txSig,txBits] = wlanVHTSIGB(cfg);

For a channel bandwidth of 80 MHz, there are 242 occupied subcarriers. The channel estimate array dimensions for this example must be [Nst,Nsts,Nr] = [242,1,1]. The example assumes a perfect channel and one receive antenna. Therefore, specify the channel estimate as a column vector of ones and the noise variance estimate as zero.

chEst = ones(242,1);
noiseVarEst = 0;

Recover the VHT-SIG-B. Verify that the received information bits are identical to the transmitted bits.

rxBits = wlanVHTSIGBRecover(txSig,chEst,noiseVarEst,'CBW80');
isequal(txBits,rxBits)

ans = logical
   1

Recover the VHT-SIG-B field using a zero-forcing equalizer in an AWGN channel with a channel bandwidth of 160 MHz, one space-time stream, and one receive antenna.

Create a wlanVHTConfig object, specifying a channel bandwidth of 160 MHz. Using the object, create a VHT-SIG-B waveform.

cfg = wlanVHTConfig('ChannelBandwidth','CBW160');
[txSig,txBits] = wlanVHTSIGB(cfg);

Pass the transmitted VHT-SIG-B through an AWGN channel.

noiseVarEst = 0.1;
awgnChan = comm.AWGNChannel('NoiseMethod','Variance','Variance',noiseVarEst);
rxSig = awgnChan(txSig);

Recover the VHT-SIG-B field, specifying zero-forcing equalization. Verify that the received information has no bit errors.

chEst = ones(484,1);
recBits = wlanVHTSIGBRecover(rxSig,chEst,noiseVarEst,'CBW160','EqualizationMethod','ZF');
numErr = biterr(txBits,recBits)

numErr = 
0

Recover VHT-SIG-B in a 2x2 MIMO channel for an SNR=10 dB and a receiver that has a 9 dB noise figure. Confirm that the information bits are recovered correctly.

Set the channel bandwidth and the corresponding sample rate.

cbw = 'CBW20';
fs = 20e6;

Create a VHT configuration object with 20 MHz bandwidth and two transmission paths. Generate the L-LTF and VHT-SIG-B waveforms.

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

txVHTLTF = wlanVHTLTF(vht);
[txVHTSIGB,txVHTSIGBBits] = wlanVHTSIGB(vht);

Pass the VHT-LTF and VHT-SIG-B waveforms through a 2x2 TGac channel.

tgacChan = wlanTGacChannel('NumTransmitAntennas',2, ...
    'NumReceiveAntennas',2, 'ChannelBandwidth',cbw,'SampleRate',fs);
rxVHTLTF = tgacChan(txVHTLTF);
rxVHTSIGB = tgacChan(txVHTSIGB);

Add white noise for an SNR = 10dB.

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

rxVHTLTF = chNoise(rxVHTLTF);
rxVHTSIGB = chNoise(rxVHTSIGB);

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);

rxVHTLTF = rxNoise(rxVHTLTF);
rxVHTSIGB = rxNoise(rxVHTSIGB);

Demodulate the VHT-LTF signal and use it to generate a channel estimate.

demodVHTLTF = wlanVHTLTFDemodulate(rxVHTLTF,vht);
chEst = wlanVHTLTFChannelEstimate(demodVHTLTF,vht);

Recover the VHT-SIG-B information bits. Display the scatter plot of the equalized symbols.

[recVHTSIGBBits,eqSym,cpe] = wlanVHTSIGBRecover(rxVHTSIGB,chEst,nVar,cbw);
scatterplot(eqSym)

Display the common phase error.

cpe

cpe = 
0.0485

Determine the number of errors between the transmitted and received VHT-SIG-B information bits.

numErr = biterr(txVHTSIGBBits,recVHTSIGBBits)

numErr = 
0