Документация

% Create a format configuration object for a 8-by-8 VHT transmission
cfgVHT = wlanVHTConfig;
cfgVHT.ChannelBandwidth = 'CBW80'; % 80 MHz channel bandwidth
cfgVHT.NumTransmitAntennas = 8;    % 8 transmit antennas
cfgVHT.NumSpaceTimeStreams = 8;    % 8 space-time streams
cfgVHT.APEPLength = 3000;          % APEP length in bytes
cfgVHT.MCS = 9;                    % 256-QAM rate-5/6

% Create and configure the channel
tgacChannel = wlanTGacChannel;
tgacChannel.DelayProfile = 'Model-D';
tgacChannel.NumReceiveAntennas = 8;
tgacChannel.TransmitReceiveDistance = 10; % Distance in meters for NLOS
tgacChannel.ChannelBandwidth = cfgVHT.ChannelBandwidth;
tgacChannel.NumTransmitAntennas = cfgVHT.NumTransmitAntennas;
tgacChannel.LargeScaleFadingEffect = 'None';

snr = 40:5:50;

maxNumErrors = 10;   % The maximum number of packet errors at an SNR point
maxNumPackets = 100; % Maximum number of packets at an SNR point

% Get the baseband sampling rate
fs = wlanSampleRate(cfgVHT);

% Get the OFDM info
ofdmInfo = wlanVHTOFDMInfo('VHT-Data',cfgVHT);

% Set the sampling rate of the channel
tgacChannel.SampleRate = fs;

% Indices for accessing each field within the time-domain packet
ind = wlanFieldIndices(cfgVHT);

S = numel(snr);
packetErrorRate = zeros(S,1);
%parfor i = 1:S % Use 'parfor' to speed up the simulation
for i = 1:S     % Use 'for' to debug the simulation
    % Set random substream index per iteration to ensure that each
    % iteration uses a repeatable set of random numbers
    stream = RandStream('combRecursive','Seed',0);
    stream.Substream = i;
    RandStream.setGlobalStream(stream);

    % Create an instance of the AWGN channel per SNR point simulated
    awgnChannel = comm.AWGNChannel;
    awgnChannel.NoiseMethod = 'Signal to noise ratio (SNR)';
    % Normalization
    awgnChannel.SignalPower = 1/tgacChannel.NumReceiveAntennas;
    % Account for energy in nulls
    awgnChannel.SNR = snr(i)-10*log10(ofdmInfo.FFTLength/ofdmInfo.NumTones);

    % Loop to simulate multiple packets
    numPacketErrors = 0;
    numPkt = 1; % Index of packet transmitted
    while numPacketErrors<=maxNumErrors && numPkt<=maxNumPackets
        % Generate a packet waveform
        txPSDU = randi([0 1],cfgVHT.PSDULength*8,1); % PSDULength in bytes
        tx = wlanWaveformGenerator(txPSDU,cfgVHT);

        % Add trailing zeros to allow for channel delay
        tx = [tx; zeros(50,cfgVHT.NumTransmitAntennas)]; %#ok<AGROW>

        % Pass the waveform through the fading channel model
        reset(tgacChannel); % Reset channel for different realization
        rx = tgacChannel(tx);

        % Add noise
        rx = awgnChannel(rx);

        % Packet detect and determine coarse packet offset
        coarsePktOffset = wlanPacketDetect(rx,cfgVHT.ChannelBandwidth);
        if isempty(coarsePktOffset) % If empty no L-STF detected; packet error
            numPacketErrors = numPacketErrors+1;
            numPkt = numPkt+1;
            continue; % Go to next loop iteration
        end

        % Extract L-STF and perform coarse frequency offset correction
        lstf = rx(coarsePktOffset+(ind.LSTF(1):ind.LSTF(2)),:);
        coarseFreqOff = wlanCoarseCFOEstimate(lstf,cfgVHT.ChannelBandwidth);
        rx = helperFrequencyOffset(rx,fs,-coarseFreqOff);

        % Extract the non-HT fields and determine fine packet offset
        nonhtfields = rx(coarsePktOffset+(ind.LSTF(1):ind.LSIG(2)),:);
        finePktOffset = wlanSymbolTimingEstimate(nonhtfields,...
                    cfgVHT.ChannelBandwidth);

        % Determine final packet offset
        pktOffset = coarsePktOffset+finePktOffset;

        % If packet detected outwith the range of expected delays from the
        % channel modeling; packet error
        if pktOffset>50
            numPacketErrors = numPacketErrors+1;
            numPkt = numPkt+1;
            continue; % Go to next loop iteration
        end

        % Extract L-LTF and perform fine frequency offset correction
        lltf = rx(pktOffset+(ind.LLTF(1):ind.LLTF(2)),:);
        fineFreqOff = wlanFineCFOEstimate(lltf,cfgVHT.ChannelBandwidth);
        rx = helperFrequencyOffset(rx,fs,-fineFreqOff);

        % Extract VHT-LTF samples from the waveform, demodulate and perform
        % channel estimation
        vhtltf = rx(pktOffset+(ind.VHTLTF(1):ind.VHTLTF(2)),:);
        vhtltfDemod = wlanVHTLTFDemodulate(vhtltf,cfgVHT);

        % Get single stream channel estimate
        chanEstSSPilots = vhtSingleStreamChannelEstimate(vhtltfDemod,cfgVHT);

        % Channel estimate
        chanEst = wlanVHTLTFChannelEstimate(vhtltfDemod,cfgVHT);

        % Extract VHT Data samples from the waveform
        vhtdata = rx(pktOffset+(ind.VHTData(1):ind.VHTData(2)),:);

        % Estimate the noise power in VHT data field
        nVarVHT = vhtNoiseEstimate(vhtdata,chanEstSSPilots,cfgVHT);

        % Recover the transmitted PSDU in VHT Data
        rxPSDU = wlanVHTDataRecover(vhtdata,chanEst,nVarVHT,cfgVHT);

        % Determine if any bits are in error, i.e. a packet error
        packetError = any(biterr(txPSDU,rxPSDU));
        numPacketErrors = numPacketErrors+packetError;
        numPkt = numPkt+1;
    end

    % Calculate packet error rate (PER) at SNR point
    packetErrorRate(i) = numPacketErrors/(numPkt-1);
    disp(['SNR ' num2str(snr(i)) ' completed after ' ...
        num2str(numPkt-1) ' packets, PER: ' ...
        num2str(packetErrorRate(i))]);
end

figure
semilogy(snr,packetErrorRate,'-ob');
grid on;
xlabel('SNR (dB)');
ylabel('PER');
title('802.11ac 80MHz, MCS9, Direct Mapping, 8x8 Channel Model D-NLOS');