HE/pktFormatDetect.m

function [cfgRx,cfgUsers,ind]= pktFormatDetect(ind,pktOffset,rx,cfgRx)
chanBW = cfgRx.ChannelBandwidth;
fs = wlanSampleRate(cfgRx);
pilotTracking = 'Joint';
%% Packet Format Detection

rxLLTF = rx(pktOffset+(ind.LLTF(1):ind.LLTF(2)),:);
lltfDemod = wlanLLTFDemodulate(rxLLTF,cfgRx.ChannelBandwidth);
lltfChanEst = wlanLLTFChannelEstimate(lltfDemod,cfgRx.ChannelBandwidth);
noiseVar = helperNoiseEstimate(lltfDemod);

% disp('Detect packet format...');
rxSIGA = rx(pktOffset+(ind.LSIG(1):ind.HESIGA(2)),:);
pktFormat = wlanFormatDetect(rxSIGA,lltfChanEst,noiseVar,cfgRx.ChannelBandwidth);
% fprintf('  %s packet detected\n\n',pktFormat);
%--------------0324----SU-special-----------
if strcmp(pktFormat,'Non-HT')
    cfgRx = wlanNonHTConfig('SignalChannelBandwidth',true, ... 
     'BandwidthOperation','Static');
%     cfgRx.PacketFormat = pktFormat;
    ind = wlanFieldIndices(cfgRx);
    cfgUsers = {cfgRx};
else  
%--------------0324----SU-special-----------

% Set the packet format in the recovery object and update the field indices
cfgRx.PacketFormat = pktFormat;
ind = wlanFieldIndices(cfgRx);

%% L-LTF Channel Estimate
lltfDemod = wlanHEDemodulate(rxLLTF,'L-LTF',chanBW);
lltfChanEst = wlanLLTFChannelEstimate(lltfDemod,chanBW);

%% L-SIG and RL-SIG Decoding
% Extract L-SIG and RL-SIG fields
rxLSIG = rx(pktOffset+(ind.LSIG(1):ind.RLSIG(2)),:);

% OFDM demodulate
helsigDemod = wlanHEDemodulate(rxLSIG,'L-SIG',chanBW);

% Estimate CPE and phase correct symbols
helsigDemod = preHECommonPhaseErrorTracking(helsigDemod,lltfChanEst,'L-SIG',chanBW);

% Estimate channel on extra 4 subcarriers per subchannel and create full
% channel estimate
preheInfo = wlanHEOFDMInfo('L-SIG',chanBW);
preHEChanEst = preHEChannelEstimate(helsigDemod,lltfChanEst,preheInfo.NumSubchannels);

% Average L-SIG and RL-SIG before equalization
helsigDemod = mean(helsigDemod,2);

% Equalize data carrying subcarriers, merging 20 MHz subchannels
[eqLSIGSym,csi] = preHESymbolEqualize(helsigDemod(preheInfo.DataIndices,:,:), ...
    preHEChanEst(preheInfo.DataIndices,:,:),noiseVar,preheInfo.NumSubchannels);

% Decode L-SIG field
[~,failCheck,lsigInfo] = wlanLSIGBitRecover(eqLSIGSym,noiseVar,csi);

if failCheck
    disp(' ** L-SIG check fail **');
else
    disp(' L-SIG check pass');
end
% Get the length information from the recovered L-SIG bits and update the
% L-SIG length property of the recovery configuration object
lsigLength = lsigInfo.Length;
cfgRx.LSIGLength = lsigLength;

% Measure EVM of L-SIG symbols
EVM = comm.EVM;
EVM.ReferenceSignalSource = 'Estimated from reference constellation';
EVM.Normalization = 'Average constellation power';
EVM.ReferenceConstellation = wlanReferenceSymbols('BPSK');
rmsEVM = EVM(eqLSIGSym);
fprintf(' L-SIG EVM: %2.2fdB\n\n',20*log10(rmsEVM/100));

% Calculate the receive time and corresponding number of samples in the
% packet
RXTime = ceil((lsigLength + 3)/3) * 4 + 20; % In microseconds
numRxSamples = round(RXTime * 1e-6 * fs);   % Number of samples in time

%% HE-SIG-A Decoding
rxSIGA = rx(pktOffset+(ind.HESIGA(1):ind.HESIGA(2)),:);
sigaDemod = wlanHEDemodulate(rxSIGA,'HE-SIG-A',chanBW);
hesigaDemod = preHECommonPhaseErrorTracking(sigaDemod,preHEChanEst,'HE-SIG-A',chanBW);

% Equalize data carrying subcarriers, merging 20 MHz subchannels
preheInfo = wlanHEOFDMInfo('HE-SIG-A',chanBW);
[eqSIGASym,csi] = preHESymbolEqualize(hesigaDemod(preheInfo.DataIndices,:,:), ...
                                      preHEChanEst(preheInfo.DataIndices,:,:), ...
                                      noiseVar,preheInfo.NumSubchannels);
% Recover HE-SIG-A bits
[sigaBits,failCRC] = wlanHESIGABitRecover(eqSIGASym,noiseVar,csi);

% Perform the CRC on HE-SIG-A bits
if failCRC
    disp(' ** HE-SIG-A CRC fail **');
else
    disp(' HE-SIG-A CRC pass');
end

% Measure EVM of HE-SIG-A symbols
% release(EVM);
% if strcmp(pktFormat,'HE-EXT-SU')
%     % The second symbol of an HE-SIG-A field for an HE-EXT-SU packet is
%     % QBPSK.
%     EVM.ReferenceConstellation = wlanReferenceSymbols('BPSK',[0 pi/2 0 0]);
%     % Account for scaling of L-LTF for an HE-EXT-SU packet
%     rmsEVM = EVM(eqSIGASym*sqrt(2));
% else
%     EVM.ReferenceConstellation = wlanReferenceSymbols('BPSK');
%     rmsEVM = EVM(eqSIGASym);
% end
% fprintf(' HE-SIG-A EVM: %2.2fdB\n\n',20*log10(mean(rmsEVM)/100));

%% Interpret Recovered HE-SIG-A bits
cfgRx = interpretHESIGABits(cfgRx,sigaBits);
ind = wlanFieldIndices(cfgRx); % Update field indices
% disp(cfgRx)


%% HE-SIG-B Decoding
if strcmp(pktFormat,'HE-MU')
    if ~cfgRx.SIGBCompression
        s = getSIGBLength(cfgRx);
        %*********************************lql03.21修改*********************************
        % 强制类型转换
        indHESIGA2 = double(ind.HESIGA(2));
        % Get common field symbols. The start of HE-SIG-B field is known
        rxSym = rx(pktOffset+(indHESIGA2+(1:s.NumSIGBCommonFieldSamples)),:);
        %*********************************lql03.21修改*********************************
        % Decode HE-SIG-B common field
        [status,cfgRx] = heSIGBCommonFieldDecode(rxSym,preHEChanEst,noiseVar,cfgRx);

        % CRC on HE-SIG-B content channels
        if strcmp(status,'Success')
            fprintf('  HE-SIG-B (common field) CRC pass\n');
        elseif strcmp(status,'ContentChannel1CRCFail')
            fprintf('  ** HE-SIG-B CRC fail for content channel-1\n **');
        elseif strcmp(status,'ContentChannel2CRCFail')
            fprintf('  ** HE-SIG-B CRC fail for content channel-2\n **');
        elseif any(strcmp(status,{'UnknownNumUsersContentChannel1','UnknownNumUsersContentChannel2'}))
            error('  ** Unknown packet length, discard packet\n **');
        else
            % Discard the packet if all HE-SIG-B content channels fail
            error('  ** HE-SIG-B CRC fail **');
        end
        % Update field indices as the number of HE-SIG-B symbols are
        % updated
        ind = wlanFieldIndices(cfgRx);
    end

    % Get complete HE-SIG-B field samples
    rxSIGB = rx(pktOffset+(ind.HESIGB(1):ind.HESIGB(2)),:);
    fprintf(' Decoding HE-SIG-B user field... \n');
    % Decode HE-SIG-B user field
    [failCRC,cfgUsers] = heSIGBUserFieldDecode(rxSIGB,preHEChanEst,noiseVar,cfgRx);

    % CRC on HE-SIG-B users
    if ~all(failCRC)
        fprintf('  HE-SIG-B (user field) CRC pass\n\n');
        numUsers = numel(cfgUsers);
    elseif all(failCRC)
        % Discard the packet if all users fail the CRC
        error('  ** HE-SIG-B CRC fail for all users **');
    else
        fprintf('  ** HE-SIG-B CRC fail for at least one user\n **');
        % Only process users with valid CRC
        numUsers = numel(cfgUsers);
    end

else % HE-SU, HE-EXT-SU
    cfgUsers = {cfgRx};
    numUsers = 1;
end
end