function rxWaveform = heSigRecGenerateWaveform(cfgMU,numRx,delayProfile,noisePower,cfo)
%heSigRecGenerateWaveform Generate an impaired waveform for the featured example

%   Copyright 2018-2019 The MathWorks, Inc.

% Specify waveform parameters
numTxPkt = 1; % Number of transmitted packets
idleTime = 20e-6; % Idle time before and after each packet

% Setup TGax Indoor channel
chanBW = cfgMU.ChannelBandwidth;
numTx = cfgMU.NumTransmitAntennas;
sr = wlanSampleRate(cfgMU);

% Create channel configuration common for all users
tgaxChannel = wlanTGaxChannel;
tgaxChannel.DelayProfile = delayProfile;  % Delay profile
tgaxChannel.NumTransmitAntennas = numTx;  % Number of transmit antennas
tgaxChannel.NumReceiveAntennas = numRx;   % Each user has two receive antennas
tgaxChannel.TransmitReceiveDistance = 10; % Non-line of sight distance
tgaxChannel.ChannelBandwidth = chanBW;
tgaxChannel.SampleRate = sr;
% Set a fixed seed for the channel
tgaxChannel.RandomStream = 'mt19937ar with seed';
tgaxChannel.Seed = 1;

rngState = rng(120); % Set random state

% Get allocation info
allocInfo = ruInfo(cfgMU);
muPSDULengths = getPSDULength(cfgMU);
% Create a MAC frame
[macFrames,cfgMU] = createMACFrames(cfgMU,allocInfo);
macFrames = addMUPadding(macFrames,muPSDULengths);
txPSDUPerUser = macFrames;

% Generate HE-MU waveform with idle period
txWaveform = wlanWaveformGenerator(txPSDUPerUser,cfgMU, ...
    'NumPackets',numTxPkt,'IdleTime',idleTime);

% Add channel
chanOut = tgaxChannel([zeros(round(idleTime*sr),numTx); txWaveform]);

% Add carrier frequency offset
chanOut = helperFrequencyOffset(chanOut,sr,cfo);

% Add noise
awgnChannel = comm.AWGNChannel( ...
    'NoiseMethod', 'Variance', ...
    'Variance',    10^(noisePower/10));

rxWaveform = awgnChannel(chanOut);
rng(rngState); % Restore random state


function [macFrames,cfgHE] = createMACFrames(cfgHE,allocInfo)
%createMACFrames Creates HE-MU MAC frames

% Limitation:
% -----------
% * wlanMACFrame does not support wlanHEMUConfig object. The MAC
% frame format is same for HE-SU and HE-MU packet, we are using
% wlanHESUConfig object to create a separate MAC frame for each user in
% an HE-MU configuration.
%
% * Channel coding option "BCC" is not supported for bandwidth > 20MHz
% in HE-SU format. If the bandwidth is > 20 MHz, we are forcing the channel
% coding value to "LDPC". This does not affect the generated MAC frame
% unless "MinimumMPDUStartSpacing" parameter is set to a value > 0. 

if isa(cfgHE,'wlanHEMUConfig')
    numUsers = allocInfo.NumUsers;
    numRUs = allocInfo.NumRUs;
    apepLength = zeros(numUsers,1);
    cfgSU = cell(numUsers,1);
    for ru = 1:numRUs
        for u = 1:numUsers
            apepLength(u) = cfgHE.User{u}.APEPLength;
            if strcmp(cfgHE.ChannelBandwidth,'CBW20')
                chCoding = cfgHE.User{u}.ChannelCoding;
            else
                chCoding = 'LDPC';
            end
            cfgSU{u} = wlanHESUConfig(...
                'APEPLength',          apepLength(u), ...
                'ChannelBandwidth',    cfgHE.ChannelBandwidth, ...
                'SpatialMapping',      cfgHE.RU{ru}.SpatialMapping, ...
                'NumSpaceTimeStreams', allocInfo.NumSpaceTimeStreamsPerRU(ru), ...
                'MCS',                 cfgHE.User{u}.MCS, ...
                'DCM',                 cfgHE.User{u}.DCM, ...
                'ChannelCoding',       chCoding, ...
                'NumTransmitAntennas', cfgHE.NumTransmitAntennas, ...
                'STBC',                cfgHE.STBC, ...
                'GuardInterval',       cfgHE.GuardInterval, ...
                'HELTFType',           cfgHE.HELTFType, ...
                'SpatialReuse',        cfgHE.SpatialReuse);
        end
    end
else % HE-SU, HE-EXT-SU
    numUsers = 1;
    apepLength = cfgHE.APEPLength;
    cfgSU = {cfgHE};
end

% Create a MAC frame configuration
cfgMAC = wlanMACFrameConfig('FrameType','QoS Data','FrameFormat',cfgSU{1}.packetFormat);

macFrames = cell(numUsers, 1);
for i = 1:numUsers
    % Create payload (MSDUs) for the MAC frame
    msduLen = wlanMSDULengths(apepLength(i),cfgMAC,cfgSU{i});
    msdu = cell(1, numel(msduLen));
    for j = 1:numel(msduLen)
        msdu{j} = randi([0,255],msduLen(j),1);
    end

    % Create the MAC frame bits
    [macFrames{i},length] = wlanMACFrame(msdu,cfgMAC,cfgSU{i},'OutputFormat','bits');

    % Update the APEP length. APEP length is always rounded off to a
    % multiple of 4-octets.
    if isa(cfgHE, 'wlanHEMUConfig')
        cfgHE.User{i}.APEPLength = length;
    else
        cfgHE.APEPLength = length;
    end
end

end

end

function macFrames = addMUPadding(macFrames, muPSDULengths)
%addMUPadding Adds or removes the padding difference between an HE-SU and HE-MU PSDU

    numFrames = numel(macFrames);
    eofDelimiter = [1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 1 1 0 0 1 1 1 0 0 1 0]';
    delimiterLength = 4;
    
    for i = 1:numFrames
        assert(rem(numel(macFrames{i}),8) == 0,'Number of bits in the MAC frame is not a multiple of 8')
        psdu = macFrames{i};
        psdu = psdu(1 : end-rem(numel(macFrames{i})/8,4)*8);
        psduLength = numel(psdu)/8;
        % Difference between the required padding for SU and MU formats
        muPadding = muPSDULengths(i) - psduLength;

        % Calculate the number of EOF delimiters and zero padding needed
        % for the MU padding
        numEOFDelimiters = floor(abs(muPadding)/4);
        wordPadding = rem(abs(muPadding),4);

        if muPadding < 0
            % Delete the extra padding created with wlanHESUConfig object
            macFrames{i} = psdu(1 : end - (numEOFDelimiters*delimiterLength*8 + wordPadding*8));
        else
            % Add MU padding to the PSDU
            macFrames{i} = [psdu; repmat(eofDelimiter, numEOFDelimiters,1); zeros(wordPadding*8,1)];
        end
    end
end