function mod_2Tx_STBC_DFUSC(modparams)
% Modulation for DL FUSC

load orig_DFUSC_QAM16.mat;  % orig_DFUSC

load Wk_preamble.mat;

map=get80216map(modparams.qam);
PwNorm=sqrt(2048/1702);     % symbol power normalization factor

tx1_opfid = fopen(modparams.tx1_outfile, 'w');
if tx1_opfid < 0
   error('unable to open tx1 data file');
end

tx2_opfid = fopen(modparams.tx2_outfile, 'w');
if tx2_opfid < 0
   error('unable to open tx2 data file');
end

% -----------Preamble modulation-----------
preamdata_tx1=zeros(1,1703);
preamdata_tx2=zeros(1,1703);
preamdata_tx1(2:2:end)=sqrt(2)*sqrt(2)*2*(0.5-Wk_preamble(2:2:end));    % first sqrt(2)--3 dB Boost, second sqrt(2)-- unitary symbol power
preamdata_tx2(1:2:end)=sqrt(2)*sqrt(2)*2*(0.5-Wk_preamble(1:2:end));    % Antenna 1 use even subcarriers, Antenna 2 use odd ones
preamdata_tx1(852)=0;  % DC carrier
preamdata_tx2(852)=0;
pream_tx1_freq=[zeros(1,173),preamdata_tx1,zeros(1,172)];
pream_tx2_freq=[zeros(1,173),preamdata_tx2,zeros(1,172)];
% IFFT
pream_tx1_time=sqrt(2048)*ifft(fftshift(pream_tx1_freq),2048);
pream_tx2_time=sqrt(2048)*ifft(fftshift(pream_tx2_freq),2048);
% add Cyclic Prefix
PreamData_tx1=[pream_tx1_time(2048*(1-modparams.Guard)+1:2048), pream_tx1_time]*PwNorm;
PreamData_tx2=[pream_tx2_time(2048*(1-modparams.Guard)+1:2048), pream_tx2_time]*PwNorm;
% write to file
fwrite(tx1_opfid, [real(PreamData_tx1);imag(PreamData_tx1)], 'float32');
fwrite(tx2_opfid, [real(PreamData_tx2);imag(PreamData_tx2)], 'float32');

% ------------Data symbols-------------------
for sym=1:2:modparams.sympf      % Alamouti Scheme
    % ######## Antenna 1 , Time 1 ###########
    symdata_tx1=zeros(1,1702);
    infodata_tx1=orig_DFUSC(sym,:);
    
    % map data
    symdata_tx1=map(infodata_tx1+1);
    symdata_tx1=[symdata_tx1(1:851), 0, symdata_tx1(852:end)];      % insert DC
    
    % expand guard carriers
    Sym2048_tx1_freq_1=[zeros(1,173),symdata_tx1,zeros(1,172)];
    % IFFT
    Sym2048_tx1_time_1=sqrt(2048)*ifft(fftshift(Sym2048_tx1_freq_1),2048);
    % add Cyclic Prefix
    TxData_tx1=[Sym2048_tx1_time_1(2048*(1-modparams.Guard)+1:2048), Sym2048_tx1_time_1]*PwNorm;
    % write symbol to file
    fwrite(tx1_opfid, [real(TxData_tx1);imag(TxData_tx1)], 'float32');
    
    % ######## Antenna 2 , Time 1 ###########
    symdata_tx2=zeros(1,1702);
    infodata_tx2=orig_DFUSC(sym+1,:);
    
    % scramble data
    symdata_tx2=map(infodata_tx2+1);
    symdata_tx2=[symdata_tx2(1:851), 0, symdata_tx2(852:end)];      % insert DC
    
    % expand guard carriers
    Sym2048_tx2_freq_1=[zeros(1,173),symdata_tx2,zeros(1,172)];
    % IFFT
    Sym2048_tx2_time_1=sqrt(2048)*ifft(fftshift(Sym2048_tx2_freq_1),2048);
    % add Cyclic Prefix
    TxData_tx2=[Sym2048_tx2_time_1(2048*(1-modparams.Guard)+1:2048), Sym2048_tx2_time_1]*PwNorm;
    % write symbol to file
    fwrite(tx2_opfid, [real(TxData_tx2);imag(TxData_tx2)], 'float32');
    
    % ######## Antenna 1 , Time 2 ###########
    Sym2048_tx1_freq_2=-conj(Sym2048_tx2_freq_1);
    Sym2048_tx1_time_2=sqrt(2048)*ifft(fftshift(Sym2048_tx1_freq_2),2048);
    TxData_tx1=[Sym2048_tx1_time_2(2048*(1-modparams.Guard)+1:2048), Sym2048_tx1_time_2]*PwNorm;
    fwrite(tx1_opfid, [real(TxData_tx1);imag(TxData_tx1)], 'float32');
    
    % ######## Antenna 2 , Time 2 ###########
    Sym2048_tx2_freq_2=conj(Sym2048_tx1_freq_1);
    Sym2048_tx2_time_2=sqrt(2048)*ifft(fftshift(Sym2048_tx2_freq_2),2048);
    TxData_tx2=[Sym2048_tx2_time_2(2048*(1-modparams.Guard)+1:2048), Sym2048_tx2_time_2]*PwNorm;
    fwrite(tx2_opfid, [real(TxData_tx2);imag(TxData_tx2)], 'float32');
end

fclose(tx1_opfid);
fclose(tx2_opfid);