I am confused if the way the code converting serial to parallel is correct or not. The comments says" convert serial to parallel" but the code below the comment does the opposite. Please advise. if you need the whole code, i can email it to you.

%%define the modems Tx/Rx
switch typ
    case 1
        Tx=modem.qammod('M',M);
        Rx=modem.qamdemod ('M',M);
    case 2
        Tx=modem.pskmod('M',M);
        Rx=modem.pskdemod ('M',M);
    otherwise
        error('Error, Constellation Family not Defined');
end
%%data generation 
D=randi ([0 M-1],m,N);
D_Mod=modulate(Tx,D);
%%serial to parallel
D_Mod_serial=D_Mod.';
%%specify Pilot & Data Locations
PLoc = 1:pilotFrequency:N; % location of pilots
DLoc = setxor(1:N,PLoc); % location of data
%%Pilot Insertion
D_Mod_serial(PLoc,:)=E*D_Mod_serial(PLoc,:);
figure;
imagesc(abs(D_Mod_serial ))
%%inverse discret Fourier transform (IFFT)
%  Amplitude Modulation
d_ifft=ifft(D_Mod_serial);
%%parallel to serial
d_ifft_parallel=d_ifft.';
%%Adding Cyclic Prefix
CP_part=d_ifft_parallel(:,end-Ncp+1:end); % this is the Cyclic Prefix part to be appended.
ofdm_cp=[CP_part d_ifft_parallel];

Answer 1

[Walter Roberson]

Ask the author http://www.mathworks.com/matlabcentral/fileexchange/46856-channel-estimation-using-ls-and-mmse-estimators

[Ray]

I did, unfortunately the author did not respond to my question.