How to construct subband filter in UFMC/OFDM transmitter?

Hello,

In the following link, UFMC vs. OFDM Modulation, I am trying to understand the bandFilter Code block within the for loop and I need some interpretation about the usage of exponential function which multiplies the prototypeFilter.

Subband filtering

% Loop over each subband for bandIdx = 1:numSubbands

    bitsIn = randi([0 1], bitsPerSubCarrier*subbandSize, 1);
    symbolsIn = qamMapper(bitsIn);
    inpData(:,bandIdx) = bitsIn; % log bits for comparison

    % Pack subband data into an OFDM symbol
    offset = subbandOffset+(bandIdx-1)*subbandSize;
    symbolsInOFDM = [zeros(offset,1); symbolsIn; ...
                     zeros(numFFT-offset-subbandSize, 1)];
    ifftOut = ifft(ifftshift(symbolsInOFDM));

% Filter for each subband is shifted in frequency
  bandFilter = prototypeFilter.*exp( 1i*2*pi*(0:filterLen-1)'/numFFT* ...
               ((bandIdx-1/2)*subbandSize+0.5+subbandOffset+numFFT/2) );
  filterOut = conv(bandFilter,ifftOut);

    % Plot power spectral density (PSD) per subband
    [psd,f] = periodogram(filterOut, rectwin(length(filterOut)), ...
                          numFFT*2, 1, 'centered');
    plot(f,10*log10(psd));

    % Sum the filtered subband responses to form the aggregate transmit
    % signal
    txSig = txSig + filterOut;
end

In bandFilter code block, what I understand is:

1. the prototypeFilter as a window function constructed with chebwin window,
2. (0:filterLen-1) : this guarantees the filter length (as window length),
3. But I don’t understand how the rest of computing parameters are selected for bandFilter.
4. What is the meaning of (((bandIdx-1/2)*subbandSize+0.5+subbandOffset+numFFT/2)), how is bandFilter designed with this parameters?
5. Please could also explain how do we decide the filter length? Why it has not the same size of the subband?

Many thanks in advance!!

[bp]

did u get the answer for your problem

[Asma Askri]

that term corresponds shiftting the filter to the center of a given subband, but the center frequency fc of each subband=(offset+subbandsize)/2 so by sibstituting terms we get fc = subbandOffset/2+ (bandIdx-1)/2*subbandSize so it does not match what we have : (bandIdx-1/2)*subbandSize+0.5+subbandOffset+numFFT/2). Does any one has an explanation ?