Method of and apparatus for providing a multi-carrier modulated signal

An apparatus for providing a multi-carrier modulated signal which comprises at least one sub-band, wherein said sub-band comprises a plurality of subcarriers, said apparatus comprising:

• at least one processor;
• and
• at least one memory including computer program code;
• the at least one memory and the computer program code configured to, when executed with the at least one processor, cause the apparatus at least to:
• receive an input signal vector, wherein each component of said input signal vector is associated with one of said plurality of subcarriers,
• expand said input signal vector by adding one or more additional vector elements at least one of in front of or after the components of said input signal vector, whereby an expanded signal vector is obtained,
• upsample the expanded signal vector, whereby an upsampled signal vector is obtained,
• filter the upsampled signal vector to obtain a filtered sub-band output signal,
• apply, by means of a first calculating unit, an inverse discrete Fourier transform, (iDFT), using an inverse fast Fourier transform, (iFFT), to said expanded signal vector, to obtain a first time domain vector,
• expand said first time domain vector by adding at least one additional vector element, at least one of in front of or after the components of said first time domain vector, to obtain a second time domain vector, and
• apply, by means of a second calculating unit, a discrete Fourier transform (DFT), using a fast Fourier transform, FFT (FFT), to said second time domain vector, to obtain said upsampled signal vector,
• wherein to apply said DFT to said second time domain vector, NFFTu many points are used, wherein NFFTu is chosen to be smaller than a system bandwidth sb, wherein said system bandwidth sb is defined in accordance with the equation sb=Bmax·ni, wherein Bmax is the number of sub-bands of said multi-carrier modulated signal, and wherein ni is the number of subcarriers per sub-band.