An OFDM-modulator for operating in a radio device (BS; UE) of a cellular radio communications network, wherein the OFDM-modulator comprises a processor (P1; P2) and a memory (M1; M2) being configured to: - receive a first and second ingress modulation-symbol stream (b 0,...,b M-1, c 0,...,c P-1); - receive a third ingress modulation-symbol stream (a 0,...,a N-1); - determine a first and second inverse Fast Fourier Transform (IFFT B1, IFFT B2) of the same first block length in dependence on the first and second ingress modulation-symbol stream (b 0,...,b M-1, c 0,...,c P-1), respectively; - determine a third inverse Fast Fourier Transform (IFFT A) of a second block length in dependence on the third ingress modulation-symbol stream (a 0,...,a N-1), wherein the first block length multiplied with an integer factor is equal to the second block length; - determine first and second frequency-shifted samples (Sb2; Sb3) of different frequency offsets (Δf2, Δf3) to a subcarrier frequency in dependence on the first and second inverse Fast Fourier Transform (IFFT B1, IFFT B2), respectively, wherein the different frequency offsets (Δf2, Δf3) are determined on a subcarrier basis in order to use subcarrier subspaces; - determine third frequency-shifted samples (Sa) of a third frequency offset (Δf1) to the subcarrier frequency in dependence on the third inverse Fast Fourier Transform (IDFT A); - determine the first frequency offset (Δf2) for the first inverse Fast Fourier Transform (IFFT B1), wherein the first inverse Fast Fourier Transform (IFFT B1) occupies a first subcarrier subset in a subcarrier range; - determine the second frequency offset (Δf3) for the second inverse Fast Fourier Transform (IFFT B2), wherein the second inverse Fast Fourier Transform (IFFT B2) occupies a second subcarrier subset in the subcarrier range; - wherein the first and second subcarrier subsets are interleaved comb-like; - determine a first and second egress sample stream (e 0,...,e B-1, f 0,...,f B-1) in dependence on the first and second frequency-shifted samples (Sb2; Sb3), respectively; - determine a third egress sample stream (c 0,...,c A-1) in dependence on the third frequency-shifted samples (Sa); and - determine a joined sample stream (g 0,...g B-1) in dependence on the first, second and third egress sample stream (e 0,...,e B-1, f 0,...,f B-1, c 0,...,c A-1) for up-converting the joined sample stream (g 0,...,g B-1) to a carrier frequency higher than respective subcarrier frequencies. - receive a first and second ingress modulation-symbol stream (b 0,...,b M-1, c 0,...,c P-1); - receive a third ingress modulation-symbol stream (a 0,...,a N-1); - determine a first and second inverse Fast Fourier Transform (IFFT B1, IFFT B2) of the same first block length in dependence on the first and second ingress modulation-symbol stream (b 0,...,b M-1, c 0,...,c P-1), respectively; - determine a third inverse Fast Fourier Transform (IFFT A) of a second block length in dependence on the third ingress modulation-symbol stream (a 0,...,a N-1), wherein the first block length multiplied with an integer factor is equal to the second block length; - determine first and second frequency-shifted samples (Sb2; Sb3) of different frequency offsets (Δf2, Δf3) to a subcarrier frequency in dependence on the first and second inverse Fast Fourier Transform (IFFT B1, IFFT B2), respectively, wherein the different frequency offsets (Δf2, Δf3) are determined on a subcarrier basis in order to use subcarrier subspaces; - determine third frequency-shifted samples (Sa) of a third frequency offset (Δf1) to the subcarrier frequency in dependence on the third inverse Fast Fourier Transform (IDFT A); - determine the first frequency offset (Δf2) for the first inverse Fast Fourier Transform (IFFT B1), wherein the first inverse Fast Fourier Transform (IFFT B1) occupies a first subcarrier subset in a subcarrier range; - determine the second frequency offset (Δf3) for the second inverse Fast Fourier Transform (IFFT B2), wherein the second inverse Fast Fourier Transform (IFFT B2) occupies a second subcarrier subset in the subcarrier range; - wherein the first and second subcarrier subsets are interleaved comb-like; - determine a first and second egress sample stream (e 0,...,e B-1, f 0,...,f B-1) in dependence on the first and second frequency-shifted samples (Sb2; Sb3), respectively; - determine a third egress sample stream (c 0,...,c A-1) in dependence on the third frequency-shifted samples (Sa); and - determine a joined sample stream (g 0,...g B-1) in dependence on the first, second and third egress sample stream (e 0,...,e B-1, f 0,...,f B-1, c 0,...,c A-1) for up-converting the joined sample stream (g 0,...,g B-1) to a carrier frequency higher than respective subcarrier frequencies.