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 (a 0,...,a N-1, b 0,...,b M-1); - determine a first and second inverse Fast Fourier Transform (IFFT A, IFFT B) of different block lengths (A, B) in dependence on the first and second ingress modulation-symbol stream (a 0,...,a N-1, b 0,...,b M-1), respectively, wherein the second block length of the second inverse Fast Fourier Transform (IFFT B) multiplied with an integer factor equals the first block length of the first inverse Fast Fourier Transform (IFFT A); - determine first and second frequency-shifted samples (Sa; Sb) of different frequency offsets to a subcarrier frequency in dependence on the first and second inverse Fast Fourier Transform (IFFT A, IFFT B), respectively; - determine a first and second egress sample stream (d 0,...,d A-1, e 0,...,e B-1) in dependence on the first and second frequency-shifted samples (Sa; Sb), respectively; - determine a joined sample stream (g 0,...,g A-1) in dependence on the first and second frequency-shifted sample streams (d 0,...,d A-1, e 0,...,e B-1) for up-converting the joined sample stream (g 0,...,g A-1) to a carrier frequency higher than respective subcarrier frequencies; - determine an inverse Fast Fourier Transform of a synchronization sequence with the first block length; and - repeat the synchronization sequence across the available bandwidth as a synchronization signal (PSS; SSS) for different block lengths and different frequency offsets such that for the second inverse Fast Fourier Transform (IFFT B) of the second block length with the integer factor being larger than one a synchronization symbol is split in symbols of reduced length. - receive a first and second ingress modulation-symbol stream (a 0,...,a N-1, b 0,...,b M-1); - determine a first and second inverse Fast Fourier Transform (IFFT A, IFFT B) of different block lengths (A, B) in dependence on the first and second ingress modulation-symbol stream (a 0,...,a N-1, b 0,...,b M-1), respectively, wherein the second block length of the second inverse Fast Fourier Transform (IFFT B) multiplied with an integer factor equals the first block length of the first inverse Fast Fourier Transform (IFFT A); - determine first and second frequency-shifted samples (Sa; Sb) of different frequency offsets to a subcarrier frequency in dependence on the first and second inverse Fast Fourier Transform (IFFT A, IFFT B), respectively; - determine a first and second egress sample stream (d 0,...,d A-1, e 0,...,e B-1) in dependence on the first and second frequency-shifted samples (Sa; Sb), respectively; - determine a joined sample stream (g 0,...,g A-1) in dependence on the first and second frequency-shifted sample streams (d 0,...,d A-1, e 0,...,e B-1) for up-converting the joined sample stream (g 0,...,g A-1) to a carrier frequency higher than respective subcarrier frequencies; - determine an inverse Fast Fourier Transform of a synchronization sequence with the first block length; and - repeat the synchronization sequence across the available bandwidth as a synchronization signal (PSS; SSS) for different block lengths and different frequency offsets such that for the second inverse Fast Fourier Transform (IFFT B) of the second block length with the integer factor being larger than one a synchronization symbol is split in symbols of reduced length.