An aspect of the invention relates to a digital generator for multi-carrier frequency division multiplexing (FDM) signals. The digital generator comprises an electronic circuit being operated under the control of a computer program. The digital generator is configured to generate FDM signals being comprised of FDM symbols, wherein at least one FDM symbol has pilot symbols which are non-equidistantly spaced in frequency. Another aspect of the invention relates to a digital receiver for multi-carrier FDM signals. The digital receiver comprises an electronic circuit being operated under the control of a computer program, and further comprises a demodulator for demodulating digital multi-carrier FDM signals, said signals being comprised of FDM symbols having pilot symbols, the pilot symbols of at least one FDM symbol being non-equidistantly spaced in frequency. Furthermore, it comprises a signal modification unit, said unit being configured to replace, on a sub-carrier basis, at least one data symbol with a pilot symbol, whereby the replacement yields a spacing of pilot symbols which is equidistant in frequency for all FDM symbols.