An interleaving method (2) and an interleaver (9) for frequency interleaving data symbols. The data symbols are for allocation to carriers in a set of NFFT carriers of a module for multiplexing and modulation by orthogonal functions in a multicarrier transmitter device (3). A block of Npm successive data symbols is interleaved in application of an interleaving law that varies over time for a given transmission mode of the transmitter device, where Npm is less than or equal to NFFT.