Signals are transmitted on sub-channels at different but mutually overlapping frequencies. A receiver separates the sub-channels into component signals Z0 . . . C254 Prior to decoding (7), interference estimates C0 . . . C254 are subtracted from the components. These estimates are deduced from the signals received on the idle sub-channels (or on sub-channels from which a known or estimated signal is subtracted), for example by calculating (10) parameters defining a model of the interference and using these (11) to generate the interference estimates.