Abstract: A method of recovering data in a line signal which is predicted to be subjected to repetitive noise impulses, the line signal comprising a series of data frames, the method comprising the steps of: predicting a group comprising one or more frames in said line signal which are expected to be corrupted by a noise signal; blanking said group of one or more frames which are predicted to be corrupted; determining the preceding and succeeding frames adjacent to said group; and including in each said group of one or more frames one or more parity blocks wherein if said noise signal deviates from its predicted timing interval or duration and corrupts the data carried in one or more of said frames adjacent to said group, the corrupted data is recovered using one or more of said parity blocks of said group of blanked frames and the other one of said adjacent frames.

Abstract: 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.

Abstract: A method of recovering data in a line signal which is predicted to be subjected to repetitive noise impulses, the line signal comprising a series of data frames, the method comprising the steps of: predicting a group comprising one or more frames in said line signal which are expected to be corrupted by a noise signal; blanking said group of one or more frames which are predicted to be corrupted; determining the preceding and succeeding frames adjacent to said group; and including in each said group or more frames one or more parity blocks wherein if said noise signal deviates from its predicted timing interval or duration and corrupts the data carried in one or more of said frames adjacent to said group, the corrupted data is recovered using one or more of said parity blocks of said group of blanked frames and the other one of said adjacent frames.

Abstract: A signal is filtered by multiplying its Fourier transform by the Fourier transform of a reference sequence to which the filtering is to be matched. The reference sequence (e.g. a Golay sequence pair) is defined as an iterative combination of shorter sequences and its Fourier transform is generated by an iterative process of combining the Fourier transforms of a shorter starting sequence.

Abstract: Multiple carriers are generated, modulated by data to be transmitted, as shown by oscillators and modulators (or using Fourier transform techniques). They follow two paths. One path via an adder takes a set of carriers at integer multiples of a windowing frequency where the odd carriers have some reference phase and the even carriers are in phase quadrature. The other path via an adder takes a second set of carriers, again at integer multiples of the windowing frequency. The even carriers have a reference phase and the odd carriers are in phase quadrature therewith. In the first path, the signal is multiplied by a windowing function with a period equal to the reciprocal of the windowing frequency. In the second path, the signal is multiplied by a similar function which is time-shifted (by a delay) by half of the period.