Abstract: The invention relates to a signal intended to be transmitted towards a plurality of receivers, of the type comprising at least two source signals and consisting of a plurality of independently modulated substantially orthogonal carrier frequencies distributed over a predetermined frequency band. According to the invention, the frequency band is divided into at least two frequency sub-bands each comprising a set of the substantially orthogonal carrier frequencies, and to each of the sub-bands is allocated one of the source signals, so that a receiver may retrieve from the transmitted signal, by filtration, at least one of the sub-bands and perform demodulation processing only on the carrier frequencies contained in the retrieved sub-bands. The invention also relates to a transmission process as well as to a receiver of such signal.

Abstract: The invention relates to a signal intended to be transmitted towards a plurality of receivers, of the type comprising at least two source signals and consisting of a plurality of independently modulated substantially orthogonal carrier frequencies distributed over a predetermined frequency band. According to the invention, said frequency band [(12)] is divided into at least two frequency sub-bands [(131-134)] each comprising a set of said substantially orthogonal carrier frequencies [(11)], and to each of said sub-bands is allocated one of said source signals, so that a receiver may retrieve from the transmitted signal, by filtration, at least one of said sub-bands and perform demodulation processing only on the carrier frequencies contained in the retrieved sub-bands. The invention also relates to a transmission process as well as to a receiver of such signal.

Abstract: The invention relates to a signal intended to be transmitted towards a plurality of receivers, of the type comprising at least two source signals and consisting of a plurality of independently modulated substantially orthogonal carrier frequencies distributed over a predetermined frequency band. According to the invention, said frequency band (12) is divided into at least two frequency sub-bands (131-134) each comprising a set of said substantially orthogonal carrier frequencies (11), and to each of said sub-bands is allocated one of said source signals, so that a receiver may retrieve from the transmitted signal, by filtration, at least one of said sub-bands and perform demodulation processing only on the carrier frequencies contained in the retrieved sub-bands. The invention also relates to a transmission process as well as to a receiver of such signal.

Abstract: A method and apparatus for the coherent demodulation of a digital signal constituted by digital elements distributed in the time-frequency space and transmitted in the form of symbols constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of said digital elements and broadcast simultaneously, the digital signal also including reference elements having a known value position in said time frequency space. The method includes a Fourier transform of at least samples of said digital signal containing said reference elements from a frequency domain into a temporal domain, a weighting of the transformed samples in the temporal domain by a rectangular temporal window f.sub.n, a thresholding of the transformed samples in the temporal domain to eliminate any samples below a predetermined threshold, and a reverse Fourier transform of the samples remaining after said weighting and thresholding from the temporal domain into the frequency domain for projection onto said digital signal.

Abstract: A method for the broadcasting of digital data, intended to be received notably by mobile receivers moving about in an urban environment, that is, under conditions of multiple propagation and in the presence of parasites and jamming, enabling a coherent demodulation under such conditions of reception. This method is one for the broadcasting of digital data, notably for radio broadcasting at a high bit rate towards mobile receivers, of the type providing for the distribution of the data in the form of digital elements in the frequency-time space f-t and the transmission of symbols each constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of digital elements and broadcast simultaneously, certain of the digital elements being reference elements with a value and position in the frequency-time space f-t that are known to the receivers.

Abstract: A method for the broadcasting of digital data, in channels to which multiple paths are assigned, the characteristics of which vary in time, with time-frequency interlacing and assistance in the acquisition of the automatic frequency control. This method is one of the type providing for the distribution of the data in the form of digital elements in the frequency-time space f-t and the transmission of frames of symbols each constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of the digital elements and broadcast simultaneously, the method providing for the transmission of a pattern of frequency synchronization, recurrent in time. It can be applied notably for radio broadcasting at a high bit rate towards mobile receivers, and for example, to COFDM radio broadcasting.

Abstract: A device for the transmission of digital data with at least two levels of protection, of the type providing for the distribution of the data to be transmitted in the form of digital elements in the time-frequency space and the transmission of symbols each formed by a multiplex of N orthogonal carriers modulated by a set of the digital elements, and transmitted simultaneously, the device including channel encoding means comprising at least two types of modulation and/or at least two encoding efficiency levels. This enables to optimize the use of the transmission channel by assigning differentiated transmission techniques to portions of data of a same digital train as a function of the different levels of protection sought, against transmission errors.

Abstract: A device for the transmission of digital data with at least two levels of protection, of the type providing for the distribution of the data to be transmitted in the form of digital elements in the time-frequency space and the transmission of symbols each formed by a multiplex of N orthogonal carriers modulated by a set of the digital elements, and transmitted simultaneously, the device including channel .[.encoding.]. .Iadd.encodes .Iaddend.means comprising at least two types of modulation and/or at least two encoding efficiency levels. This enables to optimize the use of the transmission channel by assigning differentiated transmission techniques to portions of data of a same digital train as a function of the different levels of protection sought, against transmission errors.