Abstract: A method for the time synchronization of a multi-carrier signal receiver consisting of a sequence of symbols each formed by a plurality of carrier frequencies. Each carrier frequency is modulated by a modulation coefficient. The position of some of said carrier frequencies in the time-frequency space is known to the receiver, and said frequencies are reference carrier frequencies. Each reference carrier frequency bears a reference coefficient with a value that is known to the receiver. The method includes a fine synchronization step, wherein the signal transmission channel impulse response is estimated on the basis of reference coefficients belonging to at least two received symbols. The beginning of the useful portion of each of the symbols is determined, and/or a receiver clock is controlled by analyzing the estimate of said impulse response.

Abstract: The invention relates to a method and to a system for measuring the quality of digital television signals comprising a data stream, the method including measuring quality and producing measurement signals that are representative of quality. The method comprises the following steps: a) selecting a reference time signal (PCR) from the data stream; b) generating a multibit digital clock signal (STC′) from the reference time signal, the phase of the clock signal being locked on the basis of the reference time signal (PCR) and its count being deduced unambiguously from the count of an initial time base (STC); and c) labelling the measurement signals with at least some of the bits (HDT) of the digital clock signal that are meaningful given the nature of the measurements performed.

Abstract: A method and an equipment for allocating to a television program, which is already conditionally accessed, a complementary conditional access. The television program is first received by means provided with access entitlements and the control words are restored. Complementary access control messages and complementary entitlement management messages corresponding to a complementary access control system are built up. The initial unmodified television program is rebroadcast, together with the complementary messages related to the complementary access control system.

Abstract: The invention concerns a multicarrier signal designed to be transmitted to digital receivers, especially in a non-stationary transmission channel, corresponding to the frequency multiplexing of several elementary carriers each corresponding to a series of symbols, two consecutive symbols being separated by a symbol time &tgr;0, a signal in which, firstly, the spacing &ngr;0 between two neighboring carriers is equal to half of the reverse of the symbol time &tgr;0 and, secondly, each carrier undergoes an operation of filtering for the shaping of its spectrum having a bandwidth strictly greater than twice said spacing between carriers &ngr;0 and is spectrum is chosen so that each symbol element is highly concentrated in the temporal domain and in the frequency domain. The invention also concerns the methods for the transmission and reception of such a signal.

Abstract: An antenna receives beams from telecommunication satellites in geostationary orbit close to the equator. The continuous concave reflecting surface of the reflector of the antenna has an equation deduced from a paraboloid by adding thereto the equation of a correction surface comprising a second order polynomial and a sum of N(2N−1) terms depending on distances between the projection of any point on the reflecting surface and N(2N−1) control points of a grid extending over a plane perpendicular to the plane of symmetry. The angular separation of the primary sources on a circular support with an inclination different from the angle of offset is less than approximately 3° for an aperture of more than 50°.

Abstract: To interleave or deinterleave data elements in first and second blocks transmitted alternately and each having N data elements with rank n lying between 0 and N−1, N being an integer, the data elements with ranks 0, . . . n, . . . N−1 in the first blocks are ordered in accordance with the successive ranks A(0), . . . A(n), . . . A(N−1) and the data elements with ranks 0, . . . n, . . . N−1 in the second block are ordered in accordance with the successive ranks A−1(0), . . . A−1(n), . . . A−1(N−1). A and A−1 are different functions such that A−1(A(n))=n.

Abstract: A system for broadcasting data (D) that can transmit information in the passband of a broadcast audio-frequency signal (S). The system can determine at least one frequency band (F'.sub.13, . . . , F'.sub.24) and the amplitude (A'.sub.13, . . . , A'.sub.24) of the audio-frequency signal (S). The system compares this amplitude with an auditory masking level (Nm(13), . . . , Nm(24)) associated with this frequency band and eliminates the frequency components of the audio-frequency signal in the frequency band if the amplitude of the signal is lower than the auditory masking level of the band. The system can insert the data in this frequency band at a level lower than or equal to the auditory masking level of the frequency band.

Abstract: Disclosed are a method and a device for the convolutive encoding of blocks each formed by a predetermined number N of source data elements, wherein each of said source data elements is introduced twice into one and the same convolutive encoder implementing a generating polynomial with a period L in an order such that the two instances of introduction of one and same source data element d.sub.i are separated by the introduction of (p.sub.i.L)-1 other source data elements, p.sub.i being a non-zero integer. Also disclosed are a corresponding decoding method and device that can be applied, in particular, to the transmission of short messages, for example in radiotelephony, for satellite communications or gain computer telecommunications (Internet for example). FIG. 2.

Abstract: The invention relates to a device for the reception of signals formed by a series of digital symbols corresponding to the convolutive encoding of items of source digital data comprising p cascade-connected detection and decoding modules M.sub.1 to M.sub.p, p being greater than or equal to 2, each of said modules M.sub.i including: (a) inter-symbol interference correction means supplied by a symbol input R.sub.i and delivering estimated symbols A.sub.i,1 with weighted values, (b) means for the decoding of said estimated symbols A.sub.i,1, performing operations symmetrical to said convolutive encoding and delivering decoded symbols A.sub.i,2 with weighted values, and (c) means for the computation of an item of correction information Z.sub.i+1 from said estimated symbol A.sub.i,1 and said decoded symbol A.sub.i,2, (d) said means for the correction of each of said modules M.sub.i, except for the first module M.sub.1, taking account of at least one item of correction information Z.sub.

Abstract: A method and device are provided for reducing RF transmission interference to a wanted signal of an interactive TV network which is impaired by an interfering signal present on a terrestrial and satellite RF network. The wanted signal is received in the presence of the interfering signal so as to obtain a received wanted signal in the presence of the interferer. The interfering signal transmitted by the satellite network is duplicated and delayed so as to obtain a received interfering signal similar to the interfering signal present with the wanted signal. The received interfering signal is subtracted from the wanted signal in the presence of the interfering signal, so as to deliver a received wanted signal free of interfering signal.

Abstract: A method for the dynamic reconfiguration of a signal frame structure, wherein each frame is structured in at least one subchannel having a number, order and/or format capable of being altered under the control of a reallocation command, time interleaving on N frames being selectively performed for each subchannel. According to the method, in the transient state, and for the N frames following a reallocation command, the procedure for writing data elements according to the interleaving law remains unchanged, in accordance with the new structure defined by a reallocation command, and a specific logic for rereading the memory plane is implemented so that the frames consist of uniform capacity units comprising data elements from the same source signal. The corresponding transmitters, receivers and signals are also disclosed.

Abstract: A digital signal to be received by a plurality of receivers, particularly restricted-range receivers, and divided into signal frames of which at least some include both a main data channel consisting of sub-channels, and a data transport path including at least one data channel consisting of separate data blocks dedicated to a single service and known as containers. Each container includes a header (41) consisting of a selection sub-header (44) containing, inter alia, data (46) for identifying a group of at least one container destination receiver, and a service sub-header (45) containing, inter alia, dedicated service data; a separately convolutionally coded working data field (42) containing source data for a given service; and an error detection and/or correction data field 943).

Abstract: A method for filtering a time signal (e(t)) sampled in blocks of N samples (e(n),e(k)) uses a transfer function defined in the frequency domain by LN samples (H(K)). The transfer function is filtered by a time window (g1) of width N, and a frequency subsampling of ratio N is performed to give a partial transfer function defined over N samples (H1(k)). The method enables the complexity of circuits operating in real time to be optimized. The technique is particularly suitable for correcting long echoes in television picture receivers.

Abstract: Process for the broadcasting of programmes with progressive conditional access and separation of the information flow, as well as the corresponding receiver,In order to form the elementary flow, groups of m successive elements of the multiplex are taken and for forming the complimentary flow groups of p successive elements of the multiplex are taken.Application to television with entitlement checking.

Abstract: A system for management of the usage of consultations in a telecommunication network, in which one consultation is carried out by communication between a remote server center, and a local subscriber terminal, via a telecommunication link of switched type. A usage management module is provided, which is external to the link and makes it possible, through interactive communication between the local subscriber terminal and the management module, as well as between the management module and the remote server center, to set up, monitor and acknowledge the usage between the remote server center and a subscriber terminal.

Abstract: The present invention concerns a method of controlling the mode of access to wanted signals, such as picture signals (IMAGE), whereby the user selects an access mode to a wanted signal remotely. A first access mode consists in supplying the user with the original wanted signal (IMAGE), and second access mode consists in transmitting to the user alternately and periodically the wanted signal and a jamming signal (MIRE, IT) into a jammed signal. This jammed signal remains intelligible so that the user can determine the content of the wanted signal and, if necessary, select the first access mode. The two access modes are billed differently. Hardware implementations of the method are described for switching grids of switching nodes in a centralized architecture, and for digital distribution networks with a more futuristic distributed type architecture.

Abstract: Process for the transmission and reception of conditional access programs controlled by the same operator.According to the invention, specific check words (MCSi) are formed for various programs of the same operator from a root check word individual to said operator. The check words of the access titles include a part which is common to all the programs controlled by the same operator and a part which is specific to each program.Uses in television, radio, data transmission, messaging, etc.

Abstract: A process and device for segmentation into and reconstruction from sub-bands of a digital signal each sample of which are submitted to a parallel processing on a plurality of paths by prototype filtering modulated by a periodic function and sub-sampling by the number of sub-bands. A combination of a filtering of modified polyphase type and of a processing by frequency transform is therefor performed so as to deliver a sub-band signal for each path of corresponding rank. Reconstruction comprises in combination the dual steps of frequency transform and modified polyphase filtering so as to deliver a reconstructed digital signal. Corresponding modules for frequency transform and modifyed polyphase filtering are embodied through MOT or PRMF filters.

Abstract: A neural network system is provided that includes a network of neural operators pilot controlled by a control unit. The activities calculated by the operators are memorized in associated memory spaces that are addressable by an activity address. To facilitate reconfiguring the network, the memory space of at least one portion of the operators contains the activity addresses of other operators of the network. Hence, the input activities of these operators may be issued from any other operators in a way that is modifiable by simply changing the values of the activity addresses. The invention is particularly suited to image and sound analysis and synthesis.

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.