Abstract: A message-passing iterative decoding method of an associated LFSR sequence (or M-sequence) as a simplex code, to a parity matrix H. The method includes determining a set of parity polynomials with a low weight obtained by combining the parity equations of the matrix H. For each combination of K such polynomials of this set, an extended parity matrix Hext is built by concatenating elementary parity matrices associated with the parity polynomials of said combination. The combination of parity polynomials leading to a bipartite graph not having cycles with a length 4 and having a minimum number of cycles with lengths 6 and 8 is selected. Then, the LFSR sequence is decoded using the bipartite graph corresponding to the selected combination. This decoding method enables the false-alarm rate to be substantially reduced.

Abstract: A method for acquiring a Gold code, obtained as a sum of a first M-sequence (x) and a second M-sequence (yi), the first M-sequence being generated by a first generator polynomial (gx) and the second M-sequence being generated by a second generator polynomial (gy), the weight of the first generator polynomial being lower than the weight of the second generator polynomial, the acquiring method involving a first step of message passing decoding according to a first bipartite graph the edges of which are determined by the coefficients of the first generator polynomial, a decimation step using a predetermined decimation factor, and a second step of message passing decoding according to a second bipartite graph the edges of which are determined by a third generator polynomial having a minimum weight generating a third M-sequence having the same length as that of the second M-sequence.

Abstract: A message-passing iterative decoding method of an associated LFSR sequence (or M-sequence) as a simplex code, to a parity matrix H. The method includes determining a set of parity polynomials with a low weight obtained by combining the parity equations of the matrix H. For each combination of K such polynomials of this set, an extended parity matrix Hext is built by concatenating elementary parity matrices associated with the parity polynomials of said combination. The combination of parity polynomials leading to a bipartite graph not having cycles with a length 4 and having a minimum number of cycles with lengths 6 and 8 is selected. Then, the LFSR sequence is decoded using the bipartite graph corresponding to the selected combination. This decoding method enables the false-alarm rate to be substantially reduced.

Abstract: A method for acquiring a Gold code, obtained as a sum of a first M-sequence (x) and a second M-sequence (yi), the first M-sequence being generated by a first generator polynomial (gx) and the second M-sequence being generated by a second generator polynomial (gy), the weight of the first generator polynomial being lower than the weight of the second generator polynomial, the acquiring method involving a first step of message passing decoding according to a first bipartite graph the edges of which are determined by the coefficients of the first generator polynomial, a decimation step using a predetermined decimation factor, and a second step of message passing decoding according to a second bipartite graph the edges of which are determined by a third generator polynomial having a minimum weight generating a third M-sequence having the same length as that of the second M-sequence.

Abstract: The invention relates to a method of acquiring a GPS signal, spread by a Gold sequence obtained as the sum of a first M-sequence and a second M-sequence, this second M-sequence being characteristic of a satellite among a plurality of satellites in the GPS system. The acquisition method comprises a sampling step starting from a given time (410), a multiplication step for the sequence of samples obtained with the first M-sequence (420) and an iterative decoding step for the decoded values (430) making it possible to estimate the content of the second shift register of the second M-sequence at said given time. If the content thus estimated is identical to the initial content of the second register for an identified satellite (443), the receiver is synchronized with this satellite at said given time (490).

Abstract: A method for estimating a scrambling code used on the uplink of a CDMA 2000 system. The received signal is firstly sampled at twice the chip frequency of the spreading code, and then filtered with a filter adapted to the spreading code and to pulse shaping. Differential processing of the successive samples is applied on the signal thus filtered and the differential values thus obtained are decoded using iterative belief propagation decoding. The decoded values are then used to determine the content of the shift register of the scrambling code generator at a given instant.

Abstract: A method for estimating a scrambling code used on an uplink of a WCDMA system. The scrambling code is obtained from a Gold code, sum of a first specific M-sequence of the user and of a second M-sequence known from the receiver. After sampling of the signal received at the chip frequency of the scrambling code, the successive samples are subject to a differential treatment and the sequence of differential values is multiplied by the second M-sequence. The observables thereby obtained are decoded with the aid of a belief propagation iterative decoding. The decoded values then serve to determine the content of the shift register of the generator of the first M-sequence. One then deduces therefrom the Gold code and an estimation of the scrambling code, ?.

Abstract: The invention relates to a method of acquiring a GPS signal, spread by a Gold sequence obtained as the sum of a first M-sequence and a second M-sequence, this second M-sequence being characteristic of a satellite among a plurality of satellites in the GPS system. The acquisition method comprises a sampling step starting from a given time (410), a multiplication step for the sequence of samples obtained with the first M-sequence (420) and an iterative decoding step for the decoded values (430) making it possible to estimate the content of the second shift register of the second M-sequence at said given time. If the content thus estimated is identical to the initial content of the second register for an identified satellite (443), the receiver is synchronised with this satellite at said given time (490).

Abstract: A method for estimating a scrambling code used on the uplink of a CDMA 2000 system. The received signal is firstly sampled at twice the chip frequency of the spreading code, and then filtered with a filter adapted to the spreading code and to pulse shaping. Differential processing of the successive samples is applied on the signal thus filtered and the differential values thus obtained are decoded using iterative belief propagation decoding. The decoded values are then used to determine the content of the shift register of the scrambling code generator at a given instant.

Abstract: A method for estimating a scrambling code used on an uplink of a WCDMA system. The scrambling code is obtained from a Gold code, sum of a first specific M-sequence of the user and of a second M-sequence known from the receiver. After sampling of the signal received at the chip frequency of the scrambling code the successive samples are subject to a differential treatment and the sequence of differential values is multiplied by the second M-sequence. The observables thereby obtained are decoded with the aid of a belief propagation iterative decoding. The decoded values then serve to determine the content of the shift register of the generator of the first M-sequence. One then deduces therefrom the Gold code and an estimation of the scrambling code, ?.

Abstract: A method for soft demapping of complex-valued symbols y(k) (k=1, 2, . . . , K) by calculation of a Logarithm of Likelihood Ratio (LogLR) such that: Log ? ? LR ? ( b I , q ) = ln ? ? ? ? ? S l , q ( 1 ) ? exp ( - 1 2 ? ? ? ? y ~ ? ( k ) - ? ? 2 ) ? ? ? ? S q , l ( 0 ) ? exp ( - 1 2 ? ? ? ? y ~ ? ( k ) - ? ? 2 ) wherein bI,q is the qth coded bit of an in-phase part of a transmitted signal, ? is an asymptotic Signal-to-Interference-plus-Noise Ratio, {tilde over (y)}(k) is a standardized symbol associated with y(k), ? is a reference symbol of QAM constellation associated with a M-QAM modulation, S(1)I,q and S(0)I,q are complex plane partitions that bring together, respectively, all reference symbols ? having a “1” at the position (I, q) and all reference symbols ? having a “0” at the position (I, q), a formula similar to LogLR being given for the bit bQ,p, pth coded bit of a quadrature part of the transmitted signal.

Abstract: This method for carrying out the flexible demodulation of data modulated following an amplitude modulation in quadrature is used in a communications system employing a code division multiple access technique (CDMA) and an optical frequency division multiplexing (OFDM) using non-binary spread codes. The invention includes steps for determining a simplified expression specific to the logarithm of the likelihood ratio.

Abstract: To select the frequency (SF) and/or time (ST) spreading parameters for a communication system using a quadrature amplitude modulation and implementing a CDMA technique and an OFDM multiplexing the attenuation coefficients of the propagation channel are estimated For all the F sub-bands of SF subcarriers and the T blocks of ST OFDM symbols, at least one asymptotic signal-to-interference+noise ratio (SINR) is determined, based on the attenuation coefficients of the propagation channel and the type of equalizer used by the receiver. From this, for each coded information block obtained from the modulation, the compressed asymptotic SINR is deduced, expressed by an analytical formula dependent on the frequency (SF) and time (ST) spreading parameters and the frequency (SF) and time (ST) spreading parameters which maximize the value of the compressed asymptotic SINR are selected.

Abstract: The invention relates to a method and device for the joint detection of data transmitted by direct sequence spread spectrum (DSSS). The device comprises means of using a Cholesky decomposition to calculate a matrix U such that: L=UH×U, where L is an equalization matrix and U is an upper triangular matrix. The means for using a Cholesky decomposition comprise MAC cells (MAC1, MAC2, . . . , MACN) and a diagonal cell (DIAG) of a systolic network. The MAC cells and the diagonal cell are also used to calculate an estimated vector {circumflex over (d)} of received data. For example, the invention applies to the field of digital mobile phone transmissions.

Abstract: This method for carrying out the flexible demodulation of data modulated following an amplitude modulation in quadrature is used in a communications system employing a code division multiple access technique (CDMA) and an optical frequency division multiplexing (OFDM) using non-binary spread codes. The invention includes steps for determining a simplified expression specific to the logarithm of the likelihood ratio.

Abstract: A method for soft demapping of complex-valued symbols y(k) (k=1, 2, . . . , K) by calculation of a Logarithm of Likelihood Ratio (LogLR) such that: Log ? ? LR ? ( b I , q ) = ln ? ? ? ? ? S l , q ( 1 ) ? exp ( - 1 2 ? ? ? ? y ~ ? ( k ) - ? ? 2 ) ? ? ? ? S q , l ( 0 ) ? exp ( - 1 2 ? ? ? ? y ~ ? ( k ) - ? ? 2 ) wherein bI,q is the qth coded bit of an in-phase part of a transmitted signal, ? is an asymptotic Signal-to-Interference-plus-Noise Ratio, {tilde over (y)}(k) is a standardized symbol associated with y(k), ? is a reference symbol of QAM constellation associated with a M-QAM modulation, S(1)I,q and S(0)I,q are complex plane partitions that bring together, respectively, all reference symbols ? having a “1” at the position (I, q) and all reference symbols ? having a “0” at the position (I, q), a formula similar to LogLR being given for the bit bQ,p, pth coded bit of a quadrature part of the transmitted signal.

Abstract: To select the frequency (SF) and/or time (ST) spreading parameters for a communication system using a quadrature amplitude modulation and implementing a CDMA technique and an OFDM multiplexing the attenuation coefficients of the propagation channel are estimated For all the F sub-bands of SF subcarriers and the T blocks of ST OFDM symbols, at least one asymptotic signal-to-interference+noise ratio (SINR) is determined, based on the attenuation coefficients of the propagation channel and the type of equalizer used by the receiver. From this, for each coded information block obtained from the modulation, the compressed asymptotic SINR is deduced, expressed by an analytical formula dependent on the frequency (SF) and time (ST) spreading parameters and the frequency (SF) and time (ST) spreading parameters which maximize the value of the compressed asymptotic SINR are selected.

Abstract: A method of information transmission from an interrogator system to portable objects. The information is transmitted through ternary amplitude modulation and positional pulse coding. A frame is made up of a Start Of Frame (SOF) marker made up of two like-polarity pulses, patterns that transmit binary symbols and are composed of two opposite-polarity pulses, and lastly an End Of Frame (EOF) marker that is made up only of a single pulse. The present invention is notably intended for interrogating radio frequency (RFID) tags.

Abstract: A data transmission process with auto-synchronised correcting code, auto-synchronised coder and decoder, corresponding transmitter and receiver. According to the invention, synchronisation management signals (HS, SS, ID) are formed and, under the control of these signals, a header is inserted before a data group and after it a correcting code. At receive end, these synchronisation management signals are reconstituted, the presence of a header is detected and any erroneous symbols are corrected. The invention also provides for an auto-synchronised coder and a decoder and for a transmitter and a receiver using them.

Abstract: A data transmission process with auto-synchronised correcting code, auto-synchronised coder and decoder, corresponding transmitter and receiver. According to the invention, synchronisation management signals (HS, SS, ID) are formed and, under the control of these signals, a header is inserted before a data group and after it a correcting code. At receive end, these synchronisation management signals are reconstituted, the presence of a header is detected and any erroneous symbols are corrected. The invention also provides for an auto-synchronised coder and a decoder and for a transmitter and a receiver using them.