Abstract: The present invention relates to a method for detecting the presence or the absence of a spread spectrum signal in a frequency band of interest of a received signal, wherein: the autocorrelation function of said received signal is calculated for a set (S*) of non-zero time shift values (m); at least one cyclic correlation coefficient on (Rek?(m)) of the autocorrelation function is determined for said time shift values; the energy of the autocorrelation function is estimated from the quadratic sum of the values assumed by said cyclic correlation coefficient for said time shift values; the thereby estimated energy is compared with a predetermined threshold value and the presence or absence of said spread spectrum signal in the received signal is inferred from the result of the comparison.

Abstract: A system for observing a swimming activity of a person includes a waterproof housing (BET) having a motion sensor (MS), and is furnished with fixing means (BEL) for securely fastening the housing (BET) to a part of the body of a user. The system has analysis means (AN) for analyzing the signals transmitted by the motion sensor (MS) to at least one measurement axis and which are adapted for determining the type of swimming of the user as a function of time by using a hidden Markov model with N states corresponding respectively to N types of swimming.

Abstract: This method of configuring a device for detecting a situation from among a set of situations in which it is possible to find a physical system observed by a least one sensor, comprises the following steps: receiving (102) a training sequence corresponding to a determined situation of the physical system; determining (118) parameters of a statistical hidden Markov model recorded on the detection device and related to the determined situation, based on a prior initialization (104-116) of these parameters. The prior initialization (104-116) comprises the following steps: determining (104, 106) multiple probability distributions from the training sequence; distributing (108-114) the determined probability distributions between the hidden states of the statistical model being used; and initializing the parameters of the statistical model being used from representative probability distributions determined for each hidden state of the statistical model being used.

Abstract: The present invention relates to a method for the blind estimation of at least one parameter of an OFDM signal by maximizing an objective function depending on said parameter. The objective function implements a parameterized model of the OFDM modulation and a matched filtering corresponding to that model. The OFDM signal, baseband demodulated and then sampled in an observation window, is the object of the adapted filtering to calculate the objective function. It is also proposed to include, in the parameterized model, the temporal offset between the observation window and an OFDM symbol as well as the frequency offset between the frequency of the OFDM signal carrier and the baseband demodulation frequency.

Abstract: The present invention relates to a method for blind estimation of at least one parameter of an OFDM signal according to a maximum likelihood (ML) criterion. In one embodiment, the estimation method uses a deterministic maximum likelihood criterion. In another embodiment, the estimation method assumes that the modulation symbols modulating the sub-carriers of the OFDM multiplex are i.i.d. and Gaussian random variables. The estimation of said parameter is carried out while minimizing a cost function depending on the chosen criterion.

Abstract: This invention relates to a method for the blind or semi-blind estimation of at least one modulation parameter of an OFDM signal utilising a method for adapting the covariance. According to this method, a plurality of values of this parameter are tested by calculating, for each of these values, a distance between a covariance matrix of vectors composed of samples of the signal and a theoretical covariance matrix. The estimated value of the parameter is the tested value which achieves the shortest distance. Said method provides a very good rate of good estimates, even when the OFDM prefix is short or absent. Furthermore, it makes it possible to obtain a joint estimation of several time parameters and, where applicable, of the signal-to-noise ratio.

Abstract: A cognitive telecommunication terminal designed to coexist with a primary telecommunication system using a set (B) of transmission frequencies comprising a plurality of spatially distributed transmitters, each transmitter being suitable for transmitting within a coverage area in a plurality of frequency bands in said set allocated to the transmitter. The terminal comprises positioning means, a database storing information defining the coverage area for each transmitter, calculation means suitable for determining the maximum power that the terminal can transmit for each frequency band in said set, and for sorting frequency bands as a function of the maximum powers thus obtained. Finally, the terminal comprises radio transmission/reception means suitable for detecting the presence of a signal in the frequency bands thus sorted, beginning with the frequency band associated with the highest maximum power.

Abstract: A method for detecting a cyclostationary signal in a signal to be analyzed, received from a transmitter by a receiver or read from a recording medium by a reader device. According to this method, the value of a discrimination function J is estimated, expressed as a quadratic form of the cyclic correlation coefficients of the signal to be analyzed for a set (I*M) of non-zero time shifts and a set (IK) of cyclic frequencies, and the value 1 - ? ? ( v , U ? 4 ? J ) is compared with a wrong detection rate ? in order to determine whether said cyclostationary signal is present in the signal to be analyzed, wherein ?(?,x) is the normalized lower incomplete gamma function, ? is the product of the cardinal (M) of said set of non-zero time shifts and of the cardinal (K) of said set of cyclic frequencies, U is the width of the autocorrelation window on which the cyclic correlation coefficients are calculated, and ?4 is the square of the noise variance.

Abstract: The present invention relates to a method for detecting the presence or the absence of a spread spectrum signal in a frequency band of interest of a received signal, wherein: the autocorrelation function of said received signal is calculated for a set (S*) of non-zero time shift values (m); at least one cyclic correlation coefficient on (Rek?(m)) of the autocorrelation function is determined for said time shift values; the energy of the autocorrelation function is estimated from the quadratic sum of the values assumed by said cyclic correlation coefficient for said time shift values; the thereby estimated energy is compared with a predetermined threshold value and the presence or absence of said spread spectrum signal in the received signal is inferred from the result of the comparison.

Abstract: The present invention relates to a method for detecting the presence of an OFDM signal in a received signal wherein said received signal is down converted into baseband and subjected to a passband filtering corresponding to a band of interest before being sampled. The thus sampled signal is subjected to a second filtering for eliminating at least one interfering line in the band of interest. The presence of an OFDM signal is detected if the signal filtered by the second filtering is cyclostationary.

Abstract: This invention relates to a method of searching for free band using a cognitive telecommunication terminal operating in a zone covered by a primary telecommunication system using a plurality of frequency bands (B). The terminal classifies said bands as a function of their conditional probabilities of being available (p(bmax|Bocc,Bopp)), knowing a first set of bands already occupied by the primary telecommunication system (Bocc) and a second set of bands not occupied by this primary telecommunication system but already used by another cognitive terminal (Bopp), said terminal beginning its search by the band with the highest conditional probability (bmax).

Abstract: The present invention concerns a blind estimation method of at least one temporal modulation parameter of an OFDM signal, in which a plurality of demodulation attempts of said OFDM signal are carried out using a plurality of respective values of this temporal parameter and, for each demodulation attempt, a cost function representative of the entropy of the demodulated signal is calculated, the estimate of said temporal parameter then being obtained as the value of this parameter minimising said cost function.

Abstract: This invention relates to a method for determining at least one characteristic of an OFDM signal within a received signal, characterised in that: a plurality of cyclic correlation coefficients (?k/(?+?)(?)) for the received signal is calculated (420, 520) for a correlation time difference (?) and a plurality of cyclic frequencies ( k ? + ? ) ; a discrimination function is calculated (430, 530) as a function of the amplitude of said cyclic correlation coefficients; said OFDM signal characteristic is deduced (440, 561, 562) as a function of at least one value of said discrimination function.

Abstract: A cognitive telecommunication terminal designed to coexist with a primary telecommunication system using a set (B) of transmission frequencies comprising a plurality of spatially distributed transmitters, each transmitter being suitable for transmitting within a coverage area in a plurality of frequency bands in said set allocated to the transmitter. The terminal comprises positioning means, a database storing information defining the coverage area for each transmitter, calculation means suitable for determining the maximum power that the terminal can transmit for each frequency band in said set, and for sorting frequency bands as a function of the maximum powers thus obtained. Finally, the terminal comprises radio transmission/reception means suitable for detecting the presence of a signal in the frequency bands thus sorted, beginning with the frequency band associated with the highest maximum power.