Abstract: A method for improving tracking of a data transmission signal emitted to a receiver of a satellite navigation system in addition to navigation signals emitted by satellites to a satellite positioning receiver, comprises: transmission to the receiver, during a improvement period, by an improvement signal emitted in coherence with the data transmission signal, of data Ni or other data Nai to predict the data, the data transmitted to the receiver by the data transmission signal during a transmission period starting after the improvement period, reception, by the receiver, of the data Ni or other data Nai which are transmitted by the improvement signal, generating symbols to modulate the data transmission signal during the transmission period by the data Ni received or other data Nai received, tracking the data transmission signal while removing the effect of modulation of the data transmission signal by the symbols generated.

Abstract: A method is provided for improving the acquisition of a data set transmitted repeatedly in a difficult environment, which is particularly appropriate to satellite radionavigation systems. The main characteristic of the method is to provide “contextual” aid relating to the transmitted data by indicating the nature and the possible updating of these data so that the receiver can accumulate the energy when the data are repeated in an identical manner. These aid data being short, it is possible to obtain good quality of reception and protection of this aid by virtue of its longer coding than that of the data.

Abstract: The subject of the present invention is a method providing the means for recognizing the origin and/or the content of an RF signal without requiring substantial computation means, these recognition means being accessible only to authorized persons and being practically nonmodifiable and very difficult to detect by unauthorized persons, and this being so in various applications using RF signals transmitting information that is at least partly hidden. This method is characterized in that it spreads an item of information to be hidden with the aid of a hidden code, that it distributes, with the aid of an Exclusive OR function the information thus obtained in codes that are known with the aid of a hidden distribution algorithm, that, on reception, it applies the algorithm that is the inverse of that having served for the distribution in order to gain access to the spread code, that is correlates this spread code with the hidden code in order to find the hidden information.

Abstract: The invention relates to a network making it possible to calculate and provide ionospheric corrections to the users of a satellite navigation system, wherein the network also comprises: an aeronautical segment comprising an aeronautical user segment composed of a plurality of aircraft each one having an on-board RF receiver capable of measuring delays of the navigation signals transmitted by the satellites and an aeronautical data communication means between the plurality of aircraft and the ground segment in order to transmit said measurements of delays to the ground segment, and means, at the level of the ground segment, of receiving measurements of delays used for the calculation of the grid, the measurements of delays coming from the plurality of aircraft and from the plurality of ground stations.

Abstract: A method is provided for improving the acquisition of a data set transmitted repeatedly in a difficult environment, which is particularly appropriate to satellite radionavigation systems. The main characteristic of the method is to provide “contextual” aid relating to the transmitted data by indicating the nature and the possible updating of these data so that the receiver can accumulate the energy when the data are repeated in an identical manner. These aid data being short, it is possible to obtain good quality of reception and protection of this aid by virtue of its longer coding than that of the data.

Abstract: The invention relates to a network making it possible to calculate and provide ionospheric corrections to the users of a satellite navigation system, wherein the network also comprises: an aeronautical segment comprising an aeronautical user segment composed of a plurality of aircraft each one having an on-board RF receiver capable of measuring delays of the navigation signals transmitted by the satellites and an aeronautical data communication means between the plurality of aircraft and the ground segment in order to transmit said measurements of delays to the ground segment, and means, at the level of the ground segment, of receiving measurements of delays used for the calculation of the grid, the measurements of delays coming from the plurality of aircraft and from the plurality of ground stations.

Abstract: The subject of the present invention is a method providing the means for recognizing the origin and/or the content of an RF signal without requiring substantial computation means, these recognition means being accessible only to authorized persons and being practically nonmodifiable and very difficult to detect by unauthorized persons, and this being so in various applications using RF signals transmitting information that is at least partly hidden. This method is characterized in that it spreads an item of information to be hidden with the aid of a hidden code, that it distributes, with the aid of an Exclusive OR function the information thus obtained in codes that are known with the aid of a hidden distribution algorithm, that, on reception, it applies the algorithm that is the inverse of that having served for the distribution in order to gain access to the spread code, that is correlates this spread code with the hidden code in order to find the hidden information.

Abstract: A device dedicated to generating integrity messages relating to at least one satellite navigation system including a set of satellite surveillance stations and to be sent to navigation receivers. The device includes a processor responsible for determining at chosen times the stations that are active (i.e. nominal or degraded) for each system concerned and, after each such determination, for generating an integrity message including at least primary data representative of the active (i.e. nominal or degraded) stations. The processor is also responsible, each time it detects that at least one station has become degraded or inactive between two successive chosen times, for generating an integrity alert message including at least primary data representative of each station that has become degraded or inactive.

Abstract: A device is dedicated to generating messages relating to at least one satellite navigation system and to be sent to navigation receivers. This device comprises processor means responsible for generating “description” messages to be broadcast to the navigation receivers from a chosen date and comprising a description of a format of future messages to be broadcast to the navigation receivers from a date after the chosen date.

Abstract: A device is dedicated to generating messages relating to at least one satellite navigation system and to be sent to navigation receivers. This device comprises processor means responsible for generating “description” messages to be broadcast to the navigation receivers from a chosen date and comprising a description of a format of future messages to be broadcast to the navigation receivers from a date after the chosen date.

Abstract: A device is dedicated to generating integrity messages relating to at least one satellite navigation system including a set of satellite surveillance stations and to be sent to navigation receivers. The device comprises processor means responsible for determining at chosen times the stations that are active (i.e. nominal or degraded) for each system concerned and, after each such determination, for generating an integrity message including at least primary data representative of the active (i.e. nominal or degraded) stations. The processor means are also responsible, each time they detect that at least one station has become degraded or inactive between two successive chosen times, for generating an integrity alert message including at least primary data representative of each station that has become degraded or inactive.

Abstract: A positioning satellite for a constellation of satellites of a radio navigation satellite system includes transmitter adapted to transmit operational signals intended to enable the determination of positions of radio navigation receivers, receiver adapted to receive at least some of the operational signals transmitted by positioning satellites of the constellation that are in view and processor adapted to interrupt transmission of the operational signals by the transmitter at selected times for a selected duration and to analyze during each transmission interruption at least some of the operational signals received by the receiver during at least a portion of the selected duration, for example to verify the waveform thereof and/or to determine pseudodistances.

Abstract: A positioning satellite for a constellation of satellites of a radio navigation satellite system includes transmitter means adapted to transmit operational signals intended to enable the determination of positions of radio navigation receivers, receiver means adapted to receive at least some of the operational signals transmitted by positioning satellites of the constellation that are in view and processor means adapted to interrupt transmission of the operational signals by the transmitter means at selected times for a selected duration and to analyze during each transmission interruption at least some of the operational signals received by the receiver means during at least a portion of the selected duration, for example to verify the waveform thereof and/or to determine pseudodistances.