Method for positioning by satellites
First Claim
1. A method for satellite positioning using positioning signals which are sent out by the various satellites of a satellite constellation under the control of a set of ground stations from which said satellites receive control signals, and which are available to be picked up by a plurality of user receivers, comprising:
- emitting, from said set of ground stations, periodically renewed direct transformation functions which are addressed respectively to each satellite of said satellite constellation and applying the direct transformation function received by each satellite to encode the positioning signals emitted therefrom;
verifying that a user receiver has a right to a privileged-user status upon each request from the user receiver addressed to a user servicing station and, in the event that the verification is positive, addressing to said user receiver reverse transformation functions that are inverse to the direct transformation functions applied at the satellites from which said user receiver receives positioning signals, wherein said reverse transformation functions include an interpretation key for interpreting said positioning signals by applying said reverse transformation functions for decoding them.
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Accused Products
Abstract
The invention relates to a security-protected system for positioning by satellites, comprising a constellation of satellites (11) sending out positioning signals under the control of a set of ground stations (14). A user receiver of the said positioning signals comprises means for sending, to a ground station, a request calling for a key which is necessary for interpreting them, advantageously accompanied by a recopy of the positioning signals received. User servicing ground stations comprise means for receiving this request, calculating the position of the user and verifying whether the user possesses a privileged status, and means for addressing the said key to the user receiver, in the event that the verification is positive, this key further comprising means for interpreting the positioning signals with the aid of the key so as to deduce his own position therefrom.
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Citations
20 Claims
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1. A method for satellite positioning using positioning signals which are sent out by the various satellites of a satellite constellation under the control of a set of ground stations from which said satellites receive control signals, and which are available to be picked up by a plurality of user receivers, comprising:
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emitting, from said set of ground stations, periodically renewed direct transformation functions which are addressed respectively to each satellite of said satellite constellation and applying the direct transformation function received by each satellite to encode the positioning signals emitted therefrom; verifying that a user receiver has a right to a privileged-user status upon each request from the user receiver addressed to a user servicing station and, in the event that the verification is positive, addressing to said user receiver reverse transformation functions that are inverse to the direct transformation functions applied at the satellites from which said user receiver receives positioning signals, wherein said reverse transformation functions include an interpretation key for interpreting said positioning signals by applying said reverse transformation functions for decoding them. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A system for positioning by satellites in a security-protected system for assisted navigation, comprising
a constellation of orbiting satellites, each including means for emitting positioning signals deduced from control signals which they receive from a set of ground stations, the ground stations being in communication with each other, wherein, for at least one user receiver having means for acquiring and interpreting said positioning signals, in order to calculate a position information, said user receiver further comprises emitting means for sending to said set of ground stations a request signal calling for an interpretation key which is necessary for said user receiver to have access to a privilege in using said positioning signals which is reserved for privileged users, and wherein said set of ground stations comprises at least one user servicing station including receiving means for receiving said request, calculating means for verifying, using said request whether the user for said user-receiver possesses a privileged-user status allowing him to said privilege, and emitting means for addressing said interpretation key to said receiver, in the event that the verification is positive.
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19. A user receiver for use in a satellite-navigation system enabling to reserve an access privilege to privileged users in at least one geographical area covered by the system, which, in addition to means for acquiring positioning signals from a plurality of satellites within a range of the user receiver, includes:
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request emitting means for sending to a user servicing ground station a request signal calling for a key for interpreting said positioning signals, said key comprising reverse transformation functions for inversing direct transformation functions which are applied respectively by the various satellites in the range of the user receiver for emitting the positioning signals sent therefrom, and calculating means for processing said positioning signals having undergone the direct transformation functions by applying to them the corresponding reverse transformation functions in said interpretation key, once said positioning signals have been received, and for deducing therefrom a position information obtained by interpreting said positioning signals. - View Dependent Claims (20)
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Specification