Systems and methods for clock correction
First Claim
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1. A method of correcting a local clock at a user device, the method comprising:
- receiving, at the user device, a non-GPS signal from a non-GPS satellite;
identifying a message header in the non-GPS signal;
computing, based on the local clock at the user device, a local estimate of a time of transmission of the non-GPS signal;
receiving, at the user device, a correction signal comprising (i) a message-header indication and (ii) a corrective estimate of the time of transmission of the non-GPS signal; and
correcting the local clock based on the identified message header, the message-header indication, and the local and corrective estimates of the time of transmission of the non-GPS signal.
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Abstract
A non-GPS satellite-based system enables correction of a local clock in a user device to facilitate GPS-based location determination.
33 Citations
27 Claims
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1. A method of correcting a local clock at a user device, the method comprising:
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receiving, at the user device, a non-GPS signal from a non-GPS satellite; identifying a message header in the non-GPS signal; computing, based on the local clock at the user device, a local estimate of a time of transmission of the non-GPS signal; receiving, at the user device, a correction signal comprising (i) a message-header indication and (ii) a corrective estimate of the time of transmission of the non-GPS signal; and correcting the local clock based on the identified message header, the message-header indication, and the local and corrective estimates of the time of transmission of the non-GPS signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for clock correction, comprising:
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a clock generator for generating a local clock; a first receiver for receiving a non-GPS signal from a non-GPS satellite; a correlator for identifying a message header in the non-GPS signal; a second receiver for receiving a correction signal comprising (i) a message-header indication and (ii) a corrective estimate of a time of transmission of the non-GPS signal; and a processor for (i) computing, based on the local clock, a local estimate of the time of transmission of the non-GPS signal, and (ii) correcting the local clock based on the identified message header, the message-header indication, and the local and corrective estimates of the time of transmission of the non-GPS signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of aiding in correcting a local clock at a user device, the method comprising:
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receiving, at a ground site, a non-GPS signal from a non-GPS satellite; identifying a message header in the non-GPS signal; computing, based on a precision clock, an estimate of a time of transmission of the non-GPS signal; and transmitting, from the ground site to the user device, a correction signal for correcting the local clock at the user device, the correction signal comprising (i) an indication of the message header and (ii) the estimate of the time of transmission of the non-GPS signal. - View Dependent Claims (19, 20, 21, 22)
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23. A system for aiding in correcting a local clock at a user device, the system comprising:
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a first receiver for receiving a non-GPS signal from a non-GPS satellite; a correlator for identifying a message header in the non-GPS signal; a processor for computing, based on a precision clock, an estimate of a time of transmission of the non-GPS signal; and a transmitter for transmitting, to the user device, a correction signal for correcting the local clock at the user device, the correction signal comprising (i) an indication of the message header and (ii) the estimate of the time of transmission of the non-GPS signal. - View Dependent Claims (24, 25, 26, 27)
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Specification