Fast reacquisition of a GPS signal
First Claim
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1. An apparatus, comprising:
- a receiver in receipt of a signal having a plurality of pseudo noise codes with each of the pseudo noise codes of the plurality of pseudo noise codes originating from a GPS transmitter, where a plurality of chips make up each pseudo noise code in the plurality of pseudo noise codes and the plurality of chips is offset between 511 chips before a pseudo noise code boundary and 512 chips after the pseudo noise code boundary;
a clock with an error relative to a GPS time; and
a processor connected to the receiver and the clock that identifies four pseudo range equations for at least four GPS transmitters from the plurality of GPS transmitters, and determines a location of the receiver and an estimate of the GPS time by simultaneously solving the four pseudo range equations using a determined time estimate offset,wherein the processor determines whether to utilize the estimate of the GPS time to correct the clock error, the determination being based on whether the difference between the estimate of the GPS time and the clock computed based on a previous estimate of the GPS time is within a predetermined range.
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Abstract
A receiver in receipt of a plurality of pseudo noise codes, where each of the pseudo noise codes originates from a GPS transmitter and a plurality of chips make up each pseudo noise code with an offset between 511 chips before a pseudo noise code boundary and 512 chips after the pseudo noise code boundary, and a local clock having an error of less than 0.5 ms relative to a GPS time and synchronized to a GPS signal that is able to be decoded with a decoder connected to the receiver and the local clock and by simultaneously solving the four pseudo range equations for at least four GPS transmitters a determination of the location of the receiver occurs.
214 Citations
16 Claims
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1. An apparatus, comprising:
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a receiver in receipt of a signal having a plurality of pseudo noise codes with each of the pseudo noise codes of the plurality of pseudo noise codes originating from a GPS transmitter, where a plurality of chips make up each pseudo noise code in the plurality of pseudo noise codes and the plurality of chips is offset between 511 chips before a pseudo noise code boundary and 512 chips after the pseudo noise code boundary; a clock with an error relative to a GPS time; and a processor connected to the receiver and the clock that identifies four pseudo range equations for at least four GPS transmitters from the plurality of GPS transmitters, and determines a location of the receiver and an estimate of the GPS time by simultaneously solving the four pseudo range equations using a determined time estimate offset, wherein the processor determines whether to utilize the estimate of the GPS time to correct the clock error, the determination being based on whether the difference between the estimate of the GPS time and the clock computed based on a previous estimate of the GPS time is within a predetermined range. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method, comprising:
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receiving at a receiver a signal generated at a plurality of GPS transmitters; identifying at least four pseudo noise codes in the signal at the receiver; calculating time with a clock having an error relative to a GPS time; deriving at least four pseudo range equations from each of the at least four pseudo noise codes; locating the receiver and determining an estimate of the GPS time by solving the at least four pseudo range equations simultaneously using a determined time estimate offset when a pseudo noise code boundary is less than 512 chips; and determining whether to utilize the estimate of the GPS time to correct the clock error, the determination being based on whether the difference between the estimate of the GPS time and the clock computed based on a previous estimate of the GPS time is within a predetermined range. - View Dependent Claims (8, 9, 10)
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11. An apparatus, comprising:
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receiving means for receiving a signal generated at a plurality of GPS transmitters; means for identifying at least four pseudo noise codes in the signal; means for calculating a clock time having an error relative to a GPS time; means for deriving at least four pseudo range equations from each of the at least four pseudo noise codes; means for locating the receiving means and determining an estimate of the GPS time by solving the at least four pseudo range equations simultaneously that use a determined time estimate offset when a pseudo noise code boundary is less than 512 chips; and means for determining whether to utilize the estimate of the GPS time to correct the clock error, the determination being based on whether the difference between the estimate of the GPS time and the clock time computed based on a previous estimate of the GPS time is within a predetermined range. - View Dependent Claims (12, 13)
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14. A machine-readable medium containing instructions stored thereon that, when read and executed by a controller, cause the controller to perform a method for fast satellite acquisition, the method comprising:
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receiving at a receiver a signal generated at a plurality of GPS transmitters; identifying at least four pseudo noise codes in the signal at the receiver; calculating time with a clock having an error relative to a GPS time; deriving at least four pseudo range equations from each of the at least four pseudo noise codes; locating the receiver and determining an estimate of the GPS time by solving the at least four pseudo range equations simultaneously using a determined time estimate offset when the pseudo noise code boundary is less than 512 chips; and determining whether to utilize the estimate of the GPS time to correct the clock error, the determination being based on whether the difference between the estimate of the GPS time and the clock computed based on a previous estimate of the GPS time is within a predetermined range. - View Dependent Claims (15, 16)
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Specification