Detecting lack of movement to aid GNSS receivers
First Claim
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1. A method for estimating the clock drift, said method comprising:
- receiving a signal from a satellite;
using only a portion of said signal corresponding to when said user is stationary;
forcing inputs to a correlator engine to zero;
estimating a Doppler frequency of said satellite;
receiving an assistance Doppler frequency from an aiding source that is given under the assumption that said user is stationary;
comparing said estimated Doppler frequency to said assistance Doppler frequency when said user is stationary; and
using the difference in the two Doppler frequencies to estimate clock drift.
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Abstract
Embodiments of the invention provide a method of detecting movement to aid GNSS receivers. By detecting when the user is stationary, the Doppler frequency estimation can be corrected or the SNR can be boosted more both of which lead to improved performance. The embodiments allow a GNSS receiver to process signals in when the signal level would otherwise be too low—for example indoors. The embodiments can improve performance when one or more satellites are temporarily blocked but one or more satellites are still being tracked.
20 Citations
15 Claims
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1. A method for estimating the clock drift, said method comprising:
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receiving a signal from a satellite; using only a portion of said signal corresponding to when said user is stationary; forcing inputs to a correlator engine to zero; estimating a Doppler frequency of said satellite; receiving an assistance Doppler frequency from an aiding source that is given under the assumption that said user is stationary; comparing said estimated Doppler frequency to said assistance Doppler frequency when said user is stationary; and using the difference in the two Doppler frequencies to estimate clock drift. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for estimating the clock drift, said method comprising:
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handshaking between a receiver and a mobile platform to allow said receiver to estimate a clock quality; using said estimate of clock quality to increase an integration time; receiving a signal from a satellite; estimating a Doppler frequency of said satellite; receiving an assistance Doppler frequency from an aiding source that is given under the assumption that negligible motion is present; using a plurality of low-cost sensors to identify stationary or negligible motion, wherein the output from said plurality of low-cost sensors are calibrated or uncalibrated; comparing said estimated Doppler frequency to said assistance Doppler frequency when negligible motion is present; and using the difference in the two Doppler frequencies to estimate clock drift.
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8. An apparatus comprising:
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a processor for processing a signal; a motion detector coupled to said processor for providing measurements about a user'"'"'s movement, wherein said motion detector comprises at least one low-cost sensor; a clock drift estimator coupled to said processor, for computing an estimate of a clock drift; an aiding source coupled to processor for providing Doppler information; and an alternative position estimator coupled to said processor, said clock drift estimator and said aiding source for providing a rough estimate of a user'"'"'s current position. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method of reducing a search space for a Doppler frequency of a satellite signal, said method comprising:
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a sensor module sensing a plurality of user dynamics using a plurality of low-cost sensors, searching over a plurality of time delays and Doppler frequency hypotheses around an initial estimate of each; and limit searching to a small number of Doppler frequency hypotheses around a given Doppler frequency. - View Dependent Claims (15)
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Specification