Method and apparatus for calibrating base station locations and perceived time bias offsets in an assisted GPS transceiver
First Claim
1. A method for calibrating a base station location using a satellite positioning receiver in a mobile station, comprising the steps of:
- collecting a number of time-of-arrival (TOA) measurements arriving at the mobile station from a base station;
simultaneously collecting a corresponding number of satellite position measurements of the satellite positioning receiver;
determining that the number of TOA measurements and the corresponding number of satellite position measurements is sufficient for calibrating the base station location; and
computing the base station location using the number of TOA measurements and the corresponding number of satellite position measurements.
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Abstract
A flowchart (400) includes the step (402) of collecting a predetermined number of TOA measurements arriving at the assisted satellite positioning mobile station from a base station, the step of (406) simultaneously collecting a corresponding number of GPS position measurements of a position of the GPS receiver, and the step (410) of computing the base station location and/or the step (414) of computing a perceived time bias offset required for a message to travel between the base station and the mobile station using the predetermined number of TOA measurements and the predetermined number of GPS position measurements.
133 Citations
23 Claims
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1. A method for calibrating a base station location using a satellite positioning receiver in a mobile station, comprising the steps of:
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collecting a number of time-of-arrival (TOA) measurements arriving at the mobile station from a base station;
simultaneously collecting a corresponding number of satellite position measurements of the satellite positioning receiver;
determining that the number of TOA measurements and the corresponding number of satellite position measurements is sufficient for calibrating the base station location; and
computing the base station location using the number of TOA measurements and the corresponding number of satellite position measurements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
computing a perceived time bias offset b′
using the number of TOA measurements and the corresponding number of satellite position measurements.
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3. The method of claim 2, further comprising the steps of:
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associating the perceived time bias offset b′
with a satellite positioning receiver position; and
creating at least a portion of a map of perceived time bias offset as a function of satellite positioning receiver position.
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4. The method of claim 3, further comprising the step of:
transmitting the map to another mobile station.
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5. The method of claim 3, wherein the step of creating comprised:
updating the map within a cellular infrastructure.
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6. The method of claim 5, further comprising the step of:
using the perceived time bias offset in the map to determine whether to use a multipath reduction technique.
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7. The method of claim 6, further comprising the step of:
using the perceived time bias offset in the map to compute a position of the mobile station.
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8. The method of claim 1, wherein the step of computing comprises the steps of:
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subtracting a first TOA measurement from subsequent TOA measurements to create two TOA differences TOA31, TOA21;
substituting a distance variable d1 for base station coordinates x, y in the two TOA differences TOA31, TOA21 to produce a quadratic equation for the distance variable d1, where the distance variable d1=[(x−
xt)2+(y−
yt)2];
solving the quadratic equation for the distance variable d1 to obtain an estimated range de; and
solving for the base station coordinates x, y using the estimated range de.
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9. The method of claim 8, further comprising the step of:
computing a perceived time bias offset b′
using the number of TOA measurements and the corresponding number of satellite position measurements.
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10. The method of claim 9, wherein the step of computing a perceived time bias offset b′
- comprises;
subtracting the estimated range de from a TOA measurement.
- comprises;
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11. A method for calibrating a base station location in a mobile station having a satellite positioning receiver, comprising the steps of:
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collecting at least three TOA measurements TOA1, TOA2, TOA3 arriving at the mobile station from a base station at different times t, wherein a TOA measurement is capable of being expressed as TOAt=b′
+[(x−
xt)2+(y−
yt)2], with variable b′
being a perceived time bias offset of the base station and (x, y) being base station coordinates;
simultaneously collecting at least three satellite position measurements of a position of the satellite positioning receiver, wherein a position measurement is denoted as xt and yt as a function of time;
determining through a geometry matrix that the at least three TOA measurements and the at least three satellite position measurements are sufficient for determining the base station location;
subtracting a first TOA measurement TOA1 from at least two subsequent TOA measurements TOA2, TOA3 to create at least two TOA differences TOA31, TOA21;
substituting a distance variable d1 for the base station coordinates x, y in the at least two TOA differences TOA31, TOA21 to produce a quadratic equation for the distance variable d1, where the distance variable d1=[(x−
xt)2+(y−
yt)2];
solving the quadratic equation for the distance variable d1 to obtain an estimated range de;
solving for the base station coordinates x, y using the estimated range de; and
obtaining the perceived time bias offset b′
by subtracting the estimated range de from a TOA measurement.- View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
solving the quadratic equation to produce two solutions; and
discarding a solution that is out of a geographical region of interest to leave an accepted solution.
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13. The method of claim 11, wherein the step of solving the quadratic equation comprises the steps of:
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obtaining at least a fourth TOA measurement and at least a third TOA difference; and
using the at least a third TOA difference in conjunction with the quad ratic equation to determine a solution for the distance variable d1 and for the base station coordinates x, y.
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14. The method of claim 11, further including the steps of:
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linearizing the at least three TOA measurements TOA1, TOA2, TOA3 by subtracting estimated ranges from them, with the estimated ranges determined from the base station coordinates x, y, to produce linearized TOA equations;
generating a vector of measurement residuals TOAres;
computing a weighted least squares solution xsol of the linearized TOA equations;
correcting the base station coordinates x, y using the weighted least squares solution xsol;
repeating the steps of generating, computing, and correcting until a magnitude of the weighted least squares solution xsol becomes less than a solution error variance threshold;
using a covariance matrix of the weighted least squares solution xsol to assess an accuracy of the base station coordinates x, y; and
using the accuracy to determine that the base station location calibration is complete.
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15. The method of claim 14, wherein the step of using the covariance matrix additionally makes use of measurement residual information from the weighted least squares solution xsol.
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16. The method of claim 14, wherein the step of using the accuracy additionally makes use of residual information from the weighted least squares solution xsol.
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17. The method of claim 14, wherein the vector of measurement residuals TOAres is given by TOAres=H xsol, where H is a measurement gradient vector and the weighted least squares solution xsol is a three dimensional weighted least squares solution vector, and where a row of the measurement gradient vector H has a form of hiT=[ux uy 1] with ux and uy being components of a line of sight unit vector to the base station.
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18. The method of claim 14, wherein the weighted least squares solution xsol is given as xsol=(HTR−
- 1H)−
1HTR−
1TOAres, where R is the covariance matrix.
- 1H)−
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19. The method of claim 14, wherein if the base station coordinates x, y are known but the perceived time bias offset b′
- is not known, then a TOA residual vector TOAres is given by TOAres=H be, where each row of H is unity and an estimated time bias offset be collapses to a weighted average of measurement residuals, and an accuracy of the estimated time bias offset be can be determined from the covariance matrix.
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20. An apparatus for calibrating a base station location in a mobile station, comprising:
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a satellite positioning receiver;
a radio transceiver;
a time-of-arrival (TOA) measurement storage for storing a plurality of TOA measurements;
a satellite positioning receiver position fix storage for storing a plurality of position fixes;
a base station coordinates storage;
a time bias offset storage; and
a processor, for communicating with the radio transceiver and satellite positioning receiver to receive signals from satellite positioning satellites and from a base station, and further communicating with the TOA measurement storage, the satellite positioning receiver position fix storage, the base station coordinates storage, and the time bias offset storage, with the processor capable of collecting and storing TOA measurements, collecting and storing a corresponding number of satellite position measurements, subtracting a first TOA measurement from subsequent TOA measurements to create TOA differences, substituting a distance variable d1 for base station coordinates x, y in the TOA differences to produce a quadratic equation, solving the quadratic equation for the distance variable d1 to obtain an estimated range de, solving for the base station coordinates x, y, obtaining a perceived time bias offset b′
by subtracting an estimated range de from the TOA measurements, linearizing the TOA measurements to produce linearized TOA equations, generating a vector of measurement residuals TOAres, computing a weighted least squares solution xsol of the linearized TOA equations, using the weighted least squares solution xsol to assess an accuracy of the linearized TOA equations, and repeating the generating, computing, and using until a solution error variance of the weighted least squares solution xsol becomes less than a solution error variance threshold.- View Dependent Claims (21, 22, 23)
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Specification