Hybrid GNSS and TDOA wireless location system
First Claim
1. A method for use in locating a mobile device, comprising:
- (a) at the mobile device, obtaining pseudorange measurements based on signals received from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS);
(b) computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites;
(c) obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers;
(d) providing hybrid GPS/U-TDOA baselines;
(e) computing weightings for the hybrid GPS/U-TDOA baselines; and
(f) estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings.
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Accused Products
Abstract
A method and apparatus for position determination is provided using measurements from both Global Positioning System (GPS) receivers and terrestrial-based Uplink Time Difference of Arrival (UTDOA) receivers. The method involves the transformation of downlink satellite measurements into equivalent UTDOA measurements by computing comparable cross-correlation coefficients and time differences of arrival with respect to a UTDOA reference station. The method includes a weighting operation whereby the relative weights of the UTDOA measurements and the relative weights of the GPS measurements are adjusted based on a theoretical scaling followed by empirical adjustments. The method further involves the efficient computation and combining of metrics that are used to minimize the weighted error between candidate location solutions and the UTDOA and GPS measurements. This is done efficiently in two dimensions for UTDOA and in three dimensions for GPS measurements by increasing the complexity of searching operations as the optimal location solution is approached. A technique is also described that improves upon a particular location solution by changing the measurement weightings using criteria specific to GPS and UTDOA.
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Citations
74 Claims
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1. A method for use in locating a mobile device, comprising:
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(a) at the mobile device, obtaining pseudorange measurements based on signals received from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); (b) computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; (c) obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; (d) providing hybrid GPS/U-TDOA baselines; (e) computing weightings for the hybrid GPS/U-TDOA baselines; and (f) estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings. - View Dependent Claims (7, 8, 9, 14, 21, 22, 23, 24, 25, 26, 27)
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2. A method for use in locating a mobile device, comprising:
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at the mobile device, obtaining pseudorange measurements based on signals received from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; providing hybrid GPS/U-TDOA baselines; computing weightings for the hybrid GPS/U-TDOA baselines, wherein the step of computing weightings comprises an iterative downweighting method including determining a hybrid position estimate using a current baseline weighting, and then downweighting the U-TDOA baselines and G-TDOA baselines, until either a first or second prescribed stopping condition is met; and estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings. - View Dependent Claims (3, 4, 5, 6)
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10. A method for use in locating a mobile device, comprising:
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at the mobile device, obtaining pseudorange measurements based on signals received from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; providing hybrid GPS/U-TDOA baselines; computing weightings for the hybrid GPS/U-TDOA baselines; and estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings; wherein the step of computing G-TDOA values comprises employing a process for transforming GPS pseudoranges to U-TDOA values, said process comprising comparing GPS pseudoranges with geometric distances to a reference station of the U-TDOA wireless location network and computing a TDOA value for the satellite signal received at the mobile device and the reference station, respectively, wherein the positions of the satellite and the reference station are known, and wherein the computed TDOA value represents the G-TDOA value. - View Dependent Claims (11, 12, 13)
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15. A method for use in locating a mobile device, comprising:
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at the mobile device, obtaining pseudorange measurements based on signals received from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; providing hybrid GPS/U-TDOA baselines; computing weightings for the hybrid GPS/U-TDOA baselines; estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings; and further comprising a process for weighting pseudorange measurements based on a signal-to-noise ratio (SNR) reported by the GPS receiver used to obtain the pseudorange measurements, wherein said process for weighting pseudorange measurements comprises the use of an iterative downweighting process for scaling GPS and U-TDOA weights based on prescribed factors, including measurement error distribution for U-TDOA and GPS, the number of GPS measurements available, and the number of U-TDOA measurements available.
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16. A method for use in locating a mobile device, comprising:
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at the mobile device, obtaining pseudorange measurements based on signals received from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; providing hybrid GPS/U-TDOA baselines; computing weightings for the hybrid GPS/U-TDOA baselines; estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings; and further comprising a process for weighting pseudorange measurements based on a signal-to-noise ratio (SNR) reported by the GPS receiver used to obtain the pseudorange measurements, wherein said process for weighting pseudorange measurements comprises computing, for each GPS baseline, an initial weighting based on a theoretical TDOA RMS error. - View Dependent Claims (17, 18, 19, 20)
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28. A method for use in locating a mobile device, comprising:
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at the mobile device, obtaining pseudorange measurements based on signals received from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; providing hybrid GPS/U-TDOA baselines; computing weightings for the hybrid GPS/U-TDOA baselines; estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings; and employing a hybrid weighted least squares algorithm, said algorithm providing an analytical solution for biases in the GPS and U-TDOA contributions, including performing transformation of GPS pseudorange contributions and combining the transformed and weighted GPS contributions with computed G-TDOA values obtained from the pseudorange measurements. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. A wireless location system, comprising:
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means for communicating with a mobile device and obtaining from said mobile device pseudorange measurements based on signals received by said mobile device from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); means for computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; means for obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; means for providing hybrid GPS/U-TDOA baselines; means for computing weightings for the hybrid GPS/U-TDOA baselines, wherein the means for computing weightings comprises means for carrying out an iterative downweighting including determining a hybrid position estimate using a current baseline weighting, and then downweighting the U-TDOA baselines and G-TDOA baselines, until either a first or second prescribed stopping condition is met; and means for estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73)
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74. A computer readable medium containing computer readable instructions for carrying out the following computer-implemented method for use in locating a mobile device:
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communicating with a mobile device and obtaining from said mobile device pseudorange measurements based on signals received by said mobile device from one or more satellites, wherein said one or more satellites are satellites of at least one of a Global Navigation Satellite System (GNSS) or Global Positioning System (GPS); computing GPS time difference of arrival (G-TDOA) values based on the GPS pseudorange measurements, said G-TDOA values representing baselines between the mobile device and the GPS/GNSS satellites; obtaining an uplink time difference of arrival (U-TDOA) measurement representing a first baseline between first and second terrestrial receivers; providing hybrid GPS/U-TDOA baselines; computing weightings for the hybrid GPS/U-TDOA baselines, wherein the step of computing weightings comprises an iterative downweighting method including determining a hybrid position estimate using a current baseline weighting, and then downweighting the U-TDOA baselines and G-TDOA baselines, until either a first or second prescribed stopping condition is met; and estimating the location of the mobile device using the hybrid GPS/U-TDOA baselines and the weightings.
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Specification