System framework for mobile device location
First Claim
1. A system for building a database of Wi-Fi signatures, each with an associated Wi-Fi signature location within a geographical area of interest, said system comprising:
- one or more mobile Wi-Fi database-building devices, each having a GPS receiver and a Wi-Fi signal transceiver;
a survey process, whereby each of said one or more mobile Wi-Fi database-building devices, operating within said geographical area of interest, periodically measures and records a composite GPS signal concurrently with a Wi-Fi signature comprised of the IDs and associated signal strengths of Wi-Fi access points detectable at the point of measurement;
GPS signal processing means for deriving, from each composite GPS signal, the start-of-transmission and the difference in the times of arrival (TDOA) from a pair of acquirable GPS satellites;
hyperplane of location construction means for constructing, for each pair of acquirable satellites, a hyperplane of location, comprised of points for which the difference between the distance from each point to the positions of each of said pair of acquirable satellites at the start-of-transmission is fixed by the difference in the times of arrival (TDOA);
hyperplane of location database means for storing hyperplanes of location, each with its associated Wi-Fi signature;
Wi-Fi signature location estimation means for estimating, from hyperplanes of location sharing a common Wi-Fi signature, the location of said common Wi-Fi signature, determined as the approximate location of the one or more mobile Wi-Fi database-building devices at such times as said common Wi-Fi signature was measured and recorded; and
Wi-Fi signature database means for storing each Wi-Fi signature, together with its estimated Wi-Fi signature location.
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Accused Products
Abstract
A method for estimating the location of a mobile Wi-Fi signal receiver from a database of independently obtained survey data, each survey datum consisting of a surface of location derived from a composite GPS signal, together with a Wi-Fi signature measured concurrently with the GPS signal measurement, is disclosed. The method comprises receiving a Wi-Fi signature, measured and recorded by said mobile. Wi-Fi signal receiver, at the location to be estimated; extracting from the database, an algorithmically-determined subset of surfaces of location, utilizing the Wi-Fi signature recorded by said mobile Wi-Fi signal receiver, and estimating the location of said mobile Wi-Fi signal receiver from said algorithmically-determined subset of surfaces of location. In one embodiment, the algorithmically-determined subset consists of those surfaces of location with Wi-Fi signatures identical to the mobile Wi-Fi signature; and the estimate of the location of said mobile Wi-Fi signal receiver is determined as the point for which the sum of the squares of the distances to each of the surfaces of location included in said algorithmically-determined subset is minimized.
20 Citations
15 Claims
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1. A system for building a database of Wi-Fi signatures, each with an associated Wi-Fi signature location within a geographical area of interest, said system comprising:
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one or more mobile Wi-Fi database-building devices, each having a GPS receiver and a Wi-Fi signal transceiver; a survey process, whereby each of said one or more mobile Wi-Fi database-building devices, operating within said geographical area of interest, periodically measures and records a composite GPS signal concurrently with a Wi-Fi signature comprised of the IDs and associated signal strengths of Wi-Fi access points detectable at the point of measurement; GPS signal processing means for deriving, from each composite GPS signal, the start-of-transmission and the difference in the times of arrival (TDOA) from a pair of acquirable GPS satellites; hyperplane of location construction means for constructing, for each pair of acquirable satellites, a hyperplane of location, comprised of points for which the difference between the distance from each point to the positions of each of said pair of acquirable satellites at the start-of-transmission is fixed by the difference in the times of arrival (TDOA); hyperplane of location database means for storing hyperplanes of location, each with its associated Wi-Fi signature; Wi-Fi signature location estimation means for estimating, from hyperplanes of location sharing a common Wi-Fi signature, the location of said common Wi-Fi signature, determined as the approximate location of the one or more mobile Wi-Fi database-building devices at such times as said common Wi-Fi signature was measured and recorded; and Wi-Fi signature database means for storing each Wi-Fi signature, together with its estimated Wi-Fi signature location. - View Dependent Claims (2, 3)
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4. A method for building a database of Wi-Fi signal-strength contours within a geographical area of interest, said method comprising:
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deploying one or more mobile Wi-Fi database-building devices throughout said geographical area of interest;
wherein each of said one or more mobile Wi-Fi database-building devices has a GPS receiver and a Wi-Fi signal transceiver; and
each periodically measures and records a composite GPS signal concurrently with a Wi-Fi signature comprised of signal-strength contour IDs, which in turn are comprised of the IDs and associated signal strengths of Wi-Fi access points detectable at the point of measurement;deriving, from each composite GPS signal, positioning parameters associated with acquirable GPS satellites; constructing surfaces of location using positioning parameters so derived; storing surfaces of location, each with its associated Wi-Fi signature, in a surfaces of location database; estimating, from surfaces of location sharing a common Wi-Fi signature, the location of said common Wi-Fi signature; storing Wi-Fi signatures, each with its estimated Wi-Fi signature location, in a Wi-Fi signature database; aggregating, for each unique signal-strength contour ID, the estimated Wi-Fi signature locations corresponding to the Wi-Fi signatures comprising said signal-strength contour ID, into a signal-strength contour point set; constructing a signal-strength contour for each signal-strength contour point set, by fitting the points of said signal-strength contour point set with a non-self-intersecting curve; and storing said signal-strength contours, each with its unique signal-strength contour ID, in a signal-strength contour database. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A method for estimating the location of a mobile Wi-Fi signal receiver within a geographical area of interest, said method comprising:
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building a database of independently-obtained survey data obtained within a geographical area of interest, each survey datum including a surface of location derived from a composite GPS signal, and a Wi-Fi signature, both the composite GPS signal and the Wi-Fi signature having been measured and recorded concurrently; receiving at said mobile Wi-Fi signal receiver, messages transmitted by Wi-Fi access points within range of said mobile Wi-Fi signal receiver, each message including the ID of the transmitting Wi-Fi access point; calculating the received signal strength of each of the messages received by said mobile Wi-Fi signal receiver; pairing the IDs of the transmitting Wi-Fi access points with their associated received signal strengths, to form signal-strength contour IDs; assembling said signal-strength contour IDs into a mobile Wi-Fi signature; extracting from said database of independently-obtained survey data, an algorithmically-determined subset of surfaces of location, utilizing said mobile Wi-Fi signature; and estimating the location of said mobile Wi-Fi signal receiver using said algorithmically-determined subset of surfaces of location. - View Dependent Claims (11, 12, 13)
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14. A method for estimating the location of a mobile Wi-Fi signal receiver within a geographical area of interest, said method comprising:
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building a reference database of Wi-Fi signal-strength contours within a geographical area of interest, wherein said reference data base is comprised of signal-strength contours, each with its associated signal-strength contour ID; and
wherein said reference database is compiled from a database of independently-obtained survey data, each survey datum including a surface of location derived from a composite GPS signal, and one or more signal-strength contour IDs, both the composite GPS signal and the one or more signal-strength contour IDs having been measured and recorded concurrently;receiving at said mobile Wi-Fi signal receiver, messages transmitted by Wi-Fi access points within range of said mobile Wi-Fi signal receiver, each message including the ID of the transmitting Wi-Fi access point; calculating the received signal strength of each of the messages received by said mobile Wi-Fi signal receiver; pairing the IDs of the transmitting Wi-Fi access points with their associated received signal strengths, to form signal-strength contour IDs; assembling said signal-strength contour IDs into a mobile Wi-Fi signature; extracting from said reference database of Wi-Fi signal-strength contours, the signal-strength contour(s) corresponding to the signal-strength contour IDs composing the mobile Wi-Fi signature; and estimating the location of said mobile Wi-Fi signal receiver using said signal-strength contour(s). - View Dependent Claims (15)
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Specification