Wireless Localisation System
First Claim
Patent Images
1. A method of computing a round trip delay between a pair of nodes, the method comprising:
- transmitting at least one beacon at a known transmit time from each of said nodes;
measuring the times-of-arrival of said beacons at another of said nodes;
estimating a round trip delay between said nodes from said measured times-of-arrival and said transmit times; and
correcting said round trip delay for either or both of a frequency offset between the nodes and relative motion between the nodes.
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Abstract
Disclosed is method of computing a round trip delay between a pair of nodes, the method comprising transmitting at least one beacon at a known transmit time from each of the nodes; measuring the times-of-arrival of the beacons at other of the nodes; and estimating a round trip delay between the nodes from the measured times-of-arrival and the transmit times; and correcting the round trip delay for either or both of a frequency offset between the nodes and relative motion between the nodes.
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Citations
31 Claims
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1. A method of computing a round trip delay between a pair of nodes, the method comprising:
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transmitting at least one beacon at a known transmit time from each of said nodes; measuring the times-of-arrival of said beacons at another of said nodes; estimating a round trip delay between said nodes from said measured times-of-arrival and said transmit times; and correcting said round trip delay for either or both of a frequency offset between the nodes and relative motion between the nodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 14)
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9. A method of estimating the location of a mobile object using a plurality of ranges between a node associated with said object and respective anchor nodes, the method comprising:
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estimating, for a current said range, the location of said object and an error in said location estimate from said range excluding said current range; discarding the range whose exclusion gave the lowest error estimate, if said lowest error estimate is less than a threshold; repeating said estimating and said discarding until said lowest error estimate is not less than said threshold or the number of undiscarded ranges reaches a minimum number; and estimating the location of said object from the undiscarded ranges. - View Dependent Claims (10, 11, 12, 13, 15, 24)
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16. A method of estimating the location of a mobile object using a plurality of ranges between a node associated with said object and respective anchor nodes, the method comprising:
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projecting a starting point onto a sequence of constraint sets in turn, each said constraint set being a circle centred on one said anchor node with radius equal to the corresponding range, to obtain an end point; increasing, if said end point is not less than said corresponding range from each said anchor node, at least one said range, and repeating said projecting and said increasing until said location is less than said corresponding range from each said anchor node, wherein said end point is said estimated location of said mobile object. - View Dependent Claims (17, 18, 19)
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20. A method of time synchronising a plurality of anchor nodes, the method comprising:
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measuring a plurality of trip delays of beacons transmitted between said anchor nodes; correcting said trip delays for propagation delays at said anchor nodes and frequency offsets between local clocks at respective said anchor nodes; and determining a time offset of each said local clock from said corrected trip delays. - View Dependent Claims (21)
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22. A method of estimating the location of a mobile object using a plurality of anchor nodes, the method comprising:
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synchronising said plurality of anchor nodes; measuring a plurality of times-of-arrival of beacons transmitted from said object to respective said anchor nodes; and estimating the location of said object relative to said anchor nodes using said measured times-of-arrival, corrected for a propagation delay at each said anchor node. - View Dependent Claims (23)
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25. A system for estimating the location of one or more objects, the system comprising:
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a plurality of anchor nodes; one or more mobile nodes coincident with respective said objects; beacons transmitted by some or all of said nodes according to a predetermined or dynamically determined schedule; and data capability to send measured times-of-arrival of said beacons, and transmit times of said beacons, to a location server adapted to compute the location of said objects. - View Dependent Claims (26, 27, 28, 29)
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30. (canceled)
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31. A system for estimating the location of an object, the system comprising:
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a plurality of anchor nodes adapted to communicate wirelessly with each other by either transmitting or receiving beacons; a mobile node coincident with said object, the mobile node being adapted to communicate wirelessly with said anchor nodes by either receiving or transmitting said beacons; and a localisation server adapted to; receive measurements of time-of-arrival of said beacons at said nodes, select one of a plurality of localisation algorithms dependent on attributes of said anchor nodes and said mobile node, and estimate the location of said object using said measured times-of-arrival using said selected localisation algorithm.
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Specification