Local clock-referenced DTOA geolocation system with wireless infrastructure
First Claim
1. A method of geolocating objects having signal transmitting tags coupled thereto, said method comprising the steps of:
- (a) at a plurality of spaced apart monitoring locations containing tag transmission readers, detecting a transmission from a tag and generating output signals representative of times of arrival of said transmission at respective ones of said tag transmission readers, in accordance with local clock signals generated at said spaced apart monitoring locations;
(b) transmitting said output signals to an object location processor which is operative to process said output signals from said tag transmission readers to geolocate said tags and thereby their associated objects within said monitored environment; and
(c) adjusting said output signals, as necessary, to compensate for variations in said local clock signals generated at said spaced apart monitoring locations, and thereby enable said object location processor to accurately process said output signals from said tag transmission readers and geolocate said tags and thereby their associated objects within said monitored environment.
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Accused Products
Abstract
An object tracking system for locating radio-tagged objects has a plurality tag transmission readers that detect tag transmissions, and generate time-of-arrival output signals representative of the time-of-arrival of first-to-arrive tag transmissions on the basis of clock signals generated by local clock generators at the tag reader sites. The tag reader sites may transmit time-of-arrival signals to an object location processor by way of a wireless local area network. Measurements made on transmissions from a fixed position reference tag are used to update a reader clock offset database employed by the processor to maintain the reader clocks effectively time aligned.
108 Citations
17 Claims
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1. A method of geolocating objects having signal transmitting tags coupled thereto, said method comprising the steps of:
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(a) at a plurality of spaced apart monitoring locations containing tag transmission readers, detecting a transmission from a tag and generating output signals representative of times of arrival of said transmission at respective ones of said tag transmission readers, in accordance with local clock signals generated at said spaced apart monitoring locations;
(b) transmitting said output signals to an object location processor which is operative to process said output signals from said tag transmission readers to geolocate said tags and thereby their associated objects within said monitored environment; and
(c) adjusting said output signals, as necessary, to compensate for variations in said local clock signals generated at said spaced apart monitoring locations, and thereby enable said object location processor to accurately process said output signals from said tag transmission readers and geolocate said tags and thereby their associated objects within said monitored environment. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An arrangement for geolocating objects having signal transmitting tags within a monitored environment comprising:
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a plurality of spaced apart tag transmission readers which are operative to detect a transmission from a tag and to generate output signals in accordance with clock signals generated by local clock signal generators respectively associated therewith; and
an object location processor which processes said output signals generated by said tag transmission readers to geolocate said tags and thereby their associated objects within said monitored environment, said object location processor being operative to adjust said output signals, as necessary, to compensate for variations in said local clock signals generated at said spaced apart monitoring locations, and thereby accurately process said output signals from said tag transmission readers and geolocate said tags and thereby their associated objects within said monitored environment. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A system for geolocating objects having signal transmitting tags within a monitored environment comprising:
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a plurality of tag transmission readers, a respective one of which is operative to detect a first-to-arrive tag transmission, and to generate an output signal representative of the time-of-arrival of said first-to-arrive tag transmission in accordance with a clock signal generated by a local clock generator;
an object geolocation processor to which output signals generated by said plurality of tag transmission readers are wirelessly coupled, and being operative to process said output signals generated by said tag transmission readers to geolocate said tags and thereby their associated objects within said monitored environment; and
a ‘
reference’
tag disposed within said monitored environment and whose geolocation is known, and being operative to transmit a reference tag signal, said reference tag signal being received at said transmission readers, output signals generated by which are coupled to said object location processor for processing thereby to determine the geolocation of said reference tag; and
whereinsaid object location processor is operative to generate a calibration mechanism which compares the determined geolocation of said reference tag with the known geolocation of said reference tag, and controllably compensates for variations in said local clock signal generators, in accordance with a difference between the determined geolocation of said reference tag and the known geolocation of said reference tag. - View Dependent Claims (16, 17)
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Specification