Method and apparatus for geolocating a wireless communications device
First Claim
1. A method for determining the location of a transmitting unit transmitting a signal, in response to the time difference of arrival of the signal at two or more receiving sites, comprising:
- (a) selecting a location estimate for the transmitting unit;
(b) determining the pairwise distance difference of arrival from the location estimate to at least two of the two or more receiving sites;
(c) determining the error in the location estimate in response to the distance difference of arrival value determined at the step (b); and
(d) updating the location estimate in response to the error.
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Abstract
The time difference of arrival for a signal received at two or more receiving sites as transmitted from a wireless communications device, is determined by a frequency domain technique. The constituent frequencies of the signals received at the two or more receiving sites are determined, including the phase, or a value representative of the phase, of each frequency component. The phase values for the same frequency are subtracted to yield a phase difference values as a function of frequency. The slope of the function represents the time difference of arrival for the wireless communications device signal as received at the two receiving sites. To determine the mobile location based on the determined time difference of arrival values, a seed or initial location is first assumed for the wireless communications device and the distance difference of arrival (the time difference of arrival multiplied by the speed of light) is calculated. The calculated time difference of arrival is then used to adjust the distance difference of arrival by continuously iterating the position of the wireless communications device until the calculated distance of arrival and the calculated time difference of arrival (as multiplied by the speed of light) are within a predetermined margin.
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Citations
8 Claims
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1. A method for determining the location of a transmitting unit transmitting a signal, in response to the time difference of arrival of the signal at two or more receiving sites, comprising:
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(a) selecting a location estimate for the transmitting unit;
(b) determining the pairwise distance difference of arrival from the location estimate to at least two of the two or more receiving sites;
(c) determining the error in the location estimate in response to the distance difference of arrival value determined at the step (b); and
(d) updating the location estimate in response to the error. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification