Signature matching for location determination in wireless communication systems
First Claim
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1. In a system for wireless transmitter location finding, a method for calculating a set of likely locations of a transmitter, the method comprising:
- (a) measuring at a base station a signal covariance R associated with the transmitter;
(b) evaluating a function LR (i) comparing R with a calibrated subspace associated with a location index i;
(c) evaluating a function LR.sbsb.k '"'"'(i) comparing Rk '"'"' with the calibrated subspace associated with location index i, where Rk '"'"' is a calibrated covariance associated with a location index k;
(d) calculating a distance G between the functions LR and LR.sbsb.k '"'"'; and
(e) selecting a set of location indices k such that the distance G between R and Rk '"'"' is small.
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Abstract
A method and apparatus improves the accuracy of a wireless location finding system based on the use of multipath signal signatures. A location finding apparatus measures an array covariance matrix R of a signal. The covariance matrix is compared to a database of signatures comprising calibrated signal subspaces. The comparison is based on calculating the projection of R onto each calibrated subspace. From these calculations a set of likely locations is then determined.
92 Citations
17 Claims
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1. In a system for wireless transmitter location finding, a method for calculating a set of likely locations of a transmitter, the method comprising:
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(a) measuring at a base station a signal covariance R associated with the transmitter; (b) evaluating a function LR (i) comparing R with a calibrated subspace associated with a location index i; (c) evaluating a function LR.sbsb.k '"'"'(i) comparing Rk '"'"' with the calibrated subspace associated with location index i, where Rk '"'"' is a calibrated covariance associated with a location index k; (d) calculating a distance G between the functions LR and LR.sbsb.k '"'"'; and (e) selecting a set of location indices k such that the distance G between R and Rk '"'"' is small. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for location finding in a wireless communications system, the apparatus comprising:
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(a) a multichannel receiver for coherently receiving signals originating from a transmitter; (b) a signal processor connected to the multichannel receiver for determining a set of likely locations from the received signals; and (c) a memory device accessible by the processor for storing signal signature calibration data; wherein the signal processor determines the set of likely locations from the received signals in accordance with the following procedure; (i) calculating a signal covariance R from the received signals; (ii) evaluating a function LR (i) comparing R with a calibrated subspace associated with a location index i; (iii) evaluating a function LR.sbsb.k '"'"'(i) comparing Rk '"'"' with the calibrated subspace associated with location index i, where Rk '"'"' is a calibrated covariance associated with a location index k; (iv) calculating a distance G between the functions LR and LR.sbsb.k '"'"'; and (v) selecting a set of location indices k such that the distance G between R and Rk '"'"' is small. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. In a system for wireless transmitter location finding, a method for calculating a set of likely locations of a transmitter, the method comprising:
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(a) measuring at a base station a signal covariance R associated with the transmitter; (b) calculating a projection of R onto a calibrated subspace associated with a location index i; (c) repeating step (b) for a plurality of location indices to obtain a plurality of projections; and (d) calculating from the projections the set of likely locations. - View Dependent Claims (16, 17)
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Specification