Remote terminal location algorithm
First Claim
1. A method of locating a mobile device comprising the steps of:
- obtaining a plurality of time-of-arrival measurements for communications between the mobile device and each of at least four fixed stations;
identifying at least two subsets of the time-of-arrival measurements obtained in the obtaining step;
forming, for each of the subsets identified in the identifying stop respectively, a preliminary location estimate based on the time-of-arrival measurements in the respective subset;
determining an accuracy of each preliminary location estimate formed in the forming step;
selecting at least one of the preliminary location estimates based on the accuracy determined in the determining step; and
forming a final location estimate based on the at least one of the preliminary location estimates selected in the selecting step.
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Accused Products
Abstract
The accuracy of location estimates based on time-of-arrival measurements may be improved using a variety of different approaches. In some approaches, accuracy predictions are made before a location estimate is computed, and the location estimate is only computed when a high accuracy is predicted. In other approaches, a plurality of preliminary location estimates are computed, and the accuracy of each preliminary estimate is determined. A final location estimate is then based on the preliminary location estimates with the best determined accuracy. In some approaches, the accuracy predictions and determinations are based on geometric dilution of precision (GDOP) or a known topography of a region. In another approach, a subset of time-of-arrival measurements is fed into a closed-form algorithm to produce a preliminary location estimate. This preliminary location estimate is then used to initialize an open-form location algorithm. Optionally, more than one of these approaches may be combined.
39 Citations
14 Claims
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1. A method of locating a mobile device comprising the steps of:
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obtaining a plurality of time-of-arrival measurements for communications between the mobile device and each of at least four fixed stations;
identifying at least two subsets of the time-of-arrival measurements obtained in the obtaining step;
forming, for each of the subsets identified in the identifying stop respectively, a preliminary location estimate based on the time-of-arrival measurements in the respective subset;
determining an accuracy of each preliminary location estimate formed in the forming step;
selecting at least one of the preliminary location estimates based on the accuracy determined in the determining step; and
forming a final location estimate based on the at least one of the preliminary location estimates selected in the selecting step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
wherein, in the determining step, the accuracy of each respective three-dimensional preliminary location estimate is determined by comparing the respective preliminary location estimate to a known three-dimensional topography, and assigning a low accuracy to impossible topographical locations.
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10. A method of locating a mobile device comprising the steps of:
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obtaining a set of time-of-arrival measurements;
identifying a plurality of subsets of the time-of-arrival measurements obtained in the obtaining step;
computing a preliminary location estimate for each of the subsets identified in the identifying step;
determining a geometric dilution of precision (GDOP) of a solution geometry for each respective preliminary location estimate based on (a) the respective preliminary location estimate and (b) known locations of fixed stations corresponding to each of the time-of-arrival measurements in a subset from which the respective preliminary location estimate was formed;
selecting a particular subset of time-of-arrival measurements based on the GDOP determined in the determining step for each of the preliminary location estimates; and
computing a location estimate based on the time-of-arrival measurements contained in the subset selected in the selecting step. - View Dependent Claims (11, 12, 13, 14)
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Specification