WI-FI POSITION FIX
First Claim
1. A method of forming an estimate of the two-dimensional position of a radio receiver relative to a plurality of radio transmitters each having an associated position estimate and a position uncertainty expressible as an uncertainty ellipse having major and minor axes, the method comprising:
- receiving at the radio receiver signals from the plurality of radio transmitters and forming in dependence on those received signals a set of transmitter weighting values each expressing a measure of the distance of a respective radio transmitter from the radio receiver;
for each of the plurality of radio transmitters, scaling an uncertainty vector describing the orientation of the respective uncertainty ellipse in a predetermined coordinate system by a scaling value dependent on the respective transmitter weighting value and rotating that uncertainty vector by multiplying its argument by a factor of four;
summing the scaled and rotated vectors of the plurality of radio transmitters so as to form a total vector;
dividing the argument of the total vector by a factor of four and using the resulting rotated total vector to define a compound coordinate basis comprising first and second coordinate axes; and
forming an estimate of the two-dimensional position of the radio receiver in the compound coordinate basis by;
projecting the major and minor axes of each uncertainty ellipse onto the first and second coordinate axes so as to form a set of projected components for each axis;
summing the projected components of each axis so as to form a total uncertainty along each axis;
for each uncertainty ellipse, forming first and second coordinate axis weighting values from the respective transmitter weighting values scaled such that the first/second coordinate axis weighting value decreases as the total uncertainty along that first/second coordinate axis increases; and
calculating the position of the radio receiver by means of a weighted centroid using the first and second coordinate axis weighting values and the position estimates of the plurality of the radio transmitters expressed in the compound coordinate basis.
2 Assignments
0 Petitions
Accused Products
Abstract
A method of forming an estimate of the two-dimensional position of a radio receiver relative to a plurality of radio transmitters each having an associated position estimate and a position uncertainty expressible as an uncertainty ellipse having major and minor axes, the method comprising using the uncertainty vectors describing the uncertainty ellipses of the radio transmitters in a predetermined coordinate system to define a new compound coordinate basis, and forming an estimate of the two-dimensional position of the radio receiver in the compound coordinate basis by projecting the major and minor axes of each uncertainty ellipse onto the new compound coordinate basis and calculating the position of the radio receiver by means of a weighted centroid that uses weighting values calculated in the new compound coordinate basis and position estimates of the plurality of the radio transmitters expressed in the compound coordinate basis.
-
Citations
47 Claims
-
1. A method of forming an estimate of the two-dimensional position of a radio receiver relative to a plurality of radio transmitters each having an associated position estimate and a position uncertainty expressible as an uncertainty ellipse having major and minor axes, the method comprising:
-
receiving at the radio receiver signals from the plurality of radio transmitters and forming in dependence on those received signals a set of transmitter weighting values each expressing a measure of the distance of a respective radio transmitter from the radio receiver; for each of the plurality of radio transmitters, scaling an uncertainty vector describing the orientation of the respective uncertainty ellipse in a predetermined coordinate system by a scaling value dependent on the respective transmitter weighting value and rotating that uncertainty vector by multiplying its argument by a factor of four; summing the scaled and rotated vectors of the plurality of radio transmitters so as to form a total vector; dividing the argument of the total vector by a factor of four and using the resulting rotated total vector to define a compound coordinate basis comprising first and second coordinate axes; and forming an estimate of the two-dimensional position of the radio receiver in the compound coordinate basis by; projecting the major and minor axes of each uncertainty ellipse onto the first and second coordinate axes so as to form a set of projected components for each axis; summing the projected components of each axis so as to form a total uncertainty along each axis; for each uncertainty ellipse, forming first and second coordinate axis weighting values from the respective transmitter weighting values scaled such that the first/second coordinate axis weighting value decreases as the total uncertainty along that first/second coordinate axis increases; and calculating the position of the radio receiver by means of a weighted centroid using the first and second coordinate axis weighting values and the position estimates of the plurality of the radio transmitters expressed in the compound coordinate basis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
-
-
23. A radio receiver operable to estimate its position relative to a plurality of radio transmitters, the radio receiver having access to information defining, for each radio transmitter, a position estimate and position uncertainty expressible as an uncertainty ellipse having major and minor axes, and the radio receiver comprising:
-
an antenna for receiving signals from the plurality of radio transmitters; a weighting determination unit configured to form in dependence on signals received from the radio transmitters a set of transmitter weighting values each expressing a measure of the distance of a respective radio transmitter from the radio receiver; and a position calculation unit configured to estimate the position of the radio receiver by; for each of the plurality of radio transmitters, scaling an uncertainty vector describing the orientation of the respective uncertainty ellipse in a predetermined coordinate system by a scaling value dependent on the respective transmitter weighting value and rotating that uncertainty vector by multiplying its argument by a factor of four; summing the scaled and rotated vectors of the plurality of radio transmitters so as to form a total vector; dividing the argument of the total vector by a factor of four and using the resulting rotated total vector to define a compound coordinate basis comprising first and second coordinate axes; and forming an estimate of the two-dimensional position of the radio receiver in the compound coordinate basis by; projecting the major and minor axes of each uncertainty ellipse onto the first and second coordinate axes so as to form a set of projected components for each axis; summing the projected components of each axis so as to form a total uncertainty along each axis; for each uncertainty ellipse, forming first and second coordinate axis weighting values from the respective transmitter weighting values scaled such that the first/second coordinate axis weighting value decreases as the total uncertainty along that first/second coordinate axis increases; and calculating the position of the radio receiver by means of a weighted centroid using the first and second coordinate axis weighting values and the position estimates of the plurality of the radio transmitters expressed in the compound coordinate basis.
-
-
24. A method of forming an estimate of the two-dimensional position of a radio transmitter relative to a plurality of radio receiver positions each having a corresponding position uncertainty expressible as an uncertainty ellipse having major and minor axes, the method comprising:
-
receiving at the radio receiver positions signals from the radio transmitter and forming in dependence on those received signals a set of receiver weighting values each expressing a measure of the distance of the radio transmitter from the radio receiver positions; for each of the plurality of radio receiver positions, scaling an uncertainty vector describing the orientation of the respective uncertainty ellipse in a predetermined coordinate system by a scaling value dependent on the respective receiver weighting value and rotating that uncertainty vector by multiplying its argument by a factor of four; summing the scaled vectors of the plurality of radio receiver positions so as to form a total vector; dividing the argument of the total vector by a factor of four and using the resulting rotated total vector to define a compound coordinate basis comprising first and second coordinate axes; and forming an estimate of the two-dimensional position of the radio transmitter in the compound coordinate basis by; projecting the major and minor axes of each uncertainty ellipse onto the first and second coordinate axes so as to form a set of projected components for each axis; summing the projected components of each axis so as to form a total uncertainty along each axis; for each uncertainty ellipse, forming first and second coordinate axis weighting values from the respective transmitter weighting values scaled such that the first/second coordinate axis weighting value decreases as the total uncertainty along that first/second coordinate axis increases; and calculating the position of the radio transmitter by means of a weighted centroid using the first and second coordinate axis weighting values and the radio receiver positions expressed in the compound coordinate basis. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
-
-
46. A radio receiver operable to estimate the position of a radio transmitter, the radio receiver being arranged to move between a plurality of radio receiver positions and being operable to determine its position uncertainty at each of those positions as an uncertainty ellipse having major and minor axes, and the radio receiver comprising:
-
an antenna for receiving signals from the radio transmitter; a weighting determination unit configured to form in dependence on signals received from the radio transmitter a set of transmitter weighting values each expressing a measure of the distance of the radio transmitter from the radio receiver positions; and a position calculation unit configured to estimate the position of the radio transmitter by; for each of the plurality of radio receiver positions, scaling an uncertainty vector describing the orientation of the respective uncertainty ellipse in a predetermined coordinate system by a scaling value dependent on the respective receiver weighting value and rotating that uncertainty vector by multiplying its argument by a factor of four; summing the scaled vectors of the plurality of radio receiver positions so as to form a total vector; dividing the argument of the total vector by a factor of four and using the resulting rotated total vector to define a compound coordinate basis comprising first and second coordinate axes; and forming an estimate of the two-dimensional position of the radio transmitter in the compound coordinate basis by; projecting the major and minor axes of each uncertainty ellipse onto the first and second coordinate axes so as to form a set of projected components for each axis; summing the projected components of each axis so as to form a total uncertainty along each axis; for each uncertainty ellipse, forming first and second coordinate axis weighting values from the respective transmitter weighting values scaled such that the first/second coordinate axis weighting value decreases as the total uncertainty along that first/second coordinate axis increases; and calculating the position of the radio transmitter by means of a weighted centroid using the first and second coordinate axis weighting values and the radio receiver positions expressed in the compound coordinate basis.
-
-
47. (canceled)
Specification