Method for the high accuracy geolocation of outdoor mobile emitters of CDMA cellular systems
First Claim
1. A method for an outdoor geolocation of a mobile of interest in a CDMA cellular system comprising:
- (i) dynamically and wirelessly receiving a signal from a mobile whose location is unknown at two or more interceptors, which are located at different known geographic locations inside a CDMA coverage area defined by said base station where a signal from said base station to said mobile is line-of-sight;
(ii) dynamically computing a total time-of-flight of said signal from said base station to each interceptor via said mobile;
(iii) dynamically computing an ellipse of position of said mobile for each total time-of-flight computation, where each ellipse of position has as its foci said base station and said interceptor corresponding to said total time-of-flight measurement for said interceptor;
(iv) dynamically computing intersection point(s) of each possible pair of ellipses of position, if any such intersection point exists;
(v) dynamically and wirelessly receiving said signal from said mobile and measuring an angle-of-arrival of said signal received at each of said interceptors;
(vi) dynamically computing a line of position corresponding to each angle-of-arrival measurements;
(vii) dynamically computing an intersection point of each possible pair of line of position based on angle-of-arrival measurements, if such an intersection point exists;
(viii) dynamically comparing said intersection point(s) of each pair of ellipses of position, if any such intersection point exists with the corresponding intersection point of said lines of position based on angle-of-arrival measurements, if such an intersection point exists; and
(ix) determining either(a) a geographic area within which the mobile is located that is defined by the area of intersection of all ellipses of position whenever for all possible pair of interceptors, either no intersection point of the angle-of-arrival lines of position corresponding to a pair of interceptors coincides with the intersection point(s) of the ellipses of position corresponding to the same pair of interceptors, or no intersection point of angle-of-arrival lines of position exists, or(b) the actual position of the mobile whenever the signal from the mobile to each of any pair of interceptors is line-of-sight which occurs whenever the intersection point of the angle-of-arrival lines of position corresponding to the interceptors intersects one of the two intersection points of the ellipses of position corresponding to the interceptors, corresponding to the actual position of the mobile at that time.
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Accused Products
Abstract
A high-accuracy method for the geolocation, without the collaboration of the network, of outdoor mobile emitters of a CDMA cellular system, based on the ability to distinguishing between line-of-sight and reflected signals. The method employs time-of-flight and angle-of-arrival information in order to determine whether a signal received by each of two or more interceptors situated at different locations is line-of-sight or reflected. Time-of-flight information is obtained with the aid of the reverse link of a mobile of interest. At those instances in time when the signal received at two or more interceptors is line-of-sight, the location of the mobile can be accurately determined using conventional direction-finding techniques. Since the signal received by an interceptor from a mobile may be very weak, adaptive threshold digital signal processing techniques may be employed to control the probability of detection and the probability of false alarms.
21 Citations
33 Claims
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1. A method for an outdoor geolocation of a mobile of interest in a CDMA cellular system comprising:
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(i) dynamically and wirelessly receiving a signal from a mobile whose location is unknown at two or more interceptors, which are located at different known geographic locations inside a CDMA coverage area defined by said base station where a signal from said base station to said mobile is line-of-sight; (ii) dynamically computing a total time-of-flight of said signal from said base station to each interceptor via said mobile; (iii) dynamically computing an ellipse of position of said mobile for each total time-of-flight computation, where each ellipse of position has as its foci said base station and said interceptor corresponding to said total time-of-flight measurement for said interceptor; (iv) dynamically computing intersection point(s) of each possible pair of ellipses of position, if any such intersection point exists; (v) dynamically and wirelessly receiving said signal from said mobile and measuring an angle-of-arrival of said signal received at each of said interceptors; (vi) dynamically computing a line of position corresponding to each angle-of-arrival measurements; (vii) dynamically computing an intersection point of each possible pair of line of position based on angle-of-arrival measurements, if such an intersection point exists; (viii) dynamically comparing said intersection point(s) of each pair of ellipses of position, if any such intersection point exists with the corresponding intersection point of said lines of position based on angle-of-arrival measurements, if such an intersection point exists; and (ix) determining either (a) a geographic area within which the mobile is located that is defined by the area of intersection of all ellipses of position whenever for all possible pair of interceptors, either no intersection point of the angle-of-arrival lines of position corresponding to a pair of interceptors coincides with the intersection point(s) of the ellipses of position corresponding to the same pair of interceptors, or no intersection point of angle-of-arrival lines of position exists, or (b) the actual position of the mobile whenever the signal from the mobile to each of any pair of interceptors is line-of-sight which occurs whenever the intersection point of the angle-of-arrival lines of position corresponding to the interceptors intersects one of the two intersection points of the ellipses of position corresponding to the interceptors, corresponding to the actual position of the mobile at that time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for the outdoor geolocation of a mobile of interest in a CDMA cellular system comprising of a plurality of interceptors located at known location inside a CDMA coverage area of a base station, wherein each of said interceptors comprising of:
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(i) a means for dynamically obtaining a total-time-of-flight measurement, which is a total propagation time of a signal from said base station to said mobile and from said mobile to said interceptor; (ii) a means for dynamically obtaining an angle-of-arrival measurement of a signal from said mobile; (iii) a means for dynamically distinguishing whether said signal received from said mobile is line-of-sight or reflected; and (iv) a means for dynamically determining a location of said mobile. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification