Method for locating signal sources in wireless networks

Abstract

A method of estimating the position of a wireless transmitter comprising: collecting a plurality of wireless measurements between a transmitter and a receiver; drawing a buffer circle around each measurement, having a radius defined by the timing advance delay measurements; plotting a plurality of buffer circles and identifying intersection points for adjacent measurements only; estimating the position based on the intersection of delay measurements from said plurality of wireless measurements.

What is claimed is: 
     
         1 . A method of estimating a position of a transmitter comprising:
 a. collecting a plurality of wireless measurements between the transmitter and a receiver, each of said wireless measurements comprising a delay measurement (TA value) between the transmitter and at least one receiver location;   b. drawing a buffer circle around each of the at least one receiver location, with the buffer circle having a radius equal to   
       
         
           
             
               
                 
                   1 
                   2 
                 
                 × 
                 
                   TA 
                   ⁡ 
                   
                     [ 
                     unit 
                     ] 
                   
                 
                 × 
                 
                   x 
                   ⁡ 
                   
                     [ 
                     
                       meters 
                       unit 
                     
                     ] 
                   
                 
               
               , 
             
           
         
       
       where x represents a distance measurement for each unit of TA value;
 c. extracting intersection points between adjacent wireless measurements; 
 d. identifying at least one cluster of intersection points from step (c); 
 e. identifying a cluster with a highest number of intersection points; 
 f. generating a polygon corresponding to the cluster with the highest number of intersection points; 
 g. extracting a centroid from the polygon; 
 h. circumscribing the polygon; and 
 i. determining an initial estimated location of the transmitter corresponding to a location within the circumscribed polygon. 
 
     
     
         2 . The method of  claim 1  further comprising wherein the intersection points have an inter-point distance equal to a threshold D and a minimum of M points. 
     
     
         3 . The method of  claim 2  wherein the values for D and M are D=30 meters and M=5 points. 
     
     
         4 . The method of  claim 2  wherein the values for D and M are D=10 meters and M=10 points. 
     
     
         5 . The method of  claim 1  wherein the distance unit of TA value (x) is modified based on hardware specification or software release and version of the receiver. 
     
     
         6 . The method of  claim 1  wherein the TA value reported by the receiver is specific to a device manufacturer, chipset, and software release, wherein a unique profile normalizes the TA value reported. 
     
     
         7 . The method of  claim 1  further comprising:
 j. calculating minimum distances from a first initial estimated location to all the buffer circles within the cluster with the highest number of intersection points; 
 k. shifting the first initial estimated location by a distance D and an angle A to a new location and recalculating the distances to all the buffer circles within the cluster with the highest number of intersection points; 
 l. comparing the calculated distances between step (j) and step (k); 
 m. setting a second new location where the second new location has a shorter distance to all buffer circles than the distance from the first initial estimated location to all buffer circles; and 
 n. incrementing angle A and/or distance D iteratively until a new calculated distance to all the buffer circles is no longer shorter than the previous calculation. 
 
     
     
         8 . The method of  claim 1  wherein the plurality of wireless measurements includes a signal level. 
     
     
         9 . The method of  claim 7  wherein in step (m) the second new location further measures a signal level and modifies the second new location based upon the signal level. 
     
     
         10 . The method of  claim 1  wherein the polygon is drawn by connecting the intersection points in said cluster having the highest number of intersection points. 
     
     
         11 . A method of estimating a position of a transmitter comprising:
 a. collecting a plurality of wireless measurements between a transmitter and a receiver, each measurement comprising a position of the receiver and a TA value;   b. for each of the plurality of wireless measurements, drawing a buffer circle around the position of the receiver, wherein the buffer circle has a radius equal to   
       
         
           
             
               
                 
                   1 
                   2 
                 
                 × 
                 
                   TA 
                   ⁡ 
                   
                     [ 
                     unit 
                     ] 
                   
                 
                 × 
                 
                   x 
                   ⁡ 
                   
                     [ 
                     
                       meters 
                       unit 
                     
                     ] 
                   
                 
               
               ; 
             
           
         
         c. identifying intersection points between at least two buffer circles; and 
         d. estimating the position of the transmitter based on locations of said intersection points by identifying a cluster of intersection points and circumscribing a circle around a polygon created from the cluster of intersection points, wherein the estimated position is within the circumscribed circle. 
       
     
     
         12 . The method of  claim 11  wherein the plurality of wireless measurements are adjacent measurements. 
     
     
         13 . The method of  claim 11  wherein the estimated position is estimated by plotting a location point within the circle. 
     
     
         14 . The method of  claim 12  wherein adjacent means adjacent in time or in location. 
     
     
         15 . The method of  claim 13  wherein the plotted location point is plotted to create a shortest distance to each of the intersections within the circumscribed circle. 
     
     
         16 . A method of estimating a position of a transmitter comprising:
 collecting a plurality of wireless measurements between a transmitter and a receiver;   drawing a buffer circle around a location of each wireless measurement, said buffer circle having a radius defined by a timing advance delay measurement collected by said receiver;   plotting a plurality of buffer circles and identifying intersection points for adjacent measurements only; and   estimating the position based on intersection of timing advance delay measurements from said plurality of wireless measurements by identifying a cluster of intersection points and circumscribing a circle around a polygon created from the cluster of intersection points, wherein the estimated position is within the circumscribed circle.