Method for ambiguity resolution in location determination

Abstract

A method using various heuristics techniques for resolving ambiguity in location determination in environments with or without noise. A final location determination solution may be determined from a set of ambiguous location determination solutions by using clock temporal bias value, by using consistency information of ranging signal order such as the time of arrival and/or the received power level of the ranging signals, by using the distances to the sources, and/or by using other discriminator functions to select the final location determination solution from a plurality of ambiguous location determination solutions. The main advantage of the heuristic approaches is that redundant measurements are not required for location determination solution disambiguation.

1 . A method for resolving ambiguity in location determination with a plurality of ambiguous location determination solutions for a mobile station using time of arrival of a plurality of ranging signals from base stations in a cellular communication network, the method comprising:
 receiving the plurality of ranging signals at the mobile station;   forming a first ranking of the plurality of ranging signals based on an order of actual time of arrival (TOA) of the ranging signals from earliest to latest;   forming second rankings of the plurality of ranging signals based on an expected order of time of arrival corresponding to each of the plurality of ambiguous location determination solutions;   comparing the first and second rankings of the ranging signals; and   determining a final location determination solution for the mobile station from the plurality of ambiguous location determination solutions based on a result of comparing the first and second rankings of the ranging signals.   
   
   
       2 . The method of  claim 1  wherein determining the final location determination solution comprises determining the ambiguous location determination solution for which the second ranking is a closest match to the first ranking. 
   
   
       3 . The method of  claim 1  wherein determining the final location determination solution comprises determining a combination of the plurality of ambiguous location determination solutions with a closest match in ordering. 
   
   
       4 . The method of  claim 1  further comprising assigning a score to each of the ambiguous location determination solutions based on comparing the first and second rankings of the ranging signals, wherein determining the final location determination solution comprises determining the ambiguous location determination solution having a highest score. 
   
   
       5 . The method of  claim 4  wherein assigning the score comprises determining a number of matches between the ranging signals of the first ranking and the ranging signals of each of the second rankings. 
   
   
       6 . The method of  claim 5  further comprising:
 weighting each of the matches according to an estimated distance of the base station from which the corresponding ranging signal is received.   
   
   
       7 . A method of determining a final location determination solution for a mobile station from a plurality of candidate location determination solutions, the method comprising:
 receiving a plurality of ranging signals at the mobile station;   determining an actual time of arrival for each ranging signal;   forming a first ranking of the ranging signals based on an order of the actual time of arrival of the ranging signals;   forming second rankings of the ranging signals based on an expected order of time of arrival corresponding to each of the plurality of candidate location determination solutions;   assigning a score to each of the second rankings; and   determining the final location determination solution for the mobile station based on the scores of the second rankings.   
   
   
       8 . The method of  claim 7  wherein determining the final location determination solution comprises determining the candidate location determination solution for which the corresponding second ranking has a highest score. 
   
   
       9 . The method of  claim 7  wherein assigning a score to each of the second rankings comprises determining a number of matches between the first ranking of the ranging signals and each of the second rankings. 
   
   
       10 . The method of  claim 7  wherein forming the first ranking comprises ranking the ranging signals from earliest to latest based on the actual time of arrival of each of the ranging signals. 
   
   
       11 . A computer-readable medium having stored thereon a processor-readable program of instructions configured to cause a processor to resolve ambiguity in location determination with a plurality of ambiguous location determination solutions for a mobile station using a time of arrival of each of a plurality of ranging signals, the program of instructions being configured to cause the processor to:
 form a first ranking of the plurality of ranging signals based on an order of actual time of arrival (TOA) from earliest to latest;   form second rankings of the plurality of ranging signals based on an expected order of time of arrival corresponding to each of the plurality of ambiguous location determination solutions;   compare the first and second rankings of the ranging signals; and   determine a final location determination solution for the mobile station from the plurality of ambiguous location determination solutions based on a result of comparing the first and second rankings of the ranging signals.   
   
   
       12 . The computer readable medium of  claim 11  wherein the instructions to configured to cause the processor determine the final location determination solution comprise instructions configured to cause the processor to determine an ambiguous location determination solution for which the second ranking is a closest match to the first ranking. 
   
   
       13 . The computer readable medium of  claim 11  wherein the instructions configured to cause the processor to determine the final location determination solution comprise instructions configured to cause the processor to determine a combination of the plurality of ambiguous location determination solutions with a closest match in ordering. 
   
   
       14 . The computer readable medium of  claim 11  wherein the program further comprises instructions configured to cause the processor to assign a score to each of the ambiguous location determination solutions based on comparing the first and second rankings of the ranging signals, and wherein the instructions configured to cause the processor to determine the final location determination solution comprise instructions configured to cause the processor to determine the ambiguous location determination solution having a highest score. 
   
   
       15 . The computer readable medium of  claim 14  wherein the instructions configured to cause the processor to assign the score comprise instructions configured to cause the processor to determine a number of matches between the ranging signals of the first ranking and the ranging signals of each of the second rankings. 
   
   
       16 . The computer readable medium of  claim 15  wherein the instructions configured to cause the processor to determine the final location determination solution comprise instructions configured to cause the processor to determine the ambiguous location determination solution whose corresponding second ranking has a largest total number of matches with the first ranking. 
   
   
       17 . The computer readable medium of  claim 15  wherein the program further comprises instructions configured to cause the processor to weight each match according to an estimated distance of a base station from which the corresponding ranging signal is received.