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 an order of received power levels of a plurality of ranging signals from base stations in a cellular network, the method comprising:
 receiving the plurality of ranging signals at the mobile station;   ranking the plurality of ranging signals based on the order of received power levels from strongest to weakest;   ranking the plurality of ranging signals based on an expected order of received power levels corresponding to each of the plurality of ambiguous location determination solutions;   comparing the ranking of the ranging signals based on the order of received power levels and based on the expected order of received power levels corresponding to each of the plurality of ambiguous location determination solutions; and   determining a final location determination solution based on a result of comparing the 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, from the plurality of ambiguous location determination solutions, for which the expected order of received power levels is a closest match to the order of received power levels. 
   
   
       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 . 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 ranging signals from a plurality of sources at the mobile station;   determining a received power level for each of the ranging signals;   ranking the ranging signals based on the received power level for each of the ranging signals;   determining an expected order of received power levels for each of the candidate location determination solutions;   determining a preferred candidate location determination solution from the plurality of candidate location determination solutions for which the expected order of received power levels is a closest match to the ranking of the ranging signals based on the received power level; and   determining the final location determination solution for the mobile station based on the preferred candidate location determination solution.   
   
   
       5 . The method of  claim 4 , further comprising:
 summing a number of matches between the ranging signals ranked based on the received power levels and the ranging signals ranked based on the expected order of the received power levels for each of the candidate location determination solutions.   
   
   
       6 . The method of  claim 5 , wherein summing the number of matches comprises weighting each ranging signal according to a corresponding position in the expected order of the received power levels. 
   
   
       7 . The method of  claim 5 , wherein the preferred candidate location determination solution has a greatest number of the matches among the plurality of candidate location determination solutions. 
   
   
       8 . The method of  claim 4 , wherein each of the plurality of candidate location determination solutions corresponds to a distinct noise level. 
   
   
       9 . A method for resolving ambiguity in location determination with a plurality of ambiguous location determination solutions for a mobile station using an order of received power levels of a plurality of ranging signals transmitted by base stations in a cellular network, the method comprising:
 receiving the ranging signals at the mobile station from the base stations;   determining a received power level for each of the ranging signals;   ranking the ranging signals based on the order of received power levels from strongest to weakest;   determining an expected order of the received power levels for each of the ambiguous location determination solutions;   assigning a score to each of the ambiguous location determination solutions based on a number of matches between the ranging signals in the expected order of the received power levels corresponding to each of the ambiguous location determination solutions and the ranging signals ranked based on the order of the received power levels; and   determining a final location determination solution for the mobile stations based on the scores assigned to the ambiguous location determination solutions.   
   
   
       10 . The method of  claim 9 , wherein assigning the score to each of the ambiguous location determination solutions comprises weighting each of the ranging signals according to a corresponding position in a corresponding one of the expected orders of the received power levels. 
   
   
       11 . The method of  claim 9 , wherein each of the plurality of ambiguous location determination solutions corresponds to a distinct noise level. 
   
   
       12 . A computer-readable medium having stored thereon a processor-readable program of instructions for causing a processor to resolve ambiguity in location determination with a plurality of ambiguous location determination solutions for a mobile station using an order of received power levels 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 the order of received power levels from strongest to weakest;   form a second ranking of the plurality of ranging signals based on an expected order of received power levels corresponding to each of the plurality of ambiguous location determination solutions;   compare the first ranking with each of the second rankings; 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 ranking with the second rankings.   
   
   
       13 . The computer readable medium of  claim 13 , wherein the program further comprises instructions configured to cause the processor to select as the final location determination solution an ambiguous location determination solution for which the expected order of the received power levels is a closest match to the order of the received power levels. 
   
   
       14 . The computer readable medium of  claim 13 , wherein the program further comprises instructions configured to cause the processor to select as the final location determination solution a combination of the plurality of ambiguous location determination solutions with a closest match in ordering.