Position determination system that uses a cellular communication system

Abstract

A position determination system and apparatus for utilizing a network of cellular base stations to determine position of a mobile station includes taking a plurality of statistically independent data measurements of the pilot signals from the base stations. Each of the data measurements includes an earliest time of arrival, providing multiple independent measurements for each of the pilot signals. For each cellular base station, a representative measurement is calculated responsive to the independent measurements, which is used to determine position of the mobile station using an AFLT algorithm and/or in conjunction with a GPS algorithm. In some embodiments, the data measurements for each pilot signal further include an RMSE estimate and time of measurement for each time of arrival, and an energy measurement for all resolvable paths. If the mobile station comprises a cell phone, a cell search list and a GPS search list may be provided by a cell base station.

1 . A method for determining the position of a mobile station using a plurality of cellular base stations each emitting a unique pilot signal, comprising: 
 taking a plurality of substantially independent data measurements of the pilot signals from each of said plurality of cellular base stations, each of said data measurements including an earliest time of arrival estimate for each pilot signal, thereby providing a plurality of independent measurements of the earliest time of arrival for each of the pilot signals from said plurality of cellular base stations;    for each cellular base station, calculating a representative measurement of the earliest time of arrival responsive to said independent measurements for said cellular base station; and    utilizing at least one of said representative measurements to determine the position of said mobile station.    
     
     
         2 . The method of  claim 1  wherein said data measurements further include an RMSE estimate for each time of arrival.  
     
     
         3 . The method of  claim 2  wherein said step of calculating a representative measurement comprises, for each cellular base station, calculating a representative measurement for said RMSE estimates for each of said pilot signals.  
     
     
         4 . The method of  claim 1  wherein said step of calculating representative measurements for a pilot ID includes selecting data measurements and, for said selected data measurements, averaging the time of arrival estimates that fall within a predetermined window.  
     
     
         5 . The method of  claim 1  wherein said data measurements further include a time of measurement for each time of arrival estimate.  
     
     
         6 . The method of  claim 5  wherein said step of calculating the representative measurements comprises aging the data measurements for each pilot signal responsive to the time of measurement.  
     
     
         7 . The method of  claim 1  further comprising calculating a total energy value for all paths of pilot signal.  
     
     
         8 . The method of  claim 1  further comprising utilizing said representative measurements in an AFLT algorithm to determine position.  
     
     
         9 . The method of  claim 8  further comprising utilizing said representative measurements together with a GPS algorithm to determine position.  
     
     
         10 . The method of  claim 1  wherein said mobile station comprises a cell phone, and further comprising: 
 connecting the cell phone to one of said cellular base stations prior to said data-taking step;  
 providing a cell search list of cellular base stations responsive to said cellular base station; and  
 said data-taking step includes taking data measurements from the cellular base stations provided on said cell search list.  
 
     
     
         11 . The method of  claim 10  wherein said cell search list is provided by the cell station to which said cell phone connected.  
     
     
         12 . The method of  claim 1 , further using a plurality of GPS satellites in conjunction with said plurality of cellular base stations, comprising: 
 scanning the sky to determine the respective locations of at least one of said plurality of GPS satellites;    measuring the time of arrival of the GPS signals from each of the GPS satellites whose locations have been determined; and    utilizing said time of arrival of the GPS signals, in conjunction with at least one of said representative measurements to determine the position of said mobile station.    
     
     
         13 . The method of  claim 9  wherein said mobile station comprises a cell phone, and further comprising: 
 connecting the cell phone to one of said cellular base stations;  
 providing a GPS search list including a plurality of GPS satellites. responsive to said cellular base station; and  
 said scanning step includes scanning the sky for the GPS satellites on said GPS search list.  
 
     
     
         14 . The method of  claim 1  further comprising a step, before calculating said representative measurements, of determining if sufficient data measurements are available to calculate said representative measurements.  
     
     
         15 . The method of  claim 1  further comprising the step of storing said data measurements in a database in said mobile station.  
     
     
         16 . The method of  claim 1  further comprising continuing to take data measurements and periodically calculating representative measurements in order to periodically update the position of the mobile station.  
     
     
         17 . A system for determining the position of a mobile station using a plurality of cellular base stations each emitting a unique pilot signal, comprising: 
 data taking means for taking a plurality of substantially independent data measurements of the pilot signals from each of said plurality of cellular base stations, each of said data measurements including an earliest time of arrival estimate for each pilot signal, thereby providing a plurality of independent measurements of the earliest time of arrival for each of the pilot signals from said plurality of cellular base stations;    calculation means for calculating a representative measurement for each cellular base station, including means for calculating the earliest time of arrival responsive to said independent measurements for each respective cellular base station; and    positioning means, responsive to at least one of said representative measurements, for determining the position of said mobile station.    
     
     
         18 . The position determination system of  claim 17  wherein: 
 said data taking means comprises means for taking an RMSE estimate for each time of arrival; and  
 said calculation means comprises means responsive to said RMSE estimates for calculating a representative measurement for each of said pilot signals.  
 
     
     
         19 . The position determination system of  claim 17  wherein: 
 said data taking means comprises means for taking a time of measurement for each time of arrival; and  
 said calculation means comprises means responsive to said time of measurement data for calculating a representative measurement for each of said pilot signals.  
 
     
     
         20 . The position determination system of  claim 17  wherein said calculation means comprises means for aging the data measurements for each pilot signal responsive to the time of measurement data.  
     
     
         21 . The position determination system of  claim 17  further comprising means for calculating a total energy value for all paths of pilot signal.  
     
     
         22 . The position determination system of  claim 17  wherein said positioning means includes means for utilizing said representative measurements in an AFLT algorithm.  
     
     
         23 . The position determination system of  claim 22  wherein said position means includes means for utilizing said representative measurements together with a GPS algorithm.  
     
     
         24 . The position determination system of  claim 17  wherein said mobile station comprises a cell phone, and further comprising: 
 means for providing a cell search list of cellular base stations responsive to said cellular base station; and  
 wherein said data-taking means includes taking means for data measurements from the cellular base stations provided on said cell search list.  
 
     
     
         25 . The position determination system of  claim 17  using a plurality of GPS satellites in conjunction with said plurality of cellular base stations, comprising: 
 means for scanning the sky to determine the respective locations of at least one of said plurality of GPS satellites;  
 means for measuring the time of arrival of the GPS signals from each of the GPS satellites whose locations have been determined; and  
 wherein said positioning means includes means for utilizing said time of arrival of the GPS signals, in conjunction with at least one of said representative measurements to determine the position of said mobile station.  
 
     
     
         26 . The position determination system of  claim 17  further comprising a database and means for storing said data measurements in said database.  
     
     
         27 . The position determination system of  claim 17  further comprising means for continuing to take data measurements and periodically calculating representative measurements in order to periodically update the position of the mobile station.  
     
     
         28 . A mobile station that utilizes a cellular network that includes a plurality of cellular base stations each emitting a unique pilot signal, comprising: 
 a cellular communication system for communicating with said cellular base stations;    a database that stores a plurality of data measurements including an earliest time of arrival estimate for each pilot signal, including multiple substantially independent data measurements for each pilot signal;    a representative measurement calculation system configured to receive data measurements from said database, and responsive thereto to provide a representative measurement of the time of arrival for each pilot signal; and    a position calculation and control system configured to receive said representative measurements for each pilot signal, and responsive thereto, to determine the position of the mobile station.    
     
     
         29 . The system of  claim 28  wherein said mobile station further comprises: 
 a GPS communication system; and  
 wherein said position calculation and control system is configured to receive GPS data measurements, and responsive thereto to determine the position of the mobile station.  
 
     
     
         30 . The system of  claim 28  wherein said database includes memory that stores an RMSE estimate for each time of arrival estimate, and said representative measurement calculation system further comprises means for calculating a representative measurement for the RMSE estimate for each pilot signal.  
     
     
         31 . The system of  claim 28  wherein said database includes memory that stores a time of measurement for each time of arrival estimate.  
     
     
         32 . The system of  claim 28  wherein said database includes memory that stores a total energy value for each pilot signal in the database.  
     
     
         33 . The system of  claim 28  wherein said mobile station comprises a cell phone.