Using A Priori Geographical Location Density Information To Improve Location Accuracy

Abstract

A technique for improving location accuracy based on a priori geographical location density information is disclosed. In accordance with the illustrative embodiment, geographical location density information is derived from historical wireless location data such as the locations of prior E911 emergency calls, Location Based Services (LBS) sessions, conventional voice calls, packet data sessions, vehicle routes, and so forth. The geographical location density information is represented by a probability distribution function, and is incorporated into an existing location technique. Advantageously, the technique of the present invention can be employed in conjunction with any existing location technology; moreover, the historical location data can be obtained via any technology, and from any wireless network, including those that are different than that of the future location estimates.

1 . A method comprising estimating the location of a first wireless terminal at time t based on a location of a second wireless terminal at a time prior to time t. 
   
   
       2 . The method of  claim 1  wherein the location of the first wireless terminal is estimated by a first technique, and wherein the location of the second wireless terminal is estimated by a second technique. 
   
   
       3 . The method of  claim 1  wherein the location of the first wireless terminal is estimated by a first entity, and wherein the location of the second wireless terminal is estimated by a second entity. 
   
   
       4 . The method of  claim 3  wherein the location of the second wireless terminal is estimated by the second wireless terminal, and wherein the location of the first wireless terminal is estimated by an entity other than the first wireless terminal. 
   
   
       5 . The method of  claim 4  wherein the location of the second wireless terminal is estimated based on a reading of a Global Positioning System receiver incorporated into the second wireless terminal, and wherein the estimation of the location of the first wireless terminal is estimated via a non-GPS technique. 
   
   
       6 . The method of  claim 1  wherein the location of the first wireless terminal is estimated by the first wireless terminal, and wherein the location of the second wireless terminal is estimated by an entity other than the second wireless terminal. 
   
   
       7 . The method of  claim 1  wherein the first wireless terminal and the second wireless terminal operate on different networks. 
   
   
       8 . The method of  claim 1  wherein the first wireless terminal and the second wireless terminal employ different communication protocols. 
   
   
       9 . The method of  claim 1  wherein the first wireless terminal is engaged in an E911 call at time t, and wherein the location of the second wireless terminal corresponds to a time at which the second wireless terminal was engaged in an E911 call. 
   
   
       10 . A method comprising:
 generating a first probability distribution for the location of a wireless terminal W at time t based on a non-empty set S, wherein each member of set S specifies the location of a wireless terminal at a time prior to time t, and wherein at least one member of set S corresponds to the location of a wireless terminal X that is different than wireless terminal W; and   estimating the location of wireless terminal W based, at least in part, on the first probability distribution.   
   
   
       11 . The method of  claim 10  wherein at least one of the members of set S specifies the time prior to time t. 
   
   
       12 . The method of  claim 10  further comprising obtaining set S from a superset of set S. 
   
   
       13 . The method of  claim 10  wherein set S is obtained from the superset based, at least in part, on time t. 
   
   
       14 . The method of  claim 10  wherein the estimation of the location of wireless terminal W is also based on a second probability distribution that is independent of the first probability distribution. 
   
   
       15 . The method of  claim 10  wherein a location of wireless terminal X in set S is estimated via a different technique than the location of wireless terminal W. 
   
   
       16 . The method of  claim 10  wherein a location of wireless terminal X in set S is estimated via a different entity than the location of wireless terminal W. 
   
   
       17 . The method of  claim 16  wherein a location of wireless terminal X in set S is estimated based on a reading of a Global Positioning System receiver incorporated into wireless terminal X, and wherein the estimation of the location of wireless terminal W is not based on a reading of a Global Positioning System receiver. 
   
   
       18 . The method of  claim 10  wherein wireless terminal W and wireless terminal X operate on different networks. 
   
   
       19 . The method of  claim 10  wherein wireless terminal W and wireless terminal X employ different communication protocols. 
   
   
       20 . The method of  claim 10  wherein at least one member of set S corresponds to the location of a wireless terminal Y that is different than wireless terminal W and is different than wireless terminal X.