Estimating the location of a wireless terminal based on signal path impairment
View Patent ↗A technique for estimating the location of a wireless terminal at an unknown location in a geographic region is disclosed. The technique is based on the recognition that there are traits of electromagnetic signals that are dependent on topography, the receiver, the location of the transmitter, and other factors. For example, if a particular radio station is known to be received strongly at a first location and weakly at a second location, and a given wireless terminal at an unknown location is receiving the radio station weakly, it is more likely that the wireless terminal is at the second location than at the first location.
1. A method comprising:
(1) receiving (i) a first measured pathloss for a signal that is processed by a wireless terminal at a first time T 1 and (ii) a second measured pathloss for the signal at a second time T 2 , wherein the first time does not equal the second time;
(2) estimating a first location of the wireless terminal at the second time based on (i) the first measured pathloss, (ii) the second measured pathloss, and (iii) an estimate of the probability that the wireless terminal at a second location at the first time T 1 will still be at the second location at the second time T 2 ;
wherein (2) comprises:
(2.1) comparing the first measured pathloss to:
(i) a first expected pathloss of the signal when the wireless terminal is at a third location at the first time T 1 , and
(ii) a second expected pathloss of the signal when the wireless terminal is at a fourth location at the first time T 1 ; and
(2.2) comparing the second measured pathloss to:
(i) a first expected pathloss of the signal when the wireless terminal is at a fifth location at the second time T 2 , and
(ii) a second expected pathloss of the signal when the wireless terminal is at a sixth location at the second time T 2 .
2. A method comprising:
(1) receiving (i) a first measured error rate for a signal that is processed by a wireless terminal at a first time T 1 and (ii) a second measured error rate for the signal at a second time T 2 , wherein the first time does not equal the second time;
(2) estimating a first location of the wireless terminal at the second time based on (i) the first measured error rate, (ii) the second measured error rate, and (iii) an estimate of the probability that the wireless terminal in a second location at the first time T 1 will still be in the second location at the second time T 2 ;
wherein (2) comprises:
(2.1) comparing the first measured error rate to:
(i) a first expected error rate of the signal when the wireless terminal is at a third location at the first time T 1 , and
(ii) a second expected error rate of the signal when the wireless terminal is at a fourth location at the first time T 1 ; and
(2.2) comparing the second measured error rate to:
(i) a first expected error rate the signal when the wireless terminal is at a fifth location at the second time T 2 , and
(ii) a second expected error rate of the signal when the wireless terminal is at a sixth location at the second time T 2 .
3. A method comprising:
(1) receiving (i) a first measured signal-to-impairment ratio for a signal that is processed by a wireless terminal at a first time T 1 and (ii) a second measured signal-to-impairment ratio for the signal at a second time T 2 , wherein the first time does not equal the second time; and
(2) estimating a first location of the wireless terminal at the second time based on (i) the first measured signal-to-impairment ratio, (ii) the second measured signal-to-impairment ratio, and (iii) an estimate of the probability that the wireless terminal in a second location at the first time T 1 will still be in the second location at the second time T 2 ;
wherein (2) comprises:
(2.1) comparing the first measured signal-to-impairment ratio to:
(i) a first expected signal-to-impairment ratio of the signal when the wireless terminal is at a third location at the first time T 1 , and
(ii) a second expected signal-to-impairment ratio of the signal when the wireless terminal is at a fourth location at the first time T 1 ; and
(2.2) comparing the second measured signal-to-impairment ratio to:
(i) a first expected signal-to-impairment ratio of the signal when the wireless terminal is at a fifth location at the second time T 2 , and
(ii) a second expected signal-to-impairment ratio of signal when the wireless terminal is at a sixth location at the second time T 2 .