Method to modify calibration data used to locate a mobile unit
View Patent ↗A method of modifying calibration data used to geo-locate a mobile station located in an indoor environment is disclosed. When a mobile station is located indoors, the signal strength of signals received and/or transmitted by the mobile station have the tendency to be lower than the strength of the signals received by a mobile station located outdoors. As a result of these lower signal strengths, geo-location efforts which rely on signal strengths may result in unsatisfactory location accuracy. Modifying pre-existing calibration data obtained outdoors may provide a way to simulate indoor calibration data characteristics.
1. A method for determining a location of a mobile station, comprising:
providing a database of previously-gathered calibration data for a predetermined region in a wireless network, wherein said network includes a first transmitter and a second transmitter;
collecting observed network measurement data including a first signal characteristic from said first transmitter and a second signal characteristic from said second transmitter;
determining which of said first and second signal characteristics has a greater magnitude;
modifying said observed network measurement data using the greater magnitude signal characteristic; and
comparing said modified network measurement data with said database of calibration data to thereby determine the location of the mobile station.
2. The method of claim 1 wherein said database comprises previously-gathered calibration data for one or more non-uniform grid points within said region.
3. The method of claim 1 wherein said observed network measurement data includes data collected at the mobile station.
4. The method of claim 1 wherein said previously-gathered calibration data includes calibration data gathered at a predetermined calibration point within said region wherein said predetermined calibration point is not located within a structure.
5. The method of claim 4 wherein said observed network measurement data is collected at a mobile station located within a structure.
6. The method of claim 4 wherein said first signal characteristic is signal strength.
7. The method of claim 6 wherein said second signal characteristic is signal strength.
8. The method of claim 7 wherein the modifying of said calibration data uses a difference between said first or second signal characteristics.
9. The method of claim 7 wherein said first signal characteristic is signal strength of a control channel transmitted by said first transmitter and received by said mobile station.
10. The method of claim 9 wherein said second signal characteristic is signal strength of a control channel transmitted by said second transmitter and received by said mobile station.
11. The method of claim 1 , wherein the observed network measurement data includes received signal strength of said transmitters as said mobile station.
12. The method of claim 1 wherein said observed network measurement data includes a data set comprising:
[P 1 , P 2 . . . , P n , TA]
where:
P 1 represents the signal strength of said first transmitter as measured at said mobile station,
P 2 represents a signal strength of said second transmitter as measured at said mobile station wherein P 2 >P 1
P n , represents a signal strength of a n th transmitter as measured at said mobile station wherein P 2>P n , and
TA represents a timing advance parameter;
and wherein said modified network measurement data includes a data set comprising:
[P 2 −P 1 , 0, P 2 −P n , TA]
where:
P 2 −P 1 represents a difference between P 2 and P 1 ,
0 represents a difference between P 2 and P 2 , and
P 2 −P n represents a difference between P 2 and P n .
13. The method of claim 12 wherein said first transmitter is a serving transmitter for said mobile station and said second and third transmitters are neighboring transmitters.
14. The method of claim 12 wherein said third transmitter is not a member of said wireless network.
15. A method for determining a location of a mobile station, comprising:
providing a database of previously-gathered outdoor calibration data for a predetermined region in a wireless network;
collecting network measurement data;
comparing said network measurement data with said database of calibration data to thereby determine a plurality of location estimate of the mobile station
determining a confidence measure for each of the plurality of location estimates;
determining the location of the mobile station based on the plurality of location estimates and the respective confidence measures.
16. The method of claim 15 , wherein the step of determining the location based on the plurality of location estimates and the respective confidence measures comprises selecting the location estimate having the highest respective confidence measure as the location of the mobile station.
17. The method of claim 15 , wherein the step of determining the location based on the plurality of location estimates and their respective confidence measures comprises weighing the plurality location estimates based on their respective confidence measures and obtaining a weighted average as the location of the mobile.
18. The method of 15 , wherein the confidence measures comprises one or more of the group consisting of a pdf the Mahalanobis distance, and a distortion measure.
19. The method of claim 15 , wherein the step of collecting network propagation data further comprises modifying the network propagation data.
20. The method of claim 15 , wherein the step of comparing said network propagation data with said database of calibration data to thereby determine a plurality of location estimate of the mobile station, further comprises modifying said calibration data prior to the comparison.
21. The method of claim 20 , wherein the step of comparing said network propagation data with said database of calibration data to thereby determine a plurality of location estimate of the mobile station, further comprises modifying said calibration data prior to the comparison.