Estimation of speed and direction of travel in a WLAN positioning system using multiple position estimations

• US 20070258408A1
• Filed: 05/08/2006
• Published: 11/08/2007
• Est. Priority Date: 05/08/2006
• Status: Active Grant

• Current Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Original Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Inventors: Pahlavan, Kaveh, Alizadeh-Shabdiz, Farshid, Morgan, Edward
• Granted Patent: US 7,551,929 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

A method for estimating the speed and bearing of a Wi-Fi enabled device using WLAN radio signals in a WLAN based location service is provided. A method used to estimate a speed of travel of a Wi-Fi enabled device comprises the Wi-Fi enabled device receiving signals transmitted by Wi-Fi access points in range of the Wi-Fi enabled device, and using the signals to estimate the speed of and/or direction of travel of the Wi-Fi enabled device.

Claims

1. A method used to estimate a speed of travel of a Wi-Fi enabled device, comprising:

the Wi-Fi enabled device receiving signals transmitted by Wi-Fi access points in range of the Wi-Fi enabled device;

accessing a reference database to determine if the database contains characteristics of the Wi-Fi access points; and

if the database contains characteristics of the Wi-Fi access point, using the characteristics to estimate a speed of travel of the Wi-Fi enabled device.

2. The method of claim 1, wherein the Wi-Fi enabled device communicates with at least one of the Wi-Fi access points to cause the Wi-Fi access point to transmit signals.

3. The method of claim 1, wherein the characteristics include one or more of a geographic location, a signal power-distance gradient, or a reliability measurement.

4. A method for facilitating the determination of a speed of travel of the Wi-Fi enabled device within a location-based services system having a reference database of Wi-Fi access points in a target area, each Wi-Fi access point in the target area positioned at a corresponding geographical location, the method comprising:

the Wi-Fi enabled device receiving signals transmitted by Wi-Fi access points in range of the Wi-Fi enabled device during a window of time;

accessing the reference database to retrieve the corresponding geographical locations of the identified Wi-Fi access points;

using the geographical locations of the identified Wi-Fi access points to estimate a plurality of positions of the Wi-Fi enabled device occurring during the window of time;

associating a time value with each of the estimated positions, each time value and position estimate forming one position/time pair of a plurality of pairs, the plurality having a first position occurring at a first time and a second position occurring at a second time;

calculating a lower speed bound based on a difference between the first position and time and second position and time;

calculating a plurality of speeds based on differences between consecutive pairs of the plurality of position/time pairs;

selecting as an upper speed bound the median speed from the plurality of speeds; and

calculating a speed of travel of the Wi-Fi enabled device based on the median speed of the plurality of speeds and the first speed.

5. The method of claim 4, wherein the Wi-Fi enabled device communicates with at least one of the Wi-Fi access points to cause the Wi-Fi access point to transmit signals.

6. The method of claim 4, wherein the number of position/time pairs determined varies according to the speed of travel of the Wi-Fi enabled device.

7. The method of claim 6, wherein the number of position/time pairs determined decreases as the speed of travel of the Wi-Fi enabled device increases.

8. The method of claim 4, wherein the speed of travel of the Wi-Fi enabled device is the average of the lower speed bound and the upper speed bound.

9. The method of claim 4, wherein the number of position/time pairs is between about 5 and 15, taken at a rate of one pair per second.

10. The method of claim 4, wherein the number of position/time pairs determined varies according to the rate of change of speed of travel of the Wi-Fi enabled device.

11. The method of claim 4, further comprising:

accessing the reference database to retrieve reliability measurements corresponding to the identified Wi-Fi access points; and

using the reliability measurements of the Wi-Fi access points when estimating the positions of the Wi-Fi enabled device.

12. The method of claim 4, wherein at least one of the accessing the reference database, estimating a plurality of positions, associating a time value, calculating a lower speed bound, calculating a plurality of speeds, selecting an upper speed bound, and calculating the speed of travel of the Wi-Fi enabled device is performed by the Wi-Fi enabled device.

13. A method for facilitating the determination of a speed of travel of the Wi-Fi enabled device within a location-based services system having a reference database of Wi-Fi access points in a target area, each Wi-Fi access point in the target area positioned at a corresponding geographical location, the method comprising:

the Wi-Fi enabled device receiving signals transmitted by Wi-Fi access points in range of the Wi-Fi enabled device during a window of time;

accessing the reference database to retrieve the corresponding geographical locations of the identified Wi-Fi access points;

using the geographical locations of the identified Wi-Fi access points to estimate a plurality of distances traveled by the Wi-Fi enabled device;

associating a time value with each estimated position;

calculating the speed of travel of the Wi-Fi enabled device based on the plurality of distances and associated times.

14. The method of claim 13, wherein the Wi-Fi enabled device communicates with at least one of the Wi-Fi access points to cause the Wi-Fi access point to transmit signals.

15. The method of claim 13, further comprising:

accessing the reference database to retrieve reliability measurements corresponding to the identified Wi-Fi access points; and

using the reliability measurements of the Wi-Fi access points when estimating the positions of the Wi-Fi enabled device.

16. A method used for facilitating the determination of a direction of travel of the Wi-Fi enabled device within a location-based services system having a reference database of Wi-Fi access points in a target area, each Wi-Fi access point in the target area positioned at a corresponding geographical location, the method comprising:

the Wi-Fi enabled device receiving signals transmitted by Wi-Fi access points in range of the Wi-Fi enabled device;

accessing the reference database to retrieve the corresponding geographical locations of the identified Wi-Fi access points;

using the geographical locations of the identified Wi-Fi access points to estimate a sequence of positions of the Wi-Fi enabled device occurring during the window of time, the sequence having a first position;

calculating a plurality of intermediate directions of travel of the Wi-Fi enabled device based on the first position and the later positions of the sequence, each direction calculation using a different later position for each individual calculation; and

calculating a direction of travel of the Wi-Fi enabled device based on the average of the plurality of intermediate directions of travel.

17. The method of claim 16, wherein the Wi-Fi enabled device communicates with at least one of the Wi-Fi access points to cause the Wi-Fi access point to transmit signals.

18. The method of claim 16, further comprising:

accessing the reference database to retrieve reliability measurements corresponding to the identified Wi-Fi access points; and

using the reliability measurements of the Wi-Fi access points when estimating the positions of the Wi-Fi enabled device.

19. The method of claim 16, wherein at least one of the accessing the reference database, estimating a sequence of positions, calculating a plurality of intermediate directions of travel, and calculating the direction of travel of the Wi-Fi enabled device is performed by the Wi-Fi enabled device.

20. The method of claim 16, wherein the sequence of positions estimated is between about 10 and 15.