Time of arrival based positioning system

Patent metadata

Field	Value
Publication number	US-9332383-B2
Application number	US-201214345941-A
Country	US
Kind code	B2
Filing date	Sep 19, 2012
Priority date	Sep 19, 2011
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

A TOA positioning system can be implemented that employs a calculated initial location of a wireless network device. For each of a plurality of reference wireless network devices, a distance between the wireless network device and the reference wireless network device is determined based, at least in part, on a round trip transit time between the wireless network device and the reference wireless network device. An initial location of the wireless network device can be calculated based, at least in part, on a location of each of the plurality of reference wireless network devices. A location of the wireless network device can be estimated based, at least in part, on the calculated initial location, the distance to each of the reference wireless network devices, and an initial distance calibration constant.

First claim

What is claimed is:

1. A method comprising:
determining, at a first wireless device, an estimated distance between the first wireless device and each of a plurality of reference devices, wherein the estimated distance between the first wireless device and a respective reference device is based at least in part on a round trip transit time (RTT) associated with the respective reference device;
determining an initial position of the first wireless device based, at least in part, on a known position associated with at least one of the plurality of reference devices; and
and estimating a current position of the first wireless device and the first distance calibration value by executing a time of arrival (TOA) positioning operation based, at least in part, on the estimated distance between the first wireless device and each of the plurality of reference devices, the initial position of the first wireless device, the known position associated with at least one of the plurality of reference devices and an initial distance calibration value, wherein the executing the TOA positioning operation comprises:
determining a location error matrix, represented by a difference between an estimated location coordinate of the first wireless device and a corresponding initial location coordinate of the initial position of the first wireless device;
determining a distance error matrix, represented by a difference between the estimated distance between the first wireless device and one of the plurality of reference devices and a calculated distance between the first wireless device and the one of the plurality of reference devices; and
and determining a coefficient matrix as a product of the distance error matrix and an inverse of a transpose of the location error matrix.

2. The method of claim 1 , wherein estimating the current position of the first wireless device and the first distance calibration value comprises determining the current position of the first wireless device using a set of operations to jointly determine the first distance calibration value.

3. The method of claim 1 , wherein estimating the current position of the first wireless device and the first distance calibration value comprises concurrently determining a location error and a distance calibration error.

4. The method of claim 3 , wherein the first distance calibration value comprises a sum of the initial distance calibration value and the distance calibration error and wherein the current position comprises a sum of the location error and the initial position.

5. The method of claim 1 , wherein the calculated distance is determined based, at least in part, on the known position associated with the one of the plurality of reference devices and the initial position of the first wireless device, and wherein executing the TOA positioning operation comprises:
determining the current position of the first wireless device based, at least in part, on maximizing a determinant of the product of the coefficient matrix and the transpose of the coefficient matrix.

6. The method of claim 1 , wherein the TOA positioning operation comprises:
solving an expression to determine the current position that minimizes a sum of estimation errors for each of the plurality of reference devices, each estimation error between
A) the estimated distance to i th reference device based on an i th RTT associated with the i th reference device and B) the calculated distance to the i th reference device based on a known position associated with the i th reference device.

7. The method of claim 1 , wherein the first distance calibration value does not differ from one reference device to another.

8. The method of claim 1 , wherein the initial distance calibration value is one of a zero value, a predetermined value, and a dynamically selected random value.

9. The method of claim 1 , wherein determining the initial position of the first wireless device comprises:
determining the initial position of the first wireless device as a weighted average of location coordinates associated with the plurality of reference devices.

10. The method of claim 9 , wherein weights used in the weighted average are based upon a confidence associated with the location coordinates associated with the at least one of the plurality of reference devices.

11. The method of claim 1 , further comprising:
identifying the plurality of reference devices based, at least in part, on one or more performance measurements associated with the plurality of reference devices.

12. The method of claim 1 , wherein the first wireless device and the plurality of reference devices comprise wireless local area network, WLAN, communication capabilities.

13. The method of claim 1 , further comprising:
determining, at the first wireless device, the RTT between the first wireless device and each of the plurality of reference devices.

14. The method of claim 13 , wherein determining the RTT between the first wireless device and each of the plurality of reference devices comprises, for each respective reference device:
recording a first time instant at which a first control message is transmitted from the first wireless device to the respective reference device;
recording a second time instant at which a second control message is received at the first wireless device from the respective reference device in response to the first control message;
subtracting the first time instant from the second time instant to determine a respective RTT between the first wireless device and the respective reference device; and
multiplying the respective RTT between the first wireless device and the respective reference device by a speed of light factor to yield the distance between the first wireless device and the respective reference device.

15. The method of claim 1 , further comprising:
determining location coordinates associated with at least one of the plurality of reference devices.

16. The method of claim 15 , wherein determining the location coordinates associated with at least one of the plurality of reference devices comprises:
transmitting a request for the location coordinates to at least one of the plurality of reference devices; and
receiving the location coordinates from at least one of the plurality of reference devices.

17. The method of claim 16 , wherein the request for the location coordinates is included in a control message that is also used to determine the RTT between the first wireless device and at least one of the plurality of reference devices.

18. The method of claim 15 , wherein determining the location coordinates associated with at least one of the plurality of reference devices comprises:
transmitting a request for the location coordinates to a centralized server; and
receiving the location coordinates associated with at least one of the plurality of reference devices from the centralized server.

19. The method of claim 15 , wherein determining the location coordinates associated with at least one of the plurality of reference devices comprises:
receiving a periodic broadcast message from at least one of the plurality of reference devices, the periodic broadcast message including the location coordinates from a corresponding one of the plurality of reference devices.

20. The method of claim 16 , wherein the location coordinates associated with at least one of the plurality of reference devices comprises one of two-dimensional (2-D) coordinates, three-dimensional (3-D) coordinates, geographic latitude and

Assignees

• Qualcomm Inc

Inventors

• Zhang Xiaoxin
• Zhang Ning

Classifications

• G01S5/14

  Determining absolute distances from a plurality of spaced points of known location · CPC title

• H04W4/02 Primary

  Services making use of location information · CPC title

• G01S13/876

  Combination of several spaced transponders or reflectors of known location for determining the position of a receiver (G01S13/874 takes precedence) · CPC title

• G01S5/021

  Calibration, monitoring or correction (G01S5/0252 takes precedence) · CPC title

• H04W4/029 Primary

  Location-based management or tracking services · CPC title