Synchronization-free station locator in wireless network

• US 8,565,133 B2
• Filed: 07/03/2012
• Issued: 10/22/2013
• Est. Priority Date: 09/03/2009
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chen, Qifan, Zhang, Ning, Cho, James, McFarland, William J.
• Primary Examiner(s): Phan, Tri H
• Application Number:
  US13/541,635
• Publication Number:
  US 20120269170A1
• Time in Patent Office: 476 Days
• Field of Search: 370229-239, 370310-350, 370464-468, 370498-519, 455/63.1, 4554221-423, 455455-466
• US Class Current: 370/310.2
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864

Abstract

A method of providing synchronization-free station locating in a wireless network is provided. In this method, an AP having a known location sends a unicast packet to the station and notes its time of departure TOD(D). The station receives the unicast packet, notes its time of arrival TOA(D), sends an acknowledgement packet to the AP, and notes its time of departure TOD(D_ACK). The AP receives the acknowledgment packet and notes its time of arrival TOA(D_ACK). Notably, a distance between the AP and the station can be accurately determined using a first difference between the TOA(D_ACK) and the TOD(D) and a second difference between the TOD(D_ACK) and the TOA(D). A plurality of such computed distances between a plurality of APs and the station can be used to determine an accurate location of the station.

Claims

1. A method of providing synchronization-free station locating in a wireless network, the wireless network including a first device having an unknown location and a second device having a known location, the method comprising:

(a) sending a first packet from the second device to the first device, the first packet being one of a unicast packet and a probe response packet, the first packet having a time of departure TOD(D);

(b) receiving the first packet at the first device, the first packet having a time of arrival TOA(D);

(c) sending an acknowledgement packet from the first device to the second device, the acknowledgment packet having a time of departure TOD(D_ACK);

(d) receiving the acknowledgment packet at the second device, the acknowledgment packet having a time of arrival TOA(D_ACK); and

(e) computing a distance between the first device and the second device using a first difference between the TOA(D_ACK) and the TOD(D) and a second difference between the TOD(D_ACK) and the TOA(D);

(f) moving the second device to another known location and repeating (a)-(e); and

(g) using a plurality of computed distances between the first and second devices to determine a location of the first device.

2. The method of claim 1, wherein a difference between the TOD(D_ACK) and the TOA(D) is one of a constant value and an averaged value.

3. The method of claim 1, wherein a difference between the TOD(D_ACK) and the TOA(D) is set equal to a short inter-frame space (SIFS).

4. The method of claim 1, further including recording a time stamp of the TOD(D) and the TOA(D_ACK) by driving a counter of a wireless device using a clock.

5. The method of claim 1, further including recording a time stamp of the TOA(D) and the TOD(D_ACK) by driving a counter of the first device using a clock.

6. The method of claim 1, further including:

when a transmission error occurs, aborting a transaction including the first packet and initiating a new distance measurement transaction with a second packet.

7. A method of providing synchronization-free device locating in a wireless network, the wireless network including a first device having an unknown location and a second device having a known location, the method comprising:

sending a first packet from the second device to the first device, the first packet being one of a unicast packet and a probe response packet, the first packet having a time of departure (TOD(D));

receiving the first packet at the first device, the first packet having a time of arrival TOA(D);

sending an acknowledgement packet from the first device to the second device, the acknowledgment packet having a time of departure TOD(D_ACK);

receiving the acknowledgment packet at the second device, the acknowledgment packet having a time of arrival TOA(D_ACK); and

computing a distance between the first device and the second device using a first difference between the TOA(D_ACK) and the TOD(D) and a second difference between the TOD(D_ACK) and the TOA(D);

receiving at least one constraint regarding an environment of the first device; and

using the computed distance between the first and second devices and the at least one constraint to determine a location of the first device.

8. The method of claim 7, wherein the at least one constraint is a map.

9. The method of claim 7, wherein a difference between the TOD(D_ACK) and the TOA(D) is one of a constant value and an averaged value.

10. The method of claim 7, wherein a difference between the TOD(D_ACK) and the TOA(D) is set equal to a short inter-frame space (SIFS).

11. The method of claim 7, further including recording a time stamp of the TOD(D) and the TOA(D_ACK) by driving a counter of a wireless device using a clock.

12. The method of claim 7, further including recording a time stamp of the TOA(D) and the TOD(D_ACK) by driving a counter of the first device using a clock.

13. The method of claim 7, further including:

when a transmission error occurs, aborting a transaction including the first packet and initiating a new distance measurement transaction with a second packet.

14. A wireless device forming part of a wireless network including a first device, the wireless device being coupled to a processing unit, the wireless device comprising:

an antenna;

a radio path coupled to the antenna;

a digital baseband unit coupled to the radio path; and

a medium access controller (MAC) coupled to the digital baseband unit,

wherein the wireless device is capable of;

(a) sending a first packet from the wireless device to the first device, the first packet being one of a unicast packet and a probe response packet, the first packet having a time of departure TOD(D);

(b) receiving an acknowledgment packet at the wireless device, the acknowledgment packet having a time of arrival TOA(D_ACK)

(c) receiving a time of arrival TOA(D) when the first device received the first packet, and a time of departure TOD(D_ACK) when the first device sent the acknowledgement packet; and

(d) using the processing unit, computing a distance between the first device and the wireless device using a first difference between the TOA(D_ACK) and the TOD(D) and a second difference between the TOD(D_ACK) and the TOA(D);

(e) repeating (a)-(d) when the wireless device is moved to another known location; and

(f) using a plurality of computed distances between the first device and the wireless device to determine a location of the first device.

15. The wireless device of claim 14, wherein a difference between the TOD(D_ACK) and the TOA(D) is one of a constant value and an averaged value.

16. The wireless device of claim 14, wherein a difference between the TOD(D_ACK) and the TOA(D) is set equal to a short inter-frame space (SIFS).

17. The wireless device of claim 14, the wireless device being further capable of recording a time stamp of the TOD(D) and the TOA(D_ACK) by driving a counter using a clock.

18. The wireless device of claim 14, the wireless device being further capable of:

when a transmission error occurs, aborting a transaction including the first packet and initiating a new distance measurement transaction with a second packet.

19. The wireless device of claim 14, wherein the processing unit includes at least one of a host personal computer, a central processing unit, a server, and a microprocessor.

20. A wireless device forming part of a wireless network including a first device, the wireless device being coupled to a processing unit, the wireless device comprising:

an antenna;

a radio path coupled to the antenna;

a digital baseband unit coupled to the radio path; and

a medium access controller (MAC) coupled to the digital baseband unit,

wherein the wireless device is capable of;

(a) sending a first packet from the wireless device to the first device, the first packet being one of a unicast packet and a probe response packet, the first packet having a time of departure TOD(D);

(b) receiving an acknowledgment packet at the wireless device, the acknowledgment packet having a time of arrival TOA(D_ACK)

(c) receiving a time of arrival TOA(D) when the first device received the first packet, and a time of departure TOD(D_ACK) when the first device sent the acknowledgement packet; and

(d) using the processing unit, computing a distance between the first device and the wireless device using a first difference between the TOA(D_ACK) and the TOD(D) and a second difference between the TOD(D_ACK) and the TOA(D);

(e) receiving at least one constraint regarding an environment of the first device; and

(f) using the computed distance between the first and second devices and the at least one constraint to determine a location of the first device.

21. The method of claim 20, wherein the at least one constraint is a map.

22. The wireless device of claim 20, wherein a difference between the TOD(D_ACK) and the TOA(D) is one of a constant value and an averaged value.

23. The wireless device of claim 20, wherein a difference between the TOD(D_ACK) and the TOA(D) is set equal to a short inter-frame space (SIFS).

24. The wireless device of claim 20, the wireless device being further capable of recording a time stamp of the TOD(D) and the TOA(D_ACK) by driving a counter using a clock.

25. The wireless device of claim 20, the wireless device being further capable of:

when a transmission error occurs, aborting a transaction including the first packet and initiating a new distance measurement transaction with a second packet.

26. The wireless device of claim 20, wherein the processing unit includes at least one of a host personal computer, a central processing unit, a server, and a microprocessor.

27. A wireless device forming part of a wireless network including a first device, the wireless device being coupled to a means for computing, the wireless device comprising:

means for communicating using radio signals;

means for processing a digital baseband signal coupled to the means for communicating; and

means for processing packets coupled to the means for processing the digital baseband signal,

wherein the wireless device is capable of;

(a) sending a first packet from the wireless device to the first device, the first packet being one of a unicast packet and a probe response packet, the first packet having a time of departure TOD(D);

(b) receiving an acknowledgment packet at the wireless device, the acknowledgment packet having a time of arrival TOA(D_ACK)

(c) receiving a time of arrival TOA(D) when the first device received the first packet, and a time of departure TOD(D_ACK) when the first device sent the acknowledgement packet; and

(d) using the means for computing, computing a distance between the first device and the wireless device using a first difference between the TOA(D_ACK) and the TOD(D) and a second difference between the TOD(D_ACK) and the TOA(D);

(e) repeating (a)-(d) when the wireless device is moved to another known location; and

(f) using a plurality of computed distances between the first device and the wireless device to determine a location of the first device.

28. The wireless device of claim 27, wherein a difference between the TOD(D_ACK) and the TOA(D) is one of a constant value and an averaged value.

29. The wireless device of claim 27, wherein a difference between the TOD(D_ACK) and the TOA(D) is set equal to a short inter-frame space (SIFS).

30. The wireless device of claim 27, the wireless device being further capable of recording a time stamp of the TOD(D) and the TOA(D_ACK) by driving a means for counting using a clock.

31. The wireless device of claim 27, the wireless device being further capable of:

when a transmission error occurs, aborting a transaction including the first packet and initiating a new distance measurement transaction with a second packet.

32. The wireless device of claim 27, wherein the means for computing includes at least one of a host personal computer, a central processing unit, a server, and a microprocessor.

33. A wireless device forming part of a wireless network including a first device, the wireless device being coupled to a means for computing, the wireless device comprising:

means for communicating using radio signals;

means for processing a digital baseband signal coupled to the means for communicating; and

means for processing packets coupled to the means for processing the digital baseband signal,

wherein the wireless device is capable of;

(a) sending a first packet from the wireless device to the first device, the first packet being one of a unicast packet and a probe response packet, the first packet having a time of departure TOD(D);

(b) receiving an acknowledgment packet at the wireless device, the acknowledgment packet having a time of arrival TOA(D_ACK);

(c) receiving a time of arrival TOA(D) when the first device received the first packet, and a time of departure TOD(D_ACK) when the first device sent the acknowledgement packet;

(d) using the means for computing, computing a distance between the first device and the wireless device using a first difference between the TOA(D_ACK) and the TOD(D) and a second difference between the TOD(D_ACK) and the TOA(D);

(e) receiving at least one constraint regarding an environment of the first device; and

(f) using the computed distance between the first device and the wireless device and the at least one constraint to determine a location of the first device.

34. The method of claim 33, wherein the at least one constraint is a map.

35. The wireless device of claim 33, wherein a difference between the TOD(D_ACK) and the TOA(D) is one of a constant value and an averaged value.

36. The wireless device of claim 33, wherein a difference between the TOD(D_ACK) and the TOA(D) is set equal to a short inter-frame space (SIFS).

37. The wireless device of claim 33, the wireless device being further capable of recording a time stamp of the TOD(D) and the TOA(D_ACK) by driving a counter using a clock.

38. The wireless device of claim 33, the wireless device being further capable of:

when a transmission error occurs, aborting a transaction including the first packet and initiating a new distance measurement transaction with a second packet.

39. The wireless device of claim 33, wherein the means for computing includes at least one of a host personal computer, a central processing unit, a server, and a microprocessor.