LOCATION OF MOBILE NETWORK NODES

• US 20120039310A1
• Filed: 08/10/2010
• Published: 02/16/2012
• Est. Priority Date: 08/10/2010
• Status: Active Grant

• Current Assignee: Digi International Inc.
• Original Assignee: Digi International Inc.
• Inventors: Dahl, Paul A., McCall, Scott
• Granted Patent: US 8,576,818 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

The physical position of an unknown node in a network is determined by sending a first sent WiFi signal from one of an unknown node and a first reference node having a known location, and repeating the sent WiFi signal in the other of the unknown node and first reference node with a first reply WiFi signal. A distance is derived between the unknown node and the first reference node from the time of flight of the first sent and first reply WiFi signals. A second WiFi signal is sent from one of the unknown node and a second fixed node having a known location, and repeating the sent second WiFi signal in the other of the unknown node and second reference node with a second reply WiFi signal, and A distance is derived between the unknown node and the second reference node from the time of flight of the second sent and second reply WiFi signals. A physical location of the unknown node is determined based on the derived distances between the unknown node and the first and second reference nodes.

Claims

1. A method of determining the physical position of a movable node in a network, comprising:

sending a first sent WiFi signal from one of an unknown node and a first reference node having a known location, and repeating the sent WiFi signal in the other of the unknown node and first reference node with a first reply WiFi signal;

deriving a distance between the unknown node and the first reference node from the time of flight of the first sent and first reply WiFi signals;

sending a second sent WiFi signal from one of the unknown node and a second fixed node having a known location, and repeating the sent second WiFi signal in the other of the unknown node and second reference node with a second reply WiFi signal;

deriving a distance between the unknown node and the second reference node from the time of flight of the second sent and second reply WiFi signals; and

determining a physical location of the unknown node based on the derived distances between the unknown node and the first and second reference nodes.

2. The method of determining the physical position of a movable node in a network of claim 1, further comprising:

sending a third sent WiFi signal from one of the unknown node and a third fixed node having a known location, and repeating the third sent WiFi signal in the other of the unknown node and third reference node with a third reply WiFi signal; and

deriving a distance between the unknown node and the third reference node from the time of flight of the third sent and third reply WiFi signals;

wherein determining a physical location of the unknown node is further based on the derived distance between the unknown node and the third reference node.

3. The method of determining the physical position of a movable node in a network of claim 2, further comprising:

sending a fourth sent WiFi signal from one of the unknown node and a fourth fixed node having a known location, and repeating the fourth sent WiFi signal in the other of the unknown node and fourth reference node with a fourth reply WiFi signal; and

deriving a distance between the unknown node and the fourth reference node from the time of flight of the fourth sent and fourth reply WiFi signals;

wherein determining a physical location of the unknown node is further based on the derived distance between the unknown node and the fourth reference node.

4. The method of determining the physical position of a movable node in a network of claim 1, wherein repeating at least one of the first and second sent WiFi signals comprises repeating the reply WiFi signal on a different frequency or channel than the sent signal.

5. The method of determining the physical position of a movable node in a network of claim 1, further comprising compensating for at least one of turnaround time and poor convergence of the derived distances in determining the physical location of the unknown node.

6. The method of determining the physical position of a movable node in a network of claim 1, wherein at least one of the sent and reply WiFi signals comprise 802.11 a, b, g, or n standard WiFi standard signals.

7. A wireless network, comprising:

an unknown node having an unknown physical position;

a first reference node, wherein one of the unknown node and the first reference node is operable to send a first sent signal, and the other of the unknown node and first reference node is operable to repeat the first sent signal by sending a first reply signal; and

a second reference node, wherein one of the unknown node and the second reference node is operable to send a second sent signal, and the other of the unknown node and second reference node is operable to repeat the second sent signal by sending a second reply signal;

at least one node in the wireless network further operable to derive a distance between the unknown node and the first reference node from the time of flight of the first sent and first reply signals, derive a distance between the unknown node and the second reference node from the time of flight of the second sent and second reply signals, and determine a physical location of the unknown node based on the derived distances between the unknown node and the first and second reference nodes.

8. The wireless network of claim 7, further comprising:

a third reference node, wherein one of the unknown node and the third reference node is operable to send a third sent signal, and the other of the unknown node and third reference node is operable to repeat the third sent signal by sending a third reply signal;

at least one node in the wireless network further operable to derive a distance between the unknown node and the third reference node from the time of flight of the third sent and third reply signals, and determine a physical location of the unknown node based on the derived distance between the unknown node and the third reference node.

9. The wireless network of claim 8, further comprising:

a fourth reference node, wherein one of the unknown node and the fourth reference node is operable to send a fourth sent signal, and the other of the unknown node and fourth reference node is operable to repeat the fourth sent signal by sending a fourth reply signal;

at least one node in the wireless network further operable to derive a distance between the unknown node and the fourth reference node from the time of flight of the fourth sent and fourth reply signals, and determine a physical location of the unknown node based on the derived distance between the unknown node and the fourth reference node.

10. The wireless network of claim 7, wherein repeating at least one of the first and second sent signals comprises repeating the reply signal on a different frequency or channel than the sent signal.

11. The wireless network of claim 7, wherein determining a physical location of the unknown node based on the derived distances comprises compensating for at least one of turnaround time and poor convergence of the derived distances in determining the physical location of the unknown node.

12. The wireless network of claim 7, wherein at least one of the sent and reply signals comprise 802.11 standard WiFi standard signals.

13. A wireless network node comprising a module operable to:

receive a first sent signal from one of an unknown node and a first reference node having a known location, and

reply immediately to the node that sent the first sent signal with a first reply signal on another channel or frequency, such that the reply delay is small relative to the time of flight of the first sent signal, enabling the sending node to derive a distance between the unknown node and the first reference node from the time of flight of the first sent and first reply signals.

14. The wireless network node of claim 13, wherein at least one of the sent and reply signals comprise 802.11 standard WiFi standard signals.

15. A wireless network node comprising a module operable to:

send a WiFi signal to a second network node;

receive an immediate reply WiFi signal; and

derive a distance between the sending node and the second node from the time of flight of the sent and reply WiFi signals.

16. The wireless network node of claim 15, further operable to determine a physical location of at one of the sending and second network nodes based on the derived distance between the unknown node and the second node, and a known location of the other of the sending and second network nodes.

17. The wireless network node of claim 16, wherein determining a physical location of at one of the sending and second network nodes further comprises using distance information between the unknown node and at least two nodes of known physical location.

18. The wireless network node of claim 16, further comprising compensating for at least one of turnaround time and poor convergence of the derived distances in determining the physical location of the unknown node.

19. The wireless network node of claim 15, wherein receiving an immediate reply

WiFi signal comprises receiving the reply WiFi signal on a different frequency or channel than the sent WiFi signal.

20. The wireless network node of claim 15, wherein at least one of the sent and reply WiFi signals comprise 802.11 a, b, g, or n standard WiFi standard signals.