WIRELESS LOCALISATION SYSTEM

• US 20190317184A1
• Filed: 06/27/2019
• Published: 10/17/2019
• Est. Priority Date: 07/04/2008
• Status: Active Grant

• Current Assignee: Commonwealth Scientific & Industrial Research Organisation (Commonwealth Of Australia As Represented By Department Of Industry, Innovation, Climate Change, Science, Research And Tertiary Education)
• Original Assignee: Commonwealth Scientific & Industrial Research Organisation (Commonwealth Of Australia As Represented By Department Of Industry, Innovation, Climate Change, Science, Research And Tertiary Education)
• Inventors: Hedley, Mark, Humphrey, David Eric
• Granted Patent: US 11,061,106 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 13/876 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S13/874 takes precedence
• 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 5/017 Detecting state or type of motion
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0226 Transmitters
• 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

Disclosed is method of computing a round trip delay between a pair of nodes, the method comprising transmitting at least one beacon at a known transmit time from each of the nodes; measuring the times-of-arrival of the beacons at other of the nodes; and estimating a round trip delay between the nodes from the measured times-of-arrival and the transmit times; and correcting the round trip delay for either or both of a frequency offset between the nodes and relative motion between the nodes.

Claims

1. A method of estimating a location of a mobile node using anchor nodes, the method comprising:

broadcasting beacons by nodes including said mobile node and said anchor nodes, wherein said mobile node and said anchor nodes broadcast the respective beacon at least once in a superframe;

measuring transmit times of the beacons;

measuring a time-of-arrival of each respective beacon at each of said mobile node and said anchor nodes receiving each respective beacon;

calculating parameter offsets between the nodes based on the beacons transmitted in two or more superframes, the measured transmit times of the beacons, and the measured times-of-arrival of the beacons;

calculating a plurality of round trip delays based on the calculated parameter offsets, the measured transmit times, and the measured times-of-arrival; and

estimating the location of said mobile node relative to said anchor nodes using said calculated plurality of round trip delays.

2. The method according to claim 1, wherein the parameter offsets comprise relative frequency offsets and relative doppler shifts.

3. The method according to claim 1, wherein the broadcasting of the beacons is scheduled using the superframe.

4. The method according to claim 1, wherein the broadcasting is performed using a 802.11 standard.

5. The method according to claim 1, further comprising:

correcting said round trip delays for propagation delays at said anchor nodes and said mobile node; and

computing ranges between said nodes based on the corrected round trip delays, wherein the computed ranges are used to estimate the location of the mobile node.

6. The method according to claim 1, further comprising:

computing ranges between said nodes based on corrected round trip delays, wherein the computed ranges are used to estimate the location of the mobile node.

7. The method according to claim 5, wherein the propagation delays are determined from prior calibration or calculated using the corrected round trip delays between said anchor nodes.

8. The method according to claim 5, further comprising:

pre-filtering the computed ranges between said anchor nodes and said mobile node.

9. The method according to claim 8, wherein said pre-filtering comprises any one of:

interpolating or extrapolating missing range data from the computed ranges; and

filtering the computed ranges to reduce noise and/or remove bad measurements.

10. The method according to claim 9, wherein said filtering comprises linear or non-linear filters.

11. The method according to claim 6, wherein the step of estimating the location of said mobile node relative to said anchor nodes comprises the sub-steps of:

estimating locations of said mobile node and corresponding errors in respective said location estimates, wherein each estimated location is determined from a subset of the computed ranges, and wherein each subset of the computed ranges excludes one range from the set of computed ranges;

discarding each of the computed ranges whose exclusion gave an error estimate that is less than a threshold; and

estimating the location of said mobile node from undiscarded computed ranges, the undiscarded computed ranges being those of the computed ranges that have not been discarded.

12. The method according to claim 11, wherein said threshold is an error estimate of a location estimate determined from all of the computed ranges.

13. The method according to claim 11, wherein said estimating sub-step comprises minimising a weighted sum over said anchor nodes of a squared difference between each computed range and a distance between a candidate location and the location of a corresponding anchor node.

14. The method according to claim 11, wherein each of said error estimates in the estimated locations comprises an estimate of a computed range error and a term relating the computed range error to said error in the estimated location.

15. The method according to claim 11, wherein the discarding of the computed ranges is performed until a number of the undiscarded computed ranges reaches a minimum number.