Distance estimation based on narrow-band wireless time-of-flight

Patent metadata

Field	Value
Publication number	US-10921439-B2
Application number	US-201816013296-A
Country	US
Kind code	B2
Filing date	Jun 20, 2018
Priority date	Jun 20, 2018
Publication date	Feb 16, 2021
Grant date	Feb 16, 2021

Abstract

A wireless ranging system generates, at a first device, a first plurality of counts, each of the first plurality of counts indicative of a transmit time of a corresponding packet, and further generates a second plurality of counts, each of the second plurality of counts indicative of a receive time of a corresponding packet. In response to a number of samples of the first plurality of counts exceeding a threshold, the system generates a plurality of timestamps based on the first plurality of counts and the second plurality of counts and generates a plurality of time-of-flight values based on the plurality of timestamps. Based on a combination of the plurality of the time-of-flight values, the wireless ranging system generates an effective time-of-flight value and identifies a distance between the first device and as second device based on the effective time-of-flight value.

First claim

What is claimed is:

1. A method comprising:
generating, at a first device, a first plurality of counts, each of the first plurality of counts indicative of a transmit time of a corresponding packet;
generating a second plurality of counts, each of the second plurality of counts indicative of a receive time of a corresponding packet;
in response to a number of samples of the first plurality of counts exceeding a threshold,
generating a plurality of timestamps based on the first plurality of counts and the second plurality of counts;
generating a plurality of time-of-flight values based on the plurality of timestamps;
generating an effective time-of-flight value based on a combination of the plurality of the time-of-flight values;
identifying a distance between the first device and a second device based on the effective time-of-flight value; and
keeping a count of rollovers at a counter and employing the rollover count to extract the plurality of timestamps from raw counts provided by the counter.

2. The method of claim 1 , wherein:
generating the first plurality of counts comprises:
generating a first portion of the first plurality of counts based on transmitting a first plurality of packets at a first frequency; and
generating a second portion of the first plurality of counts based on transmitting a second plurality of packets at a second frequency different from the first frequency.

3. The method of claim 2 , further comprising:
transmitting a frequency pattern indicating the first frequency and the second frequency from the first device to the second device.

4. The method of claim 1 , further comprising:
prior to generating the first plurality of counts and the second plurality of counts, synchronizing a first clock of the first device with a second clock of the second device, and wherein generating the first plurality of counts comprises generating the first plurality of counts based on the first clock.

5. The method of claim 1 , wherein generating the effective time-of-flight value comprises:
generating a statistical profile based on the first plurality of counts and the second plurality of counts;
determining quality metrics for the plurality of time-of-flight values based on the statistical profile;
selecting a subset of the plurality of time-of-flight values based on the quality metrics; and
generating the effective time-of-flight value based on the selected subset of time-of-flight values.

6. The method of claim 1 , wherein generating the first plurality of counts comprises:
generating each of the first plurality of counts by triggering a read of a counter of the first device in response to defined event at a radio of the first device.

7. The method of claim 1 , wherein generating the effective time-of-flight value comprises:
adjusting at least one of the plurality of time-of-flight values based on an automatic gain control associated with one of the first device and the second device; and
generating the effective time-of-flight value based in part on the adjusted one of the plurality of time-of-flight values.

8. A method, comprising:
generating a statistical profile for a plurality of time-of-flight values, each of the plurality of time-of-flight values based on communication of associated packets between a first device and a second device;
pruning the plurality of time-of-flight values based on the statistical profile to generate a pruned set of time-of-flight values;
generating an effective time-of-flight value based on a combination of the pruned set of time-of-flight values;
identifying a distance between the first device and as second device based on the effective time-of-flight value; and
keeping a count of rollovers at a counter and employing the rollover count to extract the plurality of timestamps from raw counts provided by the counter.

9. The method of claim 8 , wherein generating the statistical profile comprises determining an average of the plurality of the time-of-flight values.

10. The method of claim 8 , wherein generating the statistical profile comprises determining a median of the plurality of the time-of-flight values.

11. The method of claim 8 , wherein pruning the plurality of time-of-flight values comprises:
generating a quality metric for each of the plurality of time-of-flight values based on the statistical profile; and
pruning the plurality of time-of-flight values based on the generated quality metrics.

12. The method of claim 8 , wherein generating the effective time-of-flight value comprises:
generating an initial time-of-flight value based on the combination of the plurality of the time-of-flight values; and
generating the effective time-of-flight value based on a combination of the initial time-of-flight value and a calibration offset.

13. The method of claim 8 , further comprising:
generating the plurality of time-of-flight values based on a plurality of counts corresponding to transmit times and receive times of a plurality of packets.

14. A device, comprising:
a radio configured to transmit and receive packets;
a counter configured to generate a first plurality of counts, each of the first plurality of counts indicative of a transmit time of a corresponding packet;
the counter further configured to generate a second plurality of counts, each of the second plurality of counts indicative of a receive time of a corresponding packet;
a processor configured to:
in response to a number of the first plurality of counts exceeding a threshold, generating a plurality of timestamps based on the first plurality of counts and the second plurality of counts;
generate a plurality of time-of-flight values based on the plurality of timestamps;
generate an effective time-of-flight value based on a combination of the plurality of the time-of-flight values;
identify a distance between the device and another device based on the effective time-of-flight value; and
keep a count of rollovers at the counter and employ the rollover count to extract the plurality of timestamps from raw counts provided by the counter.

15. The device of claim 14 , wherein the counter is configured to generate the first plurality of counts by:
generating a first portion of the first plurality of counts based on the radio transmitting a first plurality of packets at a first frequency; and
generating a second portion of the first plurality of counts based on the radio transmitting a second plurality of packets at a second frequency different from the first frequency.

16. The device of claim 15 , wherein the radio is configured to:
transmit a frequency pattern indicating the first frequency and the second frequency.

17. The device of claim 14 , wherein the processor is configured to:
prior to the counter generating the first plurality of counts and the second plurality of counts, synchronize a first clock of the device with a clock of another device, and wherein generating the first plurality of counts comprises generating the first plurality of counts based on the first clock.

18. The device of claim 14 , wherein the processor is configured to generate the effective time-of-flight value by:
generating a statistical profile based on the first plurality of counts and the second plurality of counts;
determining quality metrics for the plurality of time-of-flight values based on the statistical profile;
selecting a subset of the plurality of time-of-flight values based on the quality metrics; and
generating the effective time-of-flight value based on the selected subset of time-of-fligh

Assignees

• Nxp Usa Inc

Inventors

• Waheed Khurram
• Neri Castellanos Carlos Alberto

Classifications

• G01S5/0244

  Accuracy or reliability of position solution or of measurements contributing thereto · CPC title

• G01S13/767 Primary

  Responders; Transponders (teaching or practice apparatus for gun-aiming or gun-laying using reflecting targets or active targets F41G3/26) · CPC title

• G01S5/021 Primary

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

• G01S7/282

  Transmitters · CPC title

• G01S7/34

  Gain of receiver varied automatically during pulse-recurrence period, e.g. anti-clutter gain control · CPC title