Dual round trip time mitigation for wireless local area network devices

Patent metadata

Field	Value
Publication number	US-12181564-B1
Application number	US-202418753241-A
Country	US
Kind code	B1
Filing date	Jun 25, 2024
Priority date	Dec 20, 2023
Publication date	Dec 31, 2024
Grant date	Dec 31, 2024

Abstract

A method and devices are disclosed for geo-location of wireless local area network (WLAN) devices. According to one aspect, a method for determining a corrected round trip times (RTT) resulting from communication with a WD is provided. The WD is configured with one or two short interframe spacings (SIFS). The method includes performing RTT measurements at successive times. The method includes determining a presence of one or two modes based at least in part on peaks of a kernel density estimation (KDE) surface. The KDE surface is determined from the RTT measurements. When there is only one mode, a corrected RTT is determined based on the RTT measurements and a first SIFS. When there are two modes, a corrected RTT is determined based on the RTT measurements and the first SIFS plus an SIFS offset (Δ), Δ being based at least in part on a difference between the two modes.

First claim

What is claimed is:

1. A method in a first wireless device (WD) for determining a corrected round trip times (RTT) resulting from communication with a second WD, the second WD being configured with one or two short interframe spacings (SIFS), the method comprising:
performing a plurality of RTT measurements (RTT i ) at successive times during a time period, T; and
determining a presence of one or two modes based at least in part on peaks of a kernel density estimation (KDE) surface, the KDE surface being determined from the plurality of RTT measurements, and:
when there is only one mode, then determining a corrected RTT based at least in part on the plurality of RTT measurements and a first SIFS; and
when there are two modes, then determining a corrected RTT based at least in part on the plurality of RTT measurements and the first SIFS plus an SIFS offset (Δ), Δ being based at least in part on a difference between the two modes.

2. The method of claim 1 , wherein the SIFS offset Δ is based at least in part on an average of previously determined SIFS offsets when there are two modes.

3. The method of claim 1 , wherein, when there is only one mode and when |RTT peak −Ts−TOF|<|RTT peak −Ts−Δ−TOF|, then the corrected RTT is determined as RTT peak −Ts, and otherwise, then the corrected RTT is determined as RTT peak −Ts−Δ, where RTT peak is a peak RTT of the one mode, Ts is an offset corresponding to the first SIFS, Δ is the SIFS offset, and TOF is a time of flight.

4. The method of claim 1 , wherein determining the corrected RTT includes minimizing a sum of squared residuals, each squared residual being based at least in part on a difference between an RTT i and a total travel time, the total travel time being based at least in part on a target location parameter, α, determined by setting a gradient of the sum of squared residuals to zero.

5. The method of claim 4 , wherein a residual R(rtt) i is based at least in part on calculating R(rtt) i =[(RTT i −α OFF )+TOFi], where the subscript i denotes an i th RTT measurement of the plurality of RTT measurements and an i th time of flight TOF i , and α OFF is determined as Ts when there is only one mode and α OFF is determined as Ts−Δ when there are two modes.

6. The method of claim 1 , wherein, when there are two modes, the corrected RTT is determined as RTT peak −α OFF , where α OFF is equal to Ts for a first mode of the two modes and α OFF is equal to Ts−Δ for a second mode of the two modes.

7. The method of claim 6 , further comprising determining whether to use α OFF =Ts or α OFF =Ts−Δ for corrected RTT determination is based at least in part on a numerical fitting process.

8. The method of claim 1 , wherein the KDE surface is determined by a superposition of kernel functions weighting each of the plurality of RTT measurements.

9. The method of claim 8 , wherein the kernel functions are Gaussian.

10. The method of claim 1 , wherein the time period T is selected to be less than the SIFS offset Δ.

11. A first wireless device (WD) configured to determine a corrected round trip time (RTT) resulting from communication with a second WD, the second WD being configured with one or two short interframe spacings (SIFS), the first WD being configured to:
perform a plurality of RTT measurements (RTT i ) at successive times during a time period, T; and
determine a presence of one or two modes based at least in part on peaks of a kernel density estimation (KDE) surface, the KDE surface being determined from the plurality of RTT measurements, and:
when there is only one mode, then determine a corrected RTT based at least in part on the plurality of RTT measurements and a first SIFS;
when there are two modes, then determine a corrected RTT based at least in part on the plurality of RTT measurements and the first SIFS plus an SIFS offset (Δ), Δ being based at least in part on a difference between the two modes.

12. The first WD of claim 11 , wherein the SIFS offset Δ is based at least in part on an average of previously determined SIFS offsets when there are two modes.

13. The first WD of claim 11 , wherein, when there is only one mode and when |RTT peak −Ts−TOF|<|RTT peak −Ts−Δ−TOF|, then the corrected RTT is determined as RTT peak −Ts, and otherwise, then the corrected RTT is determined as RTT peak −Ts−Δ, where RTT peak is a peak RTT of the one mode, Ts is an offset corresponding to the first SIFS, Δ is the SIFS offset, and TOF is a time of flight.

14. The first WD of claim 11 , wherein determining the corrected RTT includes minimizing a sum of squared residuals, each squared residual being based at least in part on a difference between an RTT i and a total travel time, the total travel time being based at least in part on a target location parameter, α, determined by setting a gradient of the sum of squared residuals to zero.

15. The first WD of claim 14 , wherein a residual R(rtt) i is based at least in part on calculating R(rtt) i =[(RTT i −α OFF )+TOFi], where the subscript i denotes an i th RTT measurement of the plurality of RTT measurements and an i th time of flight TOF i , and α OFF is determined as Ts when there is only one mode and α OFF is determined as Ts−Δ when there are two modes.

16. The first WD of claim 11 , wherein, when there are two modes, the corrected RTT is determined as RTT peak −α OFF , where α OFF is equal to Ts for a first mode of the two modes and α OFF is equal to Ts−Δ for a second mode of the two modes.

17. The first WD of claim 16 , wherein the first WD is configured to determine whether to use α OFF =Ts or α OFF =Ts−Δ for corrected RTT determination is based at least in part on a numerical fitting process.

18. The first WD of claim 11 , wherein the KDE surface is determined by a superposition of kernel functions weighting each of the plurality of RTT measurements.

19. The first WD of claim 18 , wherein the kernel functions are Gaussian.

20. The first WD of claim 11 , wherein the time period T is selected to be less than the SIFS offset Δ.

Assignees

• Sr Tech Inc

Inventors

• Passler Mark
• Kelly Kyle Patrick

Classifications

• G01S7/006

  using shared front-end circuitry, e.g. antennas (G01S13/765, G01S13/825 take precedence) · CPC title

• G01S13/765

  with exchange of information between interrogator and responder · CPC title

• H04W64/00

  Locating users or terminals {or network equipment} for network management purposes, e.g. mobility management · CPC title

• H04W56/0055 Primary

  determining timing error of reception due to propagation delay · CPC title

• G01S13/76 Primary

  wherein pulse-type signals are transmitted · CPC title