Network-centric determination of node processing delay

Patent metadata

Field	Value
Publication number	US-9645225-B2
Application number	US-62235609-A
Country	US
Kind code	B2
Filing date	Nov 19, 2009
Priority date	Nov 21, 2008
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

Apparatus and methods are directed to calibrating a delay within a wireless access point for determining a position of a mobile station. One method includes receiving an initial packet at an eavesdropping device, receiving a response packet, sent by another entity, at the eavesdropping device, computing a time difference based upon the packet arrival times, and providing the time difference to a position determination entity. Another method includes providing a request to appropriate eavesdropping devices to send information, receiving, from each appropriate eavesdropping device, a time difference which represents a difference in a time of arrival of a packet transmitted by the wireless access point and a time of arrival of a packet transmitted by the mobile station, determining a processing delay estimate based upon the time differences, and determining a position of the mobile station based upon the processing delay estimate and the received time differences.

First claim

What is claimed is:

1. A method of preparing data for determining a position of a mobile station, comprising:
receiving information from a plurality of eavesdropping devices, the information from each respective one of the plurality of eavesdropping devices comprising signal strength information of a respective signal received at the respective one of the plurality of eavesdropping devices from each of the mobile station and a wireless access point;
selecting a subset of the plurality of eavesdropping devices based at least in part on the signal strength information, the subset of the plurality of eavesdropping devices comprising at least three of the plurality of eavesdropping devices;
obtaining information, from each respective eavesdropping device of the subset of the plurality of eavesdropping devices, the information comprising an indication of a time difference representing a difference in a time of arrival at the respective eavesdropping device of a respective initial packet sent by the mobile station and a time of arrival of a respective response packet sent by the wireless access point responsive to the respective initial packet;
determining a refined processing delay based upon the indications of the time differences from the subset of the plurality of eavesdropping devices by combining the information received from each of the subset of the plurality of eavesdropping devices, the information received comprises processing delay estimates computed by each of the plurality of eavesdropping devices, wherein each processing delay estimate represents an estimated amount of time that the wireless access point took to process a respective initial packet from the mobile station and to generate the respective response packet; and
determining the position of the mobile station based upon the refined processing delay and the time differences from the subset of the plurality of eavesdropping devices.

2. The method according to claim 1 , further comprising:
measuring a first arrival time corresponding to the initial packet; and
measuring a second arrival time corresponding to the response packet;
wherein preparing the indication of the time difference comprises computing a difference between the second arrival time and the first arrival time.

3. The method according to claim 1 , wherein the eavesdropping device comprises a wireless access point.

4. The method according to claim 1 , wherein obtaining the information further comprises:
sending a request to the plurality of eavesdropping devices for the information.

5. The method according to claim 1 , further comprising:
bounding the refined processing delay based upon the time differences from the subset of the plurality of eavesdropping devices.

6. The method according to claim 5 , wherein the refined processing delay is bound by a triangle inequality.

7. The method of claim 1 , further comprising providing the position of the mobile station to a position determination entity.

8. The method according to claim 1 , further comprising:
measuring a first arrival time corresponding to the initial packet; and
measuring a second arrival time corresponding to the response packet;
wherein prepare the indication of the time difference comprises computing a difference between the second arrival time and the first arrival time; and

wherein the eavesdropping device comprises a wireless access point.

9. The method of claim 1 , wherein at least one of the plurality of eavesdropping devices is a mobile station operating in a peer-to-peer networking mode, and wherein the information from each respective at least one of the plurality of eavesdropping devices includes position information associated with a position of the respective at least one of the plurality of eavesdropping devices.

10. The method of claim 1 , wherein determining a refined processing delay based upon the indications of the time differences from the subset of the plurality of eavesdropping devices by combining the information received from each of the subset of the plurality of eavesdropping devices comprises determining a processing delay estimate for each of the indications of the time differences by estimating an amount of time that the wireless access point took to process a respective initial packet from the mobile station and to generate the respective response packet and by combining the processing delay estimates to determine the refined processing delay.

11. A method for determining a position of a mobile station, comprising:
receiving information from a plurality of eavesdropping devices, the information from each respective one of the plurality of eavesdropping devices comprising signal strength information of a respective signal received at the respective one of the plurality of eavesdropping devices from each of the mobile station and the wireless access point;
selecting a subset of the plurality of eavesdropping devices based at least in part on the signal strength information, the subset of the plurality of eavesdropping devices comprising at least three of the plurality of eavesdropping devices;
sending a request to each eavesdropping device of the subset of the plurality of eavesdropping devices for an indication of a time difference which represents a difference in a time of arrival at the respective eavesdropping device of a response packet sent by a wireless access point and a time of arrival at the respective eavesdropping device of an initial packet sent by the mobile station;
receiving, only from each of the subset of the plurality of eavesdropping devices, the indication of the time difference;
determining a refined processing delay estimate associated with the wireless access point based upon the indications of the time differences from the subset of the plurality of eavesdropping devices by combining the information received from each of the subset of the plurality of eavesdropping devices, the information received comprises processing delay estimates computed by each of the plurality of eavesdropping devices, wherein each processing delay estimate represents an estimated amount of time that the wireless access point took to process a respective initial packet from the mobile station and to generate the respective response packet; and
determining the position of the mobile station based upon the refined processing delay estimate and the time differences from the subset of the plurality of eavesdropping devices.

12. The method according to claim 11 , wherein the processing delay estimate is bound by a triangle inequality.

13. The method according to claim 11 , wherein determining the processing delay estimate further comprises:
determining a relative geometry of the mobile station and the wireless access point relative to one of the subset of the plurality of eavesdropping devices;
determining a range for the processing delay estimate by using the time differences from the subset of the plurality of eavesdropping devices in a triangle inequality; and
selecting a value from the range, as a refined processing delay, based upon the relative geometry.

14. The method according to claim 13 , wherein selecting the value from the range further comprises selecting the value from an upper end of the range;
wherein the relative geometry is substantially collinear; and
wherein the wireless access point is between the mobile station and the eavesdropping device, or the mobile station is between the wireless access point and the eavesdropping device.

15. The method according to claim 13 , wherein selecting the value from the range further comprises selecting the value from a

Assignees

• Aggarwal Alok
• Naguib Ayman Fawzy
• Sridhara Vinay
• Qualcomm Inc

Inventors

• Aggarwal Alok
• Naguib Ayman Fawzy
• Sridhara Vinay

Classifications

• G01S5/0284

  Relative positioning · CPC title

• G01S5/06 Primary

  Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence) · CPC title

• H04W4/04

  Electricity · mapped topic

• H04L29/08657

  Electricity · mapped topic

• G01S5/021 Primary

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