Methods and apparatus for clock drift mitigation

Patent metadata

Field	Value
Publication number	US-10148412-B1
Application number	US-201615193991-A
Country	US
Kind code	B1
Filing date	Jun 27, 2016
Priority date	Jun 25, 2015
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

A controller of a first communication device records a first time value of a first clock corresponding to transmission of a first communication frame associated with a timing measurement procedure. If an acknowledgment of the first communication frame was received by the first communication device, the controller records a second time value of the first clock. The controller receives a data unit corresponding to a second communication frame associated with the timing measurement procedure, wherein the data unit includes a time value of a second clock. If an acknowledgment of the first communication frame was not received, the controller compares the first time value of the first clock to the time value of the second clock, and uses i) the first time value of the first clock, and ii) the time value of the second clock to adjust time values corresponding to the first clock responsive to the comparison.

First claim

What is claimed is:

1. A method, comprising:
recording, at a controller of a first communication device, a first time value of a first clock corresponding to transmission of a first communication frame associated with a timing measurement procedure;
determining, at the controller, whether the first communication device received an acknowledgment of the first communication frame;
when the controller determines that the acknowledgment of the first communication frame was received by the first communication device:
recording, at the controller, a second time value of the first clock corresponding to reception of the acknowledgment at the first communication device;

receiving, at the controller, a data unit corresponding to a second communication frame associated with the timing measurement procedure, wherein the data unit includes a time value of a second clock;
when the controller determines that the acknowledgment of the first communication frame was received by the first communication device:
using, at the controller, i) the second time value of the first clock, and ii) the time value of the second clock to adjust time values corresponding to the first clock; and

when the controller determines that the acknowledgment of the first communication frame was not received by the first communication device:
recording, at the controller, a third time value of the first clock corresponding to reception of the second communication frame at the first communication device,
comparing, at the controller, the time value of the second clock to one or both of the first time value of the first clock and the third time value of the first clock to determine i) whether the time value of the second clock is less than the first time value of the first clock, and ii) whether the time value of the second clock is greater than the third time value of the first clock, and
using, at the controller, the time value of the second clock and one of i) the first time value of the first clock, and ii) the third time value of the first clock to adjust time values corresponding to the first clock in response to comparing the time value of the second clock to one or both of the first time value of the first clock and the third time value of the first clock,
wherein, when the controller determines that the time value of the second clock is i) not less than the first time value of the first clock, and ii) not greater than the third time value of the first clock, no adjustment of the time values is made corresponding to the first clock.

2. The method of claim 1 , further comprising:
using i) the first time value of the first clock, and ii) the time value of the second clock to adjust time values corresponding to the first clock in response to determining that the time value of the second clock is less than the first time value of the first clock.

3. The method of claim 1 , comprising:
when the controller determines that the time value of the second clock is not greater than the third time value of the first clock, determining whether the time value of the second clock is less than the first time value of the first clock.

4. The method of claim 1 , further comprising:
using i) the third time value of the first clock, and ii) the time value of the second clock to adjust time values corresponding to the first clock in response to determining that the time value of the second clock is greater than the third time value of the first clock.

5. The method of claim 1 , further comprising:
recording, at the controller, the third time value of the first clock corresponding to reception of the second communication frame at the first communication device whether or not the controller determines that the acknowledgment of the first communication frame was received by the first communication device.

6. An apparatus, comprising:
a controller of a first communication device, the controller configured to execute machine readable instructions; and
a memory coupled to the controller, the memory storing machine readable instructions that, when executed by the controller, cause the controller to:
record a first time value of a first clock corresponding to transmission of a first communication frame associated with a timing measurement procedure;
determine whether the first communication device received an acknowledgment of the first communication frame;
when the controller determines that the acknowledgment of the first communication frame was received by the first communication device:
record a second time value of the first clock corresponding to reception of the acknowledgment at the first communication device;

receive a data unit corresponding to a second communication frame associated with the timing measurement procedure, wherein the data unit includes a time value of a second clock;
when the controller determines that the acknowledgment of the first communication frame was received by the first communication device:
use i) the second time value of the first clock, and ii) the time value of the second clock to adjust time values corresponding to the first clock; and

when the controller determines that the acknowledgment of the first communication frame was not received by the first communication device:
record a third time value of the first clock corresponding to reception of the second communication frame at the first communication device,
compare the time value of the second clock to one or both of the first time value of the first clock and the third time value of the first clock to determine i) whether the time value of the second clock is less than the first time value of the first clock, and ii) whether the time value of the second clock is greater than the third time value of the first clock, and
use the time value of the second clock and one of i) the first time value of the first clock, and ii) the third time value of the first clock to adjust time values corresponding to the first clock in response to comparing the time value of the second clock to one or both of the first time value of the first clock and the third time value of the first clock,
wherein, when the controller determines that the time value of the second clock is i) not less than the first time value of the first clock, and ii) not greater than the third time value of the first clock, no adjustment of the time values is made corresponding to the first clock.

7. The apparatus of claim 6 , wherein the memory further stores machine readable instructions that, when executed by the controller, cause the controller to:
use i) the first time value of the first clock, and ii) the time value of the second clock to adjust time values corresponding to the first clock in response to determining that the time value of the second clock is less than the first time value of the first clock.

8. The apparatus of claim 6 , wherein the memory further stores machine readable instructions that, when executed by the controller, cause the controller to:
when the controller determines that the time value of the second clock is not greater than the third time value of the first clock, determine whether the time value of the second clock is less than the first time value of the first clock.

9. The apparatus of claim 6 , wherein the memory further stores machine readable instructions that, when executed by the controller, cause the controller to:
use i) the third time value of the first clock, and ii) the time value of the second clock to adjust time values corresponding to the first clock in response to determining that the time value of the second clock is greater than the third time value of the first clock.

10. The apparatus of claim 6 , wherein the memory further stores ma

Assignees

• Marvell Int Ltd

Inventors

• Chu Liwen
• Tamhane Sagar A
• Zhang Hongyuan
• Lou Hui-Ling

Classifications

• H04W88/12

  Access point controller devices · CPC title

• H04L69/28 Primary

  Timers or timing mechanisms used in protocols · CPC title

• H04L5/0055 Primary

  Physical resource allocation for ACK/NACK (for physical mapping arrangements in ARQ protocols H04L1/1861) · CPC title

• H04L7/0012 Primary

  by comparing receiver clock with transmitter clock · CPC title

• H04J3/0667

  Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays (arrangements for monitoring round trip delays in packet switching networks H04L43/0864) · CPC title