Frequency offset compensation for wifi ranging

Patent metadata

Field	Value
Publication number	US-2016119889-A1
Application number	US-201614987264-A
Country	US
Kind code	A1
Filing date	Jan 4, 2016
Priority date	Jan 31, 2013
Publication date	Apr 28, 2016
Grant date	—

Abstract

Methods, systems, and apparatus are disclosed for determining accurate ranging measurements between communication devices. Various embodiments are described for recording timestamps associated with when transmissions are sent and received between the communication devices. The communication devices are configured to determine a difference in their clock frequencies and to communicate this difference with one another. Furthermore, each of the communication devices is configured to compensate for these differences before or after the timestamps are exchanged and to send a compensation indicator of whether the compensation has been performed. If the compensation has not been performed, either of the communication devices can compensate for the clock frequency differences after receiving the timestamps based on the compensation indicator. By using compensated clock frequencies based on a single clock reference, highly accurate ranging measurements are obtained using round trip propagation time calculations.

First claim

What is claimed:

1 . A method for clock compensation with respect to i) a first communication device utilizing a first clock having a first clock frequency, and ii) a second communication device utilizing a second clock having a second clock frequency, the method comprising:
determining, at the first communication device, a first timestamp corresponding to when a first transmission is transmitted by the second communication device; determining, at the first communication device, a second timestamp corresponding to when a second transmission is received at the second communication device; and determining, at the first communication device, whether a compensation indicator has been received from the second communication device; and compensating, at the first communication device, for a difference between the first clock frequency and the second clock frequency to provide a compensated first timestamp and a compensated second timestamp when it is determined that the compensation indicator has not been received from the second communication device, wherein a presence of the compensation indicator indicates that the first timestamp and second timestamps are received in terms of the first clock frequency and do not need to be compensated.

Assignees

• Marvell World Trade Ltd

Inventors

• Zhang Hongyuan
• Yu Mao
• Yong Su Khiong
• Srinivasa Sudhir

Classifications

• H04W56/002

  Mutual synchronization · CPC title

• G01S5/06

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

• G01S11/02

  using radio waves (G01S19/00 takes precedence) · CPC title

• G01S13/767

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

• H04W56/004 Primary

  compensating for timing error of reception due to propagation delay · CPC title