Reduced power synchronization of wireless devices

• US 20120188997A1
• Filed: 06/06/2011
• Published: 07/26/2012
• Est. Priority Date: 04/16/2010
• Status: Active Grant

• Current Assignee: Simmonds Precision Products, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Simmonds Precision Products, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Zakrzewski, Radoslaw Romuald, Lynch, Michael Anthony
• Granted Patent: US 8,660,110 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04J 3/0667 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 Class Codes: H04W 4/70 Services for machine-to-machine communication [M2M] or machine type communication [MTC]
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 56/009 Closed loop measurements
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Synchronizing at least one wireless sensor includes sending at least one reference message along with a request for acquired data from an access point to the at least one wireless sensor, where the reference message includes a first timestamp indicating when the reference message was sent according to time of a clock of the access point, receiving from the at least one wireless sensor a response that includes the requested data, the first timestamp, and at least one other timestamp corresponding to time of a clock of the at least one wireless sensor, and determining a relative clock offset of the at least one wireless sensor using the timestamps.

Claims

1. A method of synchronizing at least one wireless sensor, comprising:

sending at least one reference message along with a request for acquired data from an access point to the at least one wireless sensor, wherein the reference message includes a first timestamp indicating when the reference message was sent according to time of a clock of the access point;

receiving from the at least one wireless sensor a response that includes the requested data, the first timestamp, and at least one other timestamp corresponding to time of a clock of the at least one wireless sensor; and

determining a relative clock offset of the at least one wireless sensor using the timestamps.

2. The method according to claim 1, wherein the at least one other timestamp includes a second timestamp corresponding to time of the clock of the at least one wireless sensor when the reference message is received by the at least one wireless sensor and a third timestamp corresponding to time of the clock of the at least one wireless sensor when the response is sent.

3. The method according to claim 1, wherein determining a relative clock offset includes using a fourth timestamp corresponding to when the response was received according to time of the clock of the access point.

4. The method according to claim 1, wherein the at least one wireless sensor is one of a plurality of wireless sensors, and wherein each of the wireless sensors collects data in synchronization with other of the wireless sensors according to the scheduled actions.

5. The method according to claim 4, further comprising:

providing to at least one of the wireless sensors a command to acquire data.

6. A method according to claim 5, wherein the command is provided in connection with sending the at least one reference message.

7. The method according to claim 4, further comprising:

discarding data from at least one of the wireless sensors that does not correspond to data from other ones of the wireless sensors.

8. The method according to claim 7, wherein discarding data includes determining a latest start time for data collection for all of the wireless sensors and determining an earliest end time for all of the wireless sensors and discarding data that is prior to the latest start time and after the earliest end time.

9. The method according to claim 1, further comprising:

sending at least one other reference message having a timestamp indicating when the reference message was sent according to time of the clock of the access point, wherein the reference message does not include a request for data.

10. The method according to claim 9, wherein the at least one other reference message is sent after sending the reference message that includes the request for data.

11. Computer software, provided in a non-transitory computer-readable medium, that synchronizes at least one wireless sensor, the software comprising:

executable code that sends at least one reference message along with a request for acquired data from an access point to the at least one wireless sensor, wherein the reference message includes a first timestamp indicating when the reference message was sent according to time of a clock of the access point;

executable code that receives from the at least one wireless sensor a response that includes the requested data, the first timestamp, and at least one other timestamp corresponding to time of a clock of the at least one wireless sensor; and

executable code that determines a relative clock offset of the at least one wireless sensor using the timestamps.

12. The software according to claim 11, wherein the at least one other timestamp includes a second timestamp corresponding to time of the clock of the at least one wireless sensor when the reference message is received by the at least one wireless sensor and a third timestamp corresponding to time of the clock of the at least one wireless sensor when the response is sent.

13. The software according to claim 11, wherein determining a relative clock offset includes using a fourth timestamp corresponding to when the response was received according to time of the clock of the access point.

14. The software according to claim 11, wherein the at least one wireless sensor is one of a plurality of wireless sensors, and wherein each of the wireless sensors collects data in synchronization with other of the wireless sensors according to the scheduled actions.

15. The software according to claim 14, further comprising:

executable code that provides to at least one of the wireless sensors a command to acquire data.

16. A software according to claim 15, wherein the command is provided in connection with sending the at least one reference message.

17. The software according to claim 14, further comprising:

executable code that discards data from at least one of the wireless sensors that does not correspond to data from other ones of the wireless sensors.

18. The software according to claim 17, wherein executable code that discards data includes executable code that determines a latest start time for data collection for all of the wireless sensors, determines an earliest end time for all of the wireless sensors and discards data that is prior to the latest start time and after the earliest end time.

19. The software according to claim 11, further comprising:

executable code that sends at least one other reference message having a timestamp indicating when the reference message was sent according to time of the clock of the access point, wherein the reference message does not include a request for data.

20. The software according to claim 19, wherein the at least one other reference message is sent after sending the reference message that includes the request for data.