SYSTEMS, APPARATUS AND METHODS FOR SYNCHRONIZING A GLOBAL TIME REFERENCE FOR ACCESS POINTS OVER THE AIR

• US 20150131528A1
• Filed: 11/05/2014
• Published: 05/14/2015
• Est. Priority Date: 11/08/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Abraham, Santosh Paul, Barriac, Gwendolyn Denise, Merlin, Simone, Cherian, George
• Granted Patent: US 9,655,072 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04W 56/001 Synchronization between nodes
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/12 Access point controller devices

Abstract

Methods and apparatus for synchronizing a global time reference for access points over the air are provided. In one aspect, a method for synchronizing a global time of an access point comprises receiving a message comprising a global time indication from a second access point. The method further includes updating the global time of the access point to the global time indication from the second access point by updating a timer of the access point by an increment not to exceed a predetermined value selected small enough to ensure a maintenance of synchronization between the access point and at least one associated wireless station. The global time of the access point is updated to the global time indication from the second access point when the global time indication from the second access point indicated a later global time than the global time of the access point.

Claims

1. A method for synchronizing a global time of an access point, comprising:

receiving a message comprising a global time indication from a second access point, and

updating the global time of the access point to the global time indication from the second access point by updating a timer of the access point by an increment not to exceed a predetermined value selected small enough to ensure a maintenance of synchronization between the access point and at least one associated wireless station.

2. The method of claim 1, wherein the global time of the access point is updated to the global time indication from the second access point when the global time indication from the second access point indicates a later global time than the global time of the access point.

3. The method of claim 1, wherein the global time of the access point is updated to the global time indication from the second access point when the global time indication from the second access point indicates an earlier global time than the global time of the access point.

4. The method of claim 1, wherein the global time indication is an indication of an offset of a timing synchronization function of the second access point from the global time of the second access point.

5. The method of claim 1, wherein the message comprises a beacon frame.

6. The method of claim 1, further comprising successively updating the timer by the increment until the timer is updated to correspond to the global time indication from the second access point.

7. The method of claim 6, wherein successively updating the timer of the access point is performed periodically.

8. The method of claim 1, wherein when an anchor device is a common anchor device for the access point and the second access point, updating the global time of the access point further comprises:

determining a first difference between the global time indication of the second access point and a most recent global time received by the second access point from the anchor device,

determining a second difference between a stored global time of the access point and the most recent global time received by the access point from the anchor device, and

updating the global time of the access point to the global time of the second access point when the second difference is larger than the first difference.

9. The method of claim 1, wherein the method further comprises determining whether an anchor device is a common anchor device for the access point and the second access point by comparing a media access control (MAC) address of the anchor device with a stored anchor device MAC address.

10. The method of claim 9, wherein the method further comprises updating the global time of the access point to the global time of the second access point when the anchor device is not a common anchor device for the access point and the second access point and an anchor weight of the anchor device is greater than a stored anchor weight.

11. The method of claim 1, wherein the message is received from a wireless station that forwards the message from the second access point, and wherein the message further comprises one or more of:

a field indicating a timing synchronization function of the wireless station when the message was received by the wireless station;

a field indicating an offset of the timing synchronization function from the global time indication from the second access point;

a field indicating a timing synchronization function of the second access point received by the wireless station in the message;

a field indicating a reliability of an anchor device utilized by the second access point to determine the global time indication;

a field indicating a last known global time of the anchor device; and

a field indicating a medium access control (MAC) address of the anchor device.

12. An apparatus for synchronizing a global time of the apparatus, comprising:

a receiver configured to receive a message comprising a global time indication from a second access point; and

a processor configured to update the global time of the apparatus to the global time indication from the second access point by updating a timer of the apparatus by an increment not to exceed a predetermined value selected small enough to ensure a maintenance of synchronization between the apparatus and at least one associated wireless station.

13. The apparatus of claim 12, wherein the processor is configured to update the global time of the apparatus to the global time indication from the second access point when the global time indication from the second access point indicates a later global time than the global time of the apparatus.

14. The apparatus of claim 12, wherein the processor is configured to update the global time of the apparatus to the global time indication from the second access point when the global time indication from the second access point indicates an earlier global time than the global time of the apparatus.

15. The apparatus of claim 12, the global time indication comprising an indication of an offset of a timing synchronization function of the second access point from the global time of the second access point.

16. The apparatus of claim 12, wherein the message comprises a beacon frame.

17. The apparatus of claim 12, the processor being further configured to successively update the timer by an increment until the timer is updated to correspond to the global time indication from the second access point.

18. The apparatus of claim 17, wherein the processor is configured to successively update the timer periodically.

19. The apparatus of claim 12, wherein when an anchor device is a common anchor device for the apparatus and the second access point, the processor is further configured to update the global time of the apparatus by:

determining a first difference between the global time indication of the second access point and a most recent global time received by the second access point from the anchor device,

determining a second difference between a stored global time of the apparatus and the most recent global time received by the apparatus from the anchor device, and

updating the global time of the apparatus to the global time of the second access point when the second difference is larger than the first difference.

20. The apparatus of claim 12, wherein the processor is further configured to determine whether an anchor device is a common anchor device for the apparatus and the second access point by comparing a media access control (MAC) address of the anchor device with a stored anchor device MAC address.

21. The apparatus of claim 20, wherein the processor is further configured to update the global time of the apparatus to the global time of the second access point when the anchor device is not a common anchor device for the apparatus and the second access point and an anchor weight of the anchor device is greater than a stored anchor weight.

22. The apparatus of claim 12, wherein the receiver is configured to receive the message from a wireless station that forwards the message from the second access point, and wherein the message further comprises one or more of:

a field indicating a timing synchronization function of the wireless station when the message was received by the wireless station;

a field indicating an offset of the timing synchronization function from the global time indication from the second access point;

a field indicating a timing synchronization function of the second access point received by the wireless station in the message;

a field indicating a reliability of an anchor device utilized by the second access point to determine global time indication from the second access point;

a field indicating a last known global time of the anchor device; and

a field indicating a medium access control (MAC) address of the anchor device.

23. A non-transitory computer-readable medium comprising code that, when executed, causes an apparatus to:

receive a message comprising a global time indication from a second access point, and

update the global time of the apparatus to the global time indication from the second access point by updating a timer of the apparatus by an increment not to exceed a predetermined value selected small enough to ensure a maintenance of synchronization between the apparatus and at least one associated wireless station.

24. An apparatus for synchronizing a global time of the apparatus, comprising:

means for receiving a message comprising a global time indication from a second access point; and

means for updating the global time of the apparatus to the global time indication from the second access point by updating a timer of the apparatus by an increment not to exceed a predetermined value selected small enough to ensure a maintenance of synchronization between the apparatus and at least one associated wireless station.