Partial timing synchronization function (TSF) synchronization in fine timing measurement (FTM) protocol

1. A method of timing synchronization between a first wireless device and a second wireless device, the method comprising:

sending, by the first wireless device, a first message to the second wireless device;

obtaining, by the first wireless device, a first timestamp at the first wireless device;

receiving, by the first wireless device, a fine timing measurement frame from the second wireless device in response to the first message, the fine timing measurement frame including at least a part of a second timestamp from the second wireless device, wherein the second timestamp corresponds to a timing synchronization function (TSF) timer value for synchronization with the second wireless device; and

synchronizing the first wireless device to the second wireless device, in response to determining that the first wireless device is not synchronized to the second wireless device based at least partially on the part of the second timestamp and the first timestamp.

2. The method of claim 1 , wherein synchronizing the first wireless device to the second wireless device includes:

adjusting a clock on the first wireless device based at least partially on the part of the second timestamp.

3. The method of claim 1 , wherein the first message is a fine timing measurement request frame.

4. The method of claim 1 , wherein:

the first timestamp is based on a time of departure of the first message from the first wireless device; and

the second timestamp is based on a time of arrival of the first message at the second wireless device.

5. The method of claim 1 , further comprising:

receiving, by the first wireless device, a second message from the second wireless device in response to the first message,

wherein the first timestamp is based on a time of arrival of the second message at the first wireless device; and

wherein the second timestamp is based on a time of departure of the second message from the second wireless device.

6. The method of claim 5 , wherein the second message is an acknowledgement frame.

7. The method of claim 1 , wherein:

the first timestamp is based on a time of arrival of the fine timing measurement frame at the first wireless device; and

the second timestamp is based on a time of departure of the fine timing measurement frame from the second wireless device.

8. The method of claim 1 , wherein the fine timing measurement frame includes one of 2, 3, 4, 5, or 8 octets of the second timestamp.

9. The method of claim 1 , wherein the fine timing measurement frame includes a reserved bit indicating that timestamp information is present in the fine timing measurement frame.

10. The method of claim 1 , wherein determining that the first wireless device is not synchronized to the second wireless device is further based on a round trip time between the first wireless device and the second wireless device.

11. A wireless device comprising:

a memory;

a clock;

a wireless communication subsystem configured to:

send a first message to a second wireless device; and

receive a fine timing measurement frame from the second wireless device in response to the first message, the fine timing measurement frame including at least a part of a first timestamp from the second wireless device, wherein the first timestamp corresponds to a timing synchronization function (TSF) timer value for synchronization with the second wireless device; and

a processing unit communicatively coupled with the memory, the clock and the wireless communication subsystem, the processing unit being configured to:

obtain a second timestamp at the wireless device; and

synchronize the wireless device to the second wireless device, in response to determining that the wireless device is not synchronized to the second wireless device based at least partially on the part of the first timestamp and the second timestamp.

12. The wireless device of claim 11 , wherein the processing unit is configured to synchronize the wireless device to the second wireless device by:

adjusting the clock based at least partially on the part of the first timestamp.

13. The wireless device of claim 11 , wherein the first message is a fine timing measurement request frame.

14. The wireless device of claim 11 , wherein:

the first timestamp is based on a time of arrival of the first message at the second wireless device; and

the second timestamp is based on a time of departure of the first message from the wireless device.

15. The wireless device of claim 11 , wherein:

the wireless communication subsystem is further configured to receive a second message from the second wireless device in response to the first message;

the first timestamp is based on a time of departure of the second message from the second wireless device;

the second timestamp is based on a time of arrival of the second message at the wireless device; and

the second message is an acknowledgement frame.

16. The wireless device of claim 11 , wherein:

the first timestamp is based on a time of departure of the fine timing measurement frame from the second wireless device; and

the second timestamp is based on a time of arrival of the fine timing measurement frame at the wireless device.

17. The wireless device of claim 11 , wherein the fine timing measurement frame includes one of 2, 3, 4, 5, or 8 octets of the first timestamp.

18. The wireless device of claim 11 , wherein the fine timing measurement frame includes a reserved bit indicating that timestamp information is present in the fine timing measurement frame.

19. A non-transitory computer readable storage medium including machine-readable instructions stored thereon for synchronizing a first wireless device to a second wireless device, the instructions, when executed by one or more processors, causing the first wireless device to:

send a first message to the second wireless device;

obtain a first timestamp at the first wireless device;

receive a fine timing measurement frame from the second wireless device in response to the first message, the fine timing measurement frame including at least a part of a second timestamp from the second wireless device, wherein the second timestamp corresponds to a timing synchronization function (TSF) timer value for synchronization with the second wireless device; and

synchronize the first wireless device to the second wireless device, in response to determining that the first wireless device is not synchronized to the second wireless device based at least partially on the part of the second timestamp and the first timestamp.

20. The non-transitory computer readable storage medium of claim 19 , wherein the instructions, when executed by one or more processors, cause the first wireless device to synchronize the first wireless device to the second wireless device by:

adjust a clock on the first wireless device based at least partially on the part of the second timestamp.

21. The non-transitory computer readable storage medium of claim 19 , wherein:

the first timestamp is based on a time of departure of the first message from the first wireless device; and

the second timestamp is based on a time of arrival of the first message at the second wireless device.

22. The non-transitory computer readable storage medium of claim 19 , wherein the instructions, when executed by one or more processors, further cause the first wireless device to:

receive a second message from the second wireless device in response to the first message,

wherein the first timestamp is based on a time of arrival of the second message at the first wireless device;

wherein the second timestamp is based on a time of departure of the second message from the second wireless device; and

wherein the second message is an acknowledgement frame.

23. The non-transitory computer readable storage medium of claim 19 , wherein:

the first timestamp is based on a time of arrival of the fine timing measurement frame at the first wireless device; and

the second timestamp is based on a time of departure of the fine timing measurement frame from the second wireless device.

24. The non-transitory computer readable storage medium of claim 19 , wherein the fine timing measurement frame includes one of 2, 3, 4, 5, or 8 octets of the second timestamp.

25. The non-transitory computer readable storage medium of claim 19 , wherein the fine timing measurement frame includes a reserved bit indicating that timestamp information is present in the fine timing measurement frame.

26. An apparatus comprising:

means for sending a first message from a first wireless device to a second wireless device;

means for capturing a first timestamp at the first wireless device;

means for receiving a fine timing measurement frame from the second wireless device in response to the first message, the fine timing measurement frame including at least a part of a second timestamp from the second wireless device, wherein the second timestamp corresponds to a timing synchronization function (TSF) timer value for synchronization with the second wireless device; and

means for synchronizing the first wireless device to the second wireless device, in response to determining that the first wireless device is not synchronized to the second wireless device based at least partially on the part of the second timestamp and the first timestamp.

27. The apparatus of claim 26 , wherein the means for synchronizing the first wireless device to the second wireless device includes:

means for adjusting a clock on the first wireless device based at least partially on the part of the second timestamp.

28. The apparatus of claim 26 , wherein:

the first timestamp is based on a time of departure of the first message from the first wireless device; and

the second timestamp is based on a time of arrival of the first message at the second wireless device.

29. The apparatus of claim 26 , further comprising:

means for receiving a second message from the second wireless device in response to the first message,

wherein the first timestamp is based on a time of arrival of the second message at the first wireless device;

wherein the second timestamp is based on a time of departure of the second message from the second wireless device; and

wherein the second message is an acknowledgement frame.

30. The apparatus of claim 26 , wherein:

the first timestamp is based on a time of arrival of the fine timing measurement frame at the first wireless device; and

the second timestamp is based on a time of departure of the fine timing measurement frame from the second wireless device.

31. The apparatus of claim 26 , wherein the fine timing measurement frame includes one of 2, 3, 4, 5, or 8 octets of the second timestamp.