Airframe timestamping technique for point-to-point radio links

1. A method comprising:

receiving, at a first transceiver, a request airframe from a second transceiver over a wireless link of a network, the request airframe including a first time indication indicating a first time TS 1 that the request airframe was transmitted to the first transceiver, the first transceiver and the second transceiver including a first and second counters, respectively;

timestamping a second time indication indicating a second time TS 2 that the request airframe was received;

generating a respond airframe and including within the respond airframe a third time indication indicating a third time TS 3 that the respond airframe is to be transmitted to the second transceiver;

transmitting the respond airframe to the second transceiver;

providing, by the first transceiver, a timestamp information request to the second transceiver;

receiving a timestamp information response, from the second transceiver, in response to the timestamp information request, the timestamp information response including a fourth time indication indicating a fourth time TS 4 ;

calculating, by the first transceiver, a counter offset using the first time, second time, third time, and fourth time as follows:

counter

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

;

calculating, by the first transceiver, a phase offset based on the counter offset, the calculating including determining asymmetry (ASY) in the wireless link and applying the following:

phase

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

±

Asy

2

;

and

correcting, by the first transceiver, a phase of the first transceiver.

2. The method of claim 1 , where the first and second counters are synchronized with each other before the counter offset is calculated.

3. The method of claim 2 , wherein the first counter is a precision time protocol counter.

4. The method of claim 1 , where the first transceiver and the second transceiver have synchronized frequencies.

5. The method of claim 1 , wherein the first transceiver generates and transmits the respond airframe after receiving the request airframe.

6. The method of claim 1 , wherein the first transceiver transmits the timestamp information request to the second transceiver at any time after the respond airframe is received.

7. The method of claim 1 , further comprising:

providing, by the second transceiver, a second timestamp information request to the first transceiver;

receiving a second timestamp information response from the first transceiver, in response to the second timestamp information request, the second timestamp information response including at least the second time indication;

calculating, by the second transceiver, a counter offset using the first time, second time, third time, and fourth time as follows:

counter

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

;

calculating, by the second transceiver, a phase offset based on the counter offset; and

correcting, by the second transceiver, a phase of the second transceiver.

8. The method of claim 7 , where calculating the phase offset by the first transceiver is not synchronized with calculating the phase offset by the second transceiver.

9. The method of claim 1 , wherein the wireless link is a microwave link.

10. A method comprising:

generating, by a first transceiver, a request airframe to be sent to a second transceiver over a wireless link of a network, the request airframe including a first time indication indicating a first time TS 1 that the request airframe is to be transmitted by the first transceiver, the first transceiver and the second transceiver including a first and second counters, respectively;

transmitting the request airframe to the second transceiver;

receiving a respond airframe from the second transceiver, the respond airframe including within the respond airframe a third time indication indicating a third time TS 3 that the respond airframe is to be transmitted to the first transceiver;

determining a fourth time indication indicating a fourth time TS 4 that the respond airframe was received;

providing, by the first transceiver, a timestamp information request to the second transceiver;

receiving a timestamp information response, from the second transceiver, in response to the timestamp information request, the timestamp information response including a second time indication indicating a second time TS 2 that the request airframe was received by the second transceiver;

calculating, by the first transceiver, a counter offset using the first time, second time, third time, and fourth time as follows:

counter

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

;

calculating, by the first transceiver, a phase offset based on the counter offset, the calculating including determining asymmetry (ASY) in the wireless link and applying the following:

phase

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

±

Asy

2

;

and

correcting, by the first transceiver, a phase of the first transceiver.

11. The method of claim 10 , where the first and second counters are synchronized with each other before the counter offset is calculated.

12. The method of claim 11 , wherein the first counter is a precision time protocol counter.

13. The method of claim 10 , where the first transceiver and the second transceiver have synchronized frequencies.

14. The method of claim 10 , wherein the first transceiver transmits the timestamp information request to the second transceiver at any time after the respond airframe is received.

15. The method of claim 10 , further comprising:

providing, by the second transceiver, a second timestamp information request to the first transceiver;

providing a second timestamp information response to the second transceiver, in response to the second timestamp information request, the second timestamp information response including at least the fourth time indication;

calculating, by the second transceiver, a counter offset using the first time, second time, third time, and fourth time as follows:

counter

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

;

calculating, by the second transceiver, a phase offset based on the counter offset; and

correcting, by the second transceiver, a phase of the second transceiver.

16. The method of claim 15 , where calculating the phase offset by the first transceiver is not synchronized with calculating the phase offset by the second transceiver.

17. A system comprising:

a first transceiver including memory and a processor, the first transceiver configured to:

receive a request airframe from a second transceiver over a wireless link of a network, the request airframe including a first time indication indicating a first time TS 1 that the request airframe was transmitted to the first transceiver, the first transceiver and the second transceiver including a first and second counters, respectively;

timestamp a second time indication indicating a second time TS 2 that the request airframe was received;

generate a respond airframe and including within the respond airframe a third time indication indicating a third time TS 3 that the respond airframe is to be transmitted to the second transceiver;

transmit the respond airframe to the second transceiver;

provide a timestamp information request to the second transceiver;

receive a timestamp information response, from the second transceiver, in response to the timestamp information request, the timestamp information response including a fourth time indication indicating a fourth time TS 4 ;

calculate a counter offset using the first time, second time, third time, and fourth time as follows:

counter

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

;

calculate a phase offset based on the counter offset, the calculating including determining asymmetry (ASY) in the wireless link and applying the following:

phase

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

±

Asy

2

;

 and

correct a phase of the first transceiver.

18. A system comprising:

a first transceiver including memory and a processor, the first transceiver configured to:

generate a request airframe to be sent to a second transceiver over a wireless link of a network, the request airframe including a first time indication indicating a first time TS 1 that the request airframe is to be transmitted by the first transceiver, the first transceiver and the second transceiver including a first and second counters, respectively;

transmit the request airframe to the second transceiver;

receive a respond airframe from the second transceiver, the respond airframe including within the respond airframe a third time indication indicating a third time TS 3 that the respond airframe is to be transmitted to the first transceiver;

determine a fourth time indication indicating a fourth time TS 4 that the respond airframe was received;

provide a timestamp information request to the second transceiver;

receive a timestamp information response, from the second transceiver, in response to the timestamp information request, the timestamp information response including a second time indication indicating a second time TS 2 that the request airframe was received by the second transceiver;

calculate a counter offset using the first time, second time, third time, and fourth time as follows:

counter

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

;

calculate a phase offset based on the counter offset, the calculating including determining asymmetry (ASY) in the wireless link and applying the following:

phase

⁢

⁢

offset

=

(

TS

⁢

⁢

1

+

TS

⁢

⁢

4

-

TS

⁢

⁢

3

-

TS

⁢

⁢

2

)

2

±

Asy

2

;

 and

correct a phase of the first transceiver.