Remote monitoring and calibration of system reference clock using network timing reference

• US 20080032724A1
• Filed: 08/07/2006
• Published: 02/07/2008
• Est. Priority Date: 08/07/2006
• Status: Active Grant

• Current Assignee: Aviat U.S., Inc. (Aviat Networks Incorporated)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Detwiler, Thomas F.
• Granted Patent: US 7,738,611 B2
• Time in Patent Office: Days
• US Class Current: 455/502
• CPC Class Codes: G04G 5/002 brought into action by radio
• CPC Class Codes: G04G 7/02 by radio
• CPC Class Codes: H04J 3/0685 Clock or time synchronisation in a node; Intranode synchronisation
• CPC Class Codes: H04L 7/0004 Initialisation of the receiver H04L7/0075 and H04L7/10 take precedence

Abstract

A system and method for calibrating a local radio reference clock for a radio operating in a radio network having a network reference clock. The method comprises determining at the radio an offset between the local clock and the network clock, placing the local clock in a calibration mode, and calibrating the local clock using a radio link to reduce the offset.

Claims

1. A method of calibrating a local radio reference clock for a radio operating in a radio network having a network reference clock, comprising the steps of:

(a) determining at the radio an offset between the local clock and the network clock;

(b) placing the local clock in a calibration mode;

(c) calibrating the local clock using a radio link to reduce the offset.

2. The method of claim 1 wherein information representative of the offset is transmitted from the radio to a remote location and the remote location places the local clock in calibration mode.

3. The method of claim 1 wherein radio communication between the radio and other radios in the radio network continues during the calibration.

4. The method of claim 2 wherein radio communication between the radio and the remote location continues during the calibration.

5. The method of claim 1 wherein the offset is determined as a function of measurements taken by the network reference.

6. The method of claim 1 wherein the network reference clock is a reference clock for a synchronous communication protocol.

7. The method of claim 1 wherein the radio network communicates using an asynchronous communication protocol and the network reference clock is replaced by a network reference clock signal injected into a data-carrying communication channel.

8. The method of claim 5 wherein the measurements are taken at predefined intervals.

9. The method of claim 5 wherein the measurements are taken continuously.

10. The method of claim 2 wherein the information is an alarm indication.

11. The method of claim 1 wherein the step of determining further comprises the steps of:

summing n offsets; and

dividing the sum by n.

12. The method of claim 11 wherein the step of determining further comprises comparing the sum divided by n to a predetermined threshold.

13. The method of claim 1 wherein the network reference clock is selected from the group comprising:

a Global Positioning System signal, a Pulse Code Modulated signal, a crystal oscillator, an oven controlled crystal oscillator, an oven voltage controlled crystal oscillator, and a voltage controlled oscillator.

14. The method of claim 1 wherein the local oscillator is selected from the group comprising:

a crystal oscillator, an oven controlled crystal oscillator, an oven voltage controlled crystal oscillator, and a voltage controlled oscillator.

15. The method of claim 6 wherein the synchronous communications protocol is selected from the group comprising:

Synchronous Optical Network, Synchronous Digital Hierarchy, T-carrier hierarchy, E-carrier hierarchy.

16. In a method of calibrating a local radio reference clock for a radio operating in a radio network having a network reference clock for a synchronous communication protocol, the improvement comprising calibrating the local radio clock with the network reference clock by communicating information to the radio over a radio communication channel.

17. The method of claim 16 wherein the information is representative of an offset between the local radio reference clock and the network reference clock.

18. The method of claim 16 wherein the information is transmitted from the radio to a remote location and the remote location places the local clock in calibration mode.

19. The method of claim 16 wherein radio communication between the radio and other radios in the radio network continues during the calibration.

20. The method of claim 18 wherein radio communication between the radio and the remote location continues during the calibration.

21. The method of claim 16 wherein the offset is determined as a function of measurements taken by the network reference clock.

22. The method of claim 21 wherein the measurements are taken at predefined intervals.

23. The method of claim 21 wherein the measurements are taken continuously.

24. The method of claim 16 wherein the information is an alarm indication.

25. The method of claim 17 further comprising the steps of:

summing n offsets; and

dividing the sum by n.

26. The method of claim 25 further comprising the step of comparing the sum divided by n to a predetermined threshold.

27. The method of claim 16 wherein the network reference clock is selected from the group comprising:

a Global Positioning System signal, a Pulse Code Modulated signal, a crystal oscillator, an oven controlled crystal oscillator, an oven voltage controlled crystal oscillator, and a voltage controlled oscillator.

28. The method of claim 16 wherein the local oscillator is selected from the group comprising:

a crystal oscillator, an oven controlled crystal oscillator, an oven voltage controlled crystal oscillator, and a voltage controlled oscillator.

29. The method of claim 16 wherein the synchronous communications protocol is selected from the group comprising:

Synchronous Optical Network, Synchronous Digital Hierarchy, T-carrier hierarchy, E-carrier hierarchy.