Method and system for time synchronization in communication networks

• US 20070076762A1
• Filed: 09/30/2005
• Published: 04/05/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Srinivasan, Bhaskar, Venkatraman, Lakshmi, Manjeshwar, Arati
• Granted Patent: US 7,813,382 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04B 7/2696 Over the air autonomous synchronisation, e.g. by monitoring network activity H04B7/2693 takes precedence
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines

Abstract

A method of synchronizing a network includes transmitting a tone signal to convey time information and setting a local time according to the conveyed time information.

Claims

1. A method of synchronizing a network, comprising:

transmitting a tone signal to convey time information; and

setting a local time according to the conveyed time information.

2. The method of claim 1, wherein the signal includes a preamble followed by a start symbol and the local time is set when the start symbol is received.

3. The method of claim 1, further comprising:

setting a clock of a receiver to a predefined time when one of the tone signal ends and a predefined pattern within the tone signal is received.

4. The method of claim 3, wherein the signal is a short tone.

5. The method of claim 3, wherein the network includes wireless sensor nodes.

6. A method for synchronizing a communication network, comprising:

transmitting a tone signal;

detecting an occurrence of a predefined aspect of the tone signal; and

setting a local time based on the occurrence of the predefined aspect of the signal.

7. The method of claim 6, wherein the predefined aspect is a start symbol.

8. The method of claim 6, wherein the predefined aspect is an ending of the tone signal.

9. The method of claim 6, further comprising:

periodically waking up from a sleep cycle to detect the occurrence of the predefined aspect of the tone signal.

10. The method of claim 6, wherein the tone signal is transmitted for at least a period of maximum clock skew between a transmitter and a receiver.

11. The method of claim 6, wherein the elements of the network form a chain topology and the method is repeated.

12. The method of claim 6, wherein elements of the network form a tree topology and the method is repeated.

13. A communication system, comprising:

a transmitter to transmit a signal to convey time information; and

a receiver to receive the signal and set a local time based on the conveyed time information.

14. The communication system of claim 13, wherein the local time is set when a predefined part of the signal occurs.

15. The communication system of claim 13, wherein the local time is set when the signal ends.

16. The communication system of claim 13, wherein the signal is a tone.

17. The communication system of claim 13, wherein the tone includes a preamble followed by a start symbol.

18. The communication system of claim 13, wherein the local time is set when the start symbol is received.

19. The communication system of claim 13, wherein the receiver periodically wakes up from a sleep cycle to receive the signal, and the signal is transmitted for at least a period of a maximum clock skew between the transmitter and receiver.

20. An apparatus for synchronizing a communication network comprising:

a first arrangement to transmit a tone signal;

a second arrangement to received the tone signal;

a third arrangement to detect an occurrence of a predefined aspect of the tone signal; and

a fourth arrangement to set a local time based on the occurrence of the predefined aspect of the signal.