System and method for frequency synchronization in a wireless non-hierarchical network

• US 8,036,330 B2
• Filed: 12/29/2006
• Issued: 10/11/2011
• Est. Priority Date: 12/29/2006
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Nelson, Paul
• Primary Examiner(s): Fan; Chieh M
• Assistant Examiner(s): Garcia; Santiago
• Application Number:
  US11/648,335
• Publication Number:
  US 20080159457A1
• Time in Patent Office: 1,747 Days
• Field of Search: 375/356
• US Class Current: 375/356
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase
• CPC Class Codes: H04W 92/18 between terminal devices

Abstract

The present disclosure relates generally to systems and methods for frequency synchronization in a non-hierarchical network. In one example, the method includes receiving, by a node in a wireless non-hierarchical network, frequency synchronization messages from other nodes. The method calculates an average frequency based on the frequency synchronization messages, calculates a control frequency based on the average frequency, and sets an oscillator of the node to the control frequency.

Claims

1. A method comprising:

receiving, by a first node in a wireless non-hierarchical network, a plurality of frequency synchronization messages from at least second and third nodes;

determining a frequency of the second node by comparing a difference between counter values contained in the frequency synchronization messages received from the second node to a difference between counter values of an oscillator of the first node that were saved at the time the frequency synchronization messages from the second node were received at the first node, wherein each of the counter values from the second node represents contents of a counter corresponding to an oscillator of the second node at the time one of the frequency synchronization messages was created at the second node;

determining a frequency of a third node using information contained in the frequency synchronization messages;

calculating an average frequency based on the frequency synchronization messages and the frequency of the second node and the third node;

calculating a control frequency based on the average frequency; and

setting the oscillator of the first node to the control frequency.

2. The method of claim 1 wherein calculating the control frequency includes feeding the average frequency into a control algorithm.

3. The method of claim 1 further comprising:

storing the frequency synchronization messages; and

waiting for a trigger event to occur prior to calculating the average frequency.

4. The method of claim 1 wherein calculating the average frequency further includes:

averaging the frequency of the second and third nodes to calculate the average frequency.

5. The method of claim 1 wherein determining the frequency of the second node further includes:

calculating the difference between the counter values contained in the plurality of frequency synchronization messages received from the second node.

6. The method of claim 1 further comprising:

generating, by the first node, a plurality of frequency synchronization messages; and

sending the plurality of frequency synchronization messages to at least one of the first and second nodes.

7. The method of claim 1 further comprising standardizing counter values contained in the frequency synchronization messages received from the second node to compensate for a difference between a frequency of the second node and a standard frequency.

8. The method of claim 1 further comprising identifying at least the second and third nodes as nodes from which to process frequency synchronization messages, wherein frequency synchronization messages received from nodes not so identified are not processed.

9. The method of claim 1 further comprising associating a counter value of the first node with each of the received frequency synchronization messages.

10. A method comprising:

receiving, by a first node operating at a first frequency from a second node operating at a second frequency in a wireless non-hierarchical network, first and second synchronization messages containing first and second values, respectively, corresponding to contents of a first counter of the second node at the time the first and second synchronization messages were created, wherein the contents of the first counter are regularly modified based on the second frequency;

receiving, by the first node from a third node operating at a third frequency in the wireless non-hierarchical network, third and fourth synchronization messages containing third and fourth values, respectively, corresponding to contents of a second counter of the third node at the time the third and fourth synchronization messages were created, wherein the contents of the second counter are regularly modified based on the third frequency;

storing the first, second, third, and fourth counter values with a value corresponding to contents of a third counter of the first node at approximately the time the first, second, third, and fourth synchronization messages are received, respectively, wherein the contents of the third counter are regularly modified based on the first frequency;

calculating an average frequency of the second and third nodes based on the first, second, third, and fourth values in conjunction with the corresponding value of the contents of the third counter;

feeding the average frequency into a control algorithm to calculate a control frequency; and

setting the first frequency to the control frequency.

11. The method of claim 10 wherein calculating the average frequency includes:

calculating the second frequency of the second node based on a difference between the first and second values and the corresponding values of the contents of the third counter;

calculating the third frequency of the third node based on a difference between the third and fourth values and the corresponding values of the contents of the third counter; and

averaging the second and third frequencies to find the average frequency.

12. The method of claim 10 wherein the first and second synchronization messages include a frequency identifier representing a designated frequency of an oscillator of the second node, the method further comprising:

determining whether the designated frequency of the second node'"'"'s oscillator equals a designated frequency of an oscillator of the first node; and

converting the first and second values to a standardized value if the designated frequencies are not equal.

13. The method of claim 10 further comprising waiting for trigger event to occur before calculating the average frequency.

14. The method of claim 10 further comprising:

sending, by the first node to the second node, fifth and sixth synchronization messages containing fifth and sixth values, respectively, corresponding to contents of the third counter at the time the fifth and sixth synchronization messages are created, wherein the contents of the third counter are regularly modified based on the first frequency.

15. The method of claim 10 wherein the storing and calculating are given priority over other processes within the first node.

16. A method comprising:

determining, by a first node in a wireless non-hierarchical network, that a predefined trigger event has occurred;

generating a frequency synchronization message containing a value corresponding to contents of a counter at the time the frequency synchronization message is generated, wherein the contents of the counter are regularly modified based on an oscillator frequency of the first node;

transmitting the frequency synchronization message to a second node in the wireless non-hierarchical network, wherein the value of the counter in the frequency synchronization message is configured to be used by the second node to determine a frequency of the first node; and

repeating the determining, generating, and transmitting steps in order to transmit a plurality of frequency synchronization messages to the second node, wherein a difference between values of the counter in the plurality of frequency synchronization messages is compared in the second node to a difference between counter values of an oscillator in the second node that are saved upon receipt at the second node of the plurality of frequency synchronization messages.

17. The method of claim 16 wherein generating the frequency synchronization message includes:

retrieving the value from the counter; and

inserting the value into a message with an identifier representing the first node in the wireless non-hierarchical network.

18. The method of claim 16 wherein generating the frequency synchronization message includes:

retrieving the value from the counter; and

inserting the value into a message containing information not related to the frequency synchronization message.

19. The method of claim 16 further comprising converting the value from a value based on the oscillator frequency to a value corresponding to a standardized frequency.

20. A device comprising:

a wireless communications interface configured to communicate with other devices in a wireless non-hierarchical network;

a controllable oscillator;

a memory coupled to a processor; and

a plurality of instructions stored in the memory for execution by the processor including instructions for;

receiving a plurality of synchronization messages from at least a first of the other devices;

determining a frequency of the first other device by comparing a difference between counter values contained in the synchronization messages received from the first other device to a difference between counter values associated with the controllable oscillator that were saved at the time the synchronization messages from the first other device were received, wherein each of the counter values from the first other device represents contents of a counter corresponding to an oscillator of the first other device at the time one of the frequency synchronization messages was created at the first other device;

calculating an average frequency based on the synchronization messages and the frequency of the first other device;

feeding the average frequency into a control algorithm to calculate a control frequency; and

setting a frequency of the controllable oscillator to the control frequency.

21. The device of claim 20 further comprising circuitry for priority processing of the synchronization messages.

22. The device of claim 21 wherein the circuitry includes a hardware-based counter coupled to the controllable oscillator.

23. The device of claim 22 wherein the hardware-based counter is incremented at each cycle of the controllable oscillator.

24. The device of claim 20 wherein the instructions for calculating the average frequency include instructions for:

calculating an individual frequency for at least some other devices from which synchronization messages have been received based on values contained within the synchronization messages; and

averaging the individual frequencies to calculate the average frequency.

25. The device of claim 20 wherein the instructions further include instructions for:

generating a synchronization message containing a counter value corresponding to the controllable oscillator; and

transmitting the synchronization message to at least one of the other devices via the wireless communications interface.