Timing synchronization for wireless networks

Patent metadata

Field	Value
Publication number	US-9955443-B2
Application number	US-201414586692-A
Country	US
Kind code	B2
Filing date	Dec 30, 2014
Priority date	May 13, 2009
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A system for synchronizing nodes in a wireless network comprises a first node and a second node. The first node comprising a transmitter, a receiver, and a first time keeper. The second node comprising a transmitter, a receiver, a second time keeper, a timing error measurer for making a timing error measurement between the first time keeper and the second time keeper. The second timekeeper is adjusted to target minimizing the timing error measurement.

First claim

What is claimed is:

1. A system for maintaining synchronization of nodes in a wireless network comprising:
a first node comprising a transmitter, a receiver, and a first time keeper and configured for wireless communication with a second node comprising a transmitter, a receiver, and a second time keeper,
wherein:
the first node transmits a keep-alive packet to the second node upon expiration of a keep-alive interval following transmission of a previous packet from the first node to the second node, so as to maintain synchronization between the first time keeper of the first node and the second time keeper of the second node,
the first node adjusts the keep-alive interval between transmissions of keep-alive packets based on a determination that no acknowledgment of receipt of a previous keep-alive packet is received from the second node, and
the first node adjusts the keep-alive interval by reducing the interval between transmissions of keep-alive packets upon determining that no acknowledgment of receipt of the previous keep-alive packet is received from the second node.

2. The system of claim 1 , wherein the first node transmits the keep-alive packet to the second node upon expiration of the keep-alive interval following transmission of a previous keep-alive packet from the first node to the second node.

3. The system of claim 1 , wherein the first node transmits the keep-alive packet to the second node on a periodic basis based on the keep-alive interval.

4. The system of claim 1 , wherein the first node transmits the keep-alive packet to the second node during a next transmission opportunity for transmitting packets from the first node to the second node after expiration of the keep-alive interval following transmission of the previous keep-alive packet to the second node.

5. The system of claim 1 , wherein the first node shortens the keep-alive interval between transmissions of keep-alive packets in response to detecting an increase in a timing error value between the first time keeper and the second time keeper, and lengthens the keep-alive interval between transmissions of keep-alive packets in response to detecting a decrease in the timing error value.

6. The system of claim 1 , wherein the first node receives a keep-alive response from the second node responsive to the transmitting of the keep-alive packet, and determines a timing error value between the first time keeper and the second time keeper based on the keep-alive response received from the second node.

7. The system of claim 1 , wherein the first node shortens the keep-alive interval between transmissions of keep-alive packets in response to detecting a change in temperature at the first node.

8. The system of claim 1 , wherein the second node further comprises a timing error measurer for measuring a timing error value between the first time keeper and the second time keeper based on a difference between an expected time of reception at the second node of a packet transmitted from the first node and an actual time of reception of the packet at the second node.

9. The system of claim 8 , wherein the first node receives the measured timing error value in a response message received from the second node, and adjusts the keep-alive interval between transmissions of keep-alive packets based on the received timing error value.

10. The system of claim 1 , wherein:
the first node is configured for wireless communication with a third node comprising a transmitter, a receiver, and a third time keeper, and
the first node adjusts the keep-alive interval in response to a change in a timing error value between the first time keeper and the third time keeper.

11. A method for maintaining synchronization of nodes in a wireless network comprising:
transmitting a plurality of keep-alive packets from a first node of the wireless network to a second node of the wireless network so as to maintain synchronization between a first time keeper of the first node and a second time keeper of the second node,
wherein each keep-alive packet is transmitted from the first node to the second node upon expiration of a keep-alive interval following transmission of a previous packet from the first node to the second node; and
adjusting the keep-alive interval between transmissions of the keep-alive packets based on a determination that no acknowledgment of receipt of a previous keep-alive packet is received from the second node,
wherein the adjusting the keep-alive interval comprises reducing the interval between transmissions of keep-alive packets upon determining that no acknowledgment of receipt of the previous keep-alive packet is received from the second node.

12. The method of claim 11 , wherein each keep-alive packet is transmitted from the first node to the second node upon expiration of the keep-alive interval following transmission of a previous keep-alive packet from the first node to the second node.

13. The method of claim 11 , wherein the first node transmits the keep-alive packets to the second node on a periodic basis based on the keep-alive interval.

14. The method of claim 11 , wherein the first node transmits each keep-alive packet to the second node during a next transmission opportunity for transmitting packets from the first node to the second node after expiration of the keep-alive interval following transmission of the previous keep-alive packet to the second node.

15. The method of claim 11 , wherein the first node shortens the keep-alive interval between transmissions of keep-alive packets in response to detecting an increase in a timing error value between the first time keeper and the second time keeper, and lengthens the keep-alive interval between transmissions of keep-alive packets in response to detecting a decrease in the timing error value.

16. The method of claim 11 , further comprising:
receiving in the first node a keep-alive response from the second node responsive to the transmitting of a keep-alive packet; and
determining a timing error value between the first time keeper and the second time keeper based on the keep-alive response received from the second node.

17. The method of claim 11 , wherein the first node shortens the keep-alive interval between transmissions of keep-alive packets in response to detecting a change in temperature at the first node.

18. The method of claim 16 , further comprising:
receiving in the first node a response message including a second timing error value measured in the second node, the second timing error value being based on a difference between an expected time of reception at the second node of a packet transmitted from the first node and an actual time of reception of the packet at the second node; and
adjusting the keep-alive interval between transmissions of keep-alive packets based on the received timing error value.

19. The method of claim 11 , further comprising:
adjusting the keep-alive interval between transmissions of the keep-alive packets based on a change in a timing error value between the first time keeper of the first node and a third time keeper of a third node of the wireless network.

20. A timer compensator system comprising:
an oscillator outputting an oscillator signal having a predetermined frequency;
a summing junction having a first input receiving a feedback signal based on a summing signal output by the summing junction, a second input receiving an input set-point signal, and an output producing the summing signal based on a sum of the feedback signal and the input set-poi

Assignees

• Dust Networks Inc
• Linear Tech Corp

Inventors

• Charles Gordon Alexander
• Doherty Lance Robert
• Juneau Thor Nelson
• Lemkin Mark Alan
• Simon Jonathan
• Ye Zhenqiang

Classifications

• H04W56/001 Primary

  Synchronization between nodes · CPC title

• H04J3/0658

  Clock or time synchronisation among packet nodes · CPC title

• H04W56/003

  Arrangements to increase tolerance to errors in transmission or reception timing · CPC title

• H04L7/04

  Speed or phase control by synchronisation signals {(H04L7/0075 takes precedence)} · CPC title

• H04L7/048

  using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal · CPC title