Systems and methods for synchronizing communication networks

• US 20080232344A1
• Filed: 08/24/2007
• Published: 09/25/2008
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: Raytheon BBN Technologies Corp. (Rtx Corporation)
• Original Assignee: BBN Technologies Corporation (Rtx Corporation)
• Inventors: Redi, Jason Keith, Basu, Prithwish, Tetteh, William Nii, Dai, Lillian Lei
• Granted Patent: US 8,149,733 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: G01D 9/005 Solid-state data loggers
• CPC Class Codes: H04J 3/0652 Synchronisation among time division multiple access [TDMA] nodes, e.g. time triggered protocol [TTP] bus network with centralized control in which slots are of a TDMA packet structure H04L12/4035
• CPC Class Codes: H04J 3/0679 by determining clock distribution path in a network
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04W 40/10 based on available power or energy
• CPC Class Codes: H04W 40/12 based on transmission quality or channel quality
• CPC Class Codes: H04W 56/003 Arrangements to increase tolerance to errors in transmission or reception timing
• CPC Class Codes: H04W 56/004 compensating for timing error of reception due to propagation delay

Abstract

In many aspects, the invention relates to systems and methods for synchronizing a communication network, particularly a slotted communication network, having a plurality of nodes. In slotted communication networks, the nodes are configured to transmit or receive data during selected time slots. During a selected time slot, each node transmits a synchronization message that is received by a neighboring node. The neighboring node adjusts its time slot boundary to coincide with the time of receipt of the synchronization message, thereby synchronizing each node with a neighboring node. Such systems and methods are energy efficient, accurate, fast, fault tolerant and easy to implement.

Claims

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

providing a slotted communication network, including

a first node configured to operate at least during a first time slot, and

a second node configured to operate at least during a second time slot,

wherein the second time slot corresponds to the first time slot;

transmitting, from the first node, a message during the first time slot;

receiving, at the second node, the message, at a first receipt time during the second time slot; and

aligning a boundary portion of the second time slot with the first receipt time, thereby synchronizing the second time slot with the first time slot.

2. The method of claim 1, wherein aligning a boundary portion of the second time slot includes shifting a start time or an end time of the second time slot based on the first receipt time.

3. The method of claim 1, wherein the boundary portion comprises a guard time period.

4. The method of claim 3, wherein aligning a boundary portion includes aligning an edge of the guard time period of the second time slot with the first receipt time.

5. The method of claim 4, wherein the second time slot includes a data time period in between two guard time periods.

6. The method of claim 1, wherein the message is transmitted during or at the beginning of a boundary portion of the first time slot.

7. The method of claim 1, wherein at least one of the first node and the second node is configured to operate during a plurality of time slots according to pre-determined schedule.

8. The method of claim 1, wherein at least one of the first node and the second node is configured to operate during a plurality of time slots according to dynamically determined schedule.

9. The method of claim 1, further comprising repeating the steps of transmitting the message, receiving the message and aligning the second time slot after a re-sync time period has elapsed.

10. The method of claim 9, wherein at least one of the first time slot and second time slot includes a guard time period having a length based at least in part on the re-sync time period.

11. The method of claim 1, wherein the slotted communication network further includes a third node configured to operate during a third time slot, the method further comprising:

transmitting, from the second node, a second message during the second time slot;

receiving, at the third node, the second message, at a second receipt time during the third time slot; and

aligning a boundary portion of the third time slot with the second receipt time, thereby synchronizing the third time slot with the second time slot.

12. The method of claim 1, wherein the slotted communication network comprises at least one of a mobile ad-hoc network, a wireless sensor network and a wireless mesh network.

13. The method of claim 1, wherein the message includes network topology information.

14. The method of claim 1, wherein the message includes a heartbeat signal.

15. A node in a slotted-communication network, comprising:

a receiver configured to receive a message at a receipt time during a first time slot, the message having been transmitted by a transmitting node, and

a processor configured for aligning a boundary portion of the first time slot with the receipt time.

16. The node of claim 15, wherein the processor aligns the boundary portion of the first time slot with the receipt time without synchronizing the clock of the node with the clock of the transmitting node.

17. The node of claim 15, wherein aligning a boundary portion of the first time slot includes shifting a start time or an end time of the first time slot based on the receipt time.

18. The node of claim 15, wherein the boundary portion comprises a guard time period.

19. The node of claim 18, wherein aligning a boundary portion includes aligning an edge of the guard time period of the first time slot with the receipt time.

20. The node of claim 19, wherein the first time slot includes a data time period in between two guard time periods.

21. The node of claim 15, wherein after a re-sync time period has elapsed, the receiver receives a second message and the processor aligns a second time slot to the receipt time of the second message.

22. The method of claim 21, wherein the first time slot includes a guard time period having a length based at least in part on the re-sync time period.

23. The node of claim 15, wherein the node comprises a transmitter for transmitting a message during a second time slot based on which a second node synchronizes at least one time slot to at least one time slot of the node:

24. The node of claim 15, wherein the message includes a heartbeat signal.

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

providing a network topology for a communication network including a plurality of nodes,

selecting a root node from the plurality of nodes in the network,

transmitting from a first node a first message,

aligning a slot boundary of a second node, neighboring the first node along the network topology, based on the receipt time of the first message, and

transmitting from the second node a second message, and

aligning a slot boundary of a third node, neighboring the second node along the network topology, based on the receipt time of the second message.

26. A method of synchronizing a communication network having a plurality of nodes, comprising:

transmitting a plurality of messages from the plurality of nodes,

receiving at a first node, the plurality of messages,

calculating a statistic based, at least in part, on a time of reception of each of the plurality of messages, and

synchronizing the first node based on the statistic.

27. The method of claim 26, wherein the statistic is calculated based on a set of slot deltas between neighboring nodes.

28. The method of claim 27, wherein the slot deltas comprises differences between start times of slots of the first node and start times of slots of the plurality of nodes.