Systems and methods for synchronizing communication networks

• US 8,149,733 B2
• Filed: 08/24/2007
• Issued: 04/03/2012
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: Raytheon BBN Technlogies Corp. (Rtx Corporation)
• Original Assignee: Raytheon BBN Technlogies Corp. (Rtx Corporation)
• Inventors: Basu, Prithwish, Dai, Lillian Lei, Redi, Jason Keith, Tetteh, William Nii
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): HALIYUR, VENKATESH N
• Application Number:
  US11/895,527
• Publication Number:
  US 20080232344A1
• Time in Patent Office: 1,684 Days
• Field of Search: 370335-503, 455/227, 455/522, 455/524
• US Class Current: 370/254
• 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 nodes by managing time slots in a slotted 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 having a schedule of time slots 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

adjusting the timeslot schedule of the second node by aligning a boundary portion of the second time slot with the first receipt time to synchronize the second time slot with the first time slot, thereby providing sufficient time for the second node to receive the message during the second time slot,

wherein aligning the boundary portion includes shifting at least one of a start time of the second time slot, an end time of the second time slot, and an edge of a guard time period of the second time slot based on the first receipt time.

2. The method of claim 1, wherein the second time slot includes a data time period in between two guard time periods.

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

4. 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.

5. 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.

6. 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.

7. The method of claim 6, 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.

8. 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.

9. 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.

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

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

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

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

a processor configured for adjusting the timeslot schedule by aligning a boundary portion of the first time slot with the receipt time, thereby providing sufficent time for the node to receive the message during the first time slot,

wherein aligning the boundary portion includes shifting at least one of a start time of the first time slot, an end time of the first time slot, and an edge of a guard time period of the first time slot based on the receipt time, and

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.

13. The node of claim 12, wherein the first time slot includes a data time period in between two guard time periods.

14. The node of claim 12, 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.

15. The method of claim 14, wherein the first time slot includes a guard time period having a length based at least in part on the re-sync time period.

16. The node of claim 12, 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 transmitting the message.

17. The node of claim 12, wherein the message includes a heartbeat signal.

18. A method for synchronizing nodes by managing time slots in a slotted 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,

adjusting a timeslot schedule of a second node by aligning a slot boundary of the 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

adjusting a timeslot schedule of a third node by aligning a slot boundary of the third node, neighboring the second node along the network topology, based on the receipt time of the first message, wherein a slot boundary is at least one of a start time of a time slot, an end time of a time slot, and an edge of a guard time period of a time slot.