Method and system for implementing the time division multiple access method to AD-HOC multihopping wireless networks

• US 20070008947A1
• Filed: 06/29/2005
• Published: 01/11/2007
• Est. Priority Date: 06/29/2005
• Status: Active Grant

• Current Assignee: Bison Patent Licensing, LLC
• Original Assignee: MeshNetworks, Inc. (Motorola Solutions, Inc.)
• Inventors: Belcea, John
• Granted Patent: US 7,349,362 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 56/0065 using measurement of signal travel time

Abstract

A system and method for synchronizing a wireless network comprising a first node operable pursuant to a first time-division multiple access (TDMA) scheme and a second node operable pursuant to a second TDMA scheme, wherein the first TDMA scheme and the second TDMA scheme each comprise a plurality of ticks, and wherein the first node and the second node each comprise a tick counter for determining the time moment at which a transmission is made or at which a signal is received by the node.

Claims

1. A method for synchronizing a wireless network comprising a first node operable pursuant to a first time-division multiple access (TDMA) scheme and a second node operable pursuant to a second TDMA scheme, wherein the first TDMA scheme and the second TDMA scheme each comprise a plurality of ticks, and wherein the first node and the second node each comprise a tick counter for determining the time moment at which a transmission is made or at which a signal is received by the node, the method comprising:

(i) sending from the first node a reply-requesting message to the second node;

(ii) determining a time of arrival (TOA) of the reply-requesting message at the second node, and sending from the second node a reply message to the first node, wherein the reply message comprises information as to the determined TOA of the reply-requesting message at the second node;

(iii) determining a TOA of the reply message at the first node;

(iv) comparing the determined TOA values for the reply-requesting message at the second node and for the reply message at the first node, and determining a synchronization correction value; and

(v) if the synchronization correction value is greater than a pre-determined value, applying the synchronization correction value to the tick counter of the first node, such that the tick counter of the first node is synchronized with the tick counter of the second node.

2. The method of claim 1, wherein the wireless network comprises a wireless ad-hoc peer-to-peer multi-hopping communication network in which the first and second nodes are adapted to operate.

3. The method of claim 1, wherein the first node sends the reply-requesting message to the second node when the first node encounters a timing error in relation to at least one neighboring node.

4. The method of claim 1, wherein at least one other node also receives the reply-requesting message from the first node and sends a reply message to the first node, wherein the reply message from the at least one other node comprises information as to a determined TOA of the reply-requesting message at the at least one other node, and wherein the first node determines a TOA for the reply message at the first node from the at least one other node.

5. The method of claim 4, wherein the first node adjusts the synchronization correction value based on an averaging of the synchronization correction value determined based on the reply message received from the second node and another synchronization correction value determined based on the reply message received from the at least one other node.

6. The method of claim 1, wherein the first node records determined synchronization correction values for a period of time and uses the record of determined synchronization correction values to predict future synchronization correction values.

7. The method of claim 1, wherein the synchronization is performed without the use of a time base.

8. A synchronized wireless system comprising:

a first node operable pursuant to a first time-division multiple access (TDMA) scheme; and

a second node operable pursuant to a second TDMA scheme, wherein the first TDMA scheme and the second TDMA scheme each comprise a plurality of ticks; and

wherein the first node and the second node each comprise a tick counter for determining the time moment at which a transmission is made or at which a signal is received by the node;

the first node is adapted to send a reply-requesting message to the second node;

the second node is adapted to determine a time of arrival (TOA) of the reply-requesting message, and send a reply message to the first node, wherein the reply message comprises information as to the determined TOA of the reply-requesting message at the second node;

the first node is further adapted to determine a TOA of the reply message, to compare the respective determined TOA values for the reply-requesting message at the second node and for the reply message at the first node, and to determine a synchronization correction value; and

if the first node determines that the synchronization correction value is greater than a pre-determined value, the first node applies the synchronization correction value to its tick counter, such that the tick counter of the first node is synchronized with the tick counter of the second node.

9. The system of claim 8, wherein the synchronized system is adapted to operate in a wireless ad-hoc peer-to-peer multi-hopping communication network.

10. The system of claim 8, wherein the first node is adapted to send the reply-requesting message to the second node when the first node encounters a timing error in relation to at least one neighboring node.

11. The system of claim 8, wherein at least one other node is adapted to also receive the reply-requesting message from the first node and to send a reply message to the first node, wherein the reply message from the at least one other node comprises information as to a determined TOA of the reply-requesting message at the at least one other node, and wherein the first node is adapted to determine a TOA for the reply message at the first node from the at least one other node.

12. The system of claim 11, wherein the first node is adapted to adjust the synchronization correction value based on an averaging of the synchronization correction value determined based on the reply message received from the second node and another synchronization correction value determined based on the reply message received from the at least one other node.

13. The system of claim 8, wherein the first node is adapted to record all determined synchronization correction values for a period of time and use the record of determined synchronization correction values to predict future synchronization correction values.

15. The node of claim 13, wherein the wireless network includes a wireless ad-hoc peer-to-peer multi-hopping communication network in which the node and second node are adapted to operate.

16. The node of claim 13, wherein the controller is further adapted to control the node to send the reply-requesting message to the second node when the node encounters a timing error in relation to at least one neighboring node.

17. The node of claim 13, wherein:

at least one other node also receives the reply-requesting message from the node and sends a reply message to the node, wherein the reply message from the at least one other node comprises information as to a determined TOA of the reply-requesting message at the at least one other node; and

wherein the controller is further adapted to determine a TOA for the reply message at the node from the at least one other node.

18. The node of claim 17, wherein:

the controller is further adapted to adjust a synchronization correction value based on an averaging of the synchronization correction value determined based on the reply message received from the second node and another synchronization correction value determined based on the reply message received from the at least one other node.

19. The node of claim 13, wherein:

the controller is further adapted to control the node to record all determined synchronization correction values for a period of time and uses the record of determined synchronization correction values to predict future synchronization correction values.

20. The node of claim 13, wherein the synchronization is performed without the use of a time base.

14. A node, which is adapted for use in a wireless network and to synchronize with a second node in the wireless network, wherein the node is operable pursuant to a first time-division multiple access (TDMA) scheme and the second node is operable pursuant to a second TDMA scheme, wherein the first TDMA scheme and the second TDMA scheme each comprise a plurality of ticks, and wherein the node and the second node each comprise a tick counter for determining the time moment at which a transmission is made or at which a signal is received by the node, the node comprising:

a controller, adapted to control the node to perform the following operations;

send a reply-requesting message to the second node, wherein the second node determines a time of arrival (TOA) of the reply-requesting message at the second node and sends a reply message to the first node, wherein the reply message comprises information as to the determined TOA of the reply-requesting message at the second node;

determine a TOA of the reply message at the node;

compare the determined TOA values for the reply-requesting message at the second node and for the reply message at the node, and determine a synchronization correction value; and

if the synchronization correction value is greater than a pre-determined value, apply the synchronization correction value to the tick counter of the node, such that the tick counter of the node is synchronized with the tick counter of the second node.