System and method for time synchronizing nodes in an automotive network using input capture

• US 7,623,552 B2
• Filed: 12/17/2004
• Issued: 11/24/2009
• Est. Priority Date: 10/14/2004
• Status: Active Grant

• Current Assignee: Continental Automotive Systems, Inc. (Continental AG)
• Original Assignee: Temic Automotive of North America, Incorporated (Continental AG)
• Inventors: Jordan, Patrick D., Dong, Hai, Johnson, Hugh W., Kartha, Prakash U.
• Primary Examiner(s): Patel; Ajit
• Application Number:
  US11/016,139
• Publication Number:
  US 20060083265A1
• Time in Patent Office: 1,803 Days
• Field of Search: 370/359, 370/503, 370/509, 370/510, 370/511, 370/512, 370/513, 370/514, 370/516, 375/354, 375/356, 375364-366, 375/371
• US Class Current: 370/503
• 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 3/0658 Clock or time synchronisation among packet nodes
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN
• CPC Class Codes: H04L 2012/40273 the transportation system being a vehicle
• CPC Class Codes: H04L 49/15 Interconnection of switching modules

Abstract

A system and method for time synchronizing nodes in a switch fabric network of a vehicle. A synchronization request message is transmitted from a requesting node to a neighboring node. At the time the synchronization request message is sent, the requesting node will store a unique message identification associated with the request message as well as a first timestamp that is associated with the time that the synchronization request message was transmitted by the requesting node. The neighboring node will receive the synchronization request message and store a second timestamp associated with the time that the synchronization request message was received by the neighboring node. Thereafter, the neighboring node will transmit to the requesting node a synchronization response message that includes the message identification and the second timestamp. The requesting node will then calculate a timer offset value that is based on the first timestamp and the second timestamp. The timer offset values may then be shared with other nodes in the network so that a summed offset may be used to transmit network messages across a plurality of nodes.

Claims

1. A method for time synchronizing nodes in a switch fabric of a vehicle communication network, the nodes in the switch fabric joined by at least one communication link for transmission of data packets therebetween, the method comprising the steps of:

transmitting a synchronization request message from a first node to a second node, the synchronization request message including a message identification;

storing, at the first node, a first timestamp associated with the transmission of the synchronization request message;

receiving the synchronization request message at the second node from the first node, storing, at the second node, a second timestamp associated with the reception of the synchronization request message;

transmitting a synchronization response message from the second node to the first node, the synchronization response message including the message identification and the second timestamp;

computing an onset in the first node based on the first timestamp and the second timestamp; and

storing the offset in the first node for subsequent use in time synchronizing data packets transmitted by the first node to other nodes in the switch fabric.

2. The method in claim 1, wherein the synchronization request message further includes an identification of the first node.

3. The method in claim 1 further comprising the step of determining whether another offset needs to be computed by the first node that is associated with a third node.

4. The method in claim 1 further comprising the step of broadcasting the computed offset from the first node to other nodes in the switch fabric.

5. The method in claim 1, wherein the step of storing the offset includes storing the offset in an offset table, the offset table including a listing of a plurality of offsets of different communication segments between nodes in the switch fabric.

6. The method in claim 1 further comprising the step of receiving an offset at the first node from a third node in the switch fabric, the offset received from the third node being associated with a communication link between the third node and a fourth node.

7. The method in claim 6 further comprising the step of determining a drift rate associated with the third node based on the offset received from the third node.

8. The method in claim 1 wherein the recited steps are performed during a first time and a second time to compute a first offset and a second offset, the method further comprising the step of determining a drift rate based on the first and second offsets and the first and second times.

9. A method for time synchronizing a switch fabric of a vehicle communication network, the switch fabric having at least a requesting node and a neighboring node, the requesting node and the neighboring node joined by a communication link for transmission of data packets therebetween, the method comprising the steps of:

transmitting from the requesting node a synchronization request message to the neighboring node and storing in the requesting node a first timestamp associated with the transmission of the synchronization request message, the synchronization request message including at least a message identification;

receiving the synchronization request message at the neighboring node and storing the message identification and a second timestamp associated with the reception of the synchronization request message;

transmitting from the neighboring node a synchronization response message to the requesting node, the synchronization request message including the message identification and the second timestamp;

computing an offset in the requesting node based on the first timestamp and the second timestamp.

10. The method in claim 9 further comprising the step of storing the offset in the requesting node for subsequent use in time synchronizing data packets transmitted by the requesting node to another node along a communication path that includes the neighboring node.

11. The method in claim 9 wherein the synchronization request message further includes an identification of the requesting node.

12. The method in claim 9 further comprising the step of determining whether another offset needs to be computed by the requesting node that is associated with a second neighboring node.

13. The method in claim 9 wherein the switch fabric includes a remote node, the method further comprising the step of transmitting the computed offset from the requesting node to the remote node in the switch fabric.

14. The method in claim 9 further comprising the step of broadcasting the computed offset to other nodes in the switch fabric.

15. The method in claim 10, wherein the step of storing the offset in the requesting node includes storing the offset in an offset table, the offset table including a listing of a plurality of offsets of different communication segments between different nodes in the switch fabric.

16. The method in claim 9, wherein the switch fabric includes a remote node, the method further comprising the step of receiving an offset at the requesting node from the remote node.

17. The method in claim 16 further comprising the step of determining in a requesting node a drift rate associated with the remote node based on the offset received from the remote node.

18. The method in claim 9 wherein the recited steps are performed during a first time and a second time to compute a first offset and a second offset, the method further comprising the step of determining a drift rate based on the first and second offsets and the first and second times.

19. A vehicle network comprising:

a plurality of nodes joined by at least one communication link for transmission of data therebetween;

at least one node of the plurality of nodes including a processor, a memory, and a clock, the memory being adapted to store a timestamp associated with the time that a synchronization request message is transmitted and being adapted to store a timer offset associated with a communication link between the node and at least one other node of the plurality of nodes;

and a transceiver disposed within the node, the transceiver being adapted to transmit the synchronization request message to the other node and being adapted to receive a synchronization response message from the other node;

wherein the synchronization request message includes a message identification and the synchronization response message includes the message identification and a timestamp associated with a time that the synchronization request message is received by the other node;

wherein the processor is operable to compute the timer offset based on the timestamp in the synchronization response message.

20. The vehicle network in claim 19, wherein the other node is configured to store a timestamp associated with a time that the synchronization response message is transmitted from the other node.

21. The vehicle network in claim 19, wherein the transceiver is further adapted to transmit the timer offset

22. The vehicle network in claim 19, wherein the transceiver is further adapted to receive at least one timer offset.