Circuit arrangement and method for synchronization of clocks in a network

• US 8,108,558 B2
• Filed: 02/23/2009
• Issued: 01/31/2012
• Est. Priority Date: 02/22/2008
• Status: Active Grant

• Current Assignee: Symeo GmbH (indie Semiconductor, Inc.)
• Original Assignee: Symeo GmbH (indie Semiconductor, Inc.)
• Inventors: Kirsch, Fabian, Gulden, Peter, Vossiek, Martin
• Primary Examiner(s): BARQADLE, YASIN M
• Application Number:
  US12/390,586
• Publication Number:
  US 20090222589A1
• Time in Patent Office: 1,072 Days
• Field of Search: 709201-203, 709217-232, 709248-250, 713/400
• US Class Current: 709/248
• CPC Class Codes: G04G 5/00 Setting, i.e. correcting or changing, the time-indication radio-controlled time-pieces G04R
• CPC Class Codes: G04G 7/00 Synchronisation radio-controlled time-pieces G04R
• CPC Class Codes: H04J 3/0676 Mutual
• CPC Class Codes: H04J 3/0697 Synchronisation in a packet node
• CPC Class Codes: H04W 56/002 Mutual synchronization

Abstract

A circuit arrangement and a method for synchronizing clocks in a network is provided, comprising a plurality of at least two nodes, wherein at least two of said nodes can communicated with each other and each have a local clock, wherein, in a receiving one of said nodes, from at least one transmitting other such node, a global time transmitted by said transmitting one of said node of said transmitting one of said nodes is received, and a global time of said receiving node is determined or estimated as a function of both the received global time of said transmitting node and of a local time of the receiving node'"'"'s own local clock.

Claims

1. A method for synchronizing clocks in a network comprising a plurality of nodes that includes at least one receiving node and at least one transmitting node, wherein at least two of said plurality of nodes can communicate with each other and each have a local clock, the method comprising:

receiving, in the receiving node, from the transmitting node, a global time of said transmitting node transmitted by said transmitting node;

determining or estimating a global time of said receiving node as a function of both the received global time of said transmitting node and of a local time of the receiving node'"'"'s own local clock;

determining or estimating, in at least a first and a second of said plurality of nodes, which may, but does not have to include said receiving node and said transmitting node, a transformation of pre-set characteristics of the respective first and second node'"'"'s own local time to characteristics of a global clock in such a way that at least one such deviation amount is determined in each of said first and second nodes as a behavior of a ratio between each respective first and second node'"'"'s own local clock and each respective first and second node'"'"'s own global clock; and

utilizing the deviation amount of one of said first or second nodes in at least one other of said plurality of nodes as an input value for a local state estimation in at least this at least one other node of said plurality of nodes.

2. The method according to claim 1, further comprising:

sending the determined or estimated global time of said receiving node from said receiving node to any of said plurality of nodes.

3. The method as claimed in claim 2, further comprising:

maintaining a plurality of local times and a plurality of global times respectively associated with the local times on the receiving node.

4. The method according to claim 1, further comprising:

utilizing, for the determining or estimating of the global time in the receiving node, the receiving node'"'"'s own previous global time.

5. The method according to claim 1, further comprising:

determining or estimating within the receiving node at least one of;

a) a first deviation amount between the receiving node'"'"'s own global time and the receiving node'"'"'s own local time; and

b) a second deviation amount between the receiving node'"'"'s own global time and a global time received from outside the receiving node.

6. The method according to claim 5, further comprising:

utilizing at least one of the first deviation amount and the second deviation amount by said receiving node for determining or estimating the global time.

7. The method according to claim 5, further comprising at least one of:

a) carrying out a correction to a slower setpoint speed of the global time if a predeterminable proportion of the available deviation amounts exceeds a high-speed threshold; and

b) carrying out a correction to a faster setpoint speed of the global time if a predeterminable proportion of the available deviation amounts falls short of a low-speed threshold.

8. The method according to claim 1, further comprising:

determining a confidence value, within the receiving node, in association with its momentary global time, for determining or estimating said global time.

9. The method according to claim 8, further comprising:

additionally utilizing the confidence value of the previous global time of the receiving node, within the receiving node, for determining or estimating the global time of said node.

10. The method according to claim 8, further comprising:

utilizing, by and within said receiving node, after receiving the global time of another node together with such a confidence value associated with said received global time, said received global time and its associated confidence value for determining or estimating the global time of said receiving node.

11. The method according to claim 1, further comprising:

adapting, within the receiving node, the local time of said node to the global time of said node via a time difference value; and

adapting quantities or parameters relating to the previous local time for estimating or determining the global time of said node in such a way that a subsequent estimation or determination of the global time of said node is not affected by the adapted local time.

12. The method according to claim 1, further comprising:

additionally utilizing, within the receiving node, for determining or estimating the global time of said node, an external time of a reference time source as an additional external global time, wherein the reference time source is associated with a time system independent from the network of said nodes.

13. The method according to claim 8, further comprising:

additionally utilizing, within the receiving node, for determining or estimating the global time of said node, an external time of a reference time source as an additional external global time, wherein the reference time source is associated with a time system independent from the network of said nodes, and a confidence value is associated with the external time depending on from which type of time source the reference time source originates.

14. The method according to claim 1, further comprising:

sending the determined or estimated global time of said receiving node to other such nodes at a future point in time; and

prior to transmission, determining, for the future point in time, the then valid global time point or the then valid global time point together with at least one of a deviation amount and a confidence value.

15. The method as claimed in claim 1, further comprising:

storing the determined or estimated global time while maintaining the local time by the receiving node.

16. A circuit arrangement for synchronizing clocks in a network comprising a plurality of nodes that includes at least one receiving node and one transmitting node, wherein at least two of said plurality of nodes can communicate with each other and each have a local clock and a local oscillator for clocking said local clock, the arrangement comprising:

a receiving module of at least one receiving node receiving a transmitted global time of the transmitting node;

a controller for determining or estimating a global time of said receiving node as a function of both the received global time of said transmitting node and of a local time of the receiving node'"'"'s own local clock; and

a local state estimator for determining a confidence value within the receiving node for its momentary global time;

wherein the local state estimator is implemented in a first and second of said plurality of nodes which may, but does not have to include said receiving node and said transmitting node, for determining one deviation amount as a behavior of a ratio between the first node'"'"'s own local clock and the first node'"'"'s own global clock, wherein the second node'"'"'s controller is designed for using the deviation amount of the first node in at least the second node as an input value for the local state estimation in at least this second node.

17. The circuit arrangement according to claim 16, further comprising a transmitting module for transmitting the determined or estimated global time of said receiving node from said receiving node to any of said plurality of nodes.

18. The circuit arrangement according to claim 16, comprising a voting module for determining or estimating a deviation amount between at least one of:

a) the receiving node'"'"'s own global time and the receiving node'"'"'s own local time; and

b) the receiving node'"'"'s own global time and a global time received from outside the receiving node.

19. The circuit arrangement according to claims 16, wherein said controller assists in implementing a receiving, in the receiving node, from the transmitting node, a global time of said transmitting node transmitted by the transmitting node;

and a determining or estimating a global time of the receiving node as a function of both the received global time of the transmitting node and of a local time of the receiving node'"'"'s own local clock.

20. The circuit arrangement of claim 16, wherein:

the local clock comprises a first physical oscillator and counter; and

the global time is determined by a global clock comprising either;

a second physical oscillator and counter;

or

an element having an input that is the counter value of the local clock and an output that can be used as a clock reading.