Methods and Systems for Accurate Time-Keeping on Metering and other Network Communication Devices

• US 20090179771A1
• Filed: 01/11/2008
• Published: 07/16/2009
• Est. Priority Date: 01/11/2008
• Status: Active Grant

• Current Assignee: Landis+Gyr Technology, Inc. (Landis+Gyr Group AG)
• Original Assignee: Cellnet Innovations, Inc.
• Inventors: Bettendorff, John, Seal, Brian Keith
• Granted Patent: US 7,961,554 B2
• Time in Patent Office: Days
• US Class Current: 340/870.40
• CPC Class Codes: G01D 4/002 Remote reading of utility meters
• CPC Class Codes: G04G 3/00 Producing timing pulses driving circuits for stepping motors G04C3/14; producing preselected time intervals for use as timing standards G04F5/00; pulse technique in general H03K; control, synchronisation, or stabilisation of generators in general H03L
• CPC Class Codes: G04G 9/0005 Transmission of control signals
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y04S 20/30 Smart metering, e.g. specially adapted for remote reading

Abstract

Methods and systems for providing accurate time-keeping on battery-powered communication devices used in AMI systems, mesh networks, and multi-channel radio networks. One embodiment allows the use of low power (and low cost) crystals in battery-powered endpoints by periodically correcting the poor timing of these crystals using communications with a nearby, non-battery-powered device. Such communications allow the battery-powered devices to align their timing with that of their non-battery neighbors, among other things.

Claims

1. A system comprising:

a data collection device for collecting commodity consumption-related data from endpoint devices; and

a mesh network comprising radio nodes, wherein each radio node is capable of communicating with one or more neighboring radio nodes of the mesh network and wherein at least some of the radio nodes are attached to endpoint devices;

wherein a first radio node of the mesh network comprises a first crystal oscillator and a neighboring radio node comprises a neighboring crystal oscillator having greater time-keeping precision than the first crystal oscillator, the first radio node configured to estimate an error rate of the first crystal oscillator by communicating with the neighboring radio node.

2. The system of claim 1, wherein the first radio node further comprises a battery for providing power for the first crystal oscillator and the neighboring crystal oscillator receives power from a non-battery power source.

3. The system of claim 1, wherein the first radio node is configured to estimate the error rate of the first crystal oscillator by at least comparing a first elapsed time according to the first crystal oscillator to a neighboring elapsed time according to the neighboring crystal oscillator.

4. The system of claim 1, wherein the first radio node is configured to periodically estimate the error rate of the first crystal oscillator by communicating with the neighboring radio node.

5. The system of claim 1, wherein the first radio node is configured to estimate the error rate of the first crystal oscillator by communicating with the neighboring radio node as part of communications relating to commodity consumption-related data.

6. The system of claim 1, wherein communicating with the neighboring radio node comprises only the first radio node receiving a communication from the neighboring radio node.

7. The system of claim 1, wherein communicating with the neighboring radio node comprises the first radio node transmitting a communication to the neighboring radio node and the first radio node receiving a communication from the neighboring radio node.

8. The system of claim 1, wherein the first radio node communicates with the neighboring radio node on a multi-channel network.

9. The system of claim 8, wherein the first radio node transmits data based on both a hop sequence and time-keeping based on (a) the first crystal oscillator and (b) the error rate of the first crystal oscillator.

10. The system of claim 1, wherein the error rate of the first crystal oscillator is based on an error sustained over a series of communications with the neighboring radio node.

11. The system of claim 1, wherein the first radio node is configured to use the error rate of the first crystal oscillator to adjust how many crystal ticks represents a time increment.

12. The system of claim 1, wherein the system is an AMI system.

13. A system comprising:

a data collection device for collecting commodity consumption-related data from endpoint devices; and

a mesh network comprising radio nodes, wherein each radio node is capable of communicating with one or more neighboring radio nodes of the mesh network and wherein at least some of the radio nodes are attached to endpoint devices;

wherein a first radio node of the mesh network comprises a first crystal oscillator and a neighboring radio node comprises a neighboring crystal oscillator having greater time-keeping precision than the first crystal oscillator, the first radio node configured to estimate a time-of-day by communicating with the neighboring radio node.

14. The system of claim 13, wherein the first radio node further comprises a battery for providing power for the first crystal oscillator and the neighboring crystal oscillator receives power from a non-battery power source.

15. The system of claim 13, wherein the first radio node is configured to periodically estimate the time-of-day by communicating with the neighboring radio node.

16. A method comprising:

providing a mesh network comprising radio nodes, wherein each radio node is capable of communicating with one or more neighboring radio nodes of the mesh network and wherein at least some of the radio nodes are attached to an endpoint device; and

estimating an error rate of the first crystal oscillator of a first radio node of the mesh network based on a communication from a neighboring radio node, the neighboring radio node comprising a neighboring crystal oscillator having greater time-keeping precision than the first crystal oscillator of the first device.

17. The method of claim 16 further comprising powering the first radio node with a battery and powering the neighboring radio node with a non-battery power source.

18. The method of claim 16 further comprising estimating the error rate of the first crystal oscillator each time a communication is received at the first radio node from the neighboring radio node.

19. The method of claim 16, wherein estimating the error rate comprises comparing a time elapsed according the first crystal oscillator to a time elapsed according to the neighboring crystal oscillator.

20. The method of claim 16, wherein estimating the error rate comprises determining an error sustained over a series of communications with the neighboring radio node.