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Real time clock distribution and recovery

  • US 8,462,015 B2
  • Filed: 08/17/2010
  • Issued: 06/11/2013
  • Est. Priority Date: 09/15/2006
  • Status: Active Grant
First Claim
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1. A method for resynchronizing real time clock information in an advanced metering system mesh network, comprising:

  • establishing a network including at least one root node and a plurality of node devices, at least some of which node devices comprise metrology devices;

    configuring the network for bi-directional communications between the at least one root node and each of the plurality of node devices;

    configuring the plurality of node devices such that one or more node devices correspond to one or more son node devices and one or more node devices correspond to father node devices;

    associating each son node device with one or more father node devices;

    transmitting update time information to each son node device from its associated one or more father node devices in a packet format including predetermined preamble and header portions at a predetermined bit rate;

    establishing synchronization levels among the plurality of node devices by assigning level numbers based on the number of hops between the root node and a receiving node;

    configuring every packet message to include information related to a sender, including its synchronization level, its time slot number, and its cell address; and

    configuring each node device to initiate resynchronization by recomputing a beginning of its respective time slot whenever receiving messages from synchronization levels having a lower level than their own;

    wherein recomputing the beginning of its respective time slot comprises adjusting an internal timer based on a countdown value included in said header portion;

    whereby every message transmitted in the network may be used for synchronization;

    wherein said countdown value included in said header portion comprises the time between the transmission of a first bit of said update time information in said packet format and a time slot change, as determined by the sender;

    wherein adjusting an internal timer based on a countdown value included in said header portion comprises adjusting said internal timer based on a first countdown value included in said header portion by performing operations comprising;

    reading a second countdown value from said countdown timer;

    adding a duration of said preamble portion to said second countdown value to obtain a third countdown value, said duration of said preamble portion being predefined;

    subtracting said third countdown value from said first countdown value to obtain a fourth countdown value; and

    adjusting said internal timer by said fourth countdown value.

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