Method and system for time synchronization in communication networks
First Claim
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1. A method of synchronizing a receiver clock of a receiver to a transmitter clock of a transmitter within a network, comprising:
- waking up the receiver at a wake-up time;
receiving by the receiver a tone signal transmitted by the transmitter, the tone signal beginning at a start time and ending at an end time that is different from the start time; and
at the end time, setting the receiver clock to a predefined time to synchronize the receiver clock to the transmitter clock;
wherein;
the wake-up time is a receiver clock time that is set such that a period extending from the wake-up time to the predefined time is at least as long as a maximum time skew of the receiver clock relative to the transmitter clock that occurs between two consecutive synchronizations; and
the predefined time is set at the receiver prior to the transmission of the tone signal.
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Abstract
A method of synchronizing a network includes transmitting a tone signal to convey time information and setting a local time according to the conveyed time information. The method may also include detecting an occurrence of a predefined aspect of the tone signal, and setting a local time based on the occurrence of the predefined aspect of the signal.
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Citations
22 Claims
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1. A method of synchronizing a receiver clock of a receiver to a transmitter clock of a transmitter within a network, comprising:
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waking up the receiver at a wake-up time; receiving by the receiver a tone signal transmitted by the transmitter, the tone signal beginning at a start time and ending at an end time that is different from the start time; and at the end time, setting the receiver clock to a predefined time to synchronize the receiver clock to the transmitter clock; wherein; the wake-up time is a receiver clock time that is set such that a period extending from the wake-up time to the predefined time is at least as long as a maximum time skew of the receiver clock relative to the transmitter clock that occurs between two consecutive synchronizations; and the predefined time is set at the receiver prior to the transmission of the tone signal. - View Dependent Claims (2, 3, 4, 17, 18)
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5. A method for synchronizing a receiver clock of a receiver to a transmitter clock of a transmitter in a communication network, comprising:
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scheduling the receiver to periodically wake up at wake-up times; waking up the receiver at the wake-up times; for each wake-up; receiving by the receiver a tone signal from the transmitter, the tone signal beginning at a start time, and ending at an end time that is different from the start time; detecting by the receiver an occurrence of a predefined aspect of the tone signal; and setting the receiver clock to a predefined time at an instant when the receiver detects the occurrence of the predefined aspect of the signal to synchronize the receiver clock to the transmitter clock; wherein; the predefined aspect is the ending of the tone signal; the wake-up time is a receiver clock time that is set such that a period extending from the wake-up time to the predefined time is at least as long as a maximum time skew between the receiver clock relative to the transmitter clock that occurs between two consecutive synchronizations. - View Dependent Claims (6, 7, 8, 19, 20, 21)
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9. A communication system, comprising:
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a transmitter operating under a transmitter clock to transmit a signal having a start time and an end time that is different than the start time; and a receiver operating under a receiver clock to; wake up at a wake-up time; receive the signal; and at the end time of the signal, set the receiver clock to a predefined time to synchronize the receiver clock to the transmitter clock; wherein; the wake-up time is a receiver clock time that is set such that a period extending from the wake-up time to the predefined time is at least as long as a maximum time skew of the receiver clock relative to the transmitter clock that occurs between two consecutive synchronizations; and the predefined time for synchronization is set at the receiver prior to the transmission of the signal. - View Dependent Claims (10, 11, 12, 22)
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13. An apparatus operating under a local clock for synchronizing a communication network comprising:
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a first arrangement to wake up at a wake-up time to receive a tone signal, the tone signal beginning at a start time, and ending at an end time that is different than the start time; a second arrangement to detect an occurrence of a predefined aspect of the tone signal; and a third arrangement to set the local clock to a predefined time at the occurrence of the predefined aspect of the tone signal; wherein; the wake-up time is a local clock time that is set such that a period extending from the wake-up time to the predefined time is at least as long as a maximum time skew of the local clock relative to a transmitter clock that occurs between two consecutive synchronizations; the predefined aspect is an ending of the tone signal; and the predefined time is set at the apparatus prior to the receipt of the tone signal.
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14. A method of synchronizing a network, comprising:
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predefining a first predefined time in a memory of a first receiver node; waking up the first receiver node at a wake-up time; receiving by the first receiver node a tone signal transmitted, subsequent to the predefining, by a transmitter node, the tone signal beginning at a start time, and ending at an end time that is different from the start time; responsive to the received tone signal, setting a time of a local clock of the first receiver node to the stored first predefined time, wherein the wake-up time is a local clock time that is set such that a period extending from the wake-up time to the predefined time is at least as long as a maximum time skew of the local clock relative to a transmitter clock that occurs between two consecutive synchronizations. - View Dependent Claims (15, 16)
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Specification