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US 7,688,862 B2Granted
Systems and methods for the synchronization of a real-time scheduled packet network using relative timing
AssigneeAvaya Inc.
InventorDale J. Wisler
Life of this patent
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Abstract
A node of a real-time scheduled packet network synchronizes an internal frequency reference to a master node by receiving first heartbeat packets that are transmitted by the master node at a predetermined frequency. The node calculates a link phase of a link over which the first heartbeat packets are received by subtracting a time at which the node transmitted a second heartbeat packet to another node from a time at which the node received a first heartbeat packet.
Claims13
A method of synchronizing at least one node in a real-time scheduled packet network, comprising:
- transmitting first heartbeat packets at a predetermined frequency to the at least one node;
- receiving the first heartbeat packets at the at least one node;
- synchronizing an internal frequency reference in each of the at least one node according to at least two of the received first heartbeat packets;
- and calculating a link phase of a link over which the heartbeat packets are received by the at least one node by subtracting a time at which the node transmitted a second heartbeat packet from a time at which the node received a first heartbeat packet, wherein the link phase from a first node to a second node is different than a link phase from said second node to said first node, wherein said link phase from said first node to said second node is determined in accordance with at least one of the group consisting of the formula:
- LinkPhaseAB=(DelayAB−ΦB)modT
- wherein DelayAB is the propagation delay of the link from the first node (A) to the second node (B), ΦB is the phase offset of the second node, and modT is the time interval between heartbeats, and
- LinkPhaseBA=(DelayBA+ΦB)modT
- wherein DelayBA is the propagation delay of the link from the second node (B) to the first node (A), ΦB is the phase offset of the second node, and modT is the time interval between heartbeats.
5 more elements
A system for synchronizing a real-time scheduled packet network, comprising:
- a master node;
- at least one synchronized node;
- and
- a respective link between the master node and each of the at least one synchronized node;
- wherein:
- the master node is configured to transmit first heartbeat packets via the respective link to the at least one synchronized node at a predetermined frequency;
- and
- the at least one synchronized node is configured to:
- receive the first heartbeat packets;
- synchronize an internal frequency reference according to at least two of the received first heartbeat packets;
- and
- calculate a link phase of the respective link by subtracting a time at which the synchronized node transmitted a second heartbeat packets to another node from a time at which the synchronized node received a first heartbeat packets from the master node wherein the link phase from a first node to a second node is different than a link phase from said second node to said first node, wherein said link phase from said first node to said second node is determined in accordance with at least one of the group consisting of the formula:
- LinkPhaseAB=(DelayAB−ΦB)modT
- wherein DelayAB is the propagation delay of the link from the first node (A) to the second node (B), ΦB is the phase offset of the second node, and modT is the time interval between heartbeats, and
- LinkPhaseBA=(DelayBA+ΦB)modT
- wherein DelayBA is the propagation delay of the link from the second node (B) to the first node (A), ΦB is the phase offset of the second node, and modT is the time interval between heartbeats.
13 more elements
Dependencies are inferred from the claim text.