Reference time distribution over a network
A reference time distribution system and method use a data transmission network having a plurality of nodes to distribute the House Sync signal. A network-wide time signal is generated using a reference time generator, and the network-wide time signal is then distributed over the network to the plurality of nodes. At each node, the network-wide time signal is converted to a local synchronization signal for use in performing synchronization of the timing of each node. Either network-inherent timing and/or additional time signaling is used to provide the nodes attached to this network with a network-wide notion of time. The time information is converted locally into synchronization signals or time information as required by a respective application. When data is transported over the network, delay compensation is performed to simultaneously output different data streams that have been synchronously input into the network, regardless of the data path.
1. A method for distributing a reference time in a network having a plurality of nodes, the method comprising the steps of:
generating a network-wide time signal using a reference time generator;
distributing the network-wide time signal over the network to the plurality of nodes wherein each node is configured to generate different synchronization signals for different applications connected thereto;
measuring a signal propagation delay of the network-wide time signal between the reference time generator and each of the plurality of nodes, the step of measuring further characterized by the steps of:
maintaining a network-wide time signal as a network cycle master signal at a designated cycle master node of the plurality of nodes of the network;
maintaining a local cycle master signal at each respective node of the network; and
determining the signal propagation delay at each respective node from the difference between the respective local cycle master signal and the network cycle master signal;
generating, at each respective node, local synchronization signals using the measured signal propagation delay of the respective node, each of the generated local synchronization signals being required by a respective application; and
synchronizing the timing of each node for the respective applications using the respective local synchronization signals.
2. The method of claim 1 , characterized in that the network cycle master signal and each local cycle master signal is stored in a respective network cycle master register and local cycle master register, at each respective node.
3. The method of claim 1 , characterized in that the network-wide time signal is a house synchronization (synch) signal.
4. The method of claim 1 , characterized in that the local synchronization signal has an associated frequency.
5. The method of claim 1 , characterized in that the step of synchronizing includes the step of:
phase locking the local synchronization signal to a predetermined cycle value.
6. The method of claim 1 , characterized in that the step of synchronizing includes the step of:
performing delay compensation at each respective node.
7. The method of claim 6 , characterized in that the delay compensation is performed by adding an extra signal delay to the local synchronization signal.
8. The method of claim 1 , characterized in that the plurality of nodes includes:
at least one IEEE 1394-compliant node.
9. The method of claim 1 , characterized in that the step of generating the network-wide time signal includes the step of:
utilizing a rubidium reference signal generator.
10. The method of claim 1 , characterized in that the step of generating the network-wide time signal includes the step of:
utilizing a global positioning system (GPS)-based reference signal generator.
11. A system comprising:
a network including a plurality of nodes and a reference time generator for generating a network-wide time signal, wherein a designated node of the plurality of nodes is connected to the reference time generator, and has means adapted to distribute the network-wide time signal over the network to the plurality of nodes,
characterized in that each node of the plurality of nodes of the network has means adapted to generate different synchronization signals for different respective applications connected thereto and measure a signal propagation delay of the network-wide time signal between the reference time generator and each node and generate a local synchronization signals using the measured signal propagation delay, as required by the respective applications, and has means adapted to synchronize the timing of each node for the respective applications using the local synchronization signals, and further characterized in that the designated node has means adapted to maintain the network-wide time signal as a network cycle master signal; and each respective node of the plurality of nodes has means adapted to maintain a local cycle master signal and has means adapted to determine a respective signal propagation delay at each respective node from the difference between the respective local cycle master signal and the network cycle master signal.
12. The system of claim 11 , characterized in that the designated node includes a network cycle master register for storing the network cycle master signal and each node of the plurality of nodes of the network includes a respective local cycle master register for storing the local cycle master signal.
13. The system of claim 11 , characterized in that the plurality of nodes includes:
at least one IEEE 1394-compliant node.
14. The system of claim 11 being adapted for facilitating timing functions in a network ( 100 ), the system characterized by:
each node having means adapted to perform local timing control; and
a plurality of applications using timing functions under local timing control, with each node of the plurality of nodes associated with at least one application
wherein each node of the plurality of nodes of the network has means adapted to synchronized the at least one application associated with the respective node using the local synchronization signal.
15. The system of claim 14 , characterized in that the designated node has means adapted to maintain the network-wide time signal as a network cycle master signal in a network cycle master register; and
each node has means adapted to track signal propagation delay using the network-time signal, and has means adapted to convert the network-time signal by generating the local synchronization signal using the signal propagation delay of the respective node, to maintain a respective local cycle master signal in a respective local cycle master register, and to determine a respective signal propagation delay at each respective node from the difference between the respective local cycle master signal and the network cycle master signal.
16. The system of claim 14 , characterized in that the plurality of nodes includes: at least one IEEE 1394-compliant node.