METHOD FOR THE CLOCK SYNCHRONIZATION OF A PLURALITY OF MODULES

• US 20130250976A1
• Filed: 01/28/2011
• Published: 09/26/2013
• Est. Priority Date: 01/11/2011
• Status: Active Grant

• Current Assignee: Unify Patente GmbH & Co. KG (Atos SE)
• Original Assignee: Unify Patente GmbH & Co. KG (Atos SE)
• Inventors: Lindner, Thomas
• Granted Patent: US 9,276,688 B2
• Time in Patent Office: Days
• US Class Current: 370/509
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• 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: H04J 3/0644 External master-clock
• CPC Class Codes: H04J 3/1688 the demands of the users being taken into account after redundancy removal, e.g. by predictive coding, by variable sampling reducing bandwidth of signals in general H04B1/66; in PCM-systems H04B14/046; removal of redundancy in telegraph communication H03M7/30
• CPC Class Codes: H04L 7/08 the synchronisation signals recurring cyclically

Abstract

The invention relates to a method or an arrangement for the clock synchronization of a plurality of distributed modules of an information or communication system, said modules being coupled via a packet-switched network. At least two of said modules are controlled by a local clock generator of the modules using an adjustable frequency, and a clock signal is transmitted via the network in the form of clock signal packets in a synchronous minter with respect to the local clock of the modules. One of said at least two modules takes over the function of a master module, and all remaining said at least two modules, the slave module(s), synchronize the local clock of the modules with the clock of the master module, wherein said slave modules ascertain a measurement for the deviation of the local clock generator of the modules relative to the clock generator of the master module by comparing the clock signal transmitted by the master module with the clock signal of the modules and use said measurement in order to regulate the local clock generator of the modules.

Claims

1. A method for the clock synchronization of a plurality of distributed modules in an information or communications system, said modules being coupled via a packet-switched network, comprising:

a) controlling at least two modules by a local clock generator of the modules using an adjustable frequency, and transmitting a clock signal over the network in the form of clock signal packets synchronous to the local clock rate; and

b) causing one of said at least two modules to assume the function of a master module, to whose clock rate all remaining of said at least two modules, which assume the function of the slave modules, synchronize their local clocks by determining a measurement for the deviation of their local clock generators relative to the clock generator of the master module by comparing the clock signal transmitted by the master module to their own clock signals and using said measurement to control the local clock generators of said modules.

2. The method of claim 1, wherein each of said at least two modules transmits a clock signal packet during a time window which is different from a time windows of all others of said at least two modules.

3. The method of claim 1, comprising assigning a local control unit to each module and connecting the local control unit to a central control computer over the network.

4. The method of claim 3, where each local control unit has a quartz oscillator with an adjustable frequency, said quartz oscillator controlled by a program via a digital-to-analog converter.

5. The method of claim 1, wherein the clock signal comprises at least one pulse code modulation signal, further comprising transmitting said pulse code modulation signal over the network in the form of packets, according to the real time transport protocol, synchronous to the clock rate of the pulse code modulation signal.

6. The method of claim 1, comprising determining a frequency difference and a phase difference between a packet stream transmitted from a slave module and a packet stream of the master module for each slave module.

7. The method of claim 1, comprising determining a clock signal packets in the network with higher priority compared to other signaling packets.

8. A system comprising a plurality of distributed modules in an information or communications system, said modules being coupled via a packet-switched network, wherein

a) at least two of these modules is controlled by a local clock generator of said module using an adjustable frequency and wherein said module transmits a clock signal over the network in the form of clock signal packets synchronous to the local clock rate;

and wherein

b) one of said at least two modules is set up to assume the function of a master module, to whose clock rate all remaining of said at least two modules, which assume the function of slave modules, synchronize their local clocks by determining a measurement for the deviation of their local clock generators relative to the clock generator of the master module by comparing the clock signal transmitted by the master module to their own clock signals and use said measurement to regulate their local clock generators.

9. The system of claim 8, characterized in that a local control unit is assigned to each module and is connected to a central control computer via the network.

10. The system of claim 9, wherein each local control unit has a quartz oscillator with an adjustable frequency, said quartz oscillator being controlled by a program via a digital-to-analog converter.

11. The system of claim 8, wherein the clock signal comprises at least one pulse code modulation signal, which is transmitted across the network in the form of packets, according to the real time transport protocol, synchronous to a clock rate of a pulse code modulation signal.

12. The system of claim 8, wherein a frequency difference and a phase difference between the clock signal packet stream transmitted from the slave module and the clock signal, packet stream of the master module are determined for each slave module.