System for synchronizing communications system components coupled via a communications network
View Patent ↗To synchronize communications system components coupled via a communications network, a time information transmitter is provided which is used to transmit time information, possibly on request, relating to the communications system components. The communications system components each have a clock generator, which needs to be synchronized, and a real time clock, where the clock generator both determines the transmission rate for communications data which are to be transmitted and prescribes the time base for the real time clock. In addition, the communications system components each have a comparison device for comparing received time information with a current time value indicated by the real time clock, and a clock frequency controller for regulating the clock frequency of the clock generator on the basis of the comparison result.
1. A system for synchronizing communications system components coupled via a communications network, comprising:
a time information transmitter for transmitting time information relating to the communications system components;
a time information reception device in each system component for receiving time information from the time information transmitter;
a clock generator in each system component with a controllable clock frequency for prescribing a transmission data rate for communication data which are to be transmitted;
a real time clock in each system component whose timing is controlled by the clock generator;
a comparison device in each system component for comparing received time information with a current time value indicated by the real time clock;
a clock frequency controller in each system component for controlling the clock frequency of the clock generator based on a comparison result from the comparison device;
an input buffer in each system component for buffering a data stream received via the communications network, where reading of data elements in the data stream from the input buffer is determined by the clock frequency of the clock generator;
a filling level detection device in each system component for detecting a filling level of the input buffer; and
a clock frequency controller in each system component for readjusting the clock frequency of the clock generator based on the detected filling level.
2. A system for synchronizing communications system components as claimed in claim 1 , wherein the clock generator in a system component is one of temperature stabilized and temperature compensated.
3. A system for synchronizing communications system components as claimed in claim 1 , wherein the clock generator in a system component is produced by a main oscillator outputting a timing pulse and by a reference oscillator which regulates the clock frequency of the main oscillator and otherwise freewheels, the reference oscillator being one of temperature stabilized and temperature compensated.
4. A system for synchronizing communications system components as claimed in claim 1 , wherein the time information reception device in a system component includes a radio reception device for wireless reception of time information from the time information transmitter.
5. A system for synchronizing communications system components as claimed in claim 1 , wherein the time information reception device in a system component is coupled to the communications network via a network interface, and may extract time information from a data stream transmitted to the system component via the communications network.
6. A system for synchronizing communications system components as claimed in claim 5 , further comprising a time request device in each system component for requesting time information from the time information transmitter.
7. A system for synchronizing communications system components as claimed in claim 6 , further comprising:
a timing device in each system component for measuring a time difference between a request for and reception of time information;
a delay time determination device in each system component for ascertaining an estimate for the delay time for the time information from the time information transmitter to the respective system component based on the measured time difference; and
a comparison device in each system component for comparing received time information with a current time value indicated by the real time clock, taking into account the estimated delay time.
8. A system for synchronizing communications system components as claimed in claim 7 , wherein the timing device is produced using the real time clock.
9. A system for synchronizing communications system components as claimed in claim 7 , further comprising a delay time determination device in each system component for ascertaining the estimate of the delay time based on one of averaging over a plurality of measured time differences and variables derived from the averaging.
10. A system for synchronizing communications system components as claimed in claim 6 , further comprising a time request device in each system component for requesting time information at time intervals which are dependent on how greatly the measured time differences vary.
11. A system for synchronizing communications system components as claimed in claim 6 , further comprising a time request device in each system component for requesting time information at time intervals which are dependent on the comparison result from the comparison device.
12. A system for synchronizing communications system components as claimed in claim 1 , wherein the data stream to be buffered includes communications user data received via the communications network.
13. A system for synchronizing communications system components as claimed in claim 1 , wherein the time information transmitter in a system component includes a detector device for ascertaining a temporarily low transmission volume in the communications network and a transmission controller for triggering transmission of time information when a low transmission volume is ascertained.
14. A system for synchronizing communications system components as claimed in claim 1 , further comprising a PLL circuit in each system component for regulating the clock frequency of the clock generator.