CA2456086A1 - Telecommunications network - Google Patents

Abstract

A method for generation of a clock synchronized with time references derived from input signals in an apparatus of a telecommunications network comprising an input part receiving the input signals and a part for treatment of said input signals is described. In the input part the method comprises the steps of deriving the time reference signals from the input signals, reading an edge of the reference signals, establishing the position of this edge relative to the internal data frame, inserting in the frame heading a pointer representing the established position of the edge relative to the frame and sending the frame to the treatment part. In the treatment part the method comprises the steps of receiving the frame, extracting said pointer, generating said time reference clock and synchronizing it with the position in the frame indicated by the pointer. An apparatus applying this method is also proposed.

Claims (15)

1. Method for generation of a clock synchronized with time references derived from input signals in an apparatus of a telecommunications network, in which the telecommunications network comprises an input part receiving the input signals and a part for treatment of said input signals in which the input and treatment parts are interconnected by lines for the transport of the input signal in which the input signals comprise a frame structure in which the method comprises the following steps in the input part:
- deriving the time reference signals from the input signals, - reading an edge of the reference signals, creating an internal frame structure and synchronising the internal frame structure to a selected clock for transport of the input signal, - establishing the position of the edge relative to the internal frame structure, - inserting in the internal frame a pointer representing the established position of the edge relative to the frame, - sending the frame to the treatment part, and in which the method comprises the following steps in the treatment part:
- receiving the internal frame, - extracting said pointer, and generating said clock synchronized with the position in the frame indicated by the pointer.

2. Method in accordance with claim 1 in which in the input part enters additional pointer data in the frame.

3. Method in accordance with claim 2 in which the additional data contain data indicating whether the pointer in the frame is to be considered valid or not.

4. Method in accordance with any above claim in which the pointer is copied several times in the frame.

5. Method in accordance with any above claim in which in the treatment part compares the positions indicated by the pointer in two successive frames and the pointer of the second of the two frames is not considered valid for synchronisation if a shift in relation to the first frame pointer greater than a predetermined amount is detected.

6. Method in accordance with any above claim in which the treatment part requires said clock to be synchronized with said time references.

7. Method in accordance with any above claim in which the treatment part compares pointer values in successive internal frames and considers the pointers invalid if it detects a change above a preset amount.

8. Method in accordance with any above claim in which the internal frame structure comprises a heading and in which the pointer is inserted into the heading.

9. Method in accordance with any above claim in which in the input part oversamples the reference signals by means of a clock generated by an internal clock generator.

10. Telecommunications network apparatus comprising an input part for reception of input signals and a part for treatment of said input signals with the input and treatment parts being interconnected by transport lines for the input signals in which the input means comprises means for creating an internal frame structure synchronised to a selected clock for transport of the input signals;
characterized in that the input part comprises means for deriving time reference signals from the input signal, means for reading an edge of the reference signals and establishing the position of said edge relative to the internal frame structure, and means for inserting in the internal frame transported to the treatment part a pointer representing the established position of the edge relative to the internal frame;
and in which the treatment part comprises means for extracting said pointer from the received internal frame and means for generating a time reference clock synchronized with the position in the internal frame indicated by the pointer.

11. Apparatus in accordance with claim 10 in which the treatment part comprises means for comparison of the positions indicated by the pointer in two successive received frames and for commanding the clock generation means to not utilize the pointer of the second frame for generating the clock signal if, from the comparison of the pointers, it proves that a shift relative to the pointer of the first frame is greater than a predetermined amount.

12. Apparatus in accordance with one of claims 10 and 11 in which the means for reading the reference signal edge comprise an oversampler for oversampling the reference signals by means of a clock generated by an internal clock generator.

13. Apparatus in accordance with any one of claims 10 to 12 in which the treatment part requires a clock synchronized with time references derived from the input signals.

14. Apparatus in accordance with any one of claims 10 to 13 in which the internal frame structure comprises a heading and in which the inserting means comprises means for inserting the pointer into the heading.

15 15. A synchronous data transport network comprising the apparatus in accordance with any one of claims 10 to 14.