DSL line card echo canceler-based mechanism for locating telecommunication line fault

• US 7,023,963 B1
• Filed: 03/31/2003
• Issued: 04/04/2006
• Est. Priority Date: 09/18/2002
• Status: Active Grant

• Current Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Original Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Inventors: Tidwell, Bradley Dwayne, McMahan, Dennis B., Chu, Fred T., Owen, James Ernest
• Primary Examiner(s): NGUYEN, DUC MINH
• Application Number:
  US10/403,321
• Time in Patent Office: 1,100 Days
• Field of Search: 379/1.01, 379/1.04, 379/14.01, 379 2201- 2205, 379 2701- 2703, 379/28, 379 2903- 2905, 379/32.04
• US Class Current: 379/15.05
• CPC Class Codes: H04M 3/085 Fault locating arrangements

Abstract

A digital subscriber loop line card-installed mechanism conducts parametric measurements on the wireline to which the line card is connected, and adjusts taps of an echo cancellation operator in accordance with the response of the wireline to an electrical stimulus imparted to the wireline. The echo canceler tap coefficients are then processed to determine the location of a fault, such as a short circuit, open-circuit and the like, on the wireline. Fault information measurement data is then reported to a supervisory control location, which dispatches the appropriate technician to resolve the cause of the problem.

Claims

1. A method of determining the location of a fault along a wireline, serving digital subscriber equipment at a location remote with respect to a central office facility, said location of said fault being determined relative to a DSL line card installed in said central office facility, said method comprising the steps of:

(a) applying a line card electrical stimulus to said wireline from said central office facility;

(b) at said DSL line card, measuring a response of said wireline to said electrical stimulus applied in step (a), and generating an output from which the distance from said DSL line card to said fault is determined; and

(c) processing said output generated by said DSL line card in step (b) to determine in which portion of said wireline said fault is located; and

wherein

step (b) comprises establishing attributes of a digital echo canceler, and

step (c) comprises analyzing attributes of said digital echo canceler to derive a measure of distance from said DSL line card to said fault.

2. The method according to claim 1, further including the step (d) of identifying whether said fault is located within said central office facility, between said central office facility and said remote location, or within said remote location, and generating a message that associates a service technician appropriate for the identified location.

3. The method according to claim 1, wherein step (c) comprises processing said output generated by said DSL line card in step (b) to a measure of distance from said DSL line card to said fault.

4. The method according to claim 1, wherein said fault comprises an open circuit.

5. The method according to claim 1, wherein said fault comprises a short circuit.

6. The method according to claim 1, wherein step (b) comprises transmitting from said DSL line card, to a location separate from said DSL line card, a message representative of said output associated with said response of said wireline to said electrical stimulus, and wherein step (c) comprises processing information contained in said message at said location separate from said line card, to determine in which portion of said wireline said fault is located.

12. The method according to claim 1, wherein step (c) includes adjusting a determination of in which portion of said wireline said fault is located, in accordance with a known location of a bridged-tap in said wireline.

13. The method according to claim 1, wherein step (b) includes compensating for unwanted voltage influences on said wireline.

29. The method according to claim 1, wherein step (c) is carried out by a processor in an equipment installation containing said line card.

30. The method according to claim 1, wherein step (c) is carried out by a processor in an equipment installation separate from that containing said line card.

31. The method according to claim 1, wherein step (a) includes the precursor step of examining the communication capability of said line card over said wireline to said remote location and, in response to said communication capability satisfying a prescribed criterion, preventing application of said electrical stimulus to said wireline from said central office facility, and also deferring steps (b) and (c).

7. A method of determining the location of a fault along a wireline, serving digital subscriber equipment at a location remote with respect to a central office facility, said location of said fault being determined relative to a line card installed in said central office facility, said method comprising the steps of:

(a) applying a line card electrical stimulus to said wireline from said central office facility;

(b) at said line card, measuring a response of said wireline to said electrical stimulus applied in step (a), and generating an output from which the distance from said DSL line card to said fault may be determined; and

c) processing said output generated by said DSL line card in step (b) to determine in which portion of said wireline said fault is located, and wherein

step (a) comprises applying a wideband signal to said wireline from said DSL line card, and step (b) comprises generating coefficients of an echo cancellation operator in accordance with the measured reflection response of said wireline to said wideband signal, and generating an output representative of said coefficients of said echo cancellation operator.

8. The method according to claim 7, wherein step (a) comprises the preliminary step of opening the connection between said DSL line card and said wireline and generating a first set of tap coefficients of said echo cancellation operator in accordance with the measured reflection response to said wideband signal applied to said open wireline, and thereafter closing the connection between said DSL line card and said wireline and generating a second set of tap coefficients of said echo cancellation operator in accordance with the measured reflection response of said wideband signal to said closed wireline, and step (c) comprises processing said first and second sets of tap coefficients to determine in which portion of said wireline said fault is located.

9. The method according to claim 8, wherein step (c) includes combining said first and second sets of tap coefficients of said echo cancellation operator in a manner that produces a time-domain amplitude response, and determining in which portion of said wireline said fault is located in accordance with the peak of said time-domain amplitude response.

10. The method according to claim 7, wherein step (a) comprises generating a first set of tap coefficients of said echo cancellation operator in accordance with the measured reflection response of said wireline to said wideband signal for a no fault condition of said wireline, and thereafter generating a second set of tap coefficients of said echo cancellation operator in accordance with the measured reflection response of said wideband signal for a fault condition of said wireline, and step (c) comprises processing said first and second sets of tap coefficients to determine in which portion of said wireline said fault is located.

11. The method according to claim 9, wherein step (c) includes combining said first and second sets of tap coefficients of said echo cancellation operator in a manner that produces a time-domain amplitude response, and determining in which portion of said wireline said fault is located in accordance with the peak of said time-domain amplitude response.

14. An arrangement for determining the location of a fault along a wireline serving digital subscriber equipment at a location remote with respect to a central office facility, said location of said fault being determined relative to a DSL line card installed in said central office facility, comprising:

an electrical stimulus generator within said central office facility;

a line card measurement unit installed in said DSL line card, which is operative to measure a response of said wireline to said electrical stimulus, and to generate an output representative of in which portion of said wireline said fault is located; and

a processing unit that is operative to process said output generated by said line card measurement unit to derive a measure of distance from said DSL line card to said fault; and

wherein

said electrical stimulus generator is operative to apply a wideband signal to said wireline from said DSL line card, and said DSL line card measurement unit is operative to generate coefficients of an echo cancellation operator in accordance with the measured reflection response of said wireline to said wideband signal, and generate an output representative of said coefficients of said echo cancellation operator.

15. The arrangement according to claim 14, wherein said processing unit is operative to determine whether said fault is located within said central office facility, between said central office facility and said remote location, or within said remote location, and generating a message that associates a service technician appropriate for the identified location.

16. The arrangement according to claim 14, wherein said DSL line card measurement unit includes a digital echo canceler having attributes established in accordance with said response of said wireline to said electrical stimulus.

17. The arrangement according to claim 14, wherein said fault comprises an open circuit.

18. The arrangement according to claim 14, wherein said fault comprises a short circuit.

19. The arrangement according to claim 14, wherein said DSL line card measurement unit is operative to transmit to said processing unit at a location separate from said DSL line card, a message representative of said output associated with said response of said wireline to said electrical stimulus, and wherein said processing unit is operative to process information contained in said message to determine in which portion of said wireline said fault is located.

20. The arrangement according to claim 15, wherein said electrical stimulus generator is operative to apply said wideband signal to an open connection between said DSL line card and said wireline, and said DSL line card measurement unit is operative to generate a first set of tap coefficients of said echo cancellation operator in accordance with the measured reflection response to said wideband signal applied to said open connection to said wireline, and wherein said electrical stimulus generator is thereafter operative to apply said wideband signal to a closed connection between said DSL line card and said wireline, and said line card measurement unit is operative to generate a second set of tap coefficients of said echo cancellation operator in accordance with the measured reflection response of said wideband signal to said closed connection to said wireline, and wherein said processing unit is operative to process said first and second sets of tap coefficients to determine in which portion of said wireline said fault is located.

21. The arrangement according to claim 20, wherein said processing unit is operative to combine said first and second sets of tap coefficients of said echo cancellation operator in a manner that produces a time-domain amplitude response, and to determine in which portion of said wireline said fault is located in accordance with the peak of said time-domain amplitude response.

22. The arrangement according to claim 14, wherein said DSL line card measurement is operative to generate a first set of tap coefficients of an echo cancellation operator in accordance with the measured reflection response of said wireline to said wideband signal for a no fault condition of said wireline, and thereafter to generate a second set of tap coefficients of said echo cancellation operator in accordance with the measured reflection response of said wideband signal for a fault condition of said wireline, and said processing unit is operative to process said first and second sets of tap coefficients to determine in which portion of said wireline said fault is located.

23. The arrangement according to claim 21, wherein said processing unit is operative to process said first and second sets of tap coefficients of said echo cancellation operator in a manner that produces a time-domain amplitude response, to determines in which portion of said wireline said fault is located in accordance with the peak of said time-domain amplitude response.

24. The arrangement according to claim 14, wherein said processing unit is operative to adjust a determination of in which portion of said wireline said fault is located, in accordance with a known location of a bridged-tap in said wireline.

25. The arrangement according to claim 14, wherein DSL line card measurement unit is configured to compensate for unwanted voltage influences on said wireline.

26. A method comprising:

(a) conducting electrical measurements upon a wireline from a digital subscriber loop (DSL) line card installed at a central office facility;

(b) reporting results of said electrical measurements conducted in step (a) to a processing unit separate from said DSL line card; and

(c) processing said results of said electrical measurements reported in step (b) at said processing unit to determine which portion of said wireline contains a fault; and

wherein

step (a) comprises stimulating said wireline to establish attributes of a digital echo canceler, step (b) comprises transmitting information representative of said attributes of said digital echo canceller to said processing unit, and step (c) comprises analyzing said attributes of said digital echo canceler to derive a measure of distance from said DSL line card to said fault; and

wherein

said attributes of said digital echo canceler correspond to tap coefficients thereof.

27. The method according to claim 26, wherein step (c) comprises determining whether said fault is located within said central office facility, between said central office facility and a remote location serving subscriber equipment, or within said remote location, and generating a message that associates a service technician appropriate for the identified location.

28. The method according to claim 26, wherein step (c) comprises processing said results of said electrical measurements reported in step (b) to provide a measure of distance from said DSL line card to said fault.