Loop certification and measurement for ADSL

• US 6,215,855 B1
• Filed: 01/21/1999
• Issued: 04/10/2001
• Est. Priority Date: 01/21/1999
• Status: Expired due to Term

• Current Assignee: Verizon Patent and Licensing Incorporated (Verizon Communications Inc.)
• Original Assignee: Bell Atlantic Network Services, Inc. (Verizon Communications Inc.)
• Inventors: Schneider, Allan
• Primary Examiner(s): Kuntz, Curtis A.
• Assistant Examiner(s): NGUYEN, DUC MINH
• Application Number:
  US09/234,464
• Time in Patent Office: 810 Days
• Field of Search: 379/1, 379/5-6, 379/22, 379/24, 379/26-29, 379/30, 379/32, 324/533, 324/532, 324/527-528, 324/534, 324/523, 324/525, 324/537, 324/541, 324/579, 324/76.12, 324/76.19, 324/76.21, 324/76.38, 375/229, 375/225, 375/233, 375/232
• US Class Current: 379/22
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04L 1/242 by comparing a transmitted test signal with a locally generated replica
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 25/0248 Eigen-space methods
• CPC Class Codes: H04M 1/24 Arrangements for testing
• CPC Class Codes: H04M 3/301 Circuit arrangements at the subscriber's side of the line
• CPC Class Codes: H04M 3/306 for frequencies above the voice frequency, e.g. xDSL line qualification test methods, test equipment and test arrangements for subscriber lines using xDSL modems H04M3/304; systems modifying transmission characteristics according to link quality H04L1/0001; monitoring and/or testing of line transmission systems H04B3/46

Abstract

The present invention involves a transmission of a known signal over a line intended for a digital subscriber line (xDSL) service, measurement of a resulting waveform received through the line and processing of the received signal to derive a set of eigenvalues characterizing the transfer function of the line. In the preferred embodiment, a transmitter applies a known test signal waveform to the transmission line. The test signal corresponds to a desired one of several available xDSL services. At the receiving end of the line, the output signal from the line is sampled, to capture a digitized sample waveform for the received signal. A computer processes the captured waveform, to determine eigenvalues characterizing the transfer function of the line with respect to the one service. If the eignevalues for the line bear predetermined relationships to threshold values, indicating acceptable line transfer function for the desired xDSL service, then the invention certifies the tested line for use on that service.

Claims

1. A method of testing a transmission line for a selected one of a plurality of digital subscriber line services, comprising:

selecting one waveform corresponding to the selected digital subscriber line service from waveforms corresponding to a plurality of the digital subscriber line services;

transmitting the selected waveform through the transmission line to a receiving end of the transmission line;

sampling and capturing a waveform from the receiving end of the transmission line;

processing samples of the captured waveform to obtain a set of eigenvalues characterizing a transfer function of the transmission line with respect to the selected digital subscriber service; and

comparing the set of eigenvalues to predetermined threshold values representing an acceptable transfer function of a transmission line with respect to the selected digital subscriber line service.

2. A method as in claim 1, further comprising determining if each of the eigenvalues bear a predetermined relationship with respect to a respective threshold value, and if so, certifying the transmission line for the selected digital subscriber line service.

3. A method as in claim 2, wherein one eigenvalue bears the predetermined relationship with respect to its respective threshold value if the one eigenvalue exceeds its respective threshold value.

4. A method as in claim 1, wherein the transmission line comprises a telephone line.

5. A method as in claim 4, wherein the telephone line comprises a subscriber'"'"'s loop.

6. A method as in claim 5, wherein the subscriber'"'"'s loop comprises a pair of wires.

7. A method as in claim 6, wherein the pair of wires comprises a twisted pair of copper wires.

8. A method as in claim 1, wherein the plurality of digital subscriber line services comprise xDSL services.

9. A method as in claim 8, wherein the selected digital subscriber line service comprises an asynchronous digital subscriber line (ADSL) service.

10. A method as in claim 9, wherein the ADSL service comprises a splitterless ADSL service.

11. A method of testing a transmission line for a digital subscriber line service, comprising:

transmitting a test waveform signal corresponding to the digital subscriber line service from a transmitting end of the transmission line to a receiving end of the transmission line;

sampling the waveform signal from the receiving end of the transmission line;

processing the sample of the received waveform signal to derive a plurality of eigenvalues characterizing a transfer function of the transmission line with respect to the digital subscriber line service;

comparing the eigenvalues to threshold values representing an acceptable transfer function of a transmission line with respect to the digital subscriber line service; and

from the comparison, determining a relationship of each of the eigenvalues to a respective one of the threshold values.

12. A method as in claim 11, wherein if the determined relationships satisfy predetermined conditions, recognizing that the transmission line is acceptable for the digital subscriber line service.

13. A method as in claim 12, wherein the transmission line comprises a subscriber'"'"'s telephone line.

14. A method as in claim 13, wherein the telephone line comprises twisted pair wiring.

15. A method as in claim 14, wherein the digital subscriber line service comprises an asynchronous digital subscriber line (ADSL) service.

16. A system for testing a line of a communication network for a digital subscriber line service, comprising:

a test waveform generator, for connection to a transmit-side of the line, wherein the test waveform generator comprises a generator for generating a waveform corresponding to the digital subscriber line service selected from waveforms corresponding to a plurality of digital subscriber line services available on the communication network;

a waveform sampler, for connection to a receive-side of the line, for sampling a test waveform received through the line from the generator; and

a processor, coupled to the waveform sampler and responsive to the sample of the received test waveform, for determining a set of eigenvalues characterizing a transfer function of the transmission line and for comparing the eigenvalues to threshold values corresponding to an acceptable transfer function of the transmission line, wherein the processor selects a set of threshold value corresponding to an acceptable transfer function of the transmission line from a plurality of sets of threshold values, each of the sets of the threshold values corresponding to one of the digital subscriber line services.

17. A system as in claim 16, wherein the processor comprises a programmable central processing unit.

18. A line test unit comprising:

a coupler, for connection to a line under test, having an output for a waveform signal received over the line under test;

a waveform sampler responsive to the output of the coupler, for capturing digital samples of the received waveform signal;

a storage device storing a plurality of sets of threshold values, each set of threshold values characterizing an acceptable transfer function of a line with respect to one of a plurality of digital subscriber line services; and

a processor coupled to the waveform sampler and to the storage device, wherein;

the processor processes a set of samples for a test waveform corresponding to a selected one of the digital subscriber line services and the captured digital samples, to determine a plurality of eigenvalues characterizing a transfer function of the transmission line with respect to the selected digital subscriber line service; and

the processor compares the eigenvalues to a selected one of the sets of threshold values, the selected set of threshold values corresponding to an acceptable transfer function for the selected digital subscriber line service.

19. A line test unit as in claim 18, further comprising a display responsive to signals from the processor, for generating a display of results of the comparison of the eigenvalues to the selected set of threshold values.