Method and apparatus for monitoring channel frequency response

• US 7,564,895 B2
• Filed: 12/21/2001
• Issued: 07/21/2009
• Est. Priority Date: 03/29/2001
• Status: Expired due to Fees

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Harris, Gwendolyn Kate, Dempster, Andrew, Pakravan, Mohammed Reza, Darveau, Michel M., Liu, Gin, Wingrove, Mike M. J., Humphrey, Leslie
• Primary Examiner(s): Fan, Chieh M
• Assistant Examiner(s): Ghulamali, Qutbuddin
• Application Number:
  US10/024,020
• Publication Number:
  US 20020176544A1
• Time in Patent Office: 2,769 Days
• Field of Search: 375/222, 375/260, 375/259, 375/219, 375/221, 375/224, 375/261, 375/231, 375/316, 375/220, 370/480, 370/485, 370/493, 370/252, 370/203, 370/211, 370/484, 379/22, 379/22.08
• US Class Current: 375/221
• CPC Class Codes: H04B 3/02 Details
• CPC Class Codes: H04B 3/487 Testing crosstalk effects
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04M 3/305 testing of physical copper line parameters, e.g. capacitance or resistance locating faults in cables G01R31/08

Abstract

Method and apparatus for retrieving the channel frequency response H(f), the noise N(f), measured at initialization and the signal to noise ratio SNR(f) measured at show time on a per bin basis, in the upstream or downstream direction. Initialization H(f) is used for analyzing the physical copper loop condition between tip and ring. Initialization N(f) is used for analyzing the crosstalk. Showtime SNR(f) is used for analyzing time dependent changes in crosstalk levels and line attenuation. The combination of H(f), N(f) and SNR(f) allows analysis of the line conditions for reaching the maximum data rate of a given loop, scheduling maintenance and plant update.

Claims

1. A method of retrieving channel characteristics of a Digital Subscriber Line (DSL) channel having a plurality of bins, comprising the steps of:

determining, at tip and ring terminals of a modem input port, and storing in data registers on a per bin basis a channel frequency response measurement and a noise measurement measured at initialization at a first end of the DSL channel without an effect of a filter or an automatic pain controller;

determining and storing in data registers on a per bin basis a signal-to-noise measurement measured at show time at the first end of the DSL channel without the effect of the filter or the automatic gain controller; and

transmitting the channel frequency response measurement, the noise measurement and the signal-to-noise measurement from the first end to a second end of the DSL channel.

2. A method as claimed in claim 1 wherein the first end is a central office (CO) end, and the second end is a customer premise equipment (CPE) end.

3. A method as claimed in claim 1 wherein the DSL channel is asymmetrical.

4. A method as claimed in claim 1 wherein the first end is a customer premise equipment (CPE) end, and the second end is a central office (CO) end.

5. A method as claimed in claim 1 wherein the DSL channel is non-overlapping.

6. A method as claimed in claim 1 wherein the DSL channel is an Asymmetric Digital Subscriber Line (ADSL) channel.

7. A method as claimed in claim 1 wherein the DSL channel is a very high bit-rate DSL (VDSL) channel.

8. The method as claimed in claim 1, wherein the DSL channel frequency response, H_R(f) is represented by a normalized complex number a(i)+jb(i).

9. The method as claimed in claim 1, further comprising the step of analyzing time dependent changes in cross talk levels and line attenuation at the second end of the DSL channel.

10. A method as claimed in claim 1 wherein the DSL channel is overlapping.

11. A method as claimed in claim 1 wherein the channel is symmetrical.

12. A method as claimed in claim 1 wherein the channel is overlapping.

13. An apparatus for retrieving channel characteristics of a Digital Subscriber Line (DSL) channel having a plurality of bins, the apparatus comprising:

a first circuit for determining at tip and ring terminals of a modem input port, and storing in data registers on a per bin basis a channel frequency response measurement and a noise measurement measured at a first end of the DSL channel without an effect of a filter or an automatic gain controller;

a second circuit for determining and storing in data registers on a per bin basis a signal-to-noise measurement measured at the first end without the effect of the filter or the automatic gain controller; and

a transmitter for transmitting the frequency response measurement, the noise measurement and the signal-to-noise measurement from the first end to a second end of the DSL channel.

14. An apparatus as claimed in claim 13 wherein the first end is a central office (CO) end, and the second end is a customer premise equipment (CPE) end.

15. An apparatus as claimed in claim 13 wherein the DSL channel is asymmetrical.

16. An apparatus as claimed in claim 13 wherein the first end is a customer premise equipment (CPE) end, and the second end is a central office (CO) end.

17. An apparatus as claimed in claim 13 wherein the DSL channel is non-overlapping.

18. An apparatus as claimed in claim 13 wherein the DSL channel is an Asymmetric Digital Subscriber Line (ADSL) channel.

19. An apparatus as claimed in claim 13 wherein the DSL channel is a very high bit-rate DSL (VDSL) channel.

20. The apparatus as claimed in claim 13, wherein the channel frequency response, H_R(f) is represented by a normalized complex number a(i)+jb(i).

21. The apparatus as claimed in claim 13, further comprising an analyzer at the second end for analyzing time dependent changes in cross talk levels and line attenuation.

22. An apparatus as claimed in claim 13 wherein the DSL channel is symmetrical.

23. An apparatus as claimed in claim 13 wherein the DSL channel is overlapping.

24. An apparatus as claimed in claim 13 wherein the channel is symmetrical.

25. An apparatus as claimed in claim 13 wherein the channel is overlapping.

26. A method of retrieving channel characteristics of a Digital Subscriber Line (DSL) channel having a plurality of bins, comprising the steps of:

determining at tip and ring terminals of a modem input port, and storing in data registers on a per bin basis channel a frequency response measurement and a noise measurement measured at a first end of the DSL channel without the effect of the filter or the automatic gain controller;

determining and storing in data registers on a per bin basis a signal-to-noise measurement measured at the first end of the DSL channel without an effect of a filter or an automatic gain controller; and

transmitting the channel frequency response measurement, the noise measurement and the signal-to-noise measurement from the first end to a second end of the DSL channel.