Method and apparatus for monitoring channel frequency response

• US 20020176544A1
• Filed: 12/21/2001
• Published: 11/28/2002
• Est. Priority Date: 03/29/2001
• Status: Active Grant

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Humphrey, Leslie, Harris, Gwendolyn Kate, Dempster, Andrew, Liu, Gin, Pakravan, Mohammed Reza, Wingrove, Mike M. J., Darveau, Michel M.
• Granted Patent: US 7,564,895 B2
• Time in Patent Office: Days
• US Class Current: 379/22.08
• 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

A physical layer protocol is added to retrieve the in-band downstream ADSL 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. Additionally retrieval of similar in-band information may be provided in the upstream direction. The definition of the message protocol for retrieving during show time the following ATU-R information on a per bin basis: In-band channel frequency response per bin H_R(f) measured during the initialization referred back to the receiver tip and ring copper pair by the ARU-R; In-band noise estimation per bin N_R(f) during the initialization referred back to the receiver tip and ring copper pair by the ATU-R; and the signal-to-noise ratio per bin SNR_R(f) during show time referred back to the receiver tip and ring copper pair by the ATU-R. The values of SNR_R(f) should be updated as they change. An addition of the programming interface in the ADSL ATU-C chipset level makes similar information available for the upstream direction, that is N_c(f), N_c(f) and SNR_c(f). Initialization H(f) can be used for analyzing the physical copper loop condition between tip and ring. Initialization N(f) can be used for analyzing the crosstalk. Showtime SNR(f) can be used for analyzing time dependent changes in crosstalk levels and line attenuation (such as due to moisture). The combination of H(f), N(f) and SNR(f) can be used for trouble shooting why the data rate cannot reach the maximum data rate of a given loop, scheduling maintenance and plant update.

Claims

1. A method of retrieving channel characteristics for a discrete multi-tone communication channel comprising the steps of:

at initialization, determining and storing channel frequency response and noise measurements at a CO end of the channel;

at show time, determining and storing a signal-to-noise measurement at said first end;

at a CPE end of the channel, retrieving at least one of the stored measurements; and

receiving data at the CPE end at a rate in dependence upon the one or more of the retrieved measurement.

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

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

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

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

6. A method as claimed in claim 1 wherein the channel is ADSL.

7. A method as claimed in claim 1 wherein the channel noise is N(f).

8. A method as claimed in claim 1 wherein the channel frequency response is H(f).

9. A method as claimed in claim 1 wherein the signal-to-noise measurement is SNR(f).

10. An apparatus for retrieving channel characteristics for a discrete multi-tone communication channel comprising:

a circuit for at initialization, determining and storing channel frequency response and noise measurements at a CO end of the channel;

a circuit for at show time, determining and storing a signal-to-noise measurement;

a circuit for at a CPE end of the channel, retrieving at least one of the stored measurements; and

a circuit for transmitting to the CPE end at a rate in dependence upon the retrieved measurement.

11. An apparatus as claimed in claim 10 wherein the channel is symmetrical.

12. An apparatus as claimed in claim 10 wherein the channel is asymmetrical.

13. An apparatus as claimed in claim 10 wherein the channel is overlapping.

14. An apparatus as claimed in claim 10 wherein the channel is non-overlapping.

15. An apparatus as claimed in claim 10 wherein the channel is ADSL.

16. An apparatus as claimed in claim 10 wherein the channel noise is N(f).

17. An apparatus as claimed in claim 10 wherein the channel frequency response is H(f).

18. An apparatus as claimed in claim 10 wherein the signal-to-noise measurement is SNR(f).

20. A method as claimed in claim 19 wherein the retrieved channel frequency response was determined and stored at said CPE end during the initialization of said CPE end.

21. A method as claimed in claim 19 wherein the retrieved noise measurement was determined and stored at said CPE end during the initialization of said CPE end.

22. A method as claimed in claim 19 wherein the retrieved signal-to-noise measurement was determined and stored at said CPE end during show time at said CPE end.

24. A method as claimed in claim 23 wherein the channel frequency response is determined and stored at said CPE end during the initialization of said CPE end.

25. A method as claimed in claim 19 wherein the noise measurement is determined and stored at said CPE end during the initialization of said CPE end.

26. A method as claimed in claim 19 wherein the signal-to-noise measurement is determined and stored at said CPE end during show time at said CPE end.

19. A method of retrieving channel characteristics for a discrete multi-tone communication channel comprising the steps of:

at a CO end of the channel, retrieving from a CPE end of the channel, at least one of the channel frequency response, noise measurement or signal-to-noise measurement that were previously determined and stored at said CPE end; and

,

at the CO end, receiving data from said CPE end, at a rate in dependence upon one or more of the retrieved measurements.

23. A method of retrieving channel characteristics for a discrete multi-tone communication channel comprising the steps of:

at a CPE end of the channel, transmitting to a CO end of the channel, at least one of the channel frequency response, noise measurement or signal-to-noise measurement that were previously determined and stored at said CPE end; and

,

at the CPE end, sending data from to said CO end at a rate in dependence upon one or more of the transmitted measurements.

27. A method comprising the steps of:

retrieving the in-band downstream or upstream ADSL channel frequency response H(f), the noise N(f), as measured at initialization and the signal to noise ratio SNR(f) measured at show time on a per bin basis.

28. An apparatus comprising:

a register for storing measurements of in-band downstream or upstream ADSL channel frequency response H(f), the noise N(f), measured at initialization and the signal to noise ratio SNR(f) measured at show time, respectively on a per bin basis; and

a circuit for retrieving measurements of in-band downstream or upstream ADSL channel frequency response H(f), the noise N(f) and the signal to noise ratio SNR(f) during show time.

29. A method comprising the steps of:

retrieving the in-band downstream or upstream discrete multi-tone based VDSL channel frequency response H(f), the noise N(f), as measured at initialization and the signal to noise ratio SNR(f) measured at show time on a per bin basis.

30. An apparatus comprising:

a register for storing measurements of in-band downstream or upstream discrete multi-tone based VDSL channel frequency response H(f), the noise N(f), measured at initialization and the signal to noise ratio SNR(f) measured at show time, respectively on a per bin basis; and

a circuit for retrieving measurements of in-band downstream or upstream discrete multi-tone based VDSL channel frequency response H(f), the noise N(f) and the signal to noise ratio SNR(f) during show time.