Adaptive method and apparatus for transmission line analysis

• US 6,697,768 B2
• Filed: 03/11/2002
• Issued: 02/24/2004
• Est. Priority Date: 03/16/2001
• Status: Expired due to Term

• Current Assignee: MACOM Technology Solutions Holdings, Inc.
• Original Assignee: Mindspeed Technologies Inc. (MACOM Technology Solutions Holdings, Inc.)
• Inventors: Jones, Keith R., Treviño, Gilberto Isaac Sada, Jones, William W., Jonsson, Ragnar H.
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Washburn, Douglas N
• Application Number:
  US10/095,847
• Publication Number:
  US 20020169585A1
• Time in Patent Office: 715 Days
• Field of Search: 324/533, 324/534, 370/248, 702/57, 702/58, 702/79, 702/108, 702/159, 702/182, 702/184, 702/189
• US Class Current: 702/189
• CPC Class Codes: G01R 31/11 using pulse reflection methods
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72
• CPC Class Codes: H04B 3/493 Testing echo effects or singing
• CPC Class Codes: H04L 43/50 Testing arrangements
• CPC Class Codes: Y04S 40/00 Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them

Abstract

A method and system for performing sequence time domain reflectometry to determine the location of line anomalies in a communication channel is disclosed. In one embodiment, the system generates a sequence signal and transmits the sequence signal over a channel. The system receives one or more reflection signals, and performs reflection signal processing on the reflection. In one embodiment, the reflection signal is correlated with the original sequence signal to generate a correlated signal. The system determines a time value between the start of the reflection signal and the subsequent points of correlation to determine a location of a line anomaly. In one embodiment preprocessing and post-processing occurs to counter the effects of a communication device, such as a DMT modulator/demodulator. In one embodiment sampling of the sequence and reflection signal may occur at different times or at a different phase to provide greater resolution of the line anomaly location.

Claims

1. A method for performing time domain reflectometry on a communication channel comprising:

generating a sequence signal;

preprocessing the sequence signal to counter effects of pre-transmission processing, the preprocessing creating a preprocessed sequence signal;

transmitting the sequence signal over a communication channel;

receiving a reflection signal from the communication channel in response to the transmitting the sequence signal;

post-processing the reflection signal to counter the affects of post-reception processing that occurs after receiving the reflection signal;

correlating the reflection signal with the sequence signal to generate a correlated signal;

retrieving a template signal;

aligning the template signal and the correlated signal to determine a point of alignment;

subtracting the template signal from the correlated signal to remove near-end echo from the correlated signal;

measuring a time interval between the point of alignment and a subsequent peak in the correlated signal; and

multiplying the time interval by the rate of propagation of the sequence signal through the communication channel to obtain distance information regarding a line anomaly.

2. The method of claim 1, wherein the effects of pre-transmission processing transforms the preprocessed sequence signal into the sequence signal.

3. The method of claim 1, wherein the template signal is a correlated version of a reflection created by a line interface.

4. The method of claim 1, wherein the sequence signal comprises a maximal length sequence signal.

5. The method of claim 1, wherein the communication channel comprises a twisted pair conductor.

6. The method of claim 1, wherein the preprocessing comprises DMT demodulation and post-processing comprises DMT modulation.

7. The method of claim 1, further comprising performing a circular rotation of the sequence signal to create a rotated sequence signal;

transmitting the rotated sequence signal over the communication channel;

receiving a rotated reflection signal;

correlating the rotated reflection signal with the rotated sequence signal to create a rotated correlated signal;

aligning the rotated correlated signal with the correlated signal; and

adding the rotated correlated signal to the correlated signal to reduce or remove correlation artifacts on the correlated signal.

8. A system for modifying a sequence signal to counter the effects of a communication device, the system comprising:

means for receiving a sequence signal;

means for demodulating the sequence signal, the demodulation configured to counter a pre-transmission effect of a communication device transmitter;

means for providing an output from the means for demodulating to the communication device transmitter;

means for receiving a demodulated reflection signal from a receiver of the communication device, the reflection signal generated by transmission of a sequence signal over a transmission line;

means for modulating the demodulated reflection signal to thereby counter the effects of the demodulation and restore the reflection signal; and

means for processing the reflection signal, wherein the means for demodulating comprises a dual tone multi-frequency demodulator and the means for modulating comprises a dual tone multi-frequency modulator.

9. A method for performing time domain reflectometry on a communication channel comprising:

generating an sequence signal, the sequence signal having a sampling rate with a first phase associated therewith;

transmitting the sequence signal over a communication channel;

receiving a reflection signal from the communication channel in response to the transmitting of the sequence signal;

sampling the reflection signal at a sampling rate having a second phase;

correlating the reflection signal with the sequence signal to generate a correlated signal;

repeating the steps of sampling and correlating one or more additional times to generate correlated signals, wherein during the one or more additional times the second phase is offset from the first phase; and

selecting a point correlation with the largest amplitude from a correlated signal to calculate distance information.

10. The method of claim 9 further comprising:

retrieving a template signal;

aligning the template signal and a correlated signal to determine a point of alignment;

subtracting the template signal from the correlated signal to remove near-end echo from the correlated signal;

measuring a time interval between the point of alignment and a subsequent peak in the correlated signal;

multiplying the time interval by the rate of propagation of the sequence signal through the communication channel to obtain distance information regarding a line anomaly.

11. The method of claim 10, wherein the template signal is a correlated version of a reflection created by a line interface.

12. The method of claim 9, wherein a varying offset is introduced into the second phase at each of the repeating the steps one or more additional times.

13. The method of claim 9, wherein the communication channel comprises a twisted pair conductor.

14. The method of claim 9, further comprising

performing a circular rotation of the sequence signal to create a rotated sequence signal;

transmitting the rotated sequence signal over the communication channel;

receiving a rotated reflection signal;

correlating the rotated reflection signal with the rotated sequence signal to create a rotated correlated signal;

aligning the rotated correlated signal with the correlated signal; and

adding the rotated correlated signal to the correlated signal to reduce or remove correlation artifacts on the correlated signal.

15. A method for increasing the accuracy of a time domain reflectometry operation based on sequence signal analysis, the method comprising:

generating one or more sequence signals;

transmitting the one or more sequence signals over a transmission line;

receiving a reflection signal;

sampling the reflection signal at a first phase to create a first sampled signal;

correlating the first sampled signal to create a first correlated signal;

sampling the reflection signal at a second phase, the second phase being offset from the first phase, to create a second sampled signal;

correlating the second sampled signal to create a second correlated signal; and

analyzing one or more points of correlation of the first correlated signal and the second correlated signal to determine a point of correlation with the greatest magnitude.

16. The method of claim 15, further comprising calculating a distance to a line anomaly based on the point of correlation with the greatest magnitude.

17. The method of claim 15, wherein at least one of the one or more sequence signals comprises an M-sequence.

18. The method of claim 15, wherein the correlation is cross-correlation.

19. The method of claim 15, wherein a first sequence signal is transmitted to create the first sampled signal and a second sequence signal is transmitted to create the second sampled signal.

20. A system for generating data, the data for use in locating a line anomaly, the system comprising:

a sequence source configured to provide a sequence signal;

a digital to analog converter connected to receive the sequence signal and convert the sequence signal to an analog waveform;

a transmitter configured to transmit the sequence signal;

a receiver configured to receive a reflection signal, the reflection signal comprising a reflection of the sequence signal;

an analog to digital converter configured to convert the reflection signal to a digital format, the conversion controlled at least in part by a clock signal;

a clock signal generator configured provide a clock signal to either or both of the digital to analog converter and the analog to digital converter; and

a clock signal modifier configured to modify the clock signal provided to either or both of the digital to analog converter and the analog to digital converter, wherein the clock signal modifier comprises an up-sampler, a variable delay, and a down-sampler.

21. A system for generating data, the data for use in locating a line anomaly, the system comprising:

a sequence source configured to provide a sequence signal;

a digital to analog converter connected to receive the sequence signal and convert the sequence signal to an analog waveform;

a transmitter configured to transmit the sequence signal;

a receiver configured to receive a reflection signal, the reflection signal comprising a reflection of the sequence signal;

an analog to digital converter configured to convert the reflection signal to a digital format, the conversion controlled at least in part by a clock signal;

a clock signal generator configured provide a clock signal to either or both of the digital to analog converter and the analog to digital converter; and

a clock signal modifier configured to modify the clock signal provided to either or both of the digital to analog converter and the analog to digital converter, wherein the sequence signal comprises an M-sequence.

22. A system for generating data, the data for use in locating a line anomaly, the system comprising:

a sequence source configured to provide a sequence signal;

a digital to analog converter connected to receive the sequence signal and convert the sequence signal to an analog waveform;

a transmitter configured to transmit the sequence signal;

a receiver configured to receive a reflection signal, the reflection signal comprising a reflection of the sequence signal;

an analog to digital converter configured to convert the reflection signal to a digital format, the conversion controlled at least in part by a clock signal;

a clock signal generator configured provide a clock signal to either or both of the digital to analog converter and the analog to digital converter; and

a clock signal modifier configured to modify the clock signal provided to either or both of the digital to analog converter and the analog to digital converter, wherein the receiver and the transmitter operate in accordance with a digital subscriber line protocol.

23. A system for increasing the resolution of a line probing operation, the system comprising one or more signal generation devices configured to, during two or more cycles of operation, provide an input to a transmit module sampler and an input to a receiver module sampler wherein during at least one cycle of operation the input to the transmit module sampler is out of phase with the input to the receive module sampler.

24. The system of claim 23, wherein a cycle of operation comprises a transmission of a sequence signal and receipt and processing of a reflection of the sequence signal.

25. The system of claim 23, wherein a line probe operation is configured to provide location information regarding a location of a line anomaly.

26. The system of claim 23, wherein the receive module sampler comprises an analog to digital converter and the transmit module sampler comprises a digital to analog converter.

27. The system of claim 23, wherein the receive module sampler comprises an analog to digital converter and a transmit module sampler comprises a digital to analog converter and the input comprise a clock signal.

28. The system of claim 23, wherein the signal generation device comprises an oscillator.

29. A system for locating a line anomaly in a transmission line comprising:

means for transmitting a sequence signal over the transmission line;

means for receiving a reflection signal configured to receive a reflection signal created in response to transmission of a sequence over the line;

means for sampling the reflection signal based on a signal with a first phase to create a first signal;

means for sampling the reflection signal based on a signal with a second phase to create a second signal; and

means for correlating the first signal and the second signal with the sequence signal to create one or more points of correlation;

means for calculating a distance to a line anomaly based on the one or more points of correlation.

30. The system of claim 29, wherein a point of correlation with the largest magnitude is used to determine the location of the line anomaly.

31. The system of claim 29, wherein the first phase is different from the second phase.