Sequence time domain reflectometry using complementary golay codes
View Patent ↗A method and system for performing sequence time domain reflectometry over a communication channel to determine the location of line anomalies in the communication channel is disclosed. In one embodiment, the system generates a sequence signal and transmits the sequence signal over an optical channel. The system receives one or more reflection signals over the optical channel and performs reflection signal processing on the reflection signal. In one embodiment, the optical reflection is transformed to an electrical signal and correlated with the original sequence signal to generate a correlated signal. The time between the start of the reflection signal and a subsequent point of correlation and the rate of propagation reveals a line anomaly location. A circulator, beam splitter, or any other similar device may direct the reflection signal to the apparatus configured to perform reflection signal processing.
1. A method for performing time domain reflectometry on a communication channel comprising:
obtaining a first complementary signal;
transmitting the first complementary signal over a communication channel;
receiving a first reflection signal from the communication channel in response to the transmitting of the first complementary signal;
correlating the first reflection signal with the first complementary signals to generate a first correlated signal;
obtaining a second complementary signal;
transmitting the second complementary signal over a communication channel;
receiving a second reflection signal from the communication channel in response to the transmitting of the second complementary signal;
correlating the second reflection signal with the second complementary signal to generate a second correlated signal;
processing the first correlated signal and the second correlated signal to generate a combined correlated signal;
determining a point of alignment between the transmitted signals and the combined correlated signal;
measuring a time interval between the point of alignment and a subsequent peak in the combined 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 a peak in the combined correlated signal is caused by a bridge tap.
3. The method of claim 1 , wherein the communication channel comprises a twisted pair conductor.
4. The method of claim 1 , wherein transmitting the first and second complementary signals occurs at a power level that does not introduce crosstalk into other communication channels.
5. The method of claim 1 , further comprising performing a circular rotation of the complementary signals to create two or more rotated complementary signals;
transmitting the two or more rotated complementary signals over the communication channel;
receiving two or more rotated reflection signals;
correlating the two or more rotated reflection signals with the two or more rotated sequence signals to create two or more rotated correlated signals;
aligning the two or more rotated correlated signals with the two or more correlated signals; and
adding the two or more rotated correlated signals to the two or more correlated signals to reduce or remove correlation artifacts on the two or more correlated signals.
6. The method of claim 1 , further comprising:
retrieving a template signal;
aligning the template signal and the combined correlated signal; and
subtracting the template signal from the combined correlated signal to remove near-end echo from the combined correlated signal.