Method and apparatus for transmission line analysis

A method for processing a reflection signal within a communication modem generated by transmission of a test signal onto a channel to determine a location of a line anomaly comprising:

• correlating the reflection signal with the test signal to create a correlated reflection signal, wherein the test signal is a signal that has autocorrelation properties;
• analyzing the correlated reflection signal to determine a time difference between transmission of the test signal and a point of correlation;
• multiplying the time difference by a rate of propagation of the test signal through the channel to obtain information regarding the location of a line anomaly;
• subtracting a template signal from the reflection signal or the correlated reflection signal to more clearly define a point of correlation;
• and
• adding a rotated signal to the correlated reflection signal to reduce correlation artifacts, wherein the rotated signal comprises a signal resulting from correlating a rotated test signal with a reflection of a rotated test signal.

A digital subscriber line modem for performing sequence time domain reflectometry to determine a location of impedance mismatches on a channel being configured to communicate data using a digital subscriber line standard, the digital subscriber line modem comprising:

• a sequence generator configured to generate a sequence signal, wherein the sequence generator is further configured to operate as part of the digital subscriber line modem during communication of data using a digital subscriber line standard;
• a transmitter configured to transmit the sequence signal on a channel causing the sequence signal to propagate through the channel, the channel being analyzed to determine the location of impedance mismatches that may affect data transmission, wherein the transmitter is further configured to operate as part of the digital subscriber line modem during communication of data using a digital subscriber line standard;
• a receiver configured to receive one or more reflections that result from the sequence signal encountering impedance mismatches as it propagates through the channel, wherein the receiver is further configured to operate as part of the digital subscriber line modem during communication of data using a digital subscriber line standard;
• a correlator configured to correlate the one or more reflections with the sequence signal to generate an output having one or more peaks;
• a processor, that is also configured to perform processing to achieve communication using a digital subscriber line standard, the processor further configured to:
• subtract a template signal from the one or more reflections or the output having one or more peaks to more clearly define a point of correlation;
• and
• add a rotated signal to the one or more reflections to reduce correlation artifacts, wherein the rotated signal comprises a signal resulting from correlating a rotated test signal with a reflection of a rotated test signal;
• time a period between a beginning of the sequence signal transmission by the transmitter and at least one of the one or more peaks;
• and
• calculate a value corresponding to a channel length between the digital subscriber line modem and an impedance mismatch.