Method and apparatus for designing an improved transmit signal for use in a single ended line test (SELT)

摘要

The present invention relates to methods and apparatuses of using a novel transmit signal that can be used to improve performance of various loop diagnostic features of SELT. In embodiments, a novel transmit signal uses a wide contiguous band of tones that includes frequencies in both upstream and downstream bands. In these and other embodiments of the invention, the SELT transmit signal is designed such that any crosstalk noise in adjacent lines appears as a burst of noise that falls within the limits of the FEC settings of the system such that it can be fully corrected without harming the performance of modems connected on the adjacent lines.

主权项

1. A method for examining a line coupled to a modem in a discrete multi-tone (DMT) communications system in which symbols communicated once every consecutive symbol period, comprising:
constructing symbols using tones in both upstream and downstream frequency bands of the DMT communications system; forming a test signal consisting of the constructed symbols in only certain non-consecutive portions of the symbol periods and silence in the remaining symbol periods; transmitting from the modem the test signal on the line; receiving a reflection of the test signal from the line at the modem; and analyzing the reflection to identify impairments in the line.