Patent ID: 7583727

Claim:
A method for performing a DMT test with a single test device comprising a signal transmitter and a signal receiver, without employing DSL modems, on a telephone cable, the cable having a near end and a far end, for DSL application with a frequency range comprising multiple DMT sub-channels, comprising: measuring cable noise and interference to determine a plurality of total noise levels, each noise level for a respective one of a corresponding plurality of said sub-channels; for each of said plurality of said sub-channels, measuring frequency characteristics of the cable using test tones, said measuring for each sub-channel comprising: calculating a time window within which said test tones are to be transmitted to the cable under test, transmitting, with said signal transmitter at the near end of the cable, individual test tones within the time window, one tone at a time, at up to a maximum power allowable for the cable under test, receiving, with said signal receiver at the near end of the cable, said individual test tones reflected from the far end of the cable, adjusting an AGC setting of said signal receiver to compensate for frequency-dependency of attenuation in said reflected test tones, measuring attenuation and frequency characteristics of the cable based upon the transmitted test tones and the reflected test tones, and extrapolating the frequency characteristics of the cable for DMT tones that did not fit into the time window or for which the reflected test tones were too weak; determining theoretical and practical data rates for each of said plurality of said sub-channels based on the measured frequency characteristics and determined total noise levels for that particular sub-channel, and on selected modem parameters; and determining theoretical and practical data rates for a selected DSL bandwidth based on a selected DSL DMT standard and said theoretical and practical data rates for said sub-channels within said selected DSL bandwidth.