Patent ID: 7173962

Claim:
A subscriber modem apparatus that couples to an analog subscriber line and is operative to cooperate with a cooperative modem located across a digital network, the digital network being coupled to the subscriber line via a network line interface card, the subscriber modem comprising: a remote-echo canceller coupled to receive a downlink training signal sent by the cooperative modem and to process the training signal in order to allow at least one parameter to be adjusted in the remote-echo-canceller, the remote-echo canceller operative to apply the at least one parameter to a downlink signal to produce a digital representation of a remote-echo cancellation signal, wherein the remote-echo cancellation signal is computed such that when it passes through the subscriber line and then combines with an echo signal at the input to an ADC (analog to digital converter) located within the network line interface card, a remote echo-cancellation error signal is produced at the input to the ADC in which at least some components of the echo signal have been substantially reduced, and wherein the a computation of the parameter involves a first set of computations computed at the cooperative modem and a second set of computations computed in the subscriber modem; a modem transmitter module which converts a bit stream into a digital representation of a modulated uplink signal; and a combining unit which combines the digital representation of the modulated uplink signal with the digital representation of the remote-echo cancellation signal and couples the combined signal to a DAC (digital to analog convener) for subsequent coupling as an uplink analog signal onto the subscriber line to be transmitted to the ADC; whereby the ADC samples a signal comprising a superposition of the modulated uplink signal, the echo signal and the remote echo cancellation signal; whereby the superposition of the echo signal and the remote echo cancellation combine to produce a remote echo cancellation error signal, a measure of which is reduced with respect to the echo signal.