Distributed echo cancelling

Abstract

A distributed echo cancelling architecture is provided where echo-cancelling functions are performed at locations remote from devices receiving signals with echoes. The echo cancelling functions use a reference signal, which has been corrupted with the echoes at the devices, for echo cancellation. As echo canceller resources are located at a central system and not at each individual device, the echo canceller resources can therefore be shared between the devices.

1 . A distributed echo canceller, comprising: 
 a system for applying a signal (Ro) to a network, for receiving a signal (Si, Ro′) from the network, for splitting the signal (Si, Ro′) into signals (Si) and (Ro′), the signal (Ro′) being a modified version of the signal (Ro) and the signal (Si) containing an echo of the modified signal (Ro′), and for canceling echoes from the signal (Si) using the modified version (Ro′) of the signal (Ro); and    a network of echo cancellers coupled to the system over the network for (i) receiving and outputting the modified version (Ro′) of the signal (Ro) corrupted by transmission over the network, (ii) receiving a signal (Si) containing an echo of the modified signal (Ro′), and (iii) combining and transmitting the signals (Si, Ro′) over the network to the system for echo cancellation of the signal (Si) using the modified signal (Ro′).    
     
     
         2 . The distributed echo canceller of  claim 1 , wherein the system further comprises a splitter, a subtractor, and an echo estimator and control.  
     
     
         3 . The distributed echo canceller of  claim 2 , wherein the network of echo cancellers includes at least one handsfree device.  
     
     
         4 . A method of distributed echo cancelling, comprising 
 transmitting a first reference signal from a system to a network;    receiving a second reference signal by a network of echo cancellers coupled to the system over the network, wherein the second reference signal comprises the first reference signal as modified by network effects due to transmission over the network;    outputting the second reference signal from the network of echo cancellers;    receiving within the network of echo cancellers a further signal containing an echo of the second reference signal;    combining the further signal and the second reference signal at the network of echo cancellers    transmitting the combined signal from the network of echo cancellers to the network;    receiving within the system the combined signal;    splitting the second reference signal from the further signal; and    canceling the echoes from the further signal using the second reference signal.    
     
     
         5 . A distributed echo cancelling system, comprising 
 means for transmitting a first reference signal from a system to a network;    means for receiving a second reference signal comprising the first reference signal as modified by network effects due to transmission of the first reference signal over the network, and for receiving a further signal containing an echo of the second reference signal;    means for combining the further signal and the second reference signal into a combined signal and for transmitting the combined signal to the system;    means for splitting the second reference signal from the further signal at the system, and for canceling the echoes from the further signal using the second reference signal.