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Improved Echo-Canceler Initialization Disclosure Number: IPCOM000057391D
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15

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Galand, C Derby, J [+details]


Echo cancelation in voice networks is performed by dynamically synthesizing the echo path impulse response, generating an echo replica therein, and subtracting the replica from the echo-spoiled signal. The echo-path synthesis is performed by sending a training sequence, once the telephone connection is established and prior to any significant speech traffic start. In a digital voice network as shown in the figure, when user A calls B, he dials a tie-line 55 through local PBX-1 and gets connected to Voice Terminal Equipment (VTE-A) in charge of analog-to-digital conversion and echo-processing operations. The link to VTE-B is then established by the network management system and the connection to user B is set up through one or several PBX's (e.g., PBX-2 and PBX-3).