US 7,734,036 B1Granted

Dynamic attenuation method and apparatus for optimizing voice quality using echo cancellers

AssigneeCisco Technology, Inc.

InventorsWilliam Page, Daniel Deliberato, Brian Buderman, Radley F. Kneeland

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Abstract

A method and corresponding apparatus for managing voice quality by optimizing the amount of attenuation placed in the echo return path based on the conditions observed during each telephone call. At the beginning of a telephone call, a pre-configured initial amount of attenuation is placed in the echo path of a communications connection that includes an echo canceller. After the call has begun, ERL is measured at a point in the communications connection that includes the attenuation. If the measured ERL is higher than necessary for the echo canceller to accurately perform double-talk detection, the attenuation in the echo path is slowly reduced from the initial amount. As the attenuation is reduced, the measured ERL reduces accordingly. When the measured ERL reduces to a minimum value required to perform double-talk detection, the reduction in attenuation is stopped.

Claims11

Dependent claims

Apparatus for controlling attenuation to optimize voice quality in a communications network, the apparatus comprising:

an echo canceller at a first network node through which a call supported by the first network node and a second network node is established;
the echo canceller coupled between a first network interface and a second network interface, and having:
a receive path for coupling a far-end signal from the first network interface to the second network interface;
a transmit path for coupling a near-end signal from the second network interface to the first network interface;
an echo canceller circuit coupled to the receive path and the transmit path for filtering far-end echo from the near-end signal;
a first attenuator in the receive path and a second attenuator in the transmit path, the first and second attenuators coupled immediately following the echo canceller circuit and before the second network interface;
and
a processor in communication with the echo canceller that is configured to:
set a minimum dynamic attenuation echo return loss (ERL) threshold above a minimum expected ERL associated with optimal operation of the echo canceller circuit;
set the first and second attenuators to an initial attenuation value upon establishment of the call;
and
measure ERL based on a first power level at a first point between the echo canceller circuit and the first attenuator and a second power level at a second point between the echo canceller circuit and the second attenuator and if the measured ERL is greater than the minimum dynamic attenuation ERL threshold, reduce the attenuation value of at least one of the first and second attenuators at an incremental rate until either (a) ERL, measured after each attenuation reduction, reaches the minimum dynamic attenuation ERL threshold or (b) both attenuation values reach a minimum attenuation value.

9 more elements

Dependencies are inferred from the claim text.