F. Başbuğ; "An Enhancement Front-End for Speech Codecs with Dual..."

An Enhancement Front-End for Speech Codecs with

Dual Mode Echo Cancellation

Filiz Başbuğ,
Advanced Development Group, Hughes Network Systems, Germantown, MD

ABSTRACT

The echo canceller component of an integrated speech quality enhancement front-end for speech codecs is described. Since echo and background noise are the two major factors that adversely affect the speech quality in most transmission systems, our solution originally consists of echo cancellation and noise reduction elements. These are used in conjunction with various codecs (such as the IS-641 codec, which is the enhanced full-rate standard for IS-136 systems) to form an integrated speech-processing unit. In the interest of time, the noise reduction component will not be addressed in this presentation.
An integrated solution has the advantage of utilizing the synergies among its components: the codec, the noise reduction, and the echo canceller. For example, the voice activity detector of the speech coder plays a central role for the proper operation of both the noise reduction and the echo canceller. It provides the former with information on where the noise only segments are, therefore making possible the determination of an accurate noise estimate. It also provides a reliable double-talk detection scheme for the echo canceller.
The echo canceller features a dual mode operation based on the signal to noise ratio. The dual mode operation ensures optimal echo cancellation performance under various noise conditions. In this presentation, in addition to describing the basic adaptation algorithm and control mechanisms of the echo canceller, details of the various elements of the dual-mode operation will be discussed.

July 11, 2005, 11:00, G035