Inventors:
Alexandre L Leonidov - Skokie IL
Ying Wu - Grass Valley CA
Assignee:
3Com Corporation - Santa Clara CA
International Classification:
H04B 323
Abstract:
Methods and systems pertaining to estimating and compensating for a round-trip or flat delay portion of an echo channel characteristic in an echo canceller are provided. According to a particular method, a filter coefficient vector of an adaptive filter that models the echo channel characteristic is updated. An instant flat delay is estimated by analyzing the filter coefficient vector after each update, and periodic averages of the instant flat delay estimate are performed. A final flat delay estimate average is determined when the flat delay estimate average has converged. The length of the adaptive filter is adjusted in response to the final flat delay estimate average. Further, an improved echo canceller apparatus that compensates for a flat delay portion of an echo channel characteristic is provided. The improved echo canceller includes an adaptive filter, a position detector, a periodic averager, and a level detector. The adaptive filter has an initial length N.