Patent ID: 6445792
Filing Date: 2002-09-03
Classification: H04B

Abstract:
An echo canceller including an echo level estimator in an adaptation controller which controls adaptation of an adaptive filter, said echo level estimator comprising:a first level calculator for calculating logarithmically converted power of a reception signal level; a second level calculator for calculating logarithmically converted power of a transmission signal level; an echo gain estimator for estimating an echo gain based on the reception signal level and the transmission signal level; an echo level estimating means for adding the echo gain to the reception signal level to obtain an estimated echo level; wherein said first level calculator calculates the reception signal level Lin(k) according to the following formula, Lrin&af;(k)=log10&it;{&Sum;i=k-L+1k&it;Rin&af;(i)2}â€ƒwhere, k represents a certain time of digital signal, L represents a time for L-th sampling time, Rin(k) represents a reception signal at k, said second level calculator calculates the transmission signal level Ltin(k) according to the following formula, Ltin&af;(k)=log10&it;{&Sum;i=k-L+1k&it;Tin&af;(i)2}â€ƒwhere, Tin(k) represents a transmission signal at k, said echo gain estimator estimating the echo gain EG according to the following formula, E&it;â€ƒ&it;G=&Sum;i=k-I+1k&it;{Ltin&af;(i)-Lrin&af;(i)}/Iâ€ƒwhere, I represents an average sampling number which makes the estimated echo gain EG reliable, Ltin(i) represents a transmission signal level at i, Lrin(i) represents a reception signal level at i, and said echo level estimator outputs the estimated echo level Lech(k) according to the following formula Lech(k)=Lrin(k)+EG.