ECHO CANCELLATION USING CROSS-CORRELATION OF BUFFERED RECEIVE AND TRANSMIT SAMPLE SEGMENTS TO DETERMINE CANCELLING FILTER COEFFICIENTS

摘要

An echo detection system comprises data stores (8, 18) for storing signals from up and down channels (5, 15) respectively. The signals undergo pre-processing (9, 19) to identify signals forms characteristic of speech and instruct the measurement unit (10) to carry out comparison using cross-correlation techniques between the signals stored in stores (8, 18) only when such characteristics are detected. This reduces the processing power required and raises the accuracy of the correlations. Parallel processing techniques allow echoes with longer delay periods to be detected. The results of the measurement may be used to generate an echo-cancellation signal (units 7, 17).