PERFECT SEQUENCE EXCITATION OF THE NLMS ALGORITHM AND ITS APPLICATIONTO ACOUSTIC ECHO CONTROL

Adaptive echo cancellers are currently being studied for applications such as audio teleconference systems or hands-free telephone sets with high speech quality. The purpose of the echo control is to eliminate the acoustic feedback from the loudspeaker to the microphone. One prob lem of echo cancellers using e.g. the normalized least mean square alg orithm (NLMS) for the adaptation of the coefficients is that the conve rgence properties degrade with colored signal input such as speech sig nals [8, 9, 17]. One approach to accelerate the convergence speed is t o introduce linear prediction filters in order to decorrelate the spee ch signal [1, 2, 12, 15, 20]. This paper presents a new approach, name d the excited LMS algorithm or ELMs algorithm, which prewhitens the in put signal applying perfect sequences. Coincidently, the proposed algo rithm can be interpreted as a combination of the conventional NLMS alg orithm and a system identification approach using m-sequences or relat ed sequences.