Abstract
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 problem of echo cancellers using e.g. the normalized least mean square algorithm(nlms) for the adaptation of the coefficients is that the convergence properties degrade with colored signal input such as speech signals [8, 9, 17]. One approach to accelerate the convergence speed is to introduce linear prediction filters in order to decorrelate the speech signal [1, 2, 12, 15, 20]. This paper presents a new approach, named the excited lms algorithm orelms algorithm, which prewhitens the input signal applying perfect sequences. Coincidently, the proposed algorithm can be interpreted as a combination of the conventionalnlms algorithm and a system identification approach using m-sequences or related sequences.
Résumé
Des annuleurs d’écho adaptatifs sont actuellement étudiés en vue d’applications telles que la téléconférence ou la téléphonie mains-libres de haute qualité. Le but de ces dispositifs est d’éliminer le retour dû au cou plage acoustique entre le haut-parleur et le microphone. Un problème lié à l’emploi dans les annuleurs d’écho d’algorithmes tels que le gradient stochastique normalisé (nlms) pour l’adaptation des coefficients est que la convergence est dégradée en présence de signaux d’entrée à spectre non conforme comme la parole [8, 9, 17]. Une approche pour accélérer la convergence est d’introduire des filtres de prédiction linéaire afin de décorréler le signal d’entrée [1, 2, 12, 15, 20]. Cet article présente une nouvelle approche, appelée algorithme lms excité ou algorithme elms, qui pré-blanchit le signal d’entrée au moyen de suites pseudo-aléatoires parfaites. L’algorithme proposé peut être interprété comme une combinaison de l’algorithme nlms classique avec une identification de système utilisant des suites de longueur maximale ou des suites apparentées.
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Antweiler, C., Dörbecker, M. Perfect sequence excitation of the NLMS algorithm and its application to acoustic echo control. Ann. Télécommun. 49, 386–397 (1994). https://doi.org/10.1007/BF02999427
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DOI: https://doi.org/10.1007/BF02999427
Key words
- Echo canceller
- Acoustic signal
- Telephone
- Teleconference
- Adaptive algorithm
- Whitening
- Pseudorandom sequence
- System identification
- Least square method