Acoustic-Echo Canceller for a Full-Duplex Hands-Free Mobile Phone

This paper discusses a real-time implementation of an adaptive acoustic echo canceler for a hands-free cellular (mobile) phone operating inside a car. A 512-tap adaptive-finite-impulse-response (AFIR) filter, which is the implementation of the adaptive least-mean-square (LMS) algorithm with tapped-delay-line (TDL) structure, is utilized for the acoustic echo canceller. A simple double-talk detection algorithm and the normalized convergence parameter for the LMS algorithm are discussed and implemented on the DSP56001, which is also used as a host processor for the DSP56200s, A/D and D/A converters. DSP56001 assembly codes are included as well as experimental results and the schematic diagram for the hardware implementation.