Full-Duplex Hands-Free Mobile Phone System for a Digital Cellular

This paper discusses the implementation of an adaptive acoustic echo canceler for a hands-free mobile phone operating on a digital cellular channel. Two adaptive structures based on the LMS (least mean square) algorithm are implemented. The adaptive lattice structure, which is particularly known for faster convergence relative to the conventional tapped-delay-line (TDL) structure, is used in the initialization stage. After convergence, the lattice coefficients are converted into the coefficients for the TDL structure which can accommodate a larger number of taps in real-time operation due to of its computational simplicity. The conversion method of the TDL coefficients from the lattice coefficients is derived, and the DSP56001 assembly codes for the lattice and TDL structures as well as the simulation results are included.