A multi-carrier echo canceller based on symmetric decomposition

Abstract

Echo cancellation in DMT modems is a means to improve transmission performance. It consists in extending the downstream (DS) and upstream (UP) frequency bands so that they become adjacent or even overlap, and relaxing at the same time the existing filters. Modern cancellers make use of FIR filters that emulate the echo-path, and adaptive algorithms that estimate the correspondent coefficients. In this article, we start from the circulant decomposition canceller (CDC), an efficient algorithm recently developed for ADSL, and explore new kinds of decomposition, based on the diagonalization properties of the discrete cosine and sine transforms (DCT, DST).