Dual Domain Echo Cancellers for Multirate Discrete Multitone Systems

Digital echo cancellers are used in duplex digital subscriber lines (DSL) transceivers to remove the echo, which is the leakage of the transmitted signal onto the collocated receiver. For discrete multitone (DMT) modulated systems, the computational complexity of these cancellers can be reduced by using the structure present in the transmitted signal. In [1] and [2], we have proposed a novel dual domain echo canceller for symmetric rate DMT systems. In practical DSL systems, asymmetric bandwidths are used for the upstream and downstream transmissions, therefore, echo cancellers must be designed to work in multirate cases. In this paper, we examine the implementation of the previously proposed dual domain canceller in the multirate scenario, and show that by using the polyphase decomposition of the signals, a reduced complexity implementation of this canceller can be achieved.