Block Structured Adaptive Filtering Method For Multi-channel Echo Canceller

Abstract

In the Public Land Mobile Network (PLMN), it is important to cancel the echo reflected from the Public Switched Telephone Network(PSTN) side. In case of Digital Mobile system, the round-trip delay of the echo is in excess of about 180 milliseconds due to frame-by-frame voice coding. It is necessary to cancel the echo in PLMN. We propose a block structured adaptive filter for effective FIR modeling of echo path. We have developed a multichannel echo canceller that operates with Time Switch Module in a Mobile Switching Center(MSC). The general echo canceller needs PCM trunk interface circuits and the tone detection and disabling circuits, but the multi-channel echo canceller linked with Time Switch Module does not need them.