System and method for suppressing far end echo of voice encoded

Details System and method for suppressing far end echo of voice encoded System and method for suppressing far end echo of voice encoded

1997-05-28

2000-03-28

Tse, Young T.

Pulse or digital communications

Transceivers

Modems

375240, 704500, H04B 138, H04B 166

Patent

active

060441089

ABSTRACT:
A system and method for performing far end echo suppression of compressed speech frames in a telecommunications system. The system comprises a client modem and a server modem coupled together via a communications path. A controller in the server modem receives a first series of compressed speech frames from the client modem and provides the frames to a vocoder. Each of the frames includes voice encoded speech parameters. The controller maintains a history of a volume parameter value of the most recently provided frames to the vocoder. The vocoder decompresses the first frames to produce a first speech signal for transmission onto a telephone line. An echo of the speech signal may occur due to impedance mismatches between a hybrid in the server modem and the telephone line. The echo is received by the vocoder along with a second subscriber's speech signal from the telephone line. The echo and second speech signal are compressed by the vocoder into a second series of compressed speech frames which are provided to the controller. In particular, one of the parameters is a volume parameter whose value indicates the energy in the speech which was compressed. The controller compares the volume parameter value of each of the frames it receives from the vocoder to the volume parameter value of a frame in the history, i.e., a frame previously provided to the vocoder, to determine if the echo is present. If the echo is present, the controller substitutes a quiet frame for the echo-laden frame in order to suppress, or squelch, the echo prior to transmitting the second series of frames to the client. In one embodiment, comparing the volume parameters comprises calculating a ratio of the volume parameter of the frame received from the vocoder with the volume parameter value in the history and determining if the ratio is less than a predetermined value.

REFERENCES:
patent: 5524134 (1996-06-01), Gustafson et al.
patent: 5754589 (1998-05-01), Maitra et al.
patent: 5754590 (1998-05-01), Mays et al.
patent: 5822328 (1998-10-01), Derby et al.
patent: 5864560 (1999-01-01), Li et al.
patent: 5864795 (1999-01-01), Bartkowiak

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