Linear predictive echo canceller integrated with RELP vocoder

Details Linear predictive echo canceller integrated with RELP vocoder Linear predictive echo canceller integrated with RELP vocoder

1986-09-05

1987-09-29

Safourek, Benedict V.

Multiplex communications

Wide area network

Packet switching

379410, 381 29, H04B 320

Patent

active

046972617

ABSTRACT:
A linear predictive echo canceller is integrated with a RELP vocoder in a two-way communications network, in which a received digitized speech signal synthesized by the RELP vocoder from a residual signal received with linear prediction coefficients is echoed onto a transmit channel and combined with a transmitted digitized speech input signal that is to be analyzed by a RELP vocoder for transmission. The echo canceller cancels the echoed signal from the transmit channel by generating a foreground transmit signal by subtracting a foreground estimate of the echoed signal from the combined signal; and providing the foreground transmit signal on the transmit channel for ananlysis by the RELP vocoder. In order to generate the foreground transmit signal, the echo canceller filters the received digitized speech signal with adaptation coefficients to generate the foreground estimate of the echoed signal; prewhitens the foreground transmit signal by using the received linear prediction coefficients; and generates the adaptation coefficients by cross correlating the received residual signal with the prewhitened foreground transmit signal and adding the product of said cross correlation to the adaptation coefficients used for generating the foreground estimate of the echoed signal.

REFERENCES:
patent: 4591669 (1986-05-01), Duttweiler et al.
patent: 4633046 (1986-12-01), Kitayama et al.
M. Sondi and D. Berkley, "Silencing Echoes on the Telephone Network", Proc. IEEE, 1980, pp. 948-963.
S. Yamamoto et al., "An Adaptive Echo Canceller with Linear Predictor", Trans. IECE Japan, 1979, pp. 851-857.
K. Ochiai et al., "Echo Canceller with Two Echo Path Models", IEEE Trans. COM-25, 1977, pp. 589-595.
Gingell, "A Block Mode Update Echo Canceller Using Custom LSI", 1983 IEEE, pp. 1394-1397.

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