System and method for ADPCM transmission of speech or like signa

Details System and method for ADPCM transmission of speech or like signa System and method for ADPCM transmission of speech or like signa

1983-04-13

1985-11-19

Griffin, Robert L.

Pulse or digital communications

Repeaters

Testing

332 11D, 358135, H03K 1322

Patent

active

045546703

ABSTRACT:
An adaptive differential pulse code modulated (ADPCM) transmission system includes a subtractor for providing a difference signal E.sub.j between an input signal X.sub.j and a predicted signal X.sub.j. A coder encodes the difference signal E.sub.j into a coded signal U.sub.j for transmission to a receiver. The signal U.sub.j is also decoded at the transmitter to produce a reproduced error signal E.sub.j. A prediction circuit operates to generate a prediction signal X.sub.j on the basis of the reproduced error signal E.sub.j. The prediction circuit is controlled by a control circuit which operates to detect transmitter instability. A first level detector in the control circuit compares the input signal level against the level of a transmitter produced signal representing the input signal. A second level detector of the control circuit determines when the input signal is below a specified value. Transmitter instability is judged by a decision circuit which determines when the output of the first level detector exceeds a preset value and the output of the second level detector is below another preset value.

REFERENCES:
patent: 3973199 (1976-08-01), Widmer
patent: 4179710 (1979-12-01), Ishiguro et al.
patent: 4200886 (1980-04-01), Musmann et al.
patent: 4292651 (1981-09-01), Kretz et al.
patent: 4385393 (1983-05-01), Chaure et al.
patent: 4430670 (1984-02-01), Netravali
Cohn et al., "The Residual Encoder-An improved ADPCM System for Speech Digitization", IEEE on Communication Com 23, No. 9, Sep. 1976.
Cummiskey, "Adaptive Quantization in Differentail PCM Coding or Speech", The Bell System Technical Journal, vol. 32, No. 7, Sep. 1973.

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