Digital speech interpolation system and speech detector

Details Digital speech interpolation system and speech detector Digital speech interpolation system and speech detector

1989-01-17

1990-01-30

Griffin, Robert L.

Multiplex communications

Wide area network

Packet switching

370 321, 379410, H04J 317, H04L 514

Patent

active

048978329

ABSTRACT:
A digital speech interpolation (DSI) system serves multiple PCM channels by multiplexing them to a single PCM signal, detecting the presence of speech on individual channels according to an adaptive power threshold, removing silent portions of the channel signals, and recombining them into a signal with fewer channels. A central echo canceler is provided between the DSI transmitter and the multiplexer, thus eliminating the need for a separate echo protection device at each terminal. The central echo canceler provides information to the speech detector enabling the speech dectector to avoid updating the adaptive power threshold when center clipping or double-talk occurs, thus preventing erratic speech detection performance. The speech detector also has a hangover controller that prevents speech dropouts by prolonging speech dectect intervals by an amount that is adjusted according to the length of the interval, and according to the current adaptive power threshold; this form of control enables a constant activity ratio to be maintained under varying noise levels. Benefits include improved communication quality and reduced system cost.

REFERENCES:
patent: 3699273 (1972-10-01), Montgomery
patent: 3991287 (1976-11-01), May, Jr. et al.
patent: 4360713 (1982-11-01), Joel
patent: 4408324 (1983-10-01), Black et al.
patent: 4679230 (1987-07-01), Lassaux et al.
"Alternate Architectures and Technologies for INTELSAT Type DSI Design", J. M. Keelty et al., IEEE Journal of Selected Areas in Communications, vol. SAC-1, Jan. 1983.

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