Pulse or digital communications – Repeaters – Testing
Patent
1987-09-18
1988-08-30
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
370 13, 328162, 379 6, H04B 346
Patent
active
047682035
ABSTRACT:
The adaptive and predictive capabilities of Adaptive Differential Pulse Code Modulation (ADPCM) equipment enable a telecommunication system to maintain acceptable signal
oise levels in voice transmission while utilizing a significantly lower encoding bit rate than that of conventional Pulse Code Modulation (PCM). ADPCM, however, has a deleterious effect on high-speed voiceband data transmission, yet due to its adaptive capabilities cannot readily be identified or evaluated by means of conventional ANSI/IEEE standard test signals and methods. The procedure of the present invention enables such identification and evaluation by imposing upon an ADPCM system a multiple-tone test signal which spans the voiceband and has amplitude characteristics similar to white noise. This signal thereby effectively overloads the adaptive and predictive capabilities of the system and causes the generation of a notably high level of quantizing noise. The resulting multitone signal-with-noise output from the system is processed in a spectrum analyzer where the accumulation of the signal levels in the distinct and narrow input tone bands is compared with the remainder of the accumulated signal power to obtain an accurate signal
oise measurement which, in addition to providing substantive analytical data, yields an indication of the presence of ADPCM, as distinguished even from tandem PCM, encoding equipment in the system.
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Bell Communications Research Inc.
Chin Stephen
Falk James W.
Safourek Benedict V.
White Lionel N.
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