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Encyclopedia > Equivalent pulse code modulation noise

In telecommunication, equivalent pulse code modulation noise (PCM) is the amount of thermal noise power on a frequency-division multiplexed (FDM) or wire channel necessary to approximate the same judgment of speech quality created by quantizing noise in a PCM channel.


Note 1: The speech quality judgment is based on comparative tests.


Note 2: Generally, 33.5 dBrnC ±2.5 dB is considered the approximate equivalent PCM noise of a 7-bit PCM system.


Source: from Federal Standard 1037C and from MIL-STD-188


  Results from FactBites:
 
Cisco - Waveform Coding Techniques (2204 words)
Quantization noise is equivalent to the random noise that impacts the signal-to-noise ratio (SNR) of a voice signal.
The difference between the input signal amplitude height and the quantization interval decreases as the quantization intervals are increased (increases in the intervals decrease the quantization noise).
After quantizing and coding, the difference signal is transmitted to its final destination.
Pulse code modulation radio control system - Patent 4038590 (4241 words)
The binary coded output of the code converter is utilized to modulate the phase of a unique subcarrier signal which may comprise, for example, a triangular wave.
The serial digital code forming the shaft encoder outputs is preferably a Gray code which, as is well known, is a unit-distance binary code containing 2.sup.n code words in which the code word for the largest integer (2.sup.n-1) is distance 1 from the code word for the least integer (0).
The output of modulator 14 is illustrated as waveform F of FIG.
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