The GATE Grind

GATE 2017 EC – Question 32

Communications · Digital Communications · 1 mark · Multiple choice

Which one of the following statements about differential pulse code modulation (DPCM) is true?

  1. The sum of message signal sample with its prediction is quantized
  2. The message signal sample is directly quantized, and its prediction is not used
  3. The difference of message signal sample and a random signal is quantized
  4. The difference of message signal sample with its prediction is quantized

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Correct answer: (D) The difference of message signal sample with its prediction is quantized

Explanation

In DPCM the transmitter predicts each sample from earlier ones, and then quantizes and sends the difference between the actual sample and its prediction. This difference is smaller than the sample itself, so fewer bits are needed.