Difference Between Delta Modulation (DM) And Differential Pulse Code Modulation (DPCM)


What IS Delta Modulation?

A Delta Modulation (DM) is an analog-to-digital and digital-to-analog signal conversion technique used for transmission of voice information where quality is not of primary importance. In DM each segment of the approximated signal is compared to the preceding bit and successive bits are determined by this comparison.

Features of Delta Modulation include:

  • The quantization design is simple.
  • The analog signal is approximated with a series of segments.
  • It require simpler implementation
  • The design of the modulator and demodulator is simple
  • The bit rate can be decided by the user.

What Is Differential Pulse Code Modulation (DPCM)?

Differential pulse code modulation (DPCM) is a technique of analog to digital signal conversion. This technique samples the analog signal and then quantizes the difference between the sampled value and its predicted value, then encodes the signal to form a digital value.

Features of DPCM Include:

  • As a signal encoder, it uses the baseline of pulse-code modulation (PCM) but adds some functionalities based on the prediction of the samples of the signal.
  • The input can be an analog or a digital signal.
  • The numbers of levels are fixed.
  • Requires relatively less bandwidth

Difference Between DM And Differential DPCM In Tabular Form

BASIS OF COMPARISON                 DELTA MODULATION (DM) Differential Pulse Code Modulation (DPCM)
Application DM is generally used in speeches and images. DPCM is mostly used in videos and speeches.  
Feedback In DM, feedback only exists in transmitter. In DPCM, Feedback exists in both transmitter and receiver.
Signal To Noise Ratio DM has poor signal to noise ratio.   DPCM has fair signal to noise ratio.
Distortion And Quantization Error Slop over-load distortion and granular noise exist in DM. Slop over-load distortion and quantization noise exist in DPCM.
Number Of Bits In DM, only one bit is used per sample. In DPCM, more than one but less than PCM (Pulse Code Modulation) bits are used.
Efficiency DM is less efficient than DPCM. DPCM is more efficient than DM.
Levels/Step Size In DM, step size is fixed. In DPCM the numbers of levels are fixed.
Transmission Bandwidth DM requires lowest bandwidth. DPCM requires less bandwidth than PCM.