Difference between Delta Modulation (DM) and Differential Pulse Code Modulation (DPCM)

In the domain of digital signal processing, the process of converting the continuous signal into a discrete signal is done by two methods which include Delta Modulation (DM) and Differential Pulse Code Modulation (DPCM). As for both methods, they focus on minimizing the quantity of data that needs to be transmitted or stored by encoding not the actual values, but the differences between the immediate samples. However, they are quite different in the way they are implemented and each has its advantages and disadvantages. Disparate application of these two techniques in telecommunications, audio processing, and other digital signal processing tasks requires understanding the differences inherent in these two techniques.

What is Delta Modulation (DM)?

Delta modulation is associated with analog-to-digital and digital-to-analog signal conversion techniques. Delta modulation is utilized to appreciate high signal-to-noise magnitude relation. It uses a one-bit PCM code to appreciate the digital transmission of the analog signal. With delta modulation, rather than transmitting a coded illustration of a sample, only one bit is transmitted, which simply indicates whether or not or not the sample is larger or smaller than the previous sample. it’s the most effective kind of simplest sort of Differential Pulse Code Modulation. The Delta modulation signal is smaller than the Pulse Code Modulation system.

Advantages of Delta Modulation

• Simplicity: Compared to other modulation techniques the requirement of hardware for Delta Modulation is less complex.
• Lower Bit Rate: DM usually implies fewer bits per sample and is therefore useful in some cases.
• Ease of Implementation: As can be seen based on the type of actions used, DM is rather easier to implement than TD, especially in analog systems.

Disadvantages of Delta Modulation

• Slope Overload Distortion: For the higher rate of change of the input signal, the DM may fail in tracking the change and this may lead to slope overload distortion.
• Granular Noise: When the signal changes slowly this results to small steps which in turn cause granular noise affecting the quality of the reconstructed signal.

👁 Delta Modulation

What is Differential Pulse Code Modulation (DPCM)?

DPCM stands for Differential Pulse Code Modulation, is same as Pulse Code Modulation technique used for reworking analog signal into digital signal. Differential Pulse Code Modulation has moderate signal to noise magnitude relation. Differential Pulse Code Modulation differs from Pulse Code Modulation as a results of it quantizes the excellence of the actual sample and expected value. that’s the reason it’s cited as differential Pulse Code Modulation(DPCM). 

Advantages of DPCM

• Better Compression: With DPCM, we can get even tighter compression than with DM as it employs a more complex predictor.
• Improved Signal Quality: In other words, DPCM increases the signal quality by combating two main issues – granular noise and slope overload.
• Versatility: It can be shown that DPCM can be applied for different types of signals and is used predominantly in speech- and audio coding.

Disadvantages of DPCM

• Complexity: DPCM is more complex for implementation than DM therefore the complexity of the implementation is high and may need sophisticated hardware or software.
• Prediction Errors: If the prediction model employed is not credible then it produces an error margin into the encoded signal.

DPCM Transmitter and DPCM Receiver Operations are given below:

👁 DPCM Transmitter

In the above diagram, if the signal is large then the next bit in digital data is 1 otherwise next bit is 0. 

👁 DPCM Receiver

Difference Between DM and DPCM

Conclusion

Delta Modulation (DM) was developed and used commonly for quantizing the amplitude and slope of the analog signal while Differential Pulse Code Modulation (DPCM) is often applied when we need to minimize the bandwidth demand. DM is less complex and more straightforward compared with MM while encountering certain problems such as slope overload and granular noise. In comparison to PCM, DPCM provides the higher compression and signal quality but that is at the expense of the system complexity. Thus, the choice of these two techniques is depending on the exact necessity of the application of certain method, on the ratio of simplicity and effectiveness and the degree of loss of signal.