7. Alternative Coding: Differential PCM

Question 1

Delta Modulation (DM)

Answer 1

• exploits sample-to-sample redundancy
• encodes differences between samples (not absolute values)
• fewer bits needed for differences
• binary staircase function (moves up/down one level)

Question 2

Key Parameters

Answer 2

1. Step size (d)
2. Sampling rate (usually very high)

Question 3

Noise Types:

Answer 3

• slope overload: when signal changes faster than staircase can follow (decrease as d increases)
• quantizing noise: when signal changes slowly (decreases as d decreases)

Question 4

Advantages:

Answer 4

• good error performance
• no MSB errors causing large discontinuities
• single binary digit per sample output