What is differential modulation

Differential modulation is a type of modulation used in communication systems to encode information. It's based on the idea of representing data through differences rather than absolute values. There are a few different contexts where differential modulation can be applied:

1. Differential Phase Shift Keying (DPSK): In this method, the information is encoded in the difference between successive phases of the carrier wave. Instead of encoding the absolute phase, the system transmits information based on the change in phase from one symbol to the next. This can make the system more robust to phase noise and easier to synchronize.

2. Differential Pulse Code Modulation (DPCM): In DPCM, the information is encoded based on the difference between the current sample and a predicted value. This approach reduces the redundancy in the data and often requires less bandwidth than transmitting the absolute values.