- See main article Modulation
Modulation is the process of varying a carrier signal, typically a sinusoidal signal to use that signal to convey information. One of the three key characteristics of a signal are usually modulated: its phase, frequency or amplitude.
In digital modulation, the changes in the signal are chosen from a fixed list (the modulation alphabet) each entry of which conveys a different possible piece of information (a symbol). In analogue modulation, the change is applied continuously in response to the data signal.
Modulation is generally performed to overcome signal transmission issues such as to allow
- Easy (low loss, low dispersion) propagation as electromagnetic waves
- Multiplexing — the transmission of multiple data signals in one frequency band, on different carrier frequencies.
- Smaller, more directional antennas
Carrier signals are usually high frequency electromagentic waves.
Examples of modulation include:
- amplitude modulation
- frequency modulation
- Phase-shift keying
Read more about this topic: Node-to-node Data Transfer
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