Modulation Techniques
In networks, modulation is the process of varying one or more properties of a waveform, called the carrier signal, with a signal that typically contains information to be transmitted.
Modulation of a waveform transforms a baseband (Ethernet or wireless) message signal into a passband signal (a passband [a band-pass filtered signal] is the range of frequencies or wavelengths that can pass through a filter without being attenuated). In current networks, modulation takes a digital or analog signal and puts it in another signal that can be physically transmitted.
A modulator is a device that performs modulation of a signal and a demodulator is a device that performs demodulation, the inverse of modulation. We typically just call these modems (from modulator–demodulator), which can perform both operations.
The purpose of digital modulation is to transfer a digital bit stream over an analog bandpass channel. (A good example would be data transmitting over the public...
