Modulation describes a range of techniques for encoding information on a
carrier signal, typically a sine-wave signal.
Modulation techniques include:
Pulse modulation techniques include:
- Pulse code modulation (PCM)
- [Pulse width modulation]? (PWM)
- [Pulse amplitude modulation]? (PAM)
- [Pulse position modulation]? (PPM)
Where the signal is a simple low speed on-off indication, as in morse code or radioteletype (RTTY) transmission, modulation is often known as 'keying' as in the terms
RTTY can also be regarded as a simple kind of
pulse code modulation.
Modulation is frequently used in conjunction with various channel access methods, such as
- [Frequency division multiple access]? (FDMA)
- [Time division multiple access]? (TDMA)
- [Code division multiple access]? (CDMA)
- [Space division multiple access]? (SDMA)
Where these methods are used for dividing forward and reverse communication channels, they are known as duplexing methods, such as:
- [Time division duplex]? (TDD)
- [Frequency division duplex]? (FDD)
See also: