Modulation

modulatedmodulatordigital modulationmodulatemodulatingmodulatesunmodulatedmodanalog modulationmodes
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.wikipedia
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Minimum-shift keying

GMSKGaussian minimum-shift keyingMSK
MSK and GMSK are particular cases of continuous phase modulation.
In digital modulation, minimum-shift keying (MSK) is a type of continuous-phase frequency-shift keying that was developed in the late 1950s and 1960s.

On–off keying

on-off keyingOOKkeyed
On-off keying (OOK) denotes the simplest form of amplitude-shift keying (ASK) modulation that represents digital data at the presence or absence of a carrier wave.

Radio broadcasting

radio stationradio stationsstation
Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) for radio broadcast.

Channel access method

multiple accessmultiple access methodchannel access
OFDM can be extended to multi-user channel access method in the orthogonal frequency-division multiple access (OFDMA) and multi-carrier code division multiple access (MC-CDMA) schemes, allowing several users to share the same physical medium by giving different sub-carriers or spreading codes to different users.
Each message signal (each phone call) is modulated on a specific carrier frequency.

Frequency modulation

FMfrequency modulatedfrequency-modulated
Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) for radio broadcast.

Double-sideband reduced-carrier transmission

Double-sideband reduced carrier transmissionDSB reduced-carrier
Double-sideband reduced carrier transmission (DSB-RC): transmission in which (a) the frequencies produced by amplitude modulation are symmetrically spaced above and below the carrier and (b) the carrier level is reduced for transmission at a fixed level below that which is provided to the modulator.

Direct-sequence spread spectrum

DSSSDirect Sequence Spread SpectrumDS-CDMA
In telecommunications, direct-sequence spread spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference.

Frequency-division multiplexing

frequency division multiplexingFDMfrequency division multiplex
Analog and digital modulation facilitate frequency division multiplexing (FDM), where several low pass information signals are transferred simultaneously over the same shared physical medium, using separate passband channels (several different carrier frequencies). OFDM is based on the idea of frequency-division multiplexing (FDM), but the multiplexed streams are all parts of a single original stream.
The carrier signal and the baseband signal are combined in a modulator circuit.

Superheterodyne receiver

superheterodynesuperhetimage frequency
The demodulator extracts the audio or other modulation from the IF radio frequency; the extracted signal is then amplified by the audio amplifier.

Passband

pass bandpass-bandpassband signal
The resulting so called equivalent lowpass signal or equivalent baseband signal is a complex-valued representation of the real-valued modulated physical signal (the so-called passband signal or RF signal).

Wavelet modulation

Wavelet-OFDM
Wavelet modulation, also known as fractal modulation, is a modulation technique that makes use of wavelet transformations to represent the data being transmitted.

Pulse-amplitude modulation

PAMPAM-5pulse amplitude modulated
Pulse-amplitude modulation (PAM), is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.

Pulse-position modulation

PPMpulse position amplitude modulationPulse Position Modulation
Pulse-position modulation (PPM) is a form of signal modulation in which M message bits are encoded by transmitting a single pulse in one of 2^M possible required time shifts.

Line code

line codingbaseband transmissionencoding scheme
The aim of digital baseband modulation methods, also known as line coding, is to transfer a digital bit stream over a baseband channel, typically a non-filtered copper wire such as a serial bus or a wired local area network.
By modulating the data, RLL reduces the timing uncertainty in decoding the stored data, which would lead to the possible erroneous insertion or removal of bits when reading the data back.

Baseband

baseband signalbase bandcellular baseband
The resulting so called equivalent lowpass signal or equivalent baseband signal is a complex-valued representation of the real-valued modulated physical signal (the so-called passband signal or RF signal).
Baseband can be synonymous with lowpass or non-modulated, and is differentiated from passband, bandpass, carrier-modulated, intermediate frequency, or radio frequency (RF).

Pulse-density modulation

PDMPulse density modulationpulse-density modulated
Pulse-density modulation, or PDM, is a form of modulation used to represent an analog signal with a binary signal.

Link adaptation

Adaptive modulationModulation and Coding SchemeAdaptive coding and modulation
Link adaptation, or adaptive coding and modulation (ACM), is a term used in wireless communications to denote the matching of the modulation, coding and other signal and protocol parameters to the conditions on the radio link (e.g. the pathloss, the interference due to signals coming from other transmitters, the sensitivity of the receiver, the available transmitter power margin, etc.).

Heterodyne

heterodyningHeterodyne detectionfrequency shifting
Heterodyning is used to shift one frequency range into another, new one, and is also involved in the processes of modulation and demodulation.

RF modulator

RFChannel 3/4 outputB/W or Color TV
An RF modulator (or radio frequency modulator) is an electronic device whose input is a baseband signal which is used to modulate a radio frequency source.

Types of radio emissions

J3EA2Aemission type A1A
Each type of radio emission is classified according to its bandwidth, method of modulation, nature of the modulating signal, and type of information transmitted on the carrier signal.

Orthogonal frequency-division multiplexing

OFDMCOFDMOFDM system comparison table
OFDM is based on the idea of frequency-division multiplexing (FDM), but the multiplexed streams are all parts of a single original stream.
Based on this feedback information, adaptive modulation, channel coding and power allocation may be applied across all subcarriers, or individually to each subcarrier.

Delta modulation

delta PCMDM
Derived forms of delta modulation are continuously variable slope delta modulation, delta-sigma modulation, and differential modulation.

Chirp spread spectrum

Finally, the IEEE 802.15.4a PHY standard actually mixes CSS encoding techniques with differential phase shift keying modulation (DPSK) to achieve better data rates.

Modulation order

order modulation
Modulation order can only be defined for digital modulations.

Continuous wave

CWcontinuous-wavecontinuous-wave operation
Early radio transmitters could not be modulated to transmit speech, and so CW radio telegraphy was the only form of communication available.