The modulation order of a digital communication scheme is determined by the number of the different symbols that can be transmitted using it.
Modulation order can only be defined for
digital modulation
Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information.
The process encodes information in form of the modulation or message ...
s. The simplest forms of digital modulation are of second order because they can transmit only two symbols (usually denoted as "0" and "1" or as "-1" and "1"). They are called ''binary shift keying'' (BSK).
Modulations which have an order of 4 and above usually are termed as
higher-order modulation
Higher-order modulation is a type of digital modulation usually with an order of 4 or higher. Examples: quadrature phase-shift keying (QPSK), and m-ary quadrature amplitude modulation ( m-QAM).
See also
* phase-shift keying
Phase-shift ke ...
s. Examples of these are ''quadrature phase shift keying'' (
QPSK
Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave. The modulation is accomplished by varying the sine and cosine inputs at a precise time. It is ...
) and its generalisation as
m-ary ''quadrature amplitude modulation'' (m-
QAM
Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message sign ...
).
Because existing computers and automation systems are based on binary logic most of the modulations have an order which is a power of two: 2, 4, 8, 16, etc. In principle, however, the order of a modulation can be any integer greater than one.
Telecommunication theory
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