Modulation order

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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

. 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

).

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.