Editing Frequency-division multiple access (section)

{{Short description|Signal processing technique in telecommunications}}
{{redirect|FDMA|the government agency in Japan|Fire and Disaster Management Agency}}
{{Use American English|date = March 2019}}
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'''Frequency-division multiple access''' ('''FDMA''') is a [[channel access method]] used in some multiple-access protocols.  FDMA allows multiple users to send data through a single [[channel (communications)|communication channel]], such as a [[coaxial cable]] or [[microwave]] beam, by dividing the [[bandwidth (signal processing)|bandwidth]] of the channel into separate non-overlapping [[frequency]] sub-channels and allocating each sub-channel to a separate user.  Users can send data through a subchannel by modulating it on a [[carrier wave]] at the subchannel's frequency.  It is used in [[satellite communication]] systems and telephone trunklines.

FDMA splits the total bandwidth into multiple channels. Each ground station on the earth is allocated a particular frequency group (or a range of frequencies). Within each group, the ground station can allocate different frequencies to individual channels, which are used by different stations connected to that ground station. Before the transmission begins, the transmitting ground station looks for an empty channel within the frequency range that is allocated to it and once it finds an empty channel, it allocates it to the particular transmitting station.