Editing Frequency-division multiple access (section)

==Method==
Alternatives include [[time-division multiple access]] (TDMA), [[code-division multiple access]] (CDMA), or [[space-division multiple access]] (SDMA). These protocols are utilized differently, at different levels of the theoretical [[OSI model]].

Disadvantage: [[Crosstalk]] may cause interference among frequencies and disrupt the transmission.
* In FDMA, all users share the [[Transponder (satellite communications)|satellite transponder]] or [[frequency channel]] simultaneously but each user transmits at single frequency.
* FDMA can be used with both analog and digital signal but it generally used with analog signal.
* FDMA requires high-performing filters in the radio hardware, in contrast to TDMA and [[CDMA]].
* FDMA is not vulnerable to the timing problems that TDMA has. Since a predetermined frequency band is available for the entire period of communication, stream data (a continuous flow of data that may not be packetized) can easily be used with FDMA.
* Due to the frequency filtering, FDMA is not sensitive to [[near–far problem]] which is pronounced for [[CDMA]].
* Each user transmits and receives at different frequencies as each user gets a unique frequency slot.

FDMA is distinct from [[frequency division duplexing]] (FDD). While FDMA allows multiple users simultaneous access to a transmission system, FDD refers to how the radio channel is shared between the [[uplink]] and [[downlink]] (for instance, the traffic going back and forth between a mobile-phone and a [[mobile phone base station]]). [[Frequency-division multiplexing]] (FDM) is also distinct from FDMA. FDM is a physical layer technique that combines and transmits low-bandwidth channels through a high-bandwidth channel, like in a [[car radio]]. FDMA, on the other hand, is an access method in the [[data link layer]].

FDMA also supports [[demand assignment]] in addition to fixed assignment. ''Demand assignment'' allows all users apparently continuous access of the [[radio spectrum]] by assigning carrier frequencies on a temporary basis using a statistical assignment process. The first FDMA ''demand-assignment'' system for satellite was developed by [[COMSAT]] for use on the ''[[Intelsat]]'' series ''IVA'' and ''V'' satellites.

There are two main techniques:
*Multi-channel per-carrier ([[MCPC]])
*Single-channel per-carrier ([[Single channel per carrier|SCPC]])