FDMA

Also known as: Frequency Division Multiple Access

Frequency Division Multiple Access (FDMA) is an analogue transmission technique used for mobile phone communications, in which the frequency band allocated to a network is divided into sub-bands or channels. Each frequency channel can carry either a voice conversation or digital data, and one channel will be assigned to each subscriber for the duration of a call. Using FDMA in this way, multiple users can share the available band without the risk of interference between the simultaneous calls.

FDMA is one of the three main multiplexing techniques that enable users to share the radio spectrum, and in the case of FDMA the receiver will discriminate between the signals by tuning to the particular frequency channel that carries the desired signal. Alternative multiple access techniques are TDMA and CDMA, in which the receivers discriminate between signals by using, respectively, different time slots or different codes. However, in practice TDMA and CDMA are always found in combination with FDMA, i.e. TDMA or CDMA are used to increase capacity on a channel within an FDMA system.

The term FDMA has also been used to describe the cellular technology used in the 1G (first-generation) analogue systems, such as NMT, AMPS, and TACS, because FDMA was the predominant transmission technique used in these 1G networks.

Related articles
  1. 1G - First Generation (Technology section)

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Last updated 10th September 2009, 08:33 BST