Frequency-division multiple access


Frequency-division multiple access

Frequency Division Multiple Access or FDMA is an channel access method that is used by radio systems to share a certain radio spectrum between multiple users. The users are individually allocated one or several frequency bands, allowing them to access the radio system without interfering with each other.

Features

* FDMA requires high-performing filters in the radio hardware, in contrast to TDMA and CDMA.
* FDMA is not vulnerable to timing problems as TDMA. 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.

It is important to distinguish between FDMA and frequency-division duplexing (FDD). While FDMA allows multiple users simultaneous access a certain 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 base-station). Furthermore, frequency-division multiplexing (FDM) should not be confused with FDMA. The former is a physical layer technique that combines and transmits low-bandwidth channels through a high-bandwidth channel. 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.

See also

TDMA, CDMA, SDMA

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Frequency Division Multiple Access — Multiplexverfahren (lat. multiplex „vielfach, vielfältig“) sind Methoden zur Signal und Nachrichtenübertragung, bei denen mehrere Signale zusammengefasst (gebündelt) und simultan über ein Medium (Leitung, Kabel oder Funkstrecke) übertragen werden …   Deutsch Wikipedia

  • Frequency Division Multiple Access — Accès multiple par répartition en fréquence L’accès multiple par répartition en fréquence (ou AMRF, en anglais Frequency Division Multiple Access ou FDMA) est un mode de multiplexage destiné à la téléphonie mobile. Il s agit d un découpage en… …   Wikipédia en Français

  • frequency division multiple access — daugkartinė dažninio tankinimo kreiptis statusas T sritis radioelektronika atitikmenys: angl. frequency division multiple access vok. Frequenzmultiplexzugriff, m rus. многократный доступ с частотным уплотнением, m pranc. accès multiple par… …   Radioelektronikos terminų žodynas

  • Orthogonal frequency-division multiple access — Multiplex techniques Circuit mode (constant bandwidth) TDM · FDM · SDM Polarization multiplexing Spatial multiplexing (MIMO) …   Wikipedia

  • Code division multiple access — This article is about a channel access method. For the mobile phone technology referred to as CDMA, see IS 95 and CDMA2000. Multiplex techniques Circuit mode (constant bandwidth) TDM · FDM  …   Wikipedia

  • Time division multiple access — This article is about the channel access method. The name TDMA is also commonly used in the United States to refer to Digital AMPS, which is an obsolete mobile telephone standard that uses TDMA to control channel access. Time division multiple… …   Wikipedia

  • Time Division Multiple Access — Multiplexverfahren (lat. multiplex „vielfach, vielfältig“) sind Methoden zur Signal und Nachrichtenübertragung, bei denen mehrere Signale zusammengefasst (gebündelt) und simultan über ein Medium (Leitung, Kabel oder Funkstrecke) übertragen werden …   Deutsch Wikipedia

  • Code Division Multiple Access — (abrégé en CDMA, la commission générale de terminologie et de néologie propose le terme accès multiple par répartition en code, abrégé en AMRC), est un système de codage des transmissions, utilisant la technique d étalement de spectre. Il permet… …   Wikipédia en Français

  • Polarisation division multiple access — This article refers to cellular phone technology. For other meanings, see PDMA. Polarization division multiple access (PDMA) is used in some cellular networks. Separate antennas are used in this type, each with different polarization and followed …   Wikipedia

  • Time Division Multiple Access —    Abbreviated TDMA. A technique used to allocate multiple channels on the same frequency on a cellular phone or satellite communications system.    See also Code Division Multiple Access …   Dictionary of networking


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.