frequency division multiplexing


Also found in: Dictionary, Acronyms.
Related to frequency division multiplexing: Time division multiplexing

frequency division multiplexing

(communications)
(FDM) The simultaneous transmission of multiple separate signals through a shared medium (such as a wire, optical fibre, or light beam) by modulating, at the transmitter, the separate signals into separable frequency bands, and adding those results linearly either before transmission or within the medium. While thus combined, all the signals may be amplified, conducted, translated in frequency and routed toward a destination as a single signal, resulting in economies which are the motivation for multiplexing. Apparatus at the receiver separates the multiplexed signals by means of frequency passing or rejecting filters, and demodulates the results individually, each in the manner appropriate for the modulation scheme used for that band or group.

Bands are joined to form groups, and groups may then be joined into larger groups; this process may be considered recursively, but such technique is common only in large and sophisticated systems and is not a necessary part of FDM.

Neither the transmitters nor the receivers need be close to each other; ordinary radio, television, and cable service are examples of FDM. It was once the mainstay of the long distance telephone system. The more recently developed time division multiplexing in its several forms lends itself to the handling of digital data, but the low cost and high quality of available FDM equipment, especially that intended for television signals, make it a reasonable choice for many purposes.

Compare wavelength division multiplexing, time division multiplexing, code division multiplexing.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

FDM

(1) (Fused Deposition Modeling) See 3D printing.

(2) (Frequency Division Multiplexing) Transmitting multiple data signals simultaneously over a single channel. Each data stream (text, voice, video, etc.) is modulated onto a carrier with a unique center frequency by the multiplexor and demodulated at the receving end (see modulation and carrier). FDM works in both wired and wireless applications (see FDMA).

It Started in the 1930s
In the 1930s, the telephone companies began to use FDM to combine multiple analog voice signals over one line to maximize efficiency of their long distance trunks. During the 1960s, FDM was replaced with TDM, its digital counterpart (see TDM and channel bank).

Cable TV companies use FDM to transmit hundreds of channels of analog and digital TV as well as Internet over a single coaxial cable. The set-top box or TV tuner locks onto a particular frequency (channel) and demodulates the carrier to derive the data for the TV screen. The cable modem both modulates and demodulates the appropriate carriers to provide bi-directional operation for Internet access. See FDMA, OFDM, circuit switching and WDM.

Analog FDM vs. Digital TDM
FDM separates signals by using different carrier frequencies, whereas TDM (time division multiplexing) interleaves signals as in the following illustrations.





Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in periodicals archive ?
Xin Li, "Experimental demonstration of an adaptive orthogonal frequency division multiplexing visible light communication system," Chinese Optics Letters, vol.
Bittner, "GFDM--generalized frequency division multiplexing," in Proceedings of the IEEE 69th Vehicular Technology Conference (VTC '09), pp.
Renesas Electronics Corporation has launched the third generation of its orthogonal frequency division multiplexing (OFDM) powerline communication (PLC) modem solution.
Orthogonal frequency division multiplexing (OFDM) technique mitigates the effects of fading channels.
After years of research, Huawei has developed an adaptive and software-defined air interface architecture that uses technologies including Sparse Code Multiple Access (SCMA), Filtered-Orthogonal Frequency Division Multiplexing (F-OFDM), and polar coding.
(SCMA), and Filtered-Orthogonal Frequency Division Multiplexing (F-OFDM) - as the
In the late 1990s, coded orthogonal frequency division multiplexing (COFDM) technology came along, offering far better rejection of multipath.
WiMAX technology based on orthogonal frequency division multiplexing access (OFDMA) is specified in the IEEE 802.16m standard.
Orthogonal frequency division multiplexing (OFDM) has become attractive for many current and emerging commercial applications because it provides a combination of data throughput, scalability, and robustness.
The fundamental difference between the technologies is HSPA's use of W-CDMA (wideband code division multiple access), compared to LTE's use of OFDN (orthogonal frequency division multiplexing).
one of the most popular MC communication technologies is orthogonal frequency division multiplexing (OFDM) [[1]].

Full browser ?