OFDM:Theory and applications

- M. Araújo; Melo, M.;

The Journal of the Institute of Telecommunications Professionals Vol. 4 , No. 1 , pp. 32 - 37 , March , 2010 .

ISSN (print): 1755-9278
ISSN (online): 1755-9278

Journal Impactor Factor: 0.096 (in 2009)

Abstract

Frequency division multiplexing (FDM) is a technology that transmits multiple signals simultaneously over a single transmission path, such as a cable or wireless system. Each signal travels within its own unique frequency range (carrier), which is modulated by the data (text, voice, video, etc.). Orthogonal FDM (OFDM) spread spectrum technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the orthogonality in this technique which prevents the demodulators from seeing frequencies other than their own. The benefits of OFDM are high spectral efficiency, resiliency to RF interference, and lower multi-path distortion. OFDM is currently the basis of the physical layer of the major wireless systems, such as WiMAX ou IEEE 802.11n, but it can be also found in cable technology systems such as DSL. This paper intends to give a major introduction of the OFDM technology and describe its features, advantages, mode of operation and applications in telecommunications engineering. There are several variants of OFDM, such as VOFDM (vector) or COFDM (coded), but this paper will give an emphasis on OFDM and OFDMA (access), due to their major importance.

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