OFDM Channel Estimation

2ND QUARTER 2007, VOLUME 9, NO. 2

www.comsoc.org/pubs/surveys

CHANNEL ESTIMATION FOR
WIRELESS OFDM SYSTEMS
MEHMET KEMAL OZDEMIR, LOGUS BROADBAND WIRELESS SOLUTIONS, INC. AND
HUSEYIN ARSLAN, UNIVERSITY OF SOUTH FLORIDA
ABSTRACT
Orthogonal frequency division multiplexing (OFDM) is a special case of multi-carrier transmission and it can accommodate high data rate requirement of multimedia based wireless systems. Since channel estimation is an integral part of OFDM systems, it is critical to understand the basis of channel estimation techniques for OFDM systems so that the most appropriate method can be applied. In this article, an extensive overview of channel estimation techniques employed in OFDM systems are presented. In addition, the advantages, drawbacks, and relationship of these estimation techniques with each other are analyzed and discussed. As the combination of multiple input multiple output (MIMO)-OFDM systems promises higher data rates, estimation techniques are further investigated for these systems.
Although the existing proposed techniques differ in terms of computational complexity and their mean squared error (MSE) performance, it has been observed that many channel estimation techniques are indeed a subset of
LMMSE channel estimation technique. Hence, based on a given system’s resources and specifications, a suitable method among the presented techniques can be applied.

D

riven by multimedia based applications, anticipated future wireless systems will require high data rate capable technologies. Novel techniques such as
OFDM and MIMO stand as promising choices for future high data rate systems [1, 2].
OFDM divides the available spectrum into a number of overlapping but orthogonal narrowband subchannels, and hence converts a frequency selective channel into a nonfrequency selective channel [3]. Moreover, ISI is avoided by the use of CP, which is achieved by extending an OFDM symbol with some portion of its head

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