Joint Estimation of Frequency Offset and Channel Frequency Response Using EM Algorithm for OFDM Systems

Masahiro FUJII  Makoto ITAMI  Kohji ITOH  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A    No.11    pp.3123-3130
Publication Date: 2006/11/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.11.3123
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Wide Band Systems)
OFDM systems,  frequency offset,  channel frequency responses,  EM algorithm,  Newton algorithm,  

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Orthogonal Frequency Division Multiplexing (OFDM) systems are very sensitive to the frequency offset of the local oscillator at the receiver while the symbol timing offset can be absorbed in the guard interval. For the same reason, estimation of the frequency characteristics, needed for OFDM to be adapted to the frequency selective fading, can only be carried out conventionally after the frequency offset has been compensated. And accurate estimation of large frequency offset certainly requires high precision estimate of the frequency characteristics. In this paper, we propose a new joint estimation method of the frequency offset and the channel frequency response using an Expectation-Maximization (EM) algorithm for OFDM systems. The proposed algorithm overcomes the limitation of the thus far proposed algorithm. By computer simulations, we show the proposed algorithm provides estimation accuracy close to its lower bound in a wide range of the frequency offset.