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Journal of Electrical and Computer Engineering
Volume 2012, Article ID 703243, 11 pages
http://dx.doi.org/10.1155/2012/703243
Research Article

Performance Comparison of Doppler Scale Estimation Methods for Underwater Acoustic OFDM

1Department of Electrical and Computer Engineering, University of Connecticut, 371 Fairfield Way U-2157, Storrs, CT 06269, USA
2National Sun Yat-Sen University, Kaohsiung, Taiwan
3Department of Computer Science and Engineering, University of Connecticut, 371 Fairfield Way U-2155, Storrs, CT 06269, USA

Received 13 January 2012; Accepted 5 April 2012

Academic Editor: Charalampos C. Tsimenidis

Copyright © 2012 Lei Wan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Doppler scale estimation is one critical step needed by the resampling operation in acoustic communication receivers. In this paper, we compare different Doppler scale estimation methods using either cyclic-prefixed (CP) or zero-padded (ZP) orthogonal-frequency division-multiplexing (OFDM) waveforms. For a CP-OFDM preamble, a self-correlation method allows for blind Doppler scale estimation based on an embedded repetition structure while a cross-correlation method is available with the knowledge of the waveform. For each received ZP-OFDM block, the existence of null subcarriers allows for blind Doppler scale estimation. In addition, a pilot-aided method and a decision-aided method are applicable based on cross-correlation with templates constructed from symbols on pilot subcarriers only and from symbols on all subcarriers after data decoding, respectively. This paper carries out extensive comparisons among these methods using both simulated and real experimental data. Further, the applicabilities of these methods to distributed multiuser systems are investigated.