Channel Estimation Technique Assisted by Postfixed PN Sequences with Zero Padding for Wireless OFDM Communications

Jung-Shan LIN
Hong-Yu CHEN
Jia-Chin LIN

IEICE TRANSACTIONS on Communications   Vol.E91-B    No.4    pp.1095-1102
Publication Date: 2008/04/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.4.1095
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
OFDM,  channel estimation,  pseudo-noise sequence,  zero padding,  least-squares,  maximum-likelihood,  

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This paper proposes a channel estimation technique which uses a postfixed pseudo-noise (PN) sequence combined with zero padding to accurately estimate the channel impulse response for mobile orthogonal frequency division multiplexing (OFDM) communications. The major advantage of the proposed techniques is the periodical insertion of PN sequences after each OFDM symbol within the original guard interval in conventional zero-padded OFDM or within the original cyclic prefix (CP) in conventional CP-OFDM. In addition, the proposed technique takes advantage of null samples padded after the PN sequences for reducing inter-symbol interference occurring with the information detection in conventional pseudo-random-postfix OFDM. The proposed technique successfully applies either (1) least-squares algorithm with decision-directed data-assistance, (2) approximate least-squares estimation, or (3) maximum-likelihood scheme with various observation windows for the purpose of improving channel estimation performance. Some comparative simulations are given to illustrate the excellent performance of the proposed channel estimation techniques in mobile environments.