Copyright © 2008 The Institute of Electronics, Information and Communication Engineers
Regular Section -- Papers -- Wireless Communication Technologies |
Channel Estimation Technique Assisted by Postfixed PN Sequences with Zero Padding for Wireless OFDM Communications*
1 The author is with the Department of Electrical Engineering, National Chi Nan University, Puli, Nantou, Taiwan 545, R.O.C. E-mail: jslin{at}ncnu.edu.tw, 2 The author is with Grad. Inst. of Communication Engineering, National Chi Nan University, Puli, Nantou, Taiwan 545, R.O.C., 3 The author is with the Dept. of Communication Engineering, National Central University, Jhongli, Taoyuan, Taiwan 320, R.O.C.
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Abstract |
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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.
Key Words: OFDM, channel estimation, pseudo-noise sequence, zero padding, least-squares, maximum-likelihood
Manuscript received August 6, 2007. Manuscript revised October 18, 2007.
* This work was supported in part by the National Science Council, Taiwan, Republic of China under Grant No. NSC 96-2219-E-260-002 and NSC 96-2219-E-008-002.