Title :
A Refined Channel Estimation Method for STBC/OFDM Systems in High-Mobility Wireless Channels
Author :
Ku, Meng-Lin ; Huang, Chia-Chi
Author_Institution :
Dept. of Commun. Eng., Nat. Chiao Tung Univ., Hsinchu
fDate :
11/1/2008 12:00:00 AM
Abstract :
In this paper, we investigate channel estimation for orthogonal frequency division multiplexing (OFDM) systems with space-time block code (STBC) in mobile wireless channels. Our proposed method consists of two-stage processing and is developed on the basis of the classical discrete Fourier transform (DFT)-based channel estimation method. In the initialization stage, we employ a multipath interference cancellation technique to estimate multipath delays and multipath complex gains. In the tracking stage, we develop a refined decision-feedback (DF) DFT-based channel estimation method in which a few pilot tones inserted in OFDM data symbols are applied to form an optimal gradient vector at the first iteration such that the error propagation effect is mitigated. In order to reduce computational complexity, an approximate weighting matrix is adopted to avoid matrix inversion. We demonstrate the proposed method through computer simulation of an STBC/OFDM system with two transmit antennas and a single receive antenna. The results show that our method outperforms the classical DFT-based method, the STBC-based minimum mean square error (MMSE) method, and the Kalman filtering method as well, and that significant signal-to-noise ratio (SNR) performance improvement can be achieved, especially when a high-level modulation scheme, e.g. 16QAM, is adopted in high-mobility environments.
Keywords :
OFDM modulation; channel estimation; discrete Fourier transforms; interference suppression; matrix inversion; mobile radio; multipath channels; radiofrequency interference; space-time codes; vectors; wireless channels; STBC-OFDM systems; approximate weighting matrix; classical discrete Fourier transform; decision-feedback DFT-based method; error propagation effect; high-mobility wireless channels; matrix inversion; multipath complex gain; multipath delay estimation; multipath interference cancellation technique; optimal gradient vector; orthogonal frequency division multiplexing; receive antenna; refined channel estimation method; space-time block code; transmit antennas; two-stage processing; Block codes; Channel estimation; Computational complexity; Computer errors; Computer simulation; Delay estimation; Discrete Fourier transforms; Interference cancellation; OFDM; Receiving antennas; IEEE 802.16e; Multiple-input multiple-output systems; channel estimation; orthogonal frequency division multiplexing; spacetime time coding;
Journal_Title :
Wireless Communications, IEEE Transactions on
DOI :
10.1109/T-WC.2008.070585