TY - JOUR
T1 - Optimal training design for MIMO OFDM systems in mobile wireless channels
AU - Barhumi, Imad
AU - Leus, Geert
AU - Moonen, Marc
N1 - Funding Information:
Manuscript received January 28, 2002; revised November 27, 2002. This work was carried out at the ESAT Laboratory of the Katholieke Universiteit Leuven, in the framework of the Belgian State, Prime Minister’s Office—Federal Office for Scientific, Technical and Cultural Affairs—Interuniversity Poles of Attraction Programme (2002–2007)—IUAP P5/22 (“Dynamical Systems and Control: Computation, Identification and Modeling”) and P5/11 (“Mobile multimedia communication systems and networks”), and the Concerted Research Action GOA-MEFISTO-666 (Mathematical Engineering for Information and Communication Systems Technology) of the Flemish Government under Research Project FWO nr.G.0196.02 (“Design of efficient communication techniques for wireless time-dispersive multi-user MIMO systems”), and was supported in part by the Flemish Interuniversity Microelectronics Center (IMEC). The scientific responsibility is assumed by its authors. The associate editor coordinating the review of this paper and approving it for publication was Dr. Sergios Theodoridis.
PY - 2003/6
Y1 - 2003/6
N2 - This paper describes a least squares (LS) channel estimation scheme for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems based on pilot tones. We first compute the mean square error (MSE) of the LS channel estimate. We then derive optimal pilot sequences and optimal placement of the pilot tones with respect to this MSE. It is shown that the optimal pilot sequences are equipowered, equispaced, and phase shift orthogonal. To reduce the training overhead, an LS channel estimation scheme over multiple OFDM symbols is also discussed. Moreover, to enhance channel estimation, a recursive LS (RLS) algorithm is proposed, for which we derive the optimal forgetting or tracking factor. This factor is found to be a function of both the noise variance and the channel Doppler spread. Through simulations, it is shown that the optimal pilot sequences derived in this paper outperform both the orthogonal and random pilot sequences. It is also shown that a considerable gain in signal-to-noise ratio (SNR) can be obtained by using the RLS algorithm, especially in slowly time-varying channels.
AB - This paper describes a least squares (LS) channel estimation scheme for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems based on pilot tones. We first compute the mean square error (MSE) of the LS channel estimate. We then derive optimal pilot sequences and optimal placement of the pilot tones with respect to this MSE. It is shown that the optimal pilot sequences are equipowered, equispaced, and phase shift orthogonal. To reduce the training overhead, an LS channel estimation scheme over multiple OFDM symbols is also discussed. Moreover, to enhance channel estimation, a recursive LS (RLS) algorithm is proposed, for which we derive the optimal forgetting or tracking factor. This factor is found to be a function of both the noise variance and the channel Doppler spread. Through simulations, it is shown that the optimal pilot sequences derived in this paper outperform both the orthogonal and random pilot sequences. It is also shown that a considerable gain in signal-to-noise ratio (SNR) can be obtained by using the RLS algorithm, especially in slowly time-varying channels.
KW - Channel estimation
KW - MIMO
KW - Multipath fading channels
KW - OFDM
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U2 - 10.1109/TSP.2003.811243
DO - 10.1109/TSP.2003.811243
M3 - Article
AN - SCOPUS:0037645707
SN - 1053-587X
VL - 51
SP - 1615
EP - 1624
JO - IEEE Transactions on Signal Processing
JF - IEEE Transactions on Signal Processing
IS - 6
ER -