Pilot-based channel estimation for OFDM systems by tracking the delay-subspace

被引:146
作者
Simeone, O [1 ]
Bar-Ness, Y
Spagnolini, U
机构
[1] Politecn Milan, Dipartimento Elettr & Informat, I-20133 Milan, Italy
[2] New Jersey Inst Technol, Ctr Commun & Signal Proc Res, Newark, NJ 07102 USA
基金
美国国家科学基金会;
关键词
channel estimation; fading radio channel; multiple input multiple output (MIMO); orthogonal frequency-division multiplexing (OFDM); subspace tracking;
D O I
10.1109/TWC.2003.819022
中图分类号
TM [电工技术]; TN [电子技术、通信技术];
学科分类号
0808 ; 0809 ;
摘要
In orthogonal frequency division multiplexing (OFDM) systems over fast-varying fading channels, channel estimation and tracking is generally carried out by transmitting known pilot symbols in given positions of the frequency-time grid. The traditional approach consists of two steps. First, the least-squares (LS) estimate is obtained over the pilot subcarriers. Then, this preliminary estimate is interpolated/smoothed over the entire frequency-time grid. In this paper, we propose to add an intermediate step, whose purpose is to increase the accuracy of the estimate over the pilot subcarriers. The presented techniques are based on the observation that the wireless radio channel can be parametrized as a combination of paths, each characterized by a delay and a complex amplitude. The amplitudes show fast temporal variations due to the mobility of terminals while the delays (and their associated delay-subspace) are almost constant over a large number of OFDM symbols. We propose to track the delay-subspace by a subspace tracking algorithm and the amplitudes by the least mean square algorithm (or modifications of the latter). The approach can be extended to multiple input multiple output OFDM or multicarrier code-division multiple-access systems. Analytical results and simulations prove the relevant benefits of the novel structure.
引用
收藏
页码:315 / 325
页数:11
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