利用子空间的投影和跟踪改进OFDM信道估计

OFDM系统的LS信道估计可看作真实信道频率响应的一个有噪观察值，因此可采用子空间投影方法对噪声进行压缩。分析了利用子空间投影方法改进LSOFDM信道估计性能的实质，给出了利用子空间投影改进OFDM信道估计的一般框架，在此基础上将子空间投影推广到非LS信道估计方法。当信号子空间随时间变化时，需要采用子空间跟踪技术保持对信号子空间的良好估计，因此提出了一种基于子空间跟踪的参数化信道估计方法，仿真表明这种方法在性能上优于非参数化时的相应方法。

Improving the Performance of OFDM Channel Estimation through Subspace Projecting and Tracking

The LS channel estimation of OFDM systems can be viewed as a noisy observation of the true channel frequency response, so the noise component can be compressed through subspace projecting. In this paper, the substance of the improvement of LS channel estimation is analyzed when subspace projecting is enforced, and the general framework to perform subspace projecting in the context of OFDM channel estimation is given, based on which this method is exterded to non-LS channel estimation. When signal subspace varies with time, subspace tracking should be performed to maintain a good estimation of signal subspace. At the end of this paper, a subspace tracking based parametric channel estimator is presented, and computer simulation shows that this channel estimator outperforms its nonparametric counterparts.