摘要
本文主要研究了MC-CDMA下行链路中的基于导频信号的信道估计。信道估计分为对导频处信道传递函数的估计和对该初步估计的插值。为了提高信道估计的精度，本文分别从提高导频处信道估计精度和减小插值误差的角度出发提出了基于导频双谱的信道估计算法和基于变换域滤波的插值方法。
针对导频处信道传递函数的LS估计中存在载波间干扰和加性高斯白噪声的影响的这一问题，本文将传统的LS估计方法与双谱相结合提出了一种新型的基于导频双谱信道估计算法，它利用了双谱对高斯噪声的抑制作用来减小接收到的导频信号中的载波间干扰和加性高斯白噪声的影响，从而提高了导频子载波上信道估计的精度。在得到导频处信道估计后，必须使用一种有效的插值方法。本文提出了一种改进的基于变换域滤波的插值算法，该算法将导频处的信道估计序列通过DFT转换到变换域，经过滤波和插零及IDFT后便可得到所有子载波上的信道估计，其优点在于它能通过变换域上的滤波来减少均衡中噪声的影响。
The aim of this paper is to investigate the problem of pilot-assisted channel estimation in downlink MC-CDMA. Channel estimation is divided into LS estimation at pilot tones and the interpolation of the preliminary estimate. This paper introduces a bispectrum-based channel estimation algorithm to improve the accuracy of the channel estimation at pilots and proposes an equalization method with the view of the reduction of the interpolation error.
To overcome the affection of ICI and AWGN on the LS estimate of the transfer function at pilot tones, the proposed bispectrum-based channel estimation algorithm employ the suppression of ICI and AWGN components in the received pilot signals by bispectrum and then the accuracy of the estimation is improved. With the channel estimation at pilot tones, an efficient interpolation is necessary. An improved interpolation method based on transform-domain filtering is proposed, which employs DFT/IDFT and filtering in a transform domain so that the effect of noise on the equalization is significantly reduced.
引文
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