利用ICI自消除改善OFDM系统时变信道估计与均衡的性能
doi: 10.3724/SP.J.1146.2007.00312
Performance Improvement of Time-Varing OFDM Channel Estimation and Equalization using ICI Self-Cancellation
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摘要: 正交频分复用(OFDM)系统受到时变信道的影响，产生载波间干扰(ICI)，导致系统性能严重下降。消除ICI最有效的方法是频域均衡，但这需要准确的信道估计。基扩展模型(BEM)能够准确逼近时变信道，从而将对信道的估计转化为对少量模型参数的估计。然而，在使用导频符号对参数进行估计时，来自相邻非导频符号的ICI干扰，却严重影响了估计的准确性。为此，通过分析子载波所产生的ICI系数的变化特性，该文提出采用ICI自消除方法来减小参数估计中所存在的ICI项，以提高估计的准确性，从而改善时变信道估计与均衡的性能。仿真结果验证了该方法的有效性，相比单纯基于BEM的信道估计方法，能够得到更准确的时变信道，以及更好的ICI消除效果。Abstract: Rapidly time-varying channels degrade the performance of the Orthogonal Frequency Division Multiplexing (OFDM) due to severe InterCarrier-Interference (ICI). The most effective method of canceling the ICI is frequency equalization. But, it relies on precise channel estimation. Basis Expansion Model (BEM) can approximate time-varying channel accurately. And since then, only some finite model parameters need to be estimated to reconstruct the channel. However, the pilot-symbol-aided parameter estimation is still significantly affected by ICI from near non-pilot-symbol. So, in this work an ICI-self-cancellation parameter estimation method is proposed for BEM, by utilizing the high correlation between subcarrier ICIs. Simulations show better performance than the simplex BEM methods.
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