一种快变信道中的正交频分复用系统均衡算法

当信道参数随时间的快速变化时,正交频分复用通信系统(OFDM)子载波间的正交性遭到破坏,出现了载波间的相互干扰(ICI),传统的单抽头频域均衡不再适用。虽然可采用最小均方误差(MMSE)均衡来补偿信道失真,但其计算量太大。为此,常用的方法是:先对接收信号进行ICI消除,恢复载波间的正交性,然后再进行单抽头频域或均衡。现有文献对ICI的分析均在频域进行,在此基础上提出的ICI消除与均衡算法存在计算量大或频谱利用率低的缺点。本文对ICI的产生机理和性质进行了时域和频域两方面的分析,利用现有OFDM标准中的空闲子载波信息,提出了一种ICI消除与均衡算法。理论分析和计算机仿真结果表明:该算法具有ICI消除效果好、计算量小和频谱利用率高等优点。

Equalization of OFDM Systems in Time-variant Channels

Time variations of doubly-selective channels lead to the loss of orthogonality among subcarriers, resulting in inter-carrier interference (ICI)in orthogonal frequency division multiplexing (OFDM) systems. The one tap frequency equalizer is not applicable any more in this case. In this paper, we provide an ICI analysis in both time-and frequency-domain while most existing literatures analyze the ICI effects mainly in frequency domain. Based on this analysis, we propose a novel frequency domain equalizer (FEQ) for OFDM systems in time-varying channels using the existing null subcarriers. We show that the equalizer matrix has a sparse structure, and thus a low computational complexity. Simulation results show that the proposed equalizer is capable of canceling ICI effectively with a low complexity.