在时变信道中正交频分复用( OFDM) 系统下传统信道估计方法存在估计性能差、计算复杂度高的问题．为此，文中提出了一种双对角线性最小均方误差( DD- LMMSE)的信道估计方法．首先建立基于基扩展模型( BEM) 的系统模型，然后进行两次对角线性最小均方误差估计得到 BEM 系数，从而估计出信道的时域冲击响应．仿真实验结果表明，该方法不管在慢时变信道下还是在快时变信道下均具有良好的估计性能，且计算复杂度低．

For the orthogonal frequency- division multiplexing (OFDM) systems in time- variant channels,traditionalestimation methods are of poor estimation performance and high computational complexity.In order to solve theseproblems,we propose a channel estimation method named as DD- LMMSE (Dual- Diagonal Linear Minimum MeanSquare Error).In this method,a system model is constructed on the basis of expansion model (BEM) and the esti-mated coefficients of BEM are obtained by performing the diagonal LMMSE twice,and thus achieving the channelimpulse response (CIR) in time domain.Simulation results show that,whether in slowly time- variant or rapidlytime- variant channels,the proposed method has better performance and lower computational complexity.