一种新的适用于OFDM系统的时变信道估计与均衡方案

针对高速移动环境中的OFDM接收问题，首先提出一种基于时变信道KL基扩展模型(KL-BEM)的时域信道估计方案．该方案用KL-BEM的一组基函数近似表达若干个OFDM符号时段内信道的时变，并在相邻OFDM符号之间插入短时导频簇来得到时变信道KL-BEM参数的估计．通过合理设计短时导频簇的结构，不仅提高了时变信道估计的精度，而且降低了导频率．其次，为了恢复发送符号，建议一种基于加窗的改进排序串行干扰抵消最小均方误差(MMSE-SIC)均衡算法．通过时域加窗预处理，子载波间干扰(ICI)得以短化，从而在提高均衡性能的同时降低了实现复杂度．仿真结果表明，提出的时变信道估计方案和建议的ICI均衡算法有效地提高了OFDM时变信道的估计和均衡性能．

Novel estimation and equalization of time-variant channels for OFDM system

This paper considers the orthogonal frequency division multiplexing (OFDM) transmission operated in highly mobile channels. We propose a time-domain channel estimator based on the Karhunen-Loeve basis expansion model (KL-BEM). The proposed estimator adopts the KL-BEM to approximate the channels' time variation within several OFDM symbols. The KL-BEM coefficients are estimated by using a group of short-time pilot clusters that are inserted between two successive OFDM symbols. The properly designed pilot clusters pattern enables accurate channel estimation and higher throughput. Following this, we adopt an improved linear minimum mean squared error equalizer with sorted serial interference cancellation (LMMSE-SIC) to recover the transmit symbol. Preceding the LMMSE-SIC, time-domain windowing is applied to shorten the intercarrier interference (ICI) support, thereby improving the equalization performance and reducing the complexity as well. Simulation results show that the proposed scheme can significantly improve the system performance in highly mobile channels.