自适应H_∞滤波实现MIMO-OFDM时变信道估计

Time-varying Channel Estimation of MIMO-OFDM Wireless Systems Based on Adaptive H_∞ Filter

基于多输入多输出-正交频分复用(MIMO-OFDM)无线系统,以H∞滤波理论为基础,提出一种新的MIMO-OFDM时变信道估计算法.依据H∞滤波原理,首先建立起一个线性的动态系统,系统输入和输出分别为未知干扰(包括背景噪声及其模型误差)和信道状态估计误差;然后,以该系统的H∞范数(即系统输入输出能量增益)作为代价函数,提出一种自适应H∞滤波算法;该算法的设计准则为,在未知干扰最大的情况下使得信道估计误差小于一个给定的界限(称为干扰水平值),并且该干扰水平值可以根据当前无线环境的信噪比自适应地更新变化.由于该自适应H∞滤波算法未对噪声分布做任何先验假设,因此在非高斯噪声下可以获得较好的信道估计性能.计算机仿真实验结果证明了该算法的有效性.

An adaptive H∞ filter is proposed for time-varying channel estimation of the multi-input multi-output orthogonal frequency division multiplexing （ MIMO-OFDM ） wireless communication systems based on H∞ filtering theory. Mainly on the H∞ filtering principle, a dynamic system is formulated firstly, whose inputs are unknown disturbances including noise and model error, output is the channel estimation error. Then, making the H∞ norm of this dynamic system as a cost function, an adaptive H∞ filtering algorithm is proposed whose criterion is to guarantee that the worst-cast effect of disturbance on channel estimation error is smaller than a given boundary （ called disturbance level ）, which is adaptively updating on the signal-noise-ratio of the current wireless system. Since any assumption on the noise distribution is not make in the proposed adaptive H∞ filter, the good channel estimation performance can be achieved even in the non-Gaussian noise. Simulation results show the effectiveness of the algorithm.