基于导频信号的LTE系统高移动性信道估计算法

摘要

在长期演进(Long Term Evolution,LTE)系统中,精确的信道估计是均衡和相干解调的前提.在高速移动信道下,由于LTE下行链路离散非均匀的导频模式,传统的时间方向信道估计方法性能较差.为了提高信道估计精度,首先利用离散傅里叶变换(Discrete Fourier Transform,DFT)的信道估计方法提高导频处的估计精度.然后根据LTE系统的导频结构,设计了两种时间方向信道估计方法:1)当信道的统计特性未知时,把不等间隔的导频分布转换为等间隔的导频分布,并利用三阶样条内插估计出数据处的信道频域值;2)当信道的统计特性已知时,基于最小均方误差准则,设计高性能的自适应内插器,以准确获得信道估计所需系数.仿真和分析表明,相对于传统的线性内插算法,这两种信道估计算法利用更多的导频信息,可大大提高信道估计的精度,同时提升系统的解调性能.%In the long term evolution (LTE) system,accurate channel estimation (CE) is crucial in channel equalization and coherent demodulation.Due to the discrete non-uniform pilot pattern of the LTE downlink system,the traditional CE method results in significant estimation errors over high-speed mobile channels.In order to improve the CE accuracy,firstly,the discrete Fourier transform (DFT)-based CE technique is developed to enhance the CE accuracy of pilot.Then according to the pilot pattern of the LTE system,we propose two CE methods to improve the CE accuracy of data:1) When the statistical properties of channel are unknown,the non-uniform pilot pattern is transformed into the uniform pilot pattern.Then the spline fitting is utilized to estimate the channel frequency response (CFR) of data position.2) When the statistical properties of channel are known,a high performance adaptation interpolator is designed based on the minimum mean square error criterion,which can accurately obtain the required coefficients of CE.Simulation results and analysis demonstrate that,compared to the conventional linear interpolation algorithm,the proposed schemes can exploit more pilot information,which significantly improve the CFR accuracy and enhance the demodulation performance.