超大规模非平稳MIMO信道估计问题研究与设计

Research and Design of Non-stationary Channel Estimation for Extremely Large-Scale Massive MIMO Systems

超大规模MIMO(Multiple-Input Multiple-Output)系统在未来的通信发展有巨大的潜力,随着天线阵列规模的增大,天线阵列的近场效应和无线信道的空间非平稳性对信道估计带来了更大的挑战。对于近场效应,不仅需要估计角度,还需要估计距离,本文提出将所需估计的角度和距离分开估计,减少估计的复杂度;对于非平稳性,需要判断散射体的可见子阵列的范围,本文提出对每个子阵列分别估计角度,根据角度和对子阵列接收信号的协方差矩阵做特征值分解得到的特征值大小,来判断散射体的可见子阵列范围,然后根据已得到的角度来估计距离。进一步分析发现,靠近中心的子阵列角度估计更准确,靠近边缘的子阵列距离估计更准确。在此基础上,本文给出了不同散射情况下超大规模阵列角度和距离的确定方案。仿真结果表明,所提出的针对近场效应和非平稳性的信道估计方案有更小的均方误差。

Extremely large-scale massive MIMO(Multiple-Input Multiple-Output)systems have great potential in the development of future communication industry.The large size of the base station antenna array will bring different channel environments for the close communication between the user and the antenna array:the near-field effect and spatial non-stationability of wireless channeland,and will bring more challenges to channel estimation.As to the near-field effect,it is necessary to estimate not only the angle but also the distance,this paper proposed to estimate angle and distance separately to reduce the complexity of estimation.As to the non-stationarity,range of the visible subarray of the scatterer needs to be determined.In this paper,the angle of each subarray was estimated separately,the visible region of the scatterer was judged according to the angle and the receiving signals covariance matrix to do the decomposed eigenvalue,and then the distance was estimated according to the angle obtained.Further analysis shows that the angle which is estimated by the subarray near the center and the distance which is estimated by the subarray near the edge is more accurate than other subarrays.On this basis,the scheme of determining the angle and the distance of the extremely large-scale array under different scattering conditions was given.To sum up,to deal with the near-field effect and spatial non-stationability in wireless channel of extremely large-scale massive MIMO systems,this paper estimated the angle and the distance separately in order to reduce the computation complexity,firstly,the angle was estimated by the subarray which is near the center,and thus the visible region of the scatterer could be judged according to the angle and the eigenvalue,then finally the distance was estimated using the subarray near the edge.In the end of this paper,some simulation results show that the channel estimation scheme proposed in this paper has smaller mean square error performance.Besides,we can also find from the simulation graphy that for angle estimation,the closer the subarray is to the center,the more accurate it is and for distance estimation,the closer the edge subarray is,the more accurate it is,which is consistent with the previous analysis.