信道估计是通过对基站接收信号和用户端发送的已知导频序列进行处理获得。二维嵌套阵列可以节约系统的成本并且得到大规模MIMO(multiple-input multiple-output)天线阵列的性能,然而由于二维嵌套阵列的结构不规整,直接对基站接收信号进...信道估计是通过对基站接收信号和用户端发送的已知导频序列进行处理获得。二维嵌套阵列可以节约系统的成本并且得到大规模MIMO(multiple-input multiple-output)天线阵列的性能,然而由于二维嵌套阵列的结构不规整,直接对基站接收信号进行处理具有一定的难度。本文提出一种基于2D-DFT(two-dimensional Discrete Fourier Transform)的信道重构算法,首先对接收信号做自相关处理转化为连续差分阵列的接收信号,其次通过2D-DFT估计出用户的初始DOA(the direction of arrival),然后利用角度旋转技术增强DOA估计实现超分辨率估计,再根据精确的DOA估计通过传统的LS(least squares)估计方法估计出信道增益;最后重构出用户的信道。数值仿真验证了算法的有效性。展开更多
The Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) has been used to investigate the extra-area effects of silver iodide (AgI) seeding on stratiform clouds performed at the supercooled layer.A bulk two-moment m...The Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) has been used to investigate the extra-area effects of silver iodide (AgI) seeding on stratiform clouds performed at the supercooled layer.A bulk two-moment microphysical scheme and the new software package for silver iodide are incorporated in MM5.Extra conservation equations are applied to trace the seeding agent,which is transported along the flow field and interacts with the supercooled cloud fields.In this study,the model was run using three nested grids,with 3.3 km × 3.3 km horizontal resolution in the finest grid.The model results showed that seeding with AgI at the 5 to 15℃ levels had microphysical effects on the simulated clouds and that the simulation produced a longer-lasting seeding effect because of the transport of the seeding agent by upper-level winds.Most of the AgI particles acted as deposition nuclei,and the deposition nucleation process contributed mostly to additional cloud ice formation in this study.The results showed that more precipitation results from seeded than unseeded case,and the precipitation was redistributed downwind of the target.Augmented precipitation (varying from 5% to 25% downwind) was confined in space to within 250 km of the seeding target and in time to the 3-h period after initial seeding.展开更多
文摘信道估计是通过对基站接收信号和用户端发送的已知导频序列进行处理获得。二维嵌套阵列可以节约系统的成本并且得到大规模MIMO(multiple-input multiple-output)天线阵列的性能,然而由于二维嵌套阵列的结构不规整,直接对基站接收信号进行处理具有一定的难度。本文提出一种基于2D-DFT(two-dimensional Discrete Fourier Transform)的信道重构算法,首先对接收信号做自相关处理转化为连续差分阵列的接收信号,其次通过2D-DFT估计出用户的初始DOA(the direction of arrival),然后利用角度旋转技术增强DOA估计实现超分辨率估计,再根据精确的DOA估计通过传统的LS(least squares)估计方法估计出信道增益;最后重构出用户的信道。数值仿真验证了算法的有效性。
基金supported by the National Natural Science Foundation of China (Grant No. 40805056)the National Key Technologies R&D Program of China (Grant No. 2006BAC12B00)
文摘The Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) has been used to investigate the extra-area effects of silver iodide (AgI) seeding on stratiform clouds performed at the supercooled layer.A bulk two-moment microphysical scheme and the new software package for silver iodide are incorporated in MM5.Extra conservation equations are applied to trace the seeding agent,which is transported along the flow field and interacts with the supercooled cloud fields.In this study,the model was run using three nested grids,with 3.3 km × 3.3 km horizontal resolution in the finest grid.The model results showed that seeding with AgI at the 5 to 15℃ levels had microphysical effects on the simulated clouds and that the simulation produced a longer-lasting seeding effect because of the transport of the seeding agent by upper-level winds.Most of the AgI particles acted as deposition nuclei,and the deposition nucleation process contributed mostly to additional cloud ice formation in this study.The results showed that more precipitation results from seeded than unseeded case,and the precipitation was redistributed downwind of the target.Augmented precipitation (varying from 5% to 25% downwind) was confined in space to within 250 km of the seeding target and in time to the 3-h period after initial seeding.
