基于CSI-RS赋形的大规模天线阵列预编码与反馈方法

Precoding and feedback for massive MIMO via beamformed CSIRS

大规模天线阵列的应用是5G技术中提高频谱效率的有效手段.在大规模天线阵列系统中,天线单元的数量显著增长.这些天线单元可以与不同数量的无线射频通道连接,从而映射到多个天线端口上.由于大量的天线单元可以组成不同形状的天线阵列,设计单一的反馈框架来支持不同形态的大规模天线阵列具有很大的挑战性.本文分析了在大规模天线阵列系统中实现多个维度预编码的方法,通过在水平维和垂直维分别进行预编码,充分利用了所有天线单元的天线增益和赋形增益,且所给方法只需要借助目前广泛应用于2D天线阵列的反馈机制.从我们的仿真中可以看出:基于CSI-RS赋形的CSI反馈和相应的预编码算法,相对于传统MIMO处理方式,能够获得显著的性能增益.而且,这种方法只需要一些基站侧的实现,对终端可以是完全透明的,因此对终端的影响很小.

The application of massive MIMO is an efficient method to improve spectrum efficiency in 5G mobile communication systems.The number of antenna elements increases significantly in a massive MIMO.The elements can be connected to different numbers of Tx radio chains and then mapped to different numbers of antenna ports.Since antenna elements can form different shapes of antenna arrays,e.g.tall or wide arrays,it will be challenging to design a common feedback framework for massive MIMO.In this paper,we analyze a method to implement precoding in multiple dimensions for massive MIMOs based on the widely used feedback mechanism for a 2D antenna array.This method can fully exploit the antenna gain and beamforming gain of a massive MIMO via precoding,respectively,in the vertical and horizontal dimensions.From our analysis and simulation,the implicit CSI feedback based on beamformed CSI-RS and corresponding transparent precoding can provide significant gains compared with a baseline scheme with a fixed elevation downtilt,but only needs some implementation for beam selection and precoding at the base station.This is fully transparent to UEs.