一种基于双码本结构的有限反馈预编码方案

摘要

针对基于单码本的多用户多输入多输出( MU-MIMO )有限反馈系统中反馈精度不高的缺点,基于信道容量匹配准则,结合Givens旋转,提出了一种基于双码本结构的有限反馈预编码方案。本方案中,预编码矩阵V表示成两个矩阵相乘的形式：V=FG,其中, F基于最大信道容量准则从DFT码本选择,而G则基于均方误差迹最小准则从Givens变换码本中选择,使得等效的MIMO信道实现近似对角化。用户端根据选择的最佳预编码矩阵Fopt和Gopt ,并将对应的码本索引反馈到基站( BS)端,基站端根据码本索引恢复预编码矩阵Fopt和Gopt ,确定最终的预编码Vopt=Fopt Gopt ,进一步根据最小弦距离最大化准则,从X个待调用户中选择K个用户调度。由于本方案提出的双码本结构通过两次码字选择匹配信道,从而达到提高反馈精度的目的。仿真表明,相比于传统单码本的预编码技术,本方案使得系统的容量得到明显提升。%Aiming at the deficiency of relatively low feedback accuracy in single-codebook-based multi-user MIMO ( Multi-Input Multi-Output) system with limited feedback, a precoding scheme with limited feedback and based on double codebook is proposed in accordance with channel capacity matching criteria and in combination with Givens rotation. In the scheme, the precoding matrix V could be expressed as the multi two matrices multiplying, i. e. , V=FG, where F is chosen from the DFT codebook based on maxi-mum channel capacity criteria, and G is from the Givens rotation codebook based on the criteria of mini-mum the MMSE-trace, thus to achieve the approximate diagonalization of equivalent MIMO channel. Ac-cording to the selected two optimal precoding matrix Fopt and Gopt , corresponding codeword index is fed back to base station ( BS) through users. BS recover the precoding matrix Fopt and Gopt according to code-word index and determines the final precoding matrix Vopt=Fopt Gopt . According to the criteria of maximi-zing the minimum chordal distance, BS further schedules K users from X candidate users. The proposed double codebook structure matches the channel in twice codeword selection process, and thus achieve the goal of improving feedback accuracy. Simulation indicates that as compared with the traditional single-co-debook precoding technology, this scheme could significantly enhance the system capacity.