RIS辅助的无小区大规模MIMO系统中信道估计及谱效分析

Channel estimation and spectral efficiency analysis for RIS-aided cell-free massive MIMO systems

无小区大规模多输入多输出(cell-free massive multiple input multiple output,Cell-Free mMIMO)技术打破传统蜂窝小区边界,从根本上解决了小区间干扰问题,从而大幅度提高系统吞吐量;同时,基于超材料的可重构智能表面(reconfigurable intelligent surface,RIS)可实现对无线电磁环境的智能操控。针对RIS辅助的无小区mMIMO系统,基于叠加导频(superimposed pilot,SP)复用模式,提出了一种基于吉洪诺夫正则化(Tikhonov regularization,TR)的迭代信道估计方法,在此基础上,从理论上推导了系统上行频谱效率(spectral efficiency,SE)的闭合表达式,通过最大化系统SE研究了SP复用模式的最优功率分配因子。仿真结果表明,采用该信道估计方法可有效提升系统SE。

Cell-Free massive multiple input multiple output(Cell-Free mMIMO)technique breaks the traditional cellular cell boundaries and fundamentally solves the inter-cell interference problem,thus significantly improving the system throughput.Meanwhile,the reconfigurable intelligent surface(RIS)made of metamaterials can achieve intelligent control of the radio-magnetic environments.An iterative channel estimation method based on tikhonov regularization(TR)is proposed for the RIS-aided Cell-Free mMIMO system based on the superimposed pilot(SP)multiplexing mode.Based on it,the theoretical derivation of the system uplink spectral efficiency(SE)is performed.The optimal power allocation factor of the SP multiplexing mode is then investigated by maximizing the system SE.Simulation results show that the channel estimation method can effectively improve the system SE.