This paper investigates the low-complex linear minimum mean squared error (LMMSE) channel estimation in an extra-large scale MIMO system with the spherical wave model (SWM). We model the extra-large scale MIMO channels using the SWM in the terahertz (THz) line-of-sight propagation, in which the transceiver is a uniform circular antenna array. On this basis, for the known channel covariance matrix (CCM), a low-complex LMMSE channel estimation algorithm is proposed by exploiting the spherical wave properties (SWP). Meanwhile, for the unknown CCM, a similar low-complex LMMSE channel estimation algorithm is also proposed. Both theoretical and simulation results show that the proposed algorithm has lower complexity without reducing the accuracy of channel estimation.

翻译：本文研究了基于球面波模型（SWM）的超大规模MIMO系统中的低复杂度线性最小均方误差（LMMSE）信道估计问题。我们采用SWM对太赫兹（THz）视距传播中的超大规模MIMO信道进行建模，其中收发端采用均匀圆形天线阵列。在此基础上，针对已知信道协方差矩阵（CCM）的情况，提出了一种利用球面波特性（SWP）的低复杂度LMMSE信道估计算法。同时，针对未知CCM的情况，也提出了一种类似的低复杂度LMMSE信道估计算法。理论分析与仿真结果均表明，所提算法在保证信道估计精度的前提下具有更低的复杂度。