This paper develops a linear minimum mean-square error (LMMSE) channel estimator for single and multicarrier systems that takes advantage of the mutual coupling in antenna arrays. We model the mutual coupling through multiport networks and express the single-user multiple-input multiple-output (MIMO) communication channel in terms of the impedance and scattering parameters of the antenna arrays. We put forward a novel scattering description of the communication channel which requires only the scattering parameters of the arrays as well as the terminated far-field embedded antenna patterns. In multi-antenna single-carrier systems under frequency-flat channels, we show that neglecting the mutual coupling effects leads to inaccurate characterization of the channel and noise correlations. We also extend the analysis to frequency-selective multicarrier channels wherein we further demonstrate that the coupling between the antenna elements within each array increases the number of resolvable channel taps. Standard LMMSE estimators based on existing inaccurate channel models become sub-optimal when applied to the new physically consistent model. We hence develop a new LMMSE estimator that calibrates the coupling and optimally estimates the MIMO channel. It is shown that appropriately accounting for mutual coupling through the developed physically consistent model leads to remarkable performance improvements both in terms of channel estimation accuracy and achievable rate. We demonstrate those gains in a rich-scattering environment using a connected array of slot antennas both at the transmitter and receiver sides.

翻译：本文针对单载波与多载波系统，提出了一种利用天线阵列互耦效应的线性最小均方误差（LMMSE）信道估计器。通过多端口网络对互耦进行建模，并利用天线阵列的阻抗与散射参数表述单用户多输入多输出（MIMO）通信信道。我们提出了一种新颖的信道散射描述方法，该方法仅需阵列的散射参数以及终端远场嵌入式天线方向图即可实现。在频率平坦信道下的多天线单载波系统中，研究表明忽略互耦效应会导致信道与噪声相关性的不准确表征。进一步将分析扩展至频率选择性多载波信道，并揭示阵列内天线单元间的耦合会增加可分辨信道抽头数量。基于现有非精确信道模型的标准LMMSE估计器在应用于新的物理一致模型时存在次优性，为此我们开发了一种校准耦合效应并实现MIMO信道最优估计的新型LMMSE估计器。结果表明，通过物理一致模型合理考虑互耦效应，可在信道估计精度与可达速率两方面均带来显著的性能提升。我们利用发射端与接收端均采用缝隙天线连接阵列的丰富散射环境验证了这些增益。