Hybrid transceivers are designed for linear decentralized estimation (LDE) in a mmWave multiple-input multiple-output (MIMO) IoT network (IoTNe). For a noiseless fusion center (FC), it is demonstrated that the MSE performance is determined by the number of RF chains used at each IoT node (IoTNo). Next, the minimum-MSE RF transmit precoders (TPCs) and receive combiner (RC) matrices are designed for this setup using the dominant array response vectors, and subsequently, a closed-form expression is obtained for the baseband (BB) TPC at each IoTNo using Cauchy's interlacing theorem. For a realistic noisy FC, it is shown that the resultant mean squared error (MSE) minimization problem is non-convex. To address this challenge, a block-coordinate descent-based iterative scheme is proposed to obtain the fully digital TPC and RC matrices followed by the simultaneous orthogonal matching pursuit (SOMP) technique for decomposing the fully-digital transceiver into its corresponding RF and BB components. A theoretical proof of the convergence is also presented for the proposed iterative design procedure. Furthermore, robust hybrid transceiver designs are also derived for a practical scenario in the face of channel state information (CSI) uncertainty. The centralized MMSE lower bound has also been derived that benchmarks the performance of the proposed LDE schemes. Finally, our numerical results characterize the performance of the proposed transceivers as well as corroborate our various analytical propositions.

翻译：针对毫米波多输入多输出（MIMO）物联网网络（IoTNe）中的线性分散估计（LDE），设计了混合收发器。对于无噪声融合中心（FC），研究表明MSE性能由每个物联网节点（IoTNo）使用的射频链数量决定。随后，利用主阵列响应向量，为该场景设计了最小MSE的射频发射预编码器（TPC）与接收合并器（RC）矩阵，并通过柯西交错定理推导出每个IoTNo基带（BB）TPC的闭式表达式。针对实际有噪声FC，证明所得均方误差（MSE）最小化问题为非凸。为解决该挑战，提出一种基于块坐标下降的迭代方案以获取全数字TPC与RC矩阵，随后采用同步正交匹配追踪（SOMP）技术将全数字收发器分解为对应的射频与基带分量。同时给出了所提迭代设计过程收敛性的理论证明。此外，针对信道状态信息（CSI）不确定性的实际场景，进一步推导了鲁棒混合收发器设计方案。还推导了集中式MMSE下界，作为所提LDE方案性能的基准。最后，数值结果表征了所提收发器的性能，并验证了各项分析结论。