发表机构
Centre for Wireless Communications, University of Oulu; Elisa Oyj（奥卢大学无线通信中心; Elisa公司）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对UE天线非对称的近场LoS MIMO信道获取，提出两阶段几何参数估计框架，利用单UL和双DL导频实现精确信道重建。
AI 中文摘要
近场（N-F）视距（LoS）MIMO信道可通过描述收发机相对几何结构的一小组几何参数进行紧凑表示，从而无需估计完整信道矩阵即可实现低开销信道获取。本文考虑在实际非对称用户设备（UE）天线能力下的下行链路（DL）信道获取场景，其中UE具有多个下行接收天线，但仅有一条有源上行（UL）发射链路。在此设置下，跨大型基站（BS）孔径的UL观测能够精确估计UL有源UE天线的相对位置，但不足以确定整个UE阵列的朝向。我们提出了一种基于几何的两阶段N-F LoS MIMO信道获取框架，将定义信道的几何参数的估计任务在BS和UE之间分配。首先，单个UL导频序列使BS能够估计两个BS侧参考角度，这两个角度参数化UL有源UE天线的相对位置。BS将这些估计值传送给UE，并发送两个DL导频序列，UE从中估计剩余的阵列朝向参数。我们推导了第一阶段参数的Cramer-Rao下界（CRLBs），以及UE朝向的一阶误差协方差近似，该近似显式捕获了第一阶段估计不确定性的传播。数值结果表征了由此产生的误差传播，并展示了使用一个UL和两个DL导频序列即可实现对几何参数的精确估计以及LoS MIMO信道的重建。
英文摘要
Near-field (N-F) line-of-sight (LoS) MIMO channels admit a compact representation through a small number of geometric parameters describing the relative transceiver geometry, enabling low-overhead channel acquisition without estimating the full channel matrix. This paper considers downlink (DL) channel acquisition under practical asymmetric user-equipment (UE) antenna capabilities with multiple DL receive antennas, but only a single active uplink (UL) transmit chain. In this setting, UL observations across the large BS aperture enable accurate estimation of the relative location of the UL-active UE antenna but are insufficient to determine the orientation of the entire UE array. We propose a two-stage geometry-based N-F LoS MIMO channel acquisition framework that distributes the estimation of the channel-defining geometric parameters between the BS and UE. First, a single UL pilot sequence enables the BS to estimate two BS-side reference angles that parameterize the relative location of the UL-active UE antenna. The BS conveys these estimates to the UE and transmits two DL pilot sequences, from which the UE estimates the remaining array-orientation parameter. We derive Cramer-Rao lower bounds (CRLBs) for the first-stage parameters and a first-order error-covariance approximation for the UE orientation that explicitly captures the propagation of first-stage estimation uncertainty. Numerical results characterize the resulting error propagation and demonstrate accurate estimation of the geometric parameters and reconstruction of the LoS MIMO channel using one UL and two DL pilot sequences.
