用比特反馈实现下行MIMO信道估计，突破有限回传瓶颈
Downlink MIMO Channel Estimation from Bits: Recoverability and Algorithm
- 用户端压缩+高斯抖动量化，基站用最大似然法重构信道
- 在双方向模型下证明了信道可恢复性，两种压缩方案各有优势
- 提出基于ADMM与谐波提取的算法，适合资源受限的5G/6G系统
在频分双工（FDD）大规模MIMO系统中，基站获取下行信道状态信息（CSI）的主要挑战来自用户设备（UE）有限的反馈。本文贡献有二：首先，提出一种简单反馈框架，用户端采用压缩与高斯抖动量化策略，基站侧构建最大似然估计器（MLE），并在广泛使用的双方向模型下建立了信道可恢复性；具体分析了两种压缩方案——一个更省开销，另一个在用户端计算更轻量。其次，为实现该MLE，设计了一种交替方向乘子法（ADMM）算法，其核心是集成高效的谐波检索（HR）求解器，显著提升了求解效率。大量数值实验验证了所提方法的有效性。
原文摘要 · Abstract (English)
In frequency division duplex (FDD) massive MIMO systems, a major challenge lies in acquiring the downlink channel state information}\ (CSI) at the base station (BS) from limited feedback sent by the user equipment (UE). To tackle this fundamental task, our contribution is twofold: First, a simple feedback framework is proposed, where a compression and Gaussian dithering-based quantization strategy is adopted at the UE side, and then a maximum likelihood estimator (MLE) is formulated at the BS side. Recoverability of the MIMO channel under the widely used double directional model is established. Specifically, analyses are presented for two compression schemes -- showing one being more overhead-economical and the other computationally lighter at the UE side. Second, to realize the MLE, an alternating direction method of multipliers (ADMM) algorithm is proposed. The algorithm is carefully designed to integrate a sophisticated harmonic retrieval (HR) solver as subroutine, which turns out to be the key of effectively tackling this hard MLE problem.Extensive numerical experiments are conducted to validate the efficacy of our approach.
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