As Part II of a three-part tutorial on holographic multiple-input multiple-output (HMIMO), this Letter focuses on the state-of-the-art in performance analysis and on holographic beamforming for HMIMO communications. We commence by discussing the spatial degrees of freedom (DoF) and ergodic capacity of a point-to-point HMIMO system, based on the channel model presented in Part I. Additionally, we also consider the sum-rate analysis of multi-user HMIMO systems. Moreover, we review the recent progress in holographic beamforming techniques developed for various HMIMO scenarios. Finally, we evaluate both the spatial DoF and the channel capacity through numerical simulations.

翻译：作为全息多输入多输出（HMIMO）三部分教程的第二部分，本文聚焦于HMIMO通信在性能分析与全息波束赋形领域的最新研究进展。我们首先基于第一部分提出的信道模型，讨论点对点HMIMO系统的空间自由度（DoF）与遍历容量。此外，还分析了多用户HMIMO系统的和速率。同时，综述了面向不同HMIMO场景的全息波束赋形技术最新成果。最后通过数值仿真评估了空间自由度与信道容量性能。