Holographic multiple-input multiple-output (H-MIMO) is considered as one of the most promising technologies to enable future wireless communications in supporting the expected extreme requirements, such as high energy and spectral efficiency. Empowered by the powerful capability in electromagnetic (EM) wave manipulations, H-MIMO has the potential to reach the fundamental limit of the wireless environment, and opens up the possibility of signal processing in the EM-domain, which needs to be depicted carefully from an EM perspective, especially the wireless channel. To this aim, we study the line-of-sight (LOS) H-MIMO communications with arbitrary surface placements and establish an exact expression of the wireless channel in the EM-domain. To further obtain a more explicit and computationally-efficient channel models, we solve the implicit integrals of the exact channel model with moderate and reasonable assumptions. Numerical studies are executed and the results show good agreements of our established approximated channel models to the exact channel model.

翻译：全息多输入多输出（H-MIMO）被视为未来无线通信中支持高能量效率与频谱效率等极端需求的最具前景技术之一。凭借在电磁（EM）波操控方面的强大能力，H-MIMO有望达到无线环境的性能极限，并开辟了电磁域信号处理的可能性——这需要从电磁学视角进行精细刻画，尤其是无线信道的建模。为此，我们研究了任意表面放置下的视距（LOS）H-MIMO通信系统，建立了电磁域中无线信道的精确表达式。为获得更明晰且计算高效的信道模型，我们在适度合理的假设下求解了精确信道模型中的隐式积分。数值实验表明，我们所建立的近似信道模型与精确信道模型高度吻合。