Imagine a MIMO communication system that fully exploits the propagation characteristics offered by an electromagnetic channel and ultimately approaches the limits imposed by wireless communications. This is the concept of Holographic MIMO communications. Accurate and tractable channel modeling is critical to understanding its full potential. Classical stochastic models used by communications theorists are derived under the electromagnetic far-field assumption. However, such assumption breaks down when large (compared to the wavelength) antenna arrays are considered - as envisioned in future wireless communications. In this paper, we start from the first principles of wave propagation and provide a Fourier plane-wave series expansion of the channel response, which fully captures the essence of electromagnetic propagation in arbitrary scattering and is also valid in the (radiative) near-field. The expansion is based on the Fourier spectral representation and has an intuitive physical interpretation, as it statistically describes the angular coupling between source and receiver. When discretized, it leads to a low-rank semi-unitarily equivalent approximation of the spatial electromagnetic channel in the angular domain. The developed channel model is used to compute the ergodic capacity of a point-to-point Holographic MIMO system with different degrees of channel state information.
翻译:想象一下充分利用电磁频道提供的传播特征的MIMO通信系统,并最终接近无线通信所施加的限制。这是全方位MIMO通信的概念。准确和可移动的频道模型对于了解其全部潜力至关重要。通信理论家使用的古老随机模型是根据远场电磁假设得出的。然而,在考虑大型天线(与波长相比)天线阵列时,这种假设会崩溃——正如未来无线通信所设想的那样。在本文中,我们从波波波传播的第一条原则开始,提供频道反应的四流平波系列扩展,充分捕捉到任意散布电磁传播的精髓,并在近场(辐射)也有效。扩展以Fourier光谱代表制为基础,并具有直觉的物理解释,因为它从统计学上描述了源和接收器之间的三角组合。在离散时,它导致角域空间电磁信道的近似近似近距离近。发达的频道模型用于对不同水平的轨道进行高位数据配置。