The majority of stochastic channel models rely on the electromagnetic far-field assumption. This assumption breaks down in future applications that push towards the electromagnetic near-field region such as those where the use of very large antenna arrays is envisioned. Motivated by this consideration, we show how physical principles can be used to derive a channel model that is also valid in the electromagnetic near-field. We show that wave propagation through a three-dimensional scattered medium can be generally modeled as a linear and space-variant system. We first review the physics principles that lead to a closed-form deterministic angular representation of the channel response. This serves as a basis for deriving a stochastic representation of the channel in terms of statistically independent Gaussian random coefficients for randomly spatially-stationary propagation environments. The very desirable property of spatial stationarity can always be retained by excluding reactive propagation mechanisms confined in the extreme near-field propagation region. Remarkably, the provided stochastic representation is directly connected to the Fourier spectral representation of a general spatially-stationary random field.
翻译:多数随机信道模型都依赖于远场电磁假设。 这个假设将在未来的应用中分解为向近场电磁区域推进的物理应用,例如设想使用非常大天线阵列的应用程序。 我们受此考虑的驱动,我们展示了如何利用物理原理来获取在近场电磁中同样有效的频道模型。我们显示,通过三维分散的媒体波传播一般可以模拟成线性和空间变量系统。我们首先审查导致频道反应的闭式定式角代表的物理原理。这可作为从统计上独立的高斯随机随机系数的角度得出该频道的随机代表性的基础。空间静止性非常可取的特性始终可以通过排除封闭在极端近场传播区域的被动传播机制而得以保留。值得注意的是,所提供的随机代表与一般空间静止随机场的四维光谱代表直接相连。