WLC31-1: On Spherical vs. Plane Wave Modeling of Line-of-Sight MIMO Channels

In this paper we consider pure line-of-sight multiple-input multiple-output channels employing uniform linear antenna arrays. We investigate the influence of exact spherical wave propagation modeling versus approximate plane wave propagation modeling on the properties of the channel matrix. Our earlier work on 2 times 2 systems is extended to include arbitrary MIMO dimensions. As before, when transmission distance increases, the properties of the spherical wave model converge to the properties given by the simpler plane wave model. The investigation results in a new tool which gives us analytical expressions describing when spherical wave modeling is necessary and when plane wave modeling is sufficient. The parameters of interest are the transmission distance, the frequency, and the array size, and the results show that the spherical wave model should be applied e.g. in some practical WLAN scenarios where plane wave modeling is commonly applied today.