A Geometric Interpretation of Indoor MIMO Systems using a Deterministic Model

A ray-tracing model is used to investigate the spectral efficiency of Multiple-input-multiple-output (MIMO) systems in a rectangular space representing a typical short-range geometry that could apply to an indoor wireless application. In particular, we examine the performance of uniform linear arrays (ULA) when the receiver is randomly located for several thousand trials within the space and the transmitter is fixed. This is investigated for various element spacing under line-of-sight (LOS) and non-LOS conditions for normalised receiver power levels. The results show that particular regions exist in which the system performance is either close to the maximum levels predicted by random matrix models, but also some locations have extremely poor levels of spectral efficiency. These results are explained in terms of transmission path distances between the receiver and transmitter arrays, their relative positions, the element spacing, eigenvalue distributions and delay spreads.