Three-dimensional spatial fading correlation models for compact MIMO receivers

In this paper, closed-form expressions for the spatial fading correlation (SFC) functions of antenna arrays (AAs) in a three-dimensional (3-D) multipath channel are derived. Uniform linear array (ULA), uniform circular array (UCA), uniform rectangular array (URA), electromagnetic vector sensor (EVS), and EVS in ULA, UCA, and URA configurations are considered. The SFCs are expressed in terms of the azimuth and elevation angle of arrival as well as the geometry of the AA under consideration. Verification is achieved by means of computer simulation where excellent agreement is shown between the theoretical and simulation results. The developed SFCs can be used to determine the covariance matrix at both the transmitter and receiver for capacity evaluation in multiple-input-multiple-output (MIMO) systems. The effect of the angular parameters associated with the mean azimuth of arrival (MAOA), azimuth spread (AS), mean elevation of arrival (MEOA), and elevation spread (ES) on the system performance is investigated. The present analysis shows that, in general, the system performance is more dependent on the AS than the ES, while the impact of the MAOA and MEOA is array dependent. However, it must be emphasized that in evaluating the performance of AAs, both azimuth and elevation angles must be taken into consideration. Finally, the present investigation also shows the feasibility of deploying EVS and EVS arrays as a MIMO receiver.