Tilt compensation in UCA-based LoS MIMO systems with antenna selection

Abstract

Due to the increasing interest for wireless communications at higher frequencies, line-of-sight multiple-input multiple-output (LoS MIMO) systems are expected to be deployed in many future applications. In such systems, maximum capacity is achieved with optimal antenna placement at the transmit (Tx) and receive (Rx) arrays. Regarding uniform circular arrays (UCAs), alignment of the Tx and Rx arrays is also necessary to extract full capacity. However, there are scenarios where the arrays are tilted and hence, alignment may not always be guaranteed. Recently, it was shown that the capacity performance of a tilted array is determined by its projection onto the plane perpendicular to the line between the Tx and Rx. So, an elliptical array can be designed so that when tilted, such projection results in an aligned UCA. We first propose an array design consisting of several concentric elliptical subarrays, where each subarray is selected to compensate a range of tilts, enabling large capacity over a range of tilting angles. Moreover, we propose the use of a more flexible uniform planar array with antenna selection to approximate the elliptical subarrays in order to compensate different tilts.