Antenna selection in polarized multiple input multiple output transmissions with mutual coupling

Abstract

Physical size limitations in user equipment forces multiple antennas to be spaced closely, generating a considerable amount of mutual coupling between antenna elements that cannot be neglected. Thus, the design and deployment of antenna selection schemes appropriate for next generation wireless standards such as 3GPP LTE and LTE advanced need to take these practical implementation issues into account. In this paper, we consider multiple-input multiple-output systems where antenna elements are closely placed side by side, and examine the performance of a typical antenna selection strategy in such systems under various scenarios of antenna spacing and mutual coupling with varying antenna elements. We compare a linear array with an NSpoke co-located antenna structure which comprises of antennas separated by an angular displacement rather that spatial. We further improve the performance of such systems by a new selection approach which terminates the non-selected antenna elements with a short circuit. We observe that this methodology, can improve the performance considerably. We present analytical bounds for capacity with receive antenna selection. We found that NSpoke structures perform even better than full complexity systems when used with intelligent receive antenna selection methods, with few number of antennas even in the presence of strong mutual coupling effects.