Breaking Limits of Line-of-Sight Mimo Capacity in 6G Wireless Communications
Haiyue Jing, Wenchi Cheng, Wei Zhang
Abstract
Multiple-input-multiple-output (MIMO) has proved to be a success for the fourth generation (4G) long term evolution (LTE) and is one of the key technical enablers for evolved mobile broadband (eMBB) in the fifth generation (5G) wireless communications. However, along with the number of antennas eventually increasing greatly and onehop communication distance gradually reducing, significantly increasing the capacity for line-of-sight (LOS) MIMO becomes more and more urgent. In this article, we introduce the quasi-fractal uniform circular array (QF-UCA) antenna structure-based MIMO wireless communications, which can adequately exploit the potential of MIMO in the LOS channel, and greatly increase the capacity with low complexity demodulation schemes. Specifically, three advantages regarding QF-UCA based LOS MIMO are reviewed. Then, research challenges of transceiver alignment, low-rank channel matrix, extended dimensions of QF-UCA, maximum number of orthogonal streams, and the corresponding potential solutions are discussed. Compared with traditional scattering-dependant MIMO communications, the QF-UCA based LOS MIMO wireless communication can achieve high-efficient transmission in the LOS channel.