Orbital-Angular-Momentum Versus MIMO: Orthogonality, Degree of Freedom,and Capacity

TL;DR

This paper compares orbital angular momentum (OAM) and MIMO in wireless communications, showing OAM can offer higher degrees of freedom and capacity under certain conditions, especially in line-of-sight scenarios.

Contribution

It provides a comparative analysis of OAM and MIMO, highlighting the potential of OAM to enhance capacity and degrees of freedom in wireless systems.

Findings

OAM's degree of freedom is greater than or equal to correlated MIMO.

OAM achieves larger capacity than MIMO in high SNR line-of-sight conditions.

Numerical results validate the advantages of OAM in specific scenarios.

Abstract

The plane wave based wireless communications have becoming more and more matured, along with the well utilization of the traditional resources such as time and frequency. To further increase the capacity for rapidly increasing capacity demand of wireless communications, it is potential to use the twist wave, which has the orbital angular momentum (OAM). In this paper, we discuss the OAM based wireless communications in the aspect of orthogonality, degree of freedom (DoF), and capacity, where both the transmitter and the receiver use uniform circular array (UCA) antennas. In particular, we compare OAM based wireless communications with multiple-input-multiple-output (MIMO) based wireless communications in terms of DoF and capacity. Numerical results are presented to validate and evaluate that the DoF of OAM based wireless communications is greater than or equal to that of correlated MIMO based wireless communications when the transmitter and the receiver antennas are aligned well. The OAM based wireless communications can achieve larger capacity than the correlated MIMO in high signal-to-noise ratio (SNR) region under line-of-sight scenario.