Plane Spiral OAM Mode-Group Based MIMO Communications: An Experimental Study

TL;DR

This paper experimentally demonstrates a novel PSOAM mode-group based MIMO communication system that enhances beamforming and spatial multiplexing capabilities, achieving significant SNR gains and spectrum efficiency over a 50-meter line-of-sight link at 10.2 GHz.

Contribution

First experimental verification of PSOAM mode-group based MIMO system, showing improved beam directionality, reduced correlation, and potential for long-distance LoS communications.

Findings

Beam directionality gain improves SNR levels.

Vorticity provides additional DoF to reduce spatial correlation.

Achieved 3.7 bits/s/Hz/stream spectrum efficiency over 50 meters.

Abstract

Spatial division multiplexing using conventional orbital angular momentum (OAM) has become a well-known physical layer transmission method over the past decade. The mode-group (MG) superposed by specific single mode plane spiral OAM (PSOAM) waves has been proved to be a flexible beamforming method to achieve the azimuthal pattern diversity, which inherits the spiral phase distribution of conventional OAM wave. Thus, it possesses both the beam directionality and vorticity. In this paper, it's the first time to show and verify novel PSOAM MG based multiple-in-multiple-out (MIMO) communication link (MG-MIMO) experimentally in a line-of-sight (LoS) scenario. A compact multi-mode PSOAM antenna is demonstrated experimentally to generate multiple independent controllable PSOAM waves, which can be used for constructing MGs. After several proof-of-principle tests, it has been verified that the beam directionality gain of MG can improve the receiving signal-to-noise (SNR) level in an actual system, meanwhile, the vorticity can provide another degree of freedom (DoF) to reduce the spatial correlation of MIMO system. Furthermore, a tentative long-distance transmission experiment operated at 10.2 GHz has been performed successfully at a distance of 50 m with a single-way spectrum efficiency of 3.7 bits/s/Hz/stream. The proposed MG-MIMO may have potential in the long-distance LoS back-haul scenario.