The Capacity Gain of Orbital Angular Momentum Based Multiple-Input-Multiple-Output System.

Zhuofan Zhang,Hao Chi,Shilie Zheng,Xianmin Zhang,Xiaofeng Jin,Yiling Chen

doi:10.1038/srep25418

Abstract

Wireless communication using electromagnetic wave carrying orbital angular momentum (OAM) has attracted increasing interest in recent years, and its potential to increase channel capacity has been explored widely. In this paper, we compare the technique of using uniform linear array consist of circular traveling-wave OAM antennas for multiplexing with the conventional multiple-in-multiple-out (MIMO) communication method, and numerical results show that the OAM based MIMO system can increase channel capacity while communication distance is long enough. An equivalent model is proposed to illustrate that the OAM multiplexing system is equivalent to a conventional MIMO system with a larger element spacing, which means OAM waves could decrease the spatial correlation of MIMO channel. In addition, the effects of some system parameters, such as OAM state interval and element spacing, on the capacity advantage of OAM based MIMO are also investigated. Our results reveal that OAM waves are complementary with MIMO method. OAM waves multiplexing is suitable for long-distance line-of-sight (LoS) communications or communications in open area where the multi-path effect is weak and can be used in massive MIMO systems as well.

Highlights

MIMO radio system is equivalent to conventional MIMO systems in the view of channel spatial multiplexing[28]
It is found that this kind of orbital angular momentum (OAM) based MIMO system can increase communication distance for line-of-sight (LoS) MIMO channel if the OAM states as the elements of the transmitting uniform linear array (ULA) are sorted in an ordered sequence
SAM is intrinsic since it does not depend on the choice of axis, while OAM is extrinsic because its value depends on the choice of calculation axis

Summary

Introduction

MIMO radio system is equivalent to conventional MIMO systems in the view of channel spatial multiplexing[28]. It is found that this kind of OAM based MIMO system can increase communication distance for line-of-sight (LoS) MIMO channel if the OAM states as the elements of the transmitting ULA are sorted in an ordered sequence. From this point of view, an equivalent model is proposed to explain the causation why the OAM based MIMO system can increase the capacity for LoS MIMO channel.

Results

Conclusion