Ultimate Capacity Analysis of Orbital Angular Momentum Channels

Orbital angular momentum (OAM) multiplexing has recently been proposed as a solution to the ultimate goal of increasing the channel capacity of wireless communication links because of the existence of infinite orthogonal modes. It can be combined with the existing conventional multiplexing techniques to boost up the data rate multiple times for future wireless communication systems. We analyze the fundamental behavior of the channel capacity of OAM channels based on two concepts for the most common Laguerre-Gaussian OAM beams: paraxiality and orthogonality. We also confirm our general theory by applying the proposed method to the evanescing OAM beams, circular transverse electric beams. Our study is based on calculating the paraxial estimator of these OAM beams and relating it as a parameter that limits the degree of freedom in OAM channels. In particular, we investigate the dependency on physical parameters, such as transmitter and receiver sizes, in our calculation to define the capacity of OAM channels.

Introduction

Recently, data transmission at higher data rates in wireless communication systems has been an ever-increasing demand owing to the global usage of smart technologies, including smart-phones and Internet-of-Things (IOT) devices. This sets up an ambition for multifold increments in data rates with the onset of 5G wireless networks. To meet this demand, researchers are continuously looking for unconventional methods to boost data rates, by exploring novel radio resources, because conventional radio resources, such as frequency, time, and space, are almost doomed to be exhausted.