Analysis On OAM Millimeter Wave Communication Channels Under Atmospheric Turbulence

With the growing relationship between people and mobile communication equipment,a variety of mobile applications are emerging in an endless stream.That has led to extensive research on safe,reliable,high-speed and efficient wireless communication systems.In essence,there are two main ways to improve the ability of wireless communication systems:one is to improve the utilization of existing resources that have been used for information transmission,and the other is to discover new resources that can be used for information transmission.Orbital angular momentum(OAM)is a new type of resource that can be used for information transmission.OAM is different from the traditional information dimensions(such as frequency,amplitude and phase).Therefore,OAM technology in optical communication systems has be applied to wireless microwave communication systems in recent years.On the other hand,millimeter waves have higher security and wider bandwidth in the microwave band.In order to improve the utilization of the frequency spectrum,millimeter waves have received widespread attention in recent years.Based on the advantages of OAM and millimeter waves,this paper studies the channels,purity and capacity of OAM-based millimeter wave communication systems under atmospheric turbulence.The previous research on OAM optical waves believed that OAM microwaves were less interfered by atmospheric turbulence.Therefore,the atmospheric turbulence is rarely considered in analyzing the channels of OAM-based microwave communication systems.First,this paper introduces that OAM millimeter wave is a spiral Gaussian wave.Then,the expression of the spatial coherence radius under the non-Kolmogorov turbulence and the expression of the spatial coherence radius under the Kolmogorov turbulence are derived.After pointing out the difference between the turbulent interference on OAM optical waves and the turbulent interference on OAM millimeter waves,this paper proposes the turbulence interference models on OAM millimeter waves.Then,this paper proposes a new purity model and a new capacity model for the coaxial OAM-based millimeter wave communication systems under the Kolmogorov turbulence.In order to study the OAM millimeter wave channels comprehensively,this paper also proposes a new purity model and a new capacity model for the multi-axis OAM-based millimeter wave communication systems under the non-Kolmogorov turbulence.The simulation results of the purity model and the capacity model show that the OAM-based millimeter wave communication systems are also significantly interfered by atmospheric turbulence.This paper also derives the optimal adjacent state interval that can maximize the capacity of the OAM-based millimeter wave communication systems under different atmospheric turbulence models.When the Kolmogorov turbulence is considered,the optimal adjacent state interval of the coaxial OAM-based millimeter wave communication system is 2.When the non-Kolmogorov turbulence is considered,the optimal adjacent state interval of the multi-axis OAM-based millimeter wave communication system increases with the increase of the generalized spectral index.