Array misalignment angle value estimation for OAM-based communication system

Abstract

Orbit Angular Momentum (OAM) is a potential candidate for next-generation short-distance line-of-sight wireless communication, it is assumed that the channels associated with different OAM modes are orthogonal. When there are misalignments between transmitter and receiver arrays, the assumption is incorrect. In this paper, we propose the methods to estimate the array misalignment values in the OAM-based communication system for Uniform Circular Array (UCA) in transmitter and receiver. It is shown that, when the pilot signals are transmitted in a single or all OAM modes, the absolute value of the received signal can be approximated by the polynomial functions of misalignment angle. By solving these functions, the misalignment angle can be estimated. The proposed methods are theoretically analyzed and tested for OAM Index Modulation (OAM-IM)-based communication system, The obtained results indicate that the proposed methods improve the OAM-IM based communication system in the presence of array misalignments problem.