Distributed Phase Calibration for Massive OAM Backhauling in 5G IoT Environments

Abstract

The Internet of Things (IoT) plays an important role in 5G communications. Large number of 5G end modules supports the communications of different types of IOT applications, which constantly put forward requirements for high capacity communication technology. In IOT applications, distributed end nodes can construct virtual uniform circular arrays (UCAs), thus performing high capacity UCA based orbital angular momentum (OAM) communication. However, phase deviation exists in the distributed radio chains, which destroys the orthogonality among OAM modes and deteriorates the communication performance. Therefore, phase calibrations are needed. Existing phase calibration schemes are not optimal for UCA based OAM communications, therefore, we propose a phase calibration scheme specially designed for the distributed UCA in this paper. The scheme consists of the phase deviation computation method and the signaling interaction process. Through the signaling interaction, each end node obtains different phase deviation information. Then, the target phase deviation can be calculated based on the computation method. The phase deviation computation only involves linear equations and the quantitized phase value is transmitted during the signaling interaction process. Therefore, the proposed scheme brings little overhead to the normal communications. Simulation results indicate that the proposed calibration scheme can achieve high performance under different signaling precisions, and greatly improves the capacity of the uplink communication for the distributed IOT end nodes.