Modelling and Optimization of OAM-MIMO Communication Systems with Unaligned Antennas

TL;DR

This paper models and optimizes OAM-MIMO wireless systems with unaligned antennas, addressing crosstalk issues caused by turbulence and misalignment, and proposes an algorithm that significantly enhances system capacity.

Contribution

It introduces a new channel and purity model for unaligned OAM-MIMO systems under non-Kolmogorov turbulence, and develops an optimization algorithm to improve capacity.

Findings

Capacity improved by up to 28.7% with optimization.

Capacity increase of 320.3% under certain deflection angles.

New models effectively analyze performance under turbulence and misalignment.

Abstract

The orbital angular momentum (OAM) wireless communication technique is emerging as one of potential techniques for the Sixth generation (6G) wireless communication system. The most advantage of OAM wireless communication technique is the natural orthogonality among different OAM states. However, one of the most disadvantages is the crosstalk among different OAM states which is widely caused by the atmospheric turbulence and misalignment between transmitting and receiving antennas. Considering the OAM-based multiple-input multiple-output (OAM-MIMO) transmission system with unaligned antennas, a new channel model is proposed for performance analysis. Moreover, a purity model of the OAM-MIMO transmission system with unaligned antennas is derived for the non-Kolmogorov turbulence. Furthermore, error probability and capacity models are derived for OAM-MIMO transmission systems with unaligned antennas. To overcome the disadvantage caused by unaligned antennas and non-Kolmogorov turbulence, a new optimization algorithm of OAM state interval is proposed to improve the capacity of OAM-MIMO transmission system. Numerical results indicate that the capacity of OAM-MIMO transmission system is improved by the optimization algorithm. Specifically, the capacity increment of OAM-MIMO transmission system adopting the optimization algorithm is up to 28.7% and 320.3% when the angle of deflection between transmitting and receiving antennas is -24 dB and -5 dB, respectively.