Information-Theoretic Evaluation of Orbital Angular Momentum Transmission

Abstract

The capacity of wireless communications with Orbital Angular Momentum (OAM) based on maximum mutual information is investigated in this paper. The wireless communications with OAM can be divided into the OAM multiplexing and the OAM index modulation. In this paper, the system architecture of wireless communications with OAM is established. Afterwards, the capacity of wireless communications with OAM is analyzed based on the propagation scheme. Additionally, the capacity bound of wireless communications with OAM is also presented. Then, the mutual information results for the OAM multiplexing and the OAM index modulation are derived. Since the OAM index modulation is a specific modulation of wireless communications with OAM, the mutual information of the OAM index modulation is much lower than the capacity bound. It is demonstrated by numerical results that the maximum capacity is achieved when the OAM multiplexing technique is adopted. Moreover, it is also concluded that the OAM modes and bandwidth are symmetry for the channel capacity.