Holographic MIMO communications with orbital angular momentum and polarization multiplexing

Holographic multiple-input multiple-output (HMIMO) has emerged as a promising technology for next- generation wireless communication systems with the capability to intelligently control electromagnetic waves through a nearly continuous aperture, offering unprecedented spatial degrees of freedom. In this paper, we analyze the performance of HMIMO that jointly exploits orbital angular momentum (OAM) and polarization multiplexing using a fully polarized uniform circular array (UCA) to enhance channel capacity and enable highly efficient spatial multiplexing within a compact aperture. We present the theoretical framework for the combined multiplexing scheme that utilizes the Green’s function-based polarized channel model and validate the performance of the system through extensive simulations. Furthermore, the OAM modes are approximated through the Green’s function and validated using the measurements obtained from a fabricated UCA. The results demonstrate that the proposed approach offers a significant performance gain in terms of system capacity compared to the conventional single-polarized OAM.