Comparison of UCA-OAM and UCA-MIMO systems for sub-THz band line-of-sight spatial multiplexing transmission

This paper compares the uniform circular array based orbital angular momentum (UCA-OAM) scheme, which enables spatial multiplexing transmission of data symbols via multiple OAM modes, with the UCA-MIMO scheme through numerical analysis and simulation in terms of spectral efficiency and feedback over-head. Specifically, based on the relations between the eigenmodes of the UCA-SVD-MIMO system and the modes of UCA-OAM system as well as the capacity formula, the channel capacities of the two systems are compared for the cases where equal power allocation and waterfilling power allocation are employed, and then the effectiveness of the analytical results are verified through simulation.