A Study of Close Eigenvalues and Communication Performance in Multiple-Input Multiple-Output Eigenbeam Space-Division Multiplexing

In multiple-input multiple-output (MIMO) eigenbeam space-division multiplexing (E-SDM), increased phase angle variation velocities have been reported because the transmission and reception weights become increasingly sensitive to smaller gaps between eigenvalues. In this paper, the effects of close eigenvalues were evaluated based on the number of antenna elements and spatial correlations. The evaluation is executed using the ITU-R M.2135-1 time variant channel model. As a result, it is clarified that there is a good possibility of improved communication performance in MIMO E-SDM based on adaptive control of the channel estimation time period using the eigenvalue gap as an input parameter.