Optimal Mode for Continuous Aperture MIMO Based Holographic Communications

The recent focus on communicating between apertures, particularly in the context of continuous aperture multiple-input multiple-output (CAP-MIMO) and holographic communications, has garnered significant attention. In this study, we address the problem of general wave communications under the deterministic channel of half-space Green's function and demonstrate that the circular prolate spheroidal wave function (CPSWF) remains an optimal communication mode for CAP-MIMO, consistent with free-space Green's function case. Our investigation delves into the performance of CPSWF in near-field and line-of-sight scenarios, presenting numerical results for cases with varying transmitting and receiving aperture radii under different channel models. We validate the capability of CPSWF to exploit maximal degrees of freedom while also addressing concerns related to low coupling intensity. This work marks a significant advancement by incorporating both x- and y-components of CPSWF for numerical evaluation in CAP-MIMO for the first time.