Performance Analysis of Non-paraxial Deployments Continuous Aperture MIMO for Electromagnetic Information Theory

Continuous aperture multiple-input multiple-output (CAP-MIMO) is regarded as the ultimate form of multiple-input multiple-output (MIMO) technology because of its dense antenna elements, which can enhance the system performance. For continuous-spatial electromagnetic channels, the input is the continuous current density and the output is the continuous electric field. Therefore, it is necessary to obtain the channel characteristics at any point by applying the principles of electromagnetic information theory. In this paper, we provide a closed-form expression for mutual information between continuous transceivers. Subsequently, we expand it to general network deployments beyond the widely studied paraxial setting. Theoretical capacity limits of the communication systems are analyzed to reveal the impact of non-paraxial deployments on the performance of CAP-MIMO systems. The results demonstrate that non-paraxial deployments result in more severe fading in signal transmission and different phase offsets for different antenna elements, which causes multipath effects. Moreover, we examine the impact of key parameters such as azimuth angles, sampling density, and receiver mobility on non-paraxial CAP-MIMO systems.