Can Continuous Aperture MIMO Obtain More Mutual Information Than Discrete MIMO?

The concept of continuous-aperture multiple-input multiple-output (CAP-MIMO) technology has been proposed recently, which aims at achieving high spectrum efficiency by deploying extremely dense antennas or even continuous antennas in a given aperture. The fundamental question of CAP-MIMO is whether it can achieve much better performance than the traditional discrete MIMO system. In this letter, we propose a performance comparison scheme between continuous and discrete MIMO systems based on the analysis of mutual information. Theoretical analysis show that the gap between mutual information of continuous and discrete MIMO systems converges to 0 when antenna density tends to infinity without mutual coupling. Numerical simulations verify the theoretical analysis and further show the performance degeneration caused by mutual coupling.