Multi-antenna capacities of waveguide and cavity channels

MIMO capacity of waveguide and cavity channels is analyzed in details in this paper. The rationale for this is three fold: (i) waveguide / cavity models can be used to model corridors, tunnels and other confined space channels, (ii) this is a canonical problem; its analysis allows to develop appropriate techniques, which can be further used for more complex problems, (iii) it allows to shed light on the relation between information theory and electromagnetism and, in particular, to establish the limits imposed by the laws of electromagnetism on achievable channel capacity. It is demonstrated that the number of degrees of freedom of the electromagnetic field inside of waveguides, which can be used for MIMO communication, is determined by the waveguide cross-sectional area expressed in terms of the wavelength. A system architecture is proposed, which allows using these degrees of freedom.