Capacity of MIMO channels: a volumetric approach

This paper deals with the problem of computing channel capacity for wireless communications systems with multiantennas. The system is modelled using a transmit volume, a receive volume and a set of reflective scatterers. Based on the authors’ previous work on channel modelling of such a system, we give a multi-input-multi-output model for communications between arbitrary antenna arrays in two volumes. Together with a novel noise model for describing interferences, we derive formulas for channel capacity and capacity bounds. In particular, our results give conclusions which agree with intuition: In the case where the transmitter knows the channel, the channel capacity saturates to a constant when the number of transmit/receive antennas increases beyond a certain threshold; In the case where the transmitter does not know the channel, the channel capacity still saturates when the receive antennas increases but decays when the number of transmit antennas increases beyond a certain threshold. Moreover, simulation shows that these thresholds may occur even when the antennas are much farther apart than half-wavelength.