Capacity of MIMO channels: a volumetric approach

This paper deals with the problem of computing channel capacity for wireless communications systems with multi-antennas. The system is modeled using a transmit volume, a receive volume and a set of reflective scatterers. Based on the author´s previous work on channel modeling 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: (i) 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; (ii) in the case where the transmitter des 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.