On the channel capacity of MIMO-OFDM systems

In order to study the impacts of channel model parameters including antenna spacing, scattering angle and the amount of delay spread on the channel capacity of a MIMO-OFDM (multiple input multiple output; orthogonal frequency division multiplexing) system, a novel method is proposed to explore the channel capacity with frequency selective fading. Based on uniform circular antenna at the receiver side, the model of fading spatial correlation is constructed. And also the statistical properties of the space-time channel are investigated. Then using the properties of Wishart distribution, the channel capacity and its upper and lower bounds for MIMO OFDM systems with arbitrary number of antennas are derived for the case where the channel is unknown at the transmitter and perfectly known at the receiver. Computer simulation results show that the channel capacity is maximized when the antenna spacing increases to a certain point, and further more, the larger is the scattering angle, the more quickly the channel capacity converges to its maximum. At high SNR, the upper and lower bounds on expected capacity are close to its real value.