Impacts of CEE and CBS on the capacity of MIMO-OFDM systems

In most of previous studies, the capacity of MIMO-OFDM systems was investigated by supposing that the perfect channel state information (CSI) is available and the correlation between subcarriers (CBS) is ignorable. In practical applications, the CSI is obtained by channel estimation, where the channel estimate error (CEE) exists unavoidably. On the other hand, it is proven that different MIMO subcarrier channels are correlated even though different MIMO delay spread channels are uncorrelated. Accordingly, previous capacity result is a kind of approximate solutions to the actual capacity. Different from previous models, the hybrid-domain system model (HDSM) is introduced in this paper, where the direct relation between the frequency-domain signals and the channel impulse response (CIR) is established. Based on the HDSM, the hybrid-domain channel estimation (HDCE) is proposed, its minimum normalized mean square error (MNMSE) is given, and the actual capacity result is derived, where the CEE and CBS are involved. Simulation results show that the capacity of MIMO-OFDM systems is greater than previous results. The impacts of CEE and CBS on the capacity are investigated over different propagation environments.