On the effect of channel knowledge imperfections at the transmitter on the capacity of MIMO systems

For a transmitter that has a perfect knowledge of the MIMO channel, the maximum achievable capacity corresponds to the waterfilling solution. In practice, the available knowledge may only be partial due to the time selectivity of the channel, and delay or absence of the feedback from the receiver. However, exploiting the partial knowledge leads to a significant improvement when compared to the capacity without any channel knowledge. In this paper we analyze the MIMO capacity with various types of partial knowledge of the channel under practical frequency flat channel models.