On MIMO capacity for various types of partial channel knowledge at the transmitter

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 the delay or absence of feedback from the receiver. However, exploiting the partial knowledge leads to a significant improvement when compared to the capacity without any channel knowledge. We analyze the MIMO capacity with various types of partial knowledge of the channel under practical frequency flat channel models.