  In this paper, we study the effect of feedback on two-user MIMO interference
channels. The capacity region of MIMO interference channels with feedback is
characterized within a constant number of bits, where this constant is
independent of the channel matrices. Further, it is shown that the capacity
region of a MIMO interference channel with feedback and its reciprocal
interference channel are within a constant number of bits. Finally, the
generalized degrees of freedom region for the MIMO interference channel with
feedback is characterized.
