  The two-user multiple-input multiple-output (MIMO) interference channel (IC)
with arbitrary number of antennas at each terminal is considered and the
degrees of freedom (DoF) region is characterized in the presence of noiseless
channel output feedback from each receiver to its respective transmitter and
availability of delayed channel state information at the transmitters (CSIT).
It is shown that having output feedback and delayed CSIT can strictly enlarge
the DoF region of the MIMO IC when compared to the case in which only delayed
CSIT is present. The proposed coding schemes that achieve the corresponding DoF
region with feedback and delayed CSIT utilize both resources, i.e., feedback
and delayed CSIT in a non-trivial manner. It is also shown that the DoF region
with local feedback and delayed CSIT is equal to the DoF region with global
feedback and delayed CSIT, i.e., local feedback and delayed CSIT is equivalent
to global feedback and delayed CSIT from the perspective of the degrees of
freedom region. The converse is proved for a stronger setting in which the
channels to the two receivers need not be statistically equivalent.
