The achievable degree of freedom (DoF) boosting has been
demonstrated on a single-input single-output (SISO) X channel
by using outdated and instantaneous channel state information
at transmitter (CSIT) synergistically, in contrast to
that of using completely outdated CSIT. However, the means
by which the DoF gain can be obtained in a multiple-input
multiple-output (MIMO) system remains unclear. This paper
proposes an interference alignment scheme with synergistic
CSIT for MIMO X channel. We show that the achievable
DoF is greater than the optimal DoF obtained with outdated
CSIT, and that achievable DoF equals to the optimal value
with outdated CSIT and transmitter cooperation.